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Wang Y, Wang F, Wang C, Li X, Fu L. Positive Regulation of Spoilage Potential and Biofilm Formation in Shewanella baltica OS155 via Quorum Sensing System Composed of DKP and Orphan LuxRs. Front Microbiol 2019; 10:135. [PMID: 30804914 PMCID: PMC6370745 DOI: 10.3389/fmicb.2019.00135] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 01/21/2019] [Indexed: 12/23/2022] Open
Abstract
The spoilage potential and biofilm formation of Shewanella baltica are reported to be regulated by Quorum sensing (QS) system from the phenotype point of view, but the specific mechanism is not fully understood. In the present study, the QS autoinducers were detected by UHPLC-MS/MS, cell density-dependent luxR-type genes were obtained through autoregulation experiments among a series of candidates in S. baltica OS155 (The SSO of large yellow croaker). The direct interaction between cyclo-(L-Pro-L-Phe) (PP) and LuxR01 as well as LuxR02 proteins was revealed via in vitro binding assay. Deletion of luxR-type genes (luxR01 and luxR02) impaired spoilage potential and biofilm formation of S. baltica OS155 in various degrees. Transcriptional analysis and qRT-PCR validation showed that spoilage and biofilm-related genes torS, speF, and pomA were down-regulated in luxR01 and luxR02 deletion strains. In addition, exogenous PP promoted spoilage potential and biofilm formation, which could be attenuated by luxR01 or luxR02 deletion. Our results revealed an explicit QS system employing PP as autoinducer and two orphan LuxRs as receptors which positively regulated spoilage capacity and biofilm formation via transcriptional regulation of corresponding genes in S. baltica OS155, which provides potential specific targets for seafood preservation involving QS system.
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Affiliation(s)
- Yanbo Wang
- Food Safety Key Laboratory of Zhejiang Province, School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
- Zhejiang Engineering Institute of Food Quality and Safety, Zhejiang Gongshang University, Hangzhou, China
| | - Feifei Wang
- Food Safety Key Laboratory of Zhejiang Province, School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
| | - Chong Wang
- Food Safety Key Laboratory of Zhejiang Province, School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
| | - Xiuting Li
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Technology and Business University, Beijing, China
| | - Linglin Fu
- Food Safety Key Laboratory of Zhejiang Province, School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
- Zhejiang Engineering Institute of Food Quality and Safety, Zhejiang Gongshang University, Hangzhou, China
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Complex Iron Uptake by the Putrebactin-Mediated and Feo Systems in Shewanella oneidensis. Appl Environ Microbiol 2018; 84:AEM.01752-18. [PMID: 30097446 DOI: 10.1128/aem.01752-18] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 08/07/2018] [Indexed: 01/15/2023] Open
Abstract
Shewanella oneidensis is an extensively studied bacterium capable of respiring minerals, including a variety of iron ores, as terminal electron acceptors (EAs). Although iron plays an essential and special role in iron respiration of S. oneidensis, little has been done to date to investigate the characteristics of iron transport in this bacterium. In this study, we found that all proteins encoded by the pub-putA-putB cluster for putrebactin (S. oneidensis native siderophore) synthesis (PubABC), recognition-transport of Fe3+-putrebactin across the outer membrane (PutA), and reduction of ferric putrebactin (PutB) are essential to putrebactin-mediated iron uptake. Although homologs of PutA are many, none can function as its replacement, but some are able to work with other bacterial siderophores. We then showed that Fe2+-specific Feo is the other primary iron uptake system, based on the synthetical lethal phenotype resulting from the loss of both iron uptake routes. The role of the Feo system in iron uptake appears to be more critical, as growth is significantly impaired by the absence of the system but not of putrebactin. Furthermore, we demonstrate that hydroxyl acids, especially α-types such as lactate, promote iron uptake in a Feo-dependent manner. Overall, our findings underscore the importance of the ferrous iron uptake system in metal-reducing bacteria, providing an insight into iron homeostasis by linking these two biological processes.IMPORTANCE S. oneidensis is among the first- and the best-studied metal-reducing bacteria, with great potential in bioremediation and biotechnology. However, many questions regarding mechanisms closely associated with those applications, such as iron homeostasis, including iron uptake, export, and regulation, remain to be addressed. Here we show that Feo is a primary player in iron uptake in addition to the siderophore-dependent route. The investigation also resolved a few puzzles regarding the unexpected phenotypes of the putA mutant and lactate-dependent iron uptake. By elucidating the physiological roles of these two important iron uptake systems, this work revealed the breadth of the impacts of iron uptake systems on the biological processes.
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Meng Q, Liang H, Gao H. Roles of multiple KASIII homologues of Shewanella oneidensis in initiation of fatty acid synthesis and in cerulenin resistance. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1863:1153-1163. [DOI: 10.1016/j.bbalip.2018.06.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 06/02/2018] [Accepted: 06/28/2018] [Indexed: 01/04/2023]
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Cytochromes c Constitute a Layer of Protection against Nitric Oxide but Not Nitrite. Appl Environ Microbiol 2018; 84:AEM.01255-18. [PMID: 29934335 DOI: 10.1128/aem.01255-18] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 06/20/2018] [Indexed: 11/20/2022] Open
Abstract
Nitric oxide (NO) is a radical gas that reacts with various biological molecules in complex ways to inhibit growth as a bacteriostatic agent. NO is nearly ubiquitous because it can be generated both biotically and abiotically. To protect the cell from NO damage, bacteria have evolved many strategies, with the production of detoxifying enzymatic systems being the most efficient. Here, we report that c-type cytochromes (cytochromes c) constitute a primary NO protection system in Shewanella oneidensis, a Gram-negative environmental bacterium renowned for respiratory versatility due to its high cytochrome c content. By using mutants producing cytochromes c at varying levels, we found that the content of these proteins is inversely correlated with the growth inhibition imposed by NO, whereas the effect of each individual cytochrome c is negligible. This NO-protecting system has no effect on nitrite inhibition. In the absence of cytochromes c, other NO targets and protective proteins, such as NnrS, emerge to show physiological influences during the NO stress. We further demonstrate that cytochromes c also play a similar role in Escherichia coli, albeit only modestly. Our data thus identify the in vivo function of an important group of proteins in alleviating NO stress.IMPORTANCE It is widely accepted that the antibacterial effects of nitrite are attributable to nitric oxide (NO) formation, suggesting a correlation of bacterial susceptibilities to these two chemicals. However, compared to E. coli, S. oneidensis is highly sensitive to nitrite but resistant to NO, implying the presence of robust NO-protective systems. Here, we show that c-type cytochromes (cytochromes c) play a main role in protecting S. oneidensis against damages from NO but not from nitrite. In their absence, impacts of proteins that promote NO tolerance and that are targets of NO inhibition become evident. Our data thus reveal the specific activity of cytochromes c in alleviating the stress caused by NO but not nitrite.
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Distinct Nitrite and Nitric Oxide Physiologies in Escherichia coli and Shewanella oneidensis. Appl Environ Microbiol 2018; 84:AEM.00559-18. [PMID: 29654177 DOI: 10.1128/aem.00559-18] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 04/06/2018] [Indexed: 11/20/2022] Open
Abstract
Nitrite has been used as a bacteriostatic agent for centuries in food preservation. It is widely accepted that this biologically inert molecule functions indirectly, serving as a stable reservoir of bioactive nitric oxide (NO) and other reactive nitrogen species to impact physiology. As a result, to date, we know surprisingly little about in vivo targets of nitrite. Here, we carry out comparative analyses of nitrite and NO physiology in Escherichia coli and in Shewanella oneidensis, a Gram-negative environmental bacterium renowned for respiratory versatility. These two bacteria differ from each other in many aspects of nitrite and NO physiology, including NO generation, NO degradation, and unexpectedly, their contrary susceptibility to nitrite and NO. In cell extracts of both bacteria, most of the NO targets are also susceptible to nitrite, and vice versa. However, with respect to growth inhibition caused by NO, the targets are impacted distinctly; NO targets are responsible for the inhibition of growth of E. coli but not of S. oneidensis More surprisingly, all proteins identified to be implicated in NO tolerance in other bacteria appear to play a dispensable role in protecting S. oneidensis against NO. These data suggest that S. oneidensis is equipped with a robust but yet unknown NO protecting system. In the case of nitrite, it is clear that the target of physiological significance in both bacteria is cytochrome heme-copper oxidase.IMPORTANCE Nitrite is toxic to living organisms at high levels, but such antibacterial effects of nitrite are attributable to the formation of nitric oxide (NO), a highly reactive radical gas molecule. Here, we report that Shewanella oneidensis is highly resistant to NO but sensitive to nitrite compared to Escherichia coli by approximately 4-fold. In both bacteria, nitrite inhibits bacterial growth by targeting cytochrome heme-copper oxidase. In contrast, the targets of NO are diverse. Although these targets are similar in E. coli and S. oneidensis, they are responsible for growth inhibition caused by NO in the former but not in the latter. Overall, the presented data, along with the previous data, solidify a proposal that the in vivo targets of NO and nitrite in bacteria are largely different.
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Castillo H, Li X, Schilkey F, Smith GB. Transcriptome analysis reveals a stress response of Shewanella oneidensis deprived of background levels of ionizing radiation. PLoS One 2018; 13:e0196472. [PMID: 29768440 PMCID: PMC5955497 DOI: 10.1371/journal.pone.0196472] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 04/13/2018] [Indexed: 11/21/2022] Open
Abstract
Natural ionizing background radiation has exerted a constant pressure on organisms since the first forms of life appeared on Earth, so that cells have developed molecular mechanisms to avoid or repair damages caused directly by radiation or indirectly by radiation-induced reactive oxygen species (ROS). In the present study, we investigated the transcriptional effect of depriving Shewanella oneidensis cultures of background levels of radiation by growing the cells in a mine 655 m underground, thus reducing the dose rate from 72.1 to 0.9 nGy h-1 from control to treatment, respectively. RNASeq transcriptome analysis showed the differential expression of 4.6 and 7.6% of the S. oneidensis genome during early- and late-exponential phases of growth, respectively. The greatest change observed in the treatment was the downregulation of ribosomal proteins (21% of all annotated ribosomal protein genes during early- and 14% during late-exponential) and tRNA genes (14% of all annotated tRNA genes in early-exponential), indicating a marked decrease in protein translation. Other significant changes were the upregulation of membrane transporters, implying an increase in the traffic of substrates across the cell membrane, as well as the up and downregulation of genes related to respiration, which could be interpreted as a response to insufficient oxidants in the cells. In other reports, there is evidence in multiple species that some ROS not just lead to oxidative stress, but act as signaling molecules to control cellular metabolism at the transcriptional level. Consistent with these reports, several genes involved in the metabolism of carbon and biosynthesis of amino acids were also regulated, lending support to the idea of a wide metabolic response. Our results indicate that S. oneidensis is sensitive to the withdrawal of background levels of ionizing radiation and suggest that a transcriptional response is required to maintain homeostasis and retain normal growth.
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Affiliation(s)
- Hugo Castillo
- Department of Biology, New Mexico State University, Las Cruces, NM, United States of America
| | - Xiaoping Li
- Department of Botany and Plant Pathology, Oregon State University, Hermiston, OR, United States of America
| | - Faye Schilkey
- National Center for Genome Resources, Santa Fe, NM, United States of America
| | - Geoffrey B Smith
- Department of Biology, New Mexico State University, Las Cruces, NM, United States of America
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Acyl-homoserine-lactones receptor LuxR of Shewanella baltica involved in the development of microbiota and spoilage of refrigerated shrimp. Journal of Food Science and Technology 2018; 55:2795-2800. [PMID: 30042596 DOI: 10.1007/s13197-018-3172-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Revised: 03/30/2018] [Accepted: 04/09/2018] [Indexed: 10/17/2022]
Abstract
Numerous bacterial species utilize quorum sensing molecules acyl-homoserine-lactones (AHLs) to communicate, however, crosstalk often complicates the dynamics and behaviors of mixed populations. In this study, we developed a luxR mutant of wild type Shewanella baltica SA03 (WT SA03), and aimed to investigate the role of S. baltica LuxR (AHLs receptor) involved in the spoilage of refrigerated shrimp (Litopenaeus vannamei) by inoculating WT SA03 and luxR mutant of S. baltica SA03 (ΔluxR SA03), respectively. The results indicated the maximum growth rate of total viable bacteria in shrimp inoculated with ΔluxR SA03 was 73.34% lower than that of WT SA03. The lag time of total bacteria in shrimp treated with ΔluxR SA03 were 87.6 h, significantly longer than that of WT SA03. Meanwhile, the total volatile basic nitrogen concentrations of shrimp treated with WT SA03 were significantly higher than that of ΔluxR SA03 after 2 days of storage, which were in agreement with the decrease of the content of AHLs of the shrimp. The results indicated S. baltica might utilize AHLs produced by other bacteria and accelerate the shrimp spoilage process through LuxR receptor system.
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Dissociation between Iron and Heme Biosyntheses Is Largely Accountable for Respiration Defects of Shewanella oneidensis fur Mutants. Appl Environ Microbiol 2018; 84:AEM.00039-18. [PMID: 29427425 DOI: 10.1128/aem.00039-18] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Accepted: 01/30/2018] [Indexed: 11/20/2022] Open
Abstract
Iron, a major protein cofactor, is essential for most organisms but can simultaneously be toxic. Iron homeostasis thus has to be effectively maintained under a range of iron regimes. This may be particularly true with Shewanella oneidensis, a representative of dissimilatory metal-reducing bacteria (DMRB), which are capable of respiring a variety of chemicals as electron acceptors (EAs), including iron ores. Although iron respiration and its regulation have been extensively studied in this bacterium, how iron homeostasis is maintained remains largely unknown. Here, we report that the loss of the iron homeostasis master regulator Fur negatively affects the respiration of all EAs tested. This defect appears mainly to be a result of reduced cytochrome c (cyt c) production, despite a decrease in the expression of reductases that are under the direct control of Fur. We also show that S. oneidensis Fur interacts with canonical Fur box motifs in F-F-x-R configuration rather than the palindromic motif proposed before. The fur mutant has lowered total iron and increased free iron contents. Under iron-rich conditions, overproduction of the major iron storage protein Bfr elevates the total iron levels of the fur mutant over those of the wild-type but does not affect free iron levels. Intriguingly, such an operation only marginally improves cyt c production by affecting heme b biosynthesis. It is established that iron dictates heme b/cyt c biosynthesis in S. oneidensis fur + strains, but the fur mutation annuls the dependence of heme b/cyt c biosynthesis on iron. Overall, our results suggest that Fur has a profound impact on the iron homeostasis of S. oneidensis, through which many physiological processes, especially respiration, are transformed.IMPORTANCE Iron reduction is a signature of S. oneidensis, and this process relies on a large number of type c cytochromes, which per se are iron-containing proteins. Thus, iron plays an essential and special role in iron respiration, but to date, the nature of iron metabolism and regulation of the bacterium remains largely unknown. In this study, we investigated impacts of Fur, the master regulator of iron homeostasis, on respiration. The loss of Fur causes a general defect in respiration, a result of impaired cyt c production rather than specific regulation. Additionally, the fur mutant is unresponsive to iron, resulting in imbalanced iron homeostasis and dissociation between iron and cyt c production. These findings provide important insights into the iron biology of DMRB.
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Yao J, Guo Y, Wang P, Zeng Z, Li B, Tang K, Liu X, Wang X. Type II toxin/antitoxin system ParE SO /CopA SO stabilizes prophage CP4So in Shewanella oneidensis. Environ Microbiol 2018; 20:1224-1239. [PMID: 29411516 DOI: 10.1111/1462-2920.14068] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Revised: 02/03/2018] [Accepted: 02/04/2018] [Indexed: 12/15/2022]
Abstract
Toxin/antitoxin (TA) loci are commonly found in mobile genetic elements such as plasmids and prophages. However, the physiological functions of these TA loci in prophages and cross-regulation among these TA loci remain largely unexplored. Here, we characterized a newly discovered type II TA pair, ParESO /CopASO , in the CP4So prophage in Shewanella oneidensis. We demonstrated that ParESO /CopASO plays a critical role in the maintenance of CP4So in host cells after its excision. The toxin ParESO inhibited cell growth, resulting in filamentous growth and eventually cell death. The antitoxin CopASO neutralized the toxicity of ParESO through direct protein-protein interactions and repressed transcription of the TA operon by binding to a DNA motif in the promoter region containing two inverted repeats [5'-GTANTAC (N)3 GTANTAC-3']. CopASO also repressed transcription of another TA system PemKSO /PemISO in megaplasmid pMR-1 of S. oneidensis through binding to a highly similar DNA motif in its promoter region. CopASO homologs are widely spread in Shewanella and other Proteobacteria, either as a component of a TA pair or as orphan antitoxins. Our study thus illustrated the cross-regulation of the TA systems in different mobile genetic elements and expanded our understanding of the physiological function of TA systems.
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Affiliation(s)
- Jianyun Yao
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, People's Republic of China.,University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Yunxue Guo
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, People's Republic of China
| | - Pengxia Wang
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, People's Republic of China
| | - Zhenshun Zeng
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, People's Republic of China
| | - Baiyuan Li
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, People's Republic of China
| | - Kaihao Tang
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, People's Republic of China
| | - Xiaoxiao Liu
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, People's Republic of China
| | - Xiaoxue Wang
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, People's Republic of China
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Partially Reciprocal Replacement of FlrA and FlrC in Regulation of Shewanella oneidensis Flagellar Biosynthesis. J Bacteriol 2018; 200:JB.00796-17. [PMID: 29358496 DOI: 10.1128/jb.00796-17] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Accepted: 01/17/2018] [Indexed: 12/23/2022] Open
Abstract
In some bacteria with a polar flagellum, an established regulatory hierarchy controlling stepwise assembly of the organelle consists of four regulators: FlrA, σ54, FlrBC, and σ28 Because all of these regulators mediate the expression of multiple targets, they are essential to the assembly of a functional flagellum and therefore to motility. However, this is not the case for the gammaproteobacterium Shewanella oneidensis: cells lacking FlrB, FlrC, or both remain flagellated and motile. In this study, we unravel the underlying mechanism, showing that FlrA and FlrC are partially substitutable for each other in regulating flagellar assembly. While both regulators are bacterial enhancer binding proteins (bEBPs) for σ54, FlrA differs from FlrC in its independence of σ54 for its own transcription and its inability to activate the flagellin gene flaA These differences largely account for the distinct phenotypes resulting from the loss or overproduction of FlrA and FlrC.IMPORTANCE The assembly of a polar flagellum in bacteria has been characterized as relying on four regulators, FlrA, σ54, FlrBC, and σ28, in a hierarchical manner. They all are essential to the process and therefore to motility, except in S. oneidensis, in which FlrB, FlrC, or both together are not essential. Here we show that FlrA and FlrC, as bEBPs, are partially reciprocal in functionality in this species. As a consequence, the presence of one allows flagellar assembly and motility in the other's absence. Despite this, there are significant differences in the physiological roles played by these two regulators: FlrA is the master regulator of flagellar assembly, whereas FlrC fine-tunes motility. These intriguing observations open up a new avenue to further exploration of the regulation of flagellar assembly.
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Meibom KL, Cabello EM, Bernier-Latmani R. The Small RNA RyhB Is a Regulator of Cytochrome Expression in Shewanella oneidensis. Front Microbiol 2018. [PMID: 29515549 PMCID: PMC5826389 DOI: 10.3389/fmicb.2018.00268] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Shewanella oneidensis produces an extensive electron transfer network that results in metabolic flexibility. A large number of c-type cytochromes are expressed by S. oneidensis and these function as the fundamental electron transport chain proteins. Although several S. oneidensis cytochromes have been well-characterized, little is known about how their expression is regulated. In this study, we investigate the role of the ferric uptake regulator (Fur) and the sRNA RyhB in regulation. Our results demonstrate that loss of Fur leads to diminished growth and an apparent decrease in heme-containing proteins. Remarkably, deleting the Fur-repressed ryhB gene almost completely reverses these physiological changes, indicating that the phenotypes resulting from loss of Fur are (at least partially) dependent on RyhB. RNA sequencing identified a number of possible RyhB repressed genes. A large fraction of these encode c-type cytochromes, among them two of the most abundant periplasmic cytochromes CctA (also known as STC) and ScyA. We show that RyhB destabilizes the mRNA of four of its target genes, cctA, scyA, omp35, and nrfA and this requires the presence of the RNA chaperone Hfq. Iron limitation decreases the expression of the RyhB target genes cctA and scyA and this regulation relies on the presence of both Fur and RyhB. Overall, this study suggests that controlling cytochrome expression is of importance to maintain iron homeostasis and that sRNAs molecules are important players in the regulation of fundamental processes in S. oneidensis MR-1.
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Affiliation(s)
- Karin L Meibom
- Environmental Microbiology Laboratory, School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Elena M Cabello
- Bioinformatics and Biostatistics Core Facility, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Rizlan Bernier-Latmani
- Environmental Microbiology Laboratory, School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
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Ling N, Zhang J, Li C, Zeng H, He W, Ye Y, Wu Q. The Glutaredoxin Gene, grxB, Affects Acid Tolerance, Surface Hydrophobicity, Auto-Aggregation, and Biofilm Formation in Cronobacter sakazakii. Front Microbiol 2018; 9:133. [PMID: 29459854 PMCID: PMC5807413 DOI: 10.3389/fmicb.2018.00133] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2017] [Accepted: 01/19/2018] [Indexed: 12/22/2022] Open
Abstract
Cronobacter species are foodborne pathogens that can cause neonatal meningitis, necrotizing enterocolitis, and sepsis; they have unusual abilities to survive in environmental stresses such as acid stress. However, the factors involved in acid stress responses and biofilm formation in Cronobacter species are poorly understood. In this study, we investigated the role of grxB on cellular morphology, acid tolerance, surface hydrophobicity, auto-aggregation (AAg), motility, and biofilm formation in Cronobacter sakazakii. The deletion of grxB decreased resistance to acid stresses, and notably led to weaker surface hydrophobicity, AAg, and biofilm formation under normal and acid stress conditions, compared with those of the wild type strain; however, motility was unaffected. Therefore, grxB appears to contribute to the survival of C. sakazakii in acid stresses and biofilm formation. This is the first report to provide valuable evidence for the role of grxB in acid stress responses and biofilm formation in C. sakazakii.
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Affiliation(s)
- Na Ling
- State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Open Laboratory of Applied Microbiology, Guangdong Institute of Microbiology, Guangzhou, China.,School of Food Science and Engineering, Hefei University of Technology, Hefei, China
| | - Jumei Zhang
- State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Open Laboratory of Applied Microbiology, Guangdong Institute of Microbiology, Guangzhou, China
| | - Chengsi Li
- State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Open Laboratory of Applied Microbiology, Guangdong Institute of Microbiology, Guangzhou, China
| | - Haiyan Zeng
- State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Open Laboratory of Applied Microbiology, Guangdong Institute of Microbiology, Guangzhou, China
| | - Wenjing He
- State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Open Laboratory of Applied Microbiology, Guangdong Institute of Microbiology, Guangzhou, China
| | - Yingwang Ye
- School of Food Science and Engineering, Hefei University of Technology, Hefei, China
| | - Qingping Wu
- State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Open Laboratory of Applied Microbiology, Guangdong Institute of Microbiology, Guangzhou, China
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63
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Yin J, Sun Y, Sun Y, Yu Z, Qiu J, Gao H. Deletion of Lytic Transglycosylases Increases Beta-Lactam Resistance in Shewanella oneidensis. Front Microbiol 2018; 9:13. [PMID: 29403465 PMCID: PMC5786531 DOI: 10.3389/fmicb.2018.00013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 01/05/2018] [Indexed: 01/07/2023] Open
Abstract
Production of chromosome-encoded β-lactamases confers resistance to β-lactams in many Gram-negative bacteria. Some inducible β-lactamases, especially the class C β-lactamase AmpC in Enterobacteriaceae, share a common regulatory mechanism, the ampR-ampC paradigm. Induction of ampC is intimately linked to peptidoglycan recycling, and the LysR-type transcriptional regulator AmpR plays a central role in the process. However, our previous studies have demonstrated that the expression of class D β-lactamase gene blaA in Shewanella oneidensis is distinct from the established paradigm since an AmpR homolog is absent and major peptidoglycan recycling enzymes play opposite roles in β-lactamase expression. Given that lytic transglycosylases (LTs), a class of peptidoglycan hydrolases cleaving the β-1,4 glycosidic linkage in glycan strands of peptidoglycan, can disturb peptidoglycan recycling, and thus may affect induction of blaA. In this study, we investigated impacts of such enzymes on susceptibility to β-lactams. Deletion of three LTs (SltY, MltB and MltB2) increased β-lactam resistance, while four other LTs (MltD, MltD2, MltF, and Slt2) seemed dispensable to β-lactam resistance. The double LT mutants ΔmltBΔmltB2 and ΔsltYΔmltB2 had β-lactam resistance stronger than any of the single mutants. Deletion of ampG (encoding permease AmpG) and mrcA (encoding penicillin binding protein 1a, PBP1a) from both double LT mutants further increased the resistance to β-lactams. Notably, all increased β-lactam resistance phenotypes were in accordance with enhanced blaA expression. Although significant, the increase in β-lactamase activity after inactivating LTs is much lower than that produced by PBP1a inactivation. Our data implicate that LTs play important roles in blaA expression in S. oneidensis.
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Affiliation(s)
- Jianhua Yin
- College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, China.,Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, China.,College of Life Sciences, Nanchang University, Nanchang, China
| | - Yiyang Sun
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, China
| | - Yijuan Sun
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, China
| | - Zhiliang Yu
- College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, China
| | - Juanping Qiu
- College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, China
| | - Haichun Gao
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, China
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64
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Balancing cellular redox metabolism in microbial electrosynthesis and electro fermentation - A chance for metabolic engineering. Metab Eng 2017; 45:109-120. [PMID: 29229581 DOI: 10.1016/j.ymben.2017.12.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 09/15/2017] [Accepted: 12/06/2017] [Indexed: 01/05/2023]
Abstract
More and more microbes are discovered that are capable of extracellular electron transfer, a process in which they use external electrodes as electron donors or acceptors for metabolic reactions. This feature can be used to overcome cellular redox limitations and thus optimizing microbial production. The technologies, termed microbial electrosynthesis and electro-fermentation, have the potential to open novel bio-electro production platforms from sustainable energy and carbon sources. However, the performance of reported systems is currently limited by low electron transport rates between microbes and electrodes and our limited ability for targeted engineering of these systems due to remaining knowledge gaps about the underlying fundamental processes. Metabolic engineering offers many opportunities to optimize these processes, for instance by genetic engineering of pathways for electron transfer on the one hand and target product synthesis on the other hand. With this review, we summarize the status quo of knowledge and engineering attempts around chemical production in bio-electrochemical systems from a microbe perspective. Challenges associated with the introduction or enhancement of extracellular electron transfer capabilities into production hosts versus the engineering of target compound synthesis pathways in natural exoelectrogens are discussed. Recent advances of the research community in both directions are examined critically. Further, systems biology approaches, for instance using metabolic modelling, are examined for their potential to provide insight into fundamental processes and to identify targets for metabolic engineering.
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65
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Dong Z, Guo S, Fu H, Gao H. Investigation of a spontaneous mutant reveals novel features of iron uptake in Shewanella oneidensis. Sci Rep 2017; 7:11788. [PMID: 28924168 PMCID: PMC5603553 DOI: 10.1038/s41598-017-11987-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 08/30/2017] [Indexed: 12/03/2022] Open
Abstract
Shewanella oneidensis is among the first and the best studied bacteria capable of respiring minerals as terminal electron acceptors (EAs), including a variety of iron ores. This respiration process relies on a large number of c-type cytochromes, which per se are iron-containing proteins. Thus, iron plays an essential and special role in iron respiration of S. oneidensis, prompting extensive investigations into iron physiology. Despite this, we still know surprisingly little about the components and characteristics of iron transport in this bacterium. Here, we report that TonB-dependent receptor PutA (SO_3033) is specific to the siderophore-mediated iron uptake. Although homologs of PutA are abundant, none of them can function as a replacement. In the absence of PutA, S. oneidensis suffers from an iron shortage, which leads to a severe defect in production of cytochrome c. However, proteins requiring other types of cytochromes, such as b and d, do not appear to be significantly impacted. Intriguingly, lactate, but not other carbon sources that are routinely used to support growth, is able to promote iron uptake when PutA is missing. We further show that the lactate-mediated iron import is independent of lactate permeases. Overall, our results suggest that in S. oneidensis the siderophore-dependent pathway plays a key role in iron uptake when iron is limited, but many alternative routes exist.
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Affiliation(s)
- Ziyang Dong
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Shupan Guo
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Huihui Fu
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Haichun Gao
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China.
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66
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Abstract
Because of ubiquity of thioesters, thioesterases play a critical role in metabolism, membrane biosynthesis, signal transduction, and gene regulation. In many bacteria, YbgC is such an enzyme, whose coding gene mostly resides in the tol-pal cluster. Although all other proteins encoded in the tol-pal cluster are clearly involved in maintaining cell envelope integrity and cell division, little is known about the physiological role of YbgC. In this study, we identify in Shewanella oneidensis, a γ-proteobacterium used as a research model for environmental microbes, YbgC as a motility regulator. The loss of YbgC results in enhanced motility, which is likely due to the increased rotation rate of the flagellum. The regulatory function of YbgC requires its thioesterase activity but could not be replaced by YbgC homologues of other bacteria. We further show that the regulation of YbgC is mediated by the second message c-di-GMP.
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67
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Loss of OxyR reduces efficacy of oxygen respiration in Shewanella oneidensis. Sci Rep 2017; 7:42609. [PMID: 28195212 PMCID: PMC5307378 DOI: 10.1038/srep42609] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 01/11/2017] [Indexed: 02/02/2023] Open
Abstract
In many bacteria, OxyR is the major regulator controlling cellular response to H2O2. A common phenotype resulting from OxyR loss is reduced growth rate, but the underlying mechanism is unknown. We demonstrated in Shewanella oneidensis, an important research model for applied and environmental microbes, that the defect is primarily due to an electron shortage to major terminal oxidase cytochrome cbb3. The loss of OxyR leads to enhanced production of electron carriers that compete for electrons against cytochrome cbb3, cytochrome bd in particular. We further showed that the oxyR mutation also results in increased production of menaquinone, an additional means to lessen electrons to cytochrome cbb3. Although regulation of OxyR on these biological processes appears to be indirect, these data indicate that the regulator plays a previously underappreciated role in mediating respiration.
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68
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NapB in excess inhibits growth of Shewanella oneidensis by dissipating electrons of the quinol pool. Sci Rep 2016; 6:37456. [PMID: 27857202 PMCID: PMC5114592 DOI: 10.1038/srep37456] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 10/25/2016] [Indexed: 01/22/2023] Open
Abstract
Shewanella, a group of ubiquitous bacteria renowned for respiratory versatility, thrive in environments where various electron acceptors (EAs) of different chemical and physiological characteristics coexist. Despite being extensively studied, we still know surprisingly little about strategies by which multiple EAs and their interaction define ecophysiology of these bacteria. Previously, we showed that nitrite inhibits growth of the genus representative Shewanella oneidensis on fumarate and presumably some other CymA (quinol dehydrogenase)-dependent EAs by reducing cAMP production, which in turn leads to lowered expression of nitrite and fumarate reductases. In this study, we demonstrated that inhibition of fumarate growth by nitrite is also attributable to overproduction of NapB, the cytochrome c subunit of nitrate reductase. Further investigations revealed that excessive NapB per se inhibits growth on all EAs tested, including oxygen. When overproduced, NapB acts as an electron shuttle to dissipate electrons of the quinol pool, likely to extracellullar EAs, because the Mtr system, the major electron transport pathway for extracellular electron transport, is implicated. The study not only sheds light on mechanisms by which certain EAs, especially toxic ones, impact the bacterial ecophysiology, but also provides new insights into how electron shuttle c-type cytochromes regulate multi-branched respiratory networks.
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69
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Suppression of fabB Mutation by fabF1 Is Mediated by Transcription Read-through in Shewanella oneidensis. J Bacteriol 2016; 198:3060-3069. [PMID: 27573012 DOI: 10.1128/jb.00463-16] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 08/20/2016] [Indexed: 12/19/2022] Open
Abstract
As type II fatty acid synthesis is essential for the growth of Escherichia coli, its many components are regarded as potential targets for novel antibacterial drugs. Among them, β-ketoacyl-acyl carrier protein (ACP) synthase (KAS) FabB is the exclusive factor for elongation of the cis-3-decenoyl-ACP (cis-3-C10-ACP). In our previous study, we presented evidence to suggest that this may not be the case in Shewanella oneidensis, an emerging model gammaproteobacterium renowned for its respiratory versatility. Here, we identified FabF1, another KAS, as a functional replacement for FabB in S. oneidensis In fabB+ or desA+ (encoding a desaturase) cells, which are capable of making unsaturated fatty acids (UFA), FabF1 is barely produced. However, UFA auxotroph mutants devoid of both fabB and desA genes can be spontaneously converted to suppressor strains, which no longer require exogenous UFAs for growth. Suppression is caused by a TGTTTT deletion in the region upstream of the fabF1 gene, resulting in enhanced FabF1 production. We further demonstrated that the deletion leads to transcription read-through of the terminator for acpP, an acyl carrier protein gene immediately upstream of fabF1 There are multiple tandem repeats in the region covering the terminator, and the TGTTTT deletion, as well as others, compromises the terminator efficacy. In addition, FabF2 also shows an ability to complement the FabB loss, albeit substantially less effectively than FabF1. IMPORTANCE It has been firmly established that FabB for UFA synthesis via type II fatty acid synthesis in FabA-containing bacteria such as E. coli is essential. However, S. oneidensis appears to be an exception. In this bacterium, FabF1, when sufficiently expressed, is able to fully complement the FabB loss. Importantly, such a capability can be obtained by spontaneous mutations, which lead to transcription read-through. Therefore, our data, by identifying the functional overlap between FabB and FabFs, provide new insights into the current understanding of KAS and help reveal novel ways to block UFA synthesis for therapeutic purposes.
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70
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Lemaire ON, Honoré FA, Jourlin-Castelli C, Méjean V, Fons M, Iobbi-Nivol C. Efficient respiration on TMAO requires TorD and TorE auxiliary proteins in Shewanella oneidensis. Res Microbiol 2016; 167:630-637. [DOI: 10.1016/j.resmic.2016.05.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 05/18/2016] [Accepted: 05/18/2016] [Indexed: 01/29/2023]
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71
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Regulation of Gene Expression in Shewanella oneidensis MR-1 during Electron Acceptor Limitation and Bacterial Nanowire Formation. Appl Environ Microbiol 2016; 82:5428-43. [PMID: 27342561 DOI: 10.1128/aem.01615-16] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 06/22/2016] [Indexed: 12/12/2022] Open
Abstract
UNLABELLED In limiting oxygen as an electron acceptor, the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 rapidly forms nanowires, extensions of its outer membrane containing the cytochromes MtrC and OmcA needed for extracellular electron transfer. RNA sequencing (RNA-Seq) analysis was employed to determine differential gene expression over time from triplicate chemostat cultures that were limited for oxygen. We identified 465 genes with decreased expression and 677 genes with increased expression. The coordinated increased expression of heme biosynthesis, cytochrome maturation, and transport pathways indicates that S. oneidensis MR-1 increases cytochrome production, including the transcription of genes encoding MtrA, MtrC, and OmcA, and transports these decaheme cytochromes across the cytoplasmic membrane during electron acceptor limitation and nanowire formation. In contrast, the expression of the mtrA and mtrC homologs mtrF and mtrD either remains unaffected or decreases under these conditions. The ompW gene, encoding a small outer membrane porin, has 40-fold higher expression during oxygen limitation, and it is proposed that OmpW plays a role in cation transport to maintain electrical neutrality during electron transfer. The genes encoding the anaerobic respiration regulator cyclic AMP receptor protein (CRP) and the extracytoplasmic function sigma factor RpoE are among the transcription factor genes with increased expression. RpoE might function by signaling the initial response to oxygen limitation. Our results show that RpoE activates transcription from promoters upstream of mtrC and omcA The transcriptome and mutant analyses of S. oneidensis MR-1 nanowire production are consistent with independent regulatory mechanisms for extending the outer membrane into tubular structures and for ensuring the electron transfer function of the nanowires. IMPORTANCE Shewanella oneidensis MR-1 has the capacity to transfer electrons to its external surface using extensions of the outer membrane called bacterial nanowires. These bacterial nanowires link the cell's respiratory chain to external surfaces, including oxidized metals important in bioremediation, and explain why S. oneidensis can be utilized as a component of microbial fuel cells, a form of renewable energy. In this work, we use differential gene expression analysis to focus on which genes function to produce the nanowires and promote extracellular electron transfer during oxygen limitation. Among the genes that are expressed at high levels are those encoding cytochrome proteins necessary for electron transfer. Shewanella coordinates the increased expression of regulators, metabolic pathways, and transport pathways to ensure that cytochromes efficiently transfer electrons along the nanowires.
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72
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Zeng Z, Liu X, Yao J, Guo Y, Li B, Li Y, Jiao N, Wang X. Cold adaptation regulated by cryptic prophage excision in Shewanella oneidensis. ISME JOURNAL 2016; 10:2787-2800. [PMID: 27482926 PMCID: PMC5148205 DOI: 10.1038/ismej.2016.85] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 04/30/2016] [Accepted: 05/10/2016] [Indexed: 01/18/2023]
Abstract
Among the environmental stresses experienced by bacteria, temperature shifts are one of the most important. In this study, we discovered a novel cold adaptation mechanism in Shewanella oneidensis that occurs at the DNA level and is regulated by cryptic prophage excision. Previous studies on bacterial cold tolerance mainly focus on the structural change of cell membrane and changes at the RNA and protein levels. Whether or not genomic change can also contribute to this process has not been explored. Here we employed a whole-genome deep-sequencing method to probe the changes at DNA level in a model psychrotrophic bacteria strain. We found that temperature downshift induced a 10 000-fold increase of the excision of a novel P4-like cryptic prophage. Importantly, although prophage excision only occurred in a relatively small population of bacteria, it was able to facilitate biofilm formation and promote the survival of the entire population. This prophage excision affected cell physiology by disrupting a critical gene encoding transfer-messenger RNA (tmRNA). In addition, we found that the histone-like nucleoid-structuring protein (H-NS) could silence prophage excision via binding to the promoter of the putative excisionase gene at warm temperatures. H-NS level was reduced at cold temperatures, leading to de-repression of prophage excision. Collectively, our results reveal that cryptic prophage excision acts as a regulatory switch to enable the survival of the host at low temperature by controlling the activity of tmRNA and biofilm formation.
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Affiliation(s)
- Zhenshun Zeng
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
| | - Xiaoxiao Liu
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
| | - Jianyun Yao
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yunxue Guo
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
| | - Baiyuan Li
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yangmei Li
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Nianzhi Jiao
- State Key Laboratory of Marine Environmental Sciences, Xiamen University, Xiamen, China.,Institute of Marine Microbes and Ecospheres, Xiamen University, Xiamen, China
| | - Xiaoxue Wang
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
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73
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Jin M, Fu H, Yin J, Yuan J, Gao H. Molecular Underpinnings of Nitrite Effect on CymA-Dependent Respiration in Shewanella oneidensis. Front Microbiol 2016; 7:1154. [PMID: 27493647 PMCID: PMC4954811 DOI: 10.3389/fmicb.2016.01154] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 07/11/2016] [Indexed: 12/31/2022] Open
Abstract
Shewanella exhibit a remarkable versatility of respiration, with a diverse array of electron acceptors (EAs). In environments where these bacteria thrive, multiple EAs are usually present. However, we know little about strategies by which these EAs and their interaction affect ecophysiology of Shewanella. In this study, we demonstrate in the model strain, Shewanella oneidensis MR-1, that nitrite, not through nitric oxide to which it may convert, inhibits respiration of fumarate, and probably many other EAs whose reduction depends on quinol dehydrogenase CymA. This is achieved via the repression of cyclic adenosine monophosphate (cAMP) production, a second messenger required for activation of cAMP-receptor protein (Crp) which plays a primary role in regulation of respiration. If nitrite is not promptly removed, intracellular cAMP levels drop, and this impairs Crp activity. As a result, the production of nitrite reductase NrfA, CymA, and fumarate reductase FccA is substantially reduced. In contrast, nitrite can be simultaneously respired with trimethylamine N-oxide, resulting in enhanced biomass.
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Affiliation(s)
- Miao Jin
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
| | - Huihui Fu
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
| | - Jianhua Yin
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
| | - Jie Yuan
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
| | - Haichun Gao
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
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74
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Ding D, Li L, Shu C, Sun X. K-shell Analysis Reveals Distinct Functional Parts in an Electron Transfer Network and Its Implications for Extracellular Electron Transfer. Front Microbiol 2016; 7:530. [PMID: 27148219 PMCID: PMC4837345 DOI: 10.3389/fmicb.2016.00530] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 03/31/2016] [Indexed: 01/17/2023] Open
Abstract
Shewanella oneidensis MR-1 is capable of extracellular electron transfer (EET) and hence has attracted considerable attention. The EET pathways mainly consist of c-type cytochromes, along with some other proteins involved in electron transfer processes. By whole genome study and protein interactions inquisition, we constructed a large-scale electron transfer network containing 2276 interactions among 454 electron transfer related proteins in S. oneidensis MR-1. Using the k-shell decomposition method, we identified and analyzed distinct parts of the electron transfer network. We found that there was a negative correlation between the k s (k-shell values) and the average DR_100 (disordered regions per 100 amino acids) in every shell, which suggested that disordered regions of proteins played an important role during the formation and extension of the electron transfer network. Furthermore, proteins in the top three shells of the network are mainly located in the cytoplasm and inner membrane; these proteins can be responsible for transfer of electrons into the quinone pool in a wide variety of environmental conditions. In most of the other shells, proteins are broadly located throughout the five cellular compartments (cytoplasm, inner membrane, periplasm, outer membrane, and extracellular), which ensures the important EET ability of S. oneidensis MR-1. Specifically, the fourth shell was responsible for EET and the c-type cytochromes in the remaining shells of the electron transfer network were involved in aiding EET. Taken together, these results show that there are distinct functional parts in the electron transfer network of S. oneidensis MR-1, and the EET processes could achieve high efficiency through cooperation through such an electron transfer network.
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Affiliation(s)
- Dewu Ding
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast UniversityNanjing, China; Department of Mathematics and Computer Science, Chizhou CollegeChizhou, China
| | - Ling Li
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University Nanjing, China
| | - Chuanjun Shu
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University Nanjing, China
| | - Xiao Sun
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University Nanjing, China
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75
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Reduced expression of cytochrome oxidases largely explains cAMP inhibition of aerobic growth in Shewanella oneidensis. Sci Rep 2016; 6:24449. [PMID: 27076065 PMCID: PMC4830989 DOI: 10.1038/srep24449] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 03/29/2016] [Indexed: 12/20/2022] Open
Abstract
Inhibition of bacterial growth under aerobic conditions by elevated levels of cyclic adenosine 3′,5′-monophosphate (cAMP), first revealed more than 50 years ago, was attributed to accumulation of toxic methylglyoxal (MG). Here, we report a Crp-dependent mechanism rather than MG accumulation that accounts for the phenotype in Shewanella oneidensis, an emerging research model for the bacterial physiology. We show that a similar phenotype can be obtained by removing CpdA, a cAMP phosphodiesterase that appears more effective than its Escherichia coli counterpart. Although production of heme c and cytochromes c is correlated well with cAMP levels, neither is sufficient for the retarded growth. Quantities of overall cytochromes c increased substantially in the presence of elevated cAMP, a phenomenon resembling cells respiring on non-oxygen electron acceptors. In contrast, transcription of Crp-dependent genes encoding both cytochromes bd and cbb3 oxidases is substantially repressed under the same condition. Overall, our results suggest that cAMP of elevated levels drives cells into a low-energetic status, under which aerobic respiration is inhibited.
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76
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Luo Q, Li M, Fu H, Meng Q, Gao H. Shewanella oneidensis FabB: A β-ketoacyl-ACP Synthase That Works with C16:1-ACP. Front Microbiol 2016; 7:327. [PMID: 27014246 PMCID: PMC4793157 DOI: 10.3389/fmicb.2016.00327] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 03/01/2016] [Indexed: 12/12/2022] Open
Abstract
It is established that Escherichia coli β-ketoacyl-ACP synthase (KAS) I (encoded by EcfabB) is the primary, if not exclusive, factor for elongation of the cis-3-decenoyl-ACP (C10:1-ACP) but not effective with C16:1- or longer-chain-ACPs. To test the extent to which these features apply to KAS I proteins in other species, in this study, we examined the physiological role of FabB in Shewanella oneidensis, an excellent model for researching type II fatty acid synthetic (FAS) system and its regulation. We showed that the loss of either FabA (the enzyme that introduces double bond) or FabB, in the absence of DesA which desaturizes C16 and C18 to generate respective C16:1 and C18:1, leads to a UFA auxotroph. However, fatty acid profiles of membrane phospholipid of the fabA and fabB mutants are significantly different, suggesting that FabB participates in steps beyond elongation of C10:1-ACP. Further analyses demonstrated that S. oneidensis FabB differs from EcFabB in that (i) it is not the only enzyme capable of catalyzing elongation of the cis-3-decenoyl-ACP produced by FabA, (ii) it plays a critical role in elongation of C16:1- and longer-chain-ACPs, and (iii) its overproduction is detrimental.
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Affiliation(s)
- Qixia Luo
- Institute of Microbiology and College of Life Sciences, Zhejiang UniversityHangzhou, China; State Key Laboratory for Diagnosis and Treatment of Infectious Disease, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, College of Medicine, The First Affiliated Hospital, Zhejiang UniversityHangzhou, China
| | - Meng Li
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
| | - Huihui Fu
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
| | - Qiu Meng
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
| | - Haichun Gao
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
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77
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Zhu J, Zhao A, Feng L, Gao H. Quorum sensing signals affect spoilage of refrigerated large yellow croaker (Pseudosciaena crocea) by Shewanella baltica. Int J Food Microbiol 2016; 217:146-55. [DOI: 10.1016/j.ijfoodmicro.2015.10.020] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 09/21/2015] [Accepted: 10/21/2015] [Indexed: 11/17/2022]
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78
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Gao T, Ju L, Yin J, Gao H. Positive regulation of the Shewanella oneidensis OmpS38, a major porin facilitating anaerobic respiration, by Crp and Fur. Sci Rep 2015; 5:14263. [PMID: 26381456 PMCID: PMC4585640 DOI: 10.1038/srep14263] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 08/21/2015] [Indexed: 12/20/2022] Open
Abstract
Major porins are among the most abundant proteins embedded in the outer membrane (OM) of Gram-negative bacteria, playing crucial roles in maintenance of membrane structural integrity and OM permeability. Although many OM proteins (especially c-type cytochromes) in Shewanella oneidensis, a research model for respiratory versatility, have been extensively studied, physiological significance of major porins remains largely unexplored. In this study, we show that OmpS38 and OmpA are two major porins, neither of which is responsive to changes in osmolarity or contributes to the intrinsic resistance to β-lactam antibiotics. However, OmpS38 but not OmpA is largely involved in respiration of non-oxygen electron acceptors. We then provide evidence that expression of ompS38 is transcribed from two promoters, the major of which is favored under anaerobic conditions while the other appears constitutive. The major promoter is under the direct control of Crp, the master regulator dictating respiration. As a result, the increase in the level of OmpS38 correlates with an elevated activity in Crp under anaerobic conditions. In addition, we show that the activity of the major promoter is also affected by Fur, presumably indirectly, the transcription factor for iron-dependent gene expression.
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Affiliation(s)
- Tong Gao
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Lili Ju
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Jianhua Yin
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Haichun Gao
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
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79
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A Matter of Timing: Contrasting Effects of Hydrogen Sulfide on Oxidative Stress Response in Shewanella oneidensis. J Bacteriol 2015; 197:3563-72. [PMID: 26324455 DOI: 10.1128/jb.00603-15] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 08/25/2015] [Indexed: 01/29/2023] Open
Abstract
UNLABELLED Hydrogen sulfide (H2S), well known for its toxic properties, has recently become a research focus in bacteria, in part because it has been found to prevent oxidative stress caused by treatment with some antibiotics. H2S has the ability to scavenge reactive oxygen species (ROS), thus preventing oxidative stress, but it is also toxic, leading to conflicting reports of its effects in different organisms. Here, with Shewanella oneidensis as a model, we report that the effects of H2S on the response to oxidative stress are time dependent. When added simultaneously with H2O2, H2S promoted H2O2 toxicity by inactivating catalase, KatB, a heme-containing enzyme involved in H2O2 degradation. Such an inhibitory effect may apply to other heme-containing proteins, such as cytochrome cbb3 oxidase. When H2O2 was supplied 20 min or later after the addition of H2S, the oxidative-stress-responding regulator OxyR was activated, resulting in increased resistance to H2O2. The activation of OxyR was likely triggered by the influx of iron, a response to lowered intracellular iron due to the iron-sequestering property of H2S. Given that Shewanella bacteria thrive in redox-stratified environments that have abundant sulfur and iron species, our results imply that H2S is more important for bacterial survival in such environmental niches than previously believed. IMPORTANCE Previous studies have demonstrated that H2S is either detrimental or beneficial to bacterial cells. While it can act as a growth-inhibiting molecule by damaging DNA and denaturing proteins, it helps cells to combat oxidative stress. Here we report that H2S indeed has these contrasting biological functions and that its effects are time dependent. Immediately after H2S treatment, there is growth inhibition due to damage of heme-containing proteins, at least to catalase and cytochrome c oxidase. In contrast, when added a certain time later, H2S confers an enhanced ability to combat oxidative stress by activating the H2O2-responding regulator OxyR. Our data reconcile conflicting observations about the functions of H2S.
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80
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Gao T, Shi M, Ju L, Gao H. Investigation into FlhFG reveals distinct features of FlhF in regulating flagellum polarity in Shewanella oneidensis. Mol Microbiol 2015; 98:571-85. [PMID: 26194016 DOI: 10.1111/mmi.13141] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/02/2015] [Indexed: 12/14/2022]
Abstract
Rod-shaped bacterial cells are polarized, with many organelles confined to a polar cellular site. In polar flagellates, FlhF and FlhG, a multiple-domain (B-N-G) GTPase and a MinD-like ATPase respectively, function as a cognate pair to regulate flagellar localization and number as revealed in Vibrio and Pseudomonas species. In this study, we show that FlhFG of Shewanella oneidensis (SoFlhFG), a monotrichous γ-proteobacterium renowned for respiratory diversity, also play an important role in the flagellar polar placement and number control. Despite this, SoFlhFG exhibit distinct features that are not observed in the characterized counterparts. Most strikingly, the G domain of SoFlhF determines the polar placement, contrasting the N domain of the Vibrio cholerae FlhF. The SoFlhF N domain in fact counteracts the function of the G domain with respect to the terminal targeting in the absence of the B domain. We further show that GTPase activity of SoFlhF is essential for motility but not positioning. Overall, our results suggest that mechanisms underlying the polar placement of organelles appear to be diverse, even for evolutionally relatively conserved flagellum.
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Affiliation(s)
- Tong Gao
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Miaomiao Shi
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Lili Ju
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Haichun Gao
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
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81
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Zhou G, Yuan J, Gao H. Regulation of biofilm formation by BpfA, BpfD, and BpfG in Shewanella oneidensis. Front Microbiol 2015; 6:790. [PMID: 26300859 PMCID: PMC4523816 DOI: 10.3389/fmicb.2015.00790] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 07/21/2015] [Indexed: 12/25/2022] Open
Abstract
Bacteria switch between two distinct life styles – planktonic (free living) and biofilm forming – in keeping with their ever-changing environment. Such switch involves sophisticated signaling and tight regulation, which provides a fascinating portal for studying gene function and orchestrated protein interactions. In this work, we investigated the molecular mechanism underlying biofilm formation in Shewanella oneidensis MR-1, an environmentally important model bacterium renowned for respiratory diversities, and uncovered a gene cluster coding for seven proteins involved in this process. The three key proteins, BpfA, BpfG, and BpfD, were studied in detail for the first time. BpfA directly participates in biofilm formation as extracellular “glue” BpfG is not only indispensable for BpfA export during biofilm forming but also functions to turn BpfA into active form for biofilm dispersing. BpfD regulates biofilm development by interacting with both BpfA and BpfG, likely in response to signal molecule c-di-GMP. In addition, we found that 1:1 stoichiometry between BpfD and BpfG is critical for biofilm formation. Furthermore, we demonstrated that a biofilm over-producing phenotype can be induced by C116S mutation but not loss of BpfG.
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Affiliation(s)
- Guangqi Zhou
- Institute of Microbiology, College of Life Sciences, Zijingang Campus, Zhejiang University Hangzhou, China
| | - Jie Yuan
- Institute of Microbiology, College of Life Sciences, Zijingang Campus, Zhejiang University Hangzhou, China
| | - Haichun Gao
- Institute of Microbiology, College of Life Sciences, Zijingang Campus, Zhejiang University Hangzhou, China
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82
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Shi M, Wan F, Mao Y, Gao H. Unraveling the Mechanism for the Viability Deficiency of Shewanella oneidensis oxyR Null Mutant. J Bacteriol 2015; 197:2179-2189. [PMID: 25897035 PMCID: PMC4455265 DOI: 10.1128/jb.00154-15] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2015] [Accepted: 04/16/2015] [Indexed: 01/22/2023] Open
Abstract
UNLABELLED Oxidative stresses triggered by reactive oxygen species (ROS) that damage various cellular components are unavoidable for virtually all living organisms. In defense, microorganisms have evolved sophisticated mechanisms to sense, respond to, and battle against ROS. Shewanella oneidensis, an important research model for applied and environmental microbes, employs OxyR to mediate the response to H2O2 by derepressing the production of the major H2O2 scavenger KatB as a major means toward these goals. Surprisingly, despite enhanced H2O2 degradation, the oxyR mutant carries a viability deficiency phenotype (plating defect), which can be suppressed by the addition of exogenous iron species. Experiments showed that the defect was not due to iron starvation. Rather, multiple lines of evidence suggested that H2O2 generated abiotically in lysogeny broth (LB) is responsible for the defect by quickly killing mutant cells. We then showed that the iron species suppressed the plating defect by two distinct mechanisms, either as an H2O2 scavenger without involving living cells or as an environmental cue to stimulate an OxyR-independent response to help cells cope with oxidative stress. Based on the suppression of the plating defect by overproduction of H2O2 scavengers in vivo, we propose that cellular components that are vulnerable to H2O2 and responsible for the defect may reside outside the cytoplasm. IMPORTANCE In bacteria, OxyR is the major regulator controlling the cellular response to H2O2. The loss of OxyR results in reduced viability in many species, but the underlying mechanism is unknown. We showed in S. oneidensis that this defect was due to H2O2 generated abiotically in LB. We then showed that this defect could be corrected by the addition of Fe(2+) or catalase to the LB or increased intracellular production of catalase. Further analyses revealed that Fe(2+) was able not only to decompose H2O2 directly but also to stimulate the activity of OxyR-independent H2O2-scavenging enzymes. Our data indicate that iron species play a previously underappreciated role in protecting cells from H2O2 in environments.
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Affiliation(s)
- Miaomiao Shi
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
- Key Laboratory for Agro-Microbial Research and Utilization, Zhejiang Province, Hangzhou, Zhejiang, China
| | - Fen Wan
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
- Key Laboratory for Agro-Microbial Research and Utilization, Zhejiang Province, Hangzhou, Zhejiang, China
| | - Yinting Mao
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
- Key Laboratory for Agro-Microbial Research and Utilization, Zhejiang Province, Hangzhou, Zhejiang, China
| | - Haichun Gao
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
- Key Laboratory for Agro-Microbial Research and Utilization, Zhejiang Province, Hangzhou, Zhejiang, China
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83
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Yao J, Guo Y, Zeng Z, Liu X, Shi F, Wang X. Identification and characterization of a HEPN-MNT family type II toxin-antitoxin in Shewanella oneidensis. Microb Biotechnol 2015; 8:961-73. [PMID: 26112399 PMCID: PMC4621449 DOI: 10.1111/1751-7915.12294] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Revised: 04/20/2015] [Accepted: 05/02/2015] [Indexed: 11/30/2022] Open
Abstract
Toxin-antitoxin (TA) systems are prevalent in bacteria and archaea. However, related studies in the ecologically and bioelectrochemically important strain Shewanella oneidensis are limited. Here, we show that SO_3166, a member of the higher eukaryotes and prokaryotes nucleotide-binding (HEPN) superfamily, strongly inhibited cell growth in S. oneidensis and Escherichia coli. SO_3165, a putative minimal nucleotidyltransferase (MNT), neutralized the toxicity of SO_3166. Gene SO_3165 lies upstream of SO_3166, and they are co-transcribed. Moreover, the SO_3165 and SO_3166 proteins interact with each other directly in vivo, and antitoxin SO_3165 bound to the promoter of the TA operon and repressed its activity. Finally, the conserved Rx4-6H domain in HEPN family was identified in SO_3166. Mutating either the R or H abolished SO_3166 toxicity, confirming that Rx4-6H domain is critical for SO_3166 activity. Taken together, these results demonstrate that SO_3166 and SO_3165 in S. oneidensis form a typical type II TA pair. This TA pair plays a critical role in regulating bacterial functions because its disruption led to impaired cell motility in S. oneidensis. Thus, we demonstrated for the first time that HEPN-MNT can function as a TA system, thereby providing important insights into the understanding of the function and regulation of HEPNs and MNTs in prokaryotes.
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Affiliation(s)
- Jianyun Yao
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yunxue Guo
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
| | - Zhenshun Zeng
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaoxiao Liu
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
| | - Fei Shi
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
| | - Xiaoxue Wang
- Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China
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84
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Wan F, Mao Y, Dong Y, Ju L, Wu G, Gao H. Impaired cell envelope resulting from arcA mutation largely accounts for enhanced sensitivity to hydrogen peroxide in Shewanella oneidensis. Sci Rep 2015; 5:10228. [PMID: 25975178 PMCID: PMC4432559 DOI: 10.1038/srep10228] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 04/07/2015] [Indexed: 01/06/2023] Open
Abstract
Oxidative stress is one of the major challenges that Shewanella encounter routinely because they thrive in redox-stratified environments prone to reactive oxygen species (ROS) formation, letting alone that ROS can be generated endogenously. As respiration is the predominant process for endogenous ROS, regulators mediating respiration have been demonstrated and/or implicated to play a role in oxidative stress response. In our efforts to unveil the involvement of global regulators for respiration in the oxidative stress response, we found that loss of the Arc system increases S. oneidensis sensitivity to H2O2 whereas neither Fnr nor Crp has a significant role. A comparison of transcriptomic profiles of the wild-type and its isogenic arcA mutant revealed that the OxyR regulon is independent of the Arc system. We then provided evidence that the enhanced H2O2 sensitivity of the arcA mutant is due to an increased H2O2 uptake rate, a result of a cell envelope defect. Although one of three proteases of the ArcA regulon when in excess is partially accountable for the envelope defect, the major contributors remain elusive. Overall, our data indicate that the Arc system influences the bacterial cell envelope biosynthesis, a physiological aspect that has not been associated with the regulator before.
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Affiliation(s)
- Fen Wan
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Yinting Mao
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Yangyang Dong
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Lili Ju
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Genfu Wu
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
| | - Haichun Gao
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
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85
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Wu G, Li N, Mao Y, Zhou G, Gao H. Endogenous generation of hydrogen sulfide and its regulation in Shewanella oneidensis. Front Microbiol 2015; 6:374. [PMID: 25972854 PMCID: PMC4412017 DOI: 10.3389/fmicb.2015.00374] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2015] [Accepted: 04/12/2015] [Indexed: 11/21/2022] Open
Abstract
Hydrogen sulfide (H2S) has been recognized as a physiological mediator with a variety of functions across all domains of life. In this study, mechanisms of endogenous H2S generation in Shewanella oneidensis were investigated. As a research model with highly diverse anaerobic respiratory pathways, the microorganism is able to produce H2S by respiring on a variety of sulfur-containing compounds with SirACD and PsrABC enzymatic complexes, as well as through cysteine degradation with three enzymes, MdeA, SO_1095, and SseA. We showed that the SirACD and PsrABC complexes, which are predominantly, if not exclusively, responsible for H2S generation via respiration of sulfur species, do not interplay with each other. Strikingly, a screen for regulators controlling endogenous H2S generation by transposon mutagenesis identified global regulator Crp to be essential to all H2S-generating processes. In contrast, Fnr and Arc, two other global regulators that have a role in respiration, are dispensable in regulating H2S generation via respiration of sulfur species. Interestingly, Arc is involved in the H2S generation through cysteine degradation by repressing expression of the mdeA gene. We further showed that expression of the sirA and psrABC operons is subjected to direct regulation of Crp, but the mechanisms underlying the requirement of Crp for H2S generation through cysteine degradation remain elusive.
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Affiliation(s)
- Genfu Wu
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
| | - Ning Li
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
| | - Yinting Mao
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
| | - Guangqi Zhou
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
| | - Haichun Gao
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
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86
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PBP1a/LpoA but not PBP1b/LpoB are involved in regulation of the major β-lactamase gene blaA in Shewanella oneidensis. Antimicrob Agents Chemother 2015; 59:3357-64. [PMID: 25824223 DOI: 10.1128/aac.04669-14] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Accepted: 03/19/2015] [Indexed: 11/20/2022] Open
Abstract
β-Lactamase production is one of the most important strategies for Gram-negative bacteria to combat β-lactam antibiotics. Studies of the regulation of β-lactamase expression have largely been focused on the class C β-lactamase AmpC, whose induction by β-lactams requires LysR-type regulator AmpR and permease AmpG-dependent peptidoglycan recycling intermediates. In Shewanella, which is ubiquitous in aquatic environments and is a reservoir for antibiotic resistance, production of the class D β-lactamase BlaA confers bacteria with natural resistance to many β-lactams. Expression of the blaA gene in the genus representative Shewanella oneidensis is distinct from the AmpC paradigm because of the lack of an AmpR homologue and the presence of an additional AmpG-independent regulatory pathway. In this study, using transposon mutagenesis, we identify proteins that are involved in blaA regulation. Inactivation of mrcA and lpoA, which encode penicillin binding protein 1a (PBP1a) and its lipoprotein cofactor, LpoA, respectively, drastically enhances blaA expression in the absence of β-lactams. Although PBP1b and its cognate, LpoB, also exist in S. oneidensis, their roles in blaA induction are dispensable. We further show that the mrcA-mediated blaA expression is independent of AmpG.
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87
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Zhang H, Luo Q, Gao H, Feng Y. A new regulatory mechanism for bacterial lipoic acid synthesis. Microbiologyopen 2015; 4:282-300. [PMID: 25611823 PMCID: PMC4398509 DOI: 10.1002/mbo3.237] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 12/01/2014] [Accepted: 12/09/2014] [Indexed: 01/15/2023] Open
Abstract
Lipoic acid, an essential enzyme cofactor, is required in three domains of life. In the past 60 years since its discovery, most of the pathway for lipoic acid synthesis and metabolism has been elucidated. However, genetic control of lipoic acid synthesis remains unclear. Here, we report integrative evidence that bacterial cAMP-dependent signaling is linked to lipoic acid synthesis in Shewanella species, the certain of unique marine-borne bacteria with special ability of metal reduction. Physiological requirement of protein lipoylation in γ-proteobacteria including Shewanella oneidensis was detected using Western blotting with rabbit anti-lipoyl protein primary antibody. The two genes (lipB and lipA) encoding lipoic acid synthesis pathway were proved to be organized into an operon lipBA in Shewanella, and the promoter was mapped. Electrophoretic mobility shift assays confirmed that the putative CRP-recognizable site (AAGTGTGATCTATCTTACATTT) binds to cAMP-CRP protein with origins of both Escherichia coli and Shewanella. The native lipBA promoter of Shewanella was fused to a LacZ reporter gene to create a chromosome lipBA-lacZ transcriptional fusion in E. coli and S. oneidensis, allowing us to directly assay its expression level by β-galactosidase activity. As anticipated, the removal of E. coli crp gene gave above fourfold increment of lipBA promoter-driven β-gal expression. The similar scenario was confirmed by both the real-time quantitative PCR and the LacZ transcriptional fusion in the crp mutant of Shewanella. Furthermore, the glucose effect on the lipBA expression of Shewanella was evaluated in the alternative microorganism E. coli. As anticipated, an addition of glucose into media effectively induces the transcriptional level of Shewanella lipBA in that the lowered cAMP level relieves the repression of lipBA by cAMP-CRP complex. Therefore, our finding might represent a first paradigm mechanism for genetic control of bacterial lipoic acid synthesis.
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Affiliation(s)
- Huimin Zhang
- Center for Infection and Immunity, Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Qixia Luo
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Haichun Gao
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Youjun Feng
- Center for Infection and Immunity, Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences, Zhejiang University, Hangzhou, Zhejiang, China
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88
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Luo Q, Shi M, Ren Y, Gao H. Transcription factors FabR and FadR regulate both aerobic and anaerobic pathways for unsaturated fatty acid biosynthesis in Shewanella oneidensis. Front Microbiol 2014; 5:736. [PMID: 25566241 PMCID: PMC4273635 DOI: 10.3389/fmicb.2014.00736] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 12/05/2014] [Indexed: 01/01/2023] Open
Abstract
As genes for type II fatty acid synthesis are essential to the growth of Escherichia coli, its sole (anaerobic) pathway has significant potential as a target for novel antibacterial drug, and has been extensively studied. Despite this, we still know surprisingly little about fatty acid synthesis in bacteria because this anaerobic pathway in fact is not widely distributed. In this study, we show a novel model of unsaturated fatty acid (UFA) synthesis in Shewanella, emerging human pathogens in addition to well-known metal reducers. We identify both anaerobic and aerobic UFA biosynthesis pathways in the representative species, S. oneidensis. Uniquely, the bacterium also contains two regulators FabR and FadR, whose counterparts in other bacteria control the anaerobic pathway. However, we show that in S. oneidensis these two regulators are involved in regulation of both pathways, in either direct or indirect manner. Overall, our results indicate that the UFA biosynthesis and its regulation are far more complex than previously expected, and S. oneidensis serves as a good research model for further work.
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Affiliation(s)
- Qixia Luo
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
| | - Miaomiao Shi
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
| | - Yedan Ren
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
| | - Haichun Gao
- Institute of Microbiology and College of Life Sciences, Zhejiang University Hangzhou, China
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89
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Fu H, Jin M, Wan F, Gao H. Shewanella oneidensis cytochrome c maturation component CcmI is essential for heme attachment at the non-canonical motif of nitrite reductase NrfA. Mol Microbiol 2014; 95:410-25. [PMID: 25402661 DOI: 10.1111/mmi.12865] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/12/2014] [Indexed: 11/28/2022]
Abstract
Shewanella oneidensis is renowned for its respiratory versatility, which is largely due to abundant c-type cytochromes. Maturation of these proteins depends on a Ccm system encoded by genes in an unusual chromosomal arrangement, but the detailed mechanism is not understood. In this study, we identify SO0265 as CcmI, an apocytochrome c chaperone that is important and essential for maturation of c-type cytochromes with the canonical heme binding motif(s) (HBM; CX(2)CH) and nitrite reductase NrfA carrying a non-canonical CX(2)CK motif respectively. We show that the N-terminal transmembrane segment of CcmI, CcmI-1, is sufficient for maturation of the former but the entire protein is required for maturation of the latter. Although S. oneidensis possesses a heme lyase, SirEFG, dedicated for non-canonical HBMs, it is specific for SirA, a sulfite reductase with a CX(15)CH motif. By presenting evidence that the periplasmic portion of CcmI, CcmI-2, interacts with NrfA, we suggest that CcmI also takes the role of Escherichia coli NrfG for chaperoning apo-NrfA for maturation at CX(2)CK. Moreover, intact CcmI is required for maturation of NrfA, presumably by ensuring that heme attachment at canonical HBMs occurs before apoprotein degradation.
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Affiliation(s)
- Huihui Fu
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
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90
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Li N, Luo Q, Jiang Y, Wu G, Gao H. Managing oxidative stresses in Shewanella oneidensis: intertwined roles of the OxyR and OhrR regulons. Environ Microbiol 2014; 16:1821-34. [PMID: 25009841 DOI: 10.1111/1462-2920.12418] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Shewanella oneidensis, renowned for its remarkable respiratory abilities, inhabit redox-stratified environments prone to reactive oxygen species (ROS)formation. Two major oxidative stress regulators,analogues of OxyR and OhrR, specifically respond to H(2)O(2) and organic peroxides (OP), respectively, are encoded in the genome based on sequence comparison to well-studied models. Presumably, these analogues provide protection from ROS. An understanding of S. oneidensis OxyR has been established recently, which functions as both repressor and activator to mediate H(2)O(2)-induced oxidative stress. Here,we report the first study of elucidating molecular mechanisms underlying the S. oneidensis response to OP-induced oxidative stress. We show tha tS. oneidensis has OhrR, an OP stress regulator with two novel features. The sensing and responding residues of OhrR are not equally important for regulation and the regulator directly controls transcription of the SO1563 gene, in addition to the ohr gene which encodes the major OP scavenging protein. Importantly,we present evidence suggesting that the OxyR and OhrR regulons of S. oneidensis appear to be functionally intertwined as both OxyR and OhrR systems can sense and response to H(2)O(2) and OP agents.
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91
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Yin J, Jin M, Zhang H, Ju L, Zhang L, Gao H. Regulation of nitrite resistance of the cytochrome cbb3 oxidase by cytochrome c ScyA in Shewanella oneidensis. Microbiologyopen 2014; 4:84-99. [PMID: 25417822 PMCID: PMC4335978 DOI: 10.1002/mbo3.224] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 10/24/2014] [Accepted: 11/03/2014] [Indexed: 12/03/2022] Open
Abstract
Cytochrome c proteins, as enzymes to exchange electrons with substrates or as pure electron carriers to shuttle electrons, play vital roles in bacterial respiration and photosynthesis. In Shewanella oneidensis, a research model for the respiratory diversity, at least 42 c-type cytochromes are predicted to be encoded in the genome and are regarded to be the foundation of its highly branched electron transport pathways. However, only a small number of c-type cytochromes have been extensively studied. In this study, we identify soluble cytochrome c ScyA as an important factor influencing the nitrite resistance of a strain devoid of the bd oxidase by utilizing a newly developed transposon mutagenesis vector, which enables overexpression of the gene(s) downstream of the insertion site. We show that when in overabundance ScyA facilitates growth against nitrite inhibition by enhancing nitrite resistance of the cbb3 oxidase. Based on the data presented in this study, we suggest two possible mechanisms underlying the observed effect of ScyA: (1) ScyA increases electron flow to the cbb3 oxidase; (2) ScyA promotes nitrite resistance of the cbb3 oxidase, possibly by direct interaction.
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Affiliation(s)
- Jianhua Yin
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, 310058, China
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92
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Chen H, Luo Q, Yin J, Gao T, Gao H. Evidence for the requirement of CydX in function but not assembly of the cytochrome bd oxidase in Shewanella oneidensis. Biochim Biophys Acta Gen Subj 2014; 1850:318-28. [PMID: 25316290 DOI: 10.1016/j.bbagen.2014.10.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Revised: 09/25/2014] [Accepted: 10/06/2014] [Indexed: 12/19/2022]
Abstract
BACKGROUND Cytochrome bd oxidase, existing widely in bacteria, produces a proton motive force by the vectorial charge transfer of protons and more importantly, endows bacteria with a number of vitally important physiological functions, such as enhancing tolerance to various stresses. Although extensively studied as a CydA-CydB two-subunit complex for decades, the complex in certain groups of bacteria is recently found to in fact consist of an additional subunit, which is functionally essential. METHODS We investigated the assembly of the CydA-CydB complex using BiFC. We investigated the function of CydX using mutational analysis. RESULTS CydX, a 38-amino-acid inner-membrane protein, is associated with the CydA-CydB complex in Shewanella oneidensis, a facultative anaerobe renowned for its respiratory versatility. It is clear that CydX is neither required for the in vivo assembly of the CydA-CydB complex nor relies on the complex for its translocation and integration into the membrane. The N-terminal segment (1-25 amino acid residues) and short periplasmic overhang of CydX, with respect to functionality, are important whereas the remaining C-terminal segment is rather flexible. CONCLUSION Based on these findings, we postulate that CydX may function by positioning and stabilizing the prosthetic hemes, especially heme d in the CydA-CydB complex although a role of participating in catalytic reaction is not excluded. GENERAL SIGNIFICANCE The work provides novel insights into our understanding of the small subunit of the cytochrome bd oxidase.
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Affiliation(s)
- Haijiang Chen
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Qixia Luo
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Jianhua Yin
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Tong Gao
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Haichun Gao
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China.
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93
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Distinct roles of major peptidoglycan recycling enzymes in β-Lactamase production in Shewanella oneidensis. Antimicrob Agents Chemother 2014; 58:6536-43. [PMID: 25136029 DOI: 10.1128/aac.03238-14] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
β-Lactam antibiotics were the earliest discovered and are the most widely used group of antibiotics that work by inactivating penicillin-binding proteins to inhibit peptidoglycan biosynthesis. As one of the most efficient defense strategies, many bacteria produce β-lactam-degrading enzymes, β-lactamases, whose biochemical functions and regulation have been extensively studied. A signal transduction pathway for β-lactamase induction by β-lactam antibiotics, consisting of the major peptidoglycan recycling enzymes and the LysR-type transcriptional regulator, AmpR, has been recently unveiled in some bacteria. Because inactivation of some of these proteins, especially the permease AmpG and the β-hexosaminidase NagZ, results in substantially elevated susceptibility to the antibiotics, these have been recognized as potential therapeutic targets. Here, we show a contrasting scenario in Shewanella oneidensis, in which the homologue of AmpR is absent. Loss of AmpG or NagZ enhances β-lactam resistance drastically, whereas other identified major peptidoglycan recycling enzymes are dispensable. Moreover, our data indicate that there exists a parallel signal transduction pathway for β-lactamase induction, which is independent of either AmpG or NagZ.
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94
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Shi M, Gao T, Ju L, Yao Y, Gao H. Effects of FlrBC on flagellar biosynthesis of Shewanella oneidensis. Mol Microbiol 2014; 93:1269-83. [PMID: 25074236 DOI: 10.1111/mmi.12731] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/24/2014] [Indexed: 11/27/2022]
Abstract
As a most conserved complex molecular machine made up of a large number of structural subunits, the flagellum is under tight regulation by hierarchical arrangements. Although variations in polar flagellar systems are found, most of them are restricted to multiple-copy components, such as flagellins and stators. Therefore, these features are regarded to be peripheral relative to the comprehensive conservation. In this study, however, we present evidence to show that the difference in highly conserved polar flagellar systems can be surprisingly profound, even at the heart of the classical regulatory hierarchy. In Gram-negative Shewanella oneidensis, two-component system FlrBC, whose counterpart is essential for flagellar biosynthesis and motility by directly controlling expression of class III genes in polarly flagellated bacteria such as Vibrio cholerae, is dispensable for the process. The system directly controls expression of the flaA gene, encoding a flagellin of weak motility. We further show that the ratio of two flagellins, FlaA and FlaB, determines motility of a flagellum. More strikingly, overproduction of FlrC results in a peritrichously multi-flagellated phenotype, and FlrC is likely to function as an activator in its unphosphorylated form for transcription of the flaA gene, contrasting the previously characterized counterpart.
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Affiliation(s)
- Miaomiao Shi
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, 310058, Zhejiang, China; Key Laboratory for Agro-Microbial Research and Utilization, Hangzhou, 310058, Zhejiang, China
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95
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Fu H, Jin M, Ju L, Mao Y, Gao H. Evidence for function overlapping of CymA and the cytochrome bc1 complex in the Shewanella oneidensis nitrate and nitrite respiration. Environ Microbiol 2014; 16:3181-95. [PMID: 24650148 DOI: 10.1111/1462-2920.12457] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 02/23/2014] [Accepted: 03/16/2014] [Indexed: 11/29/2022]
Abstract
Shewanella oneidensis is an important model organism for its versatility of anaerobic respiration. CymA, a cytoplasmic membrane-bound tetraheme c-type cytochrome, plays a central role in anaerobic respiration by transferring electrons from the quinone pool to a variety of terminal reductases. Although loss of CymA results in defect in respiration of many electron acceptors (EAs), a significant share of the capacity remains in general. In this study, we adopted a transposon random mutagenesis method in a cymA null mutant to identify substituent(s) of CymA with respect to nitrite and nitrate respiration. A total of 87 insertion mutants, whose ability to reduce nitrite was further impaired, were obtained. Among the interrupted genes, the petABC operon appeared to be the most likely candidate given the involvement of the cytochrome bc1 complex that it encodes in electron transport. Subsequent analyses not only confirmed that the complex and CymA were indeed functionally overlapping in nitrate/nitrite respiration but also revealed that both proteins were able to draw electrons from ubiquinone and menaquinone. Furthermore, we found that expression of the bc1 complex was affected by oxygen but not nitrate or nitrite and by global regulators ArcA and Crp in an indirect manner.
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Affiliation(s)
- Huihui Fu
- Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
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96
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Sun L, Dong Y, Shi M, Jin M, Zhou Q, Luo ZQ, Gao H. Two residues predominantly dictate functional difference in motility between Shewanella oneidensis flagellins FlaA and FlaB. J Biol Chem 2014; 289:14547-59. [PMID: 24733391 DOI: 10.1074/jbc.m114.552000] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Nearly half of flagellated microorganisms possess a multiple-flagellin system. Although a functional filament can be formed from one of multiple flagellins alone in many bacteria, it is more common that one flagellin is the major constituent and others contribute. Underlying mechanisms proposed for such scenarios cover flagellin regulation of various levels, including transcription, translation, post-translational modification, secretion, and filament assembly. In Shewanella oneidensis, the flagellar filament is composed of FlaA and FlaB flagellins; the latter is the major one in terms of motility. In this study, we showed that regulation of all levels except for filament assembly is indistinguishable between these two flagellins. Further analyses revealed that two amino acid residues predominantly dictated functional difference with respect to motility. Given that Shewanella prefer a solid surface-associated life style, of which filaments consisting of either FlaA or FlaB are equally supportive, we envision that roles of flagella in surface adhesion and formation of bacterial communities are particularly important for their survival and proliferation in these specific niches.
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Affiliation(s)
- Linlin Sun
- From the Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China and
| | - Yangyang Dong
- From the Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China and
| | - Miaomiao Shi
- From the Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China and
| | - Miao Jin
- From the Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China and
| | - Qing Zhou
- the Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907
| | - Zhao-Qing Luo
- the Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907
| | - Haichun Gao
- From the Institute of Microbiology and College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang 310058, China and
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97
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Protection from oxidative stress relies mainly on derepression of OxyR-dependent KatB and Dps in Shewanella oneidensis. J Bacteriol 2013; 196:445-58. [PMID: 24214945 DOI: 10.1128/jb.01077-13] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Shewanella thrives in redox-stratified environments where accumulation of H2O2 becomes inevitable because of the chemical oxidation of reduced metals, sulfur species, or organic molecules. As a research model, the representative species Shewanella oneidensis has been extensively studied for its response to various stresses. However, little progress has been made toward an understanding of the physiological and genetic responses of this bacterium to oxidative stress, which is critically relevant to its application as a dissimilatory metal-reducing bacterium. In this study, we systematically investigated the mechanism underlying the response to H2O2 at cellular, genomic, and molecular levels. Using transcriptional profiling, we found that S. oneidensis is hypersensitive to H2O2 in comparison with Escherichia coli, and well-conserved defense genes such as ahpCF, katB, katG, and dps appear to form the first line of defense, whereas iron-sulfur-protecting proteins may not play a significant role. Subsequent identification and characterization of an analogue of the E. coli oxyR gene revealed that S. oneidensis OxyR is the master regulator that mediates the bacterial response to H2O2-induced oxidative stress by directly repressing or activating the defense genes. The sensitivity of S. oneidensis to H2O2 is likely attributable to the lack of an inducible manganese import mechanism during stress. To cope with stress, major strategies that S. oneidensis adopts include rapid removal of the oxidant and restriction of intracellular iron concentrations, both of which are achieved predominantly by derepression of the katB and dps genes.
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