1
|
Kaviraj M, Kumar U, Snigdha A, Chatterjee S. Nitrate reduction to ammonium: a phylogenetic, physiological, and genetic aspects in Prokaryotes and eukaryotes. Arch Microbiol 2024; 206:297. [PMID: 38861039 DOI: 10.1007/s00203-024-04009-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2024] [Revised: 05/15/2024] [Accepted: 05/16/2024] [Indexed: 06/12/2024]
Abstract
The microbe-mediated conversion of nitrate (NO3-) to ammonium (NH4+) in the nitrogen cycle has strong implications for soil health and crop productivity. The role of prokaryotes, eukaryotes and their phylogeny, physiology, and genetic regulations are essential for understanding the ecological significance of this empirical process. Several prokaryotes (bacteria and archaea), and a few eukaryotes (fungi and algae) are reported as NO3- reducers under certain conditions. This process involves enzymatic reactions which has been catalysed by nitrate reductases, nitrite reductases, and NH4+-assimilating enzymes. Earlier reports emphasised that single-cell prokaryotic or eukaryotic organisms are responsible for this process, which portrayed a prominent gap. Therefore, this study revisits the similarities and uniqueness of mechanism behind NO3- -reduction to NH4+ in both prokaryotes and eukaryotes. Moreover, phylogenetic, physiological, and genetic regulation also shed light on the evolutionary connections between two systems which could help us to better explain the NO3--reduction mechanisms over time. Reports also revealed that certain transcription factors like NtrC/NtrB and Nit2 have shown a major role in coordinating the expression of NO3- assimilation genes in response to NO3- availability. Overall, this review provides a comprehensive information about the complex fermentative and respiratory dissimilatory nitrate reduction to ammonium (DNRA) processes. Uncovering the complexity of this process across various organisms may further give insight into sustainable nitrogen management practices and might contribute to addressing global environmental challenges.
Collapse
Affiliation(s)
- Megha Kaviraj
- ICAR- National Rice Research Institute, Cuttack, 753006, Odisha, India.
- The University of Burdwan, Burdwan, 713104, West Bengal, India.
| | - Upendra Kumar
- ICAR- National Rice Research Institute, Cuttack, 753006, Odisha, India.
| | - Alisha Snigdha
- Siksha 'O' Anusandhan University, Bhubaneswar, 751003, Odisha, India
| | | |
Collapse
|
2
|
Zhao H, He Y, Wang Y, He X, Zhao R, Liu B. Analysis of microbial community evolution, autolysis phenomena, and energy metabolism pathways in Pholiota nameko endophytes. Front Microbiol 2024; 15:1319886. [PMID: 38690362 PMCID: PMC11059008 DOI: 10.3389/fmicb.2024.1319886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 03/21/2024] [Indexed: 05/02/2024] Open
Abstract
Introduction Pholiota nameko is a widely consumed edible fungus. This study focuses on two crucial developmental stages of Pholiota nameko, namely, mycelium and ascospores. The objectives of this research were to investigate changes in microbial diversity and community structure during the growth of Pholiota nameko and to analyze the adaptability of the dominant strains to their respective habitats through metabolic. Methods Specifically, we conducted second-generation sequencing of the 16S rRNA gene (Illumina) on samples obtained from these stages. In addition, we isolated and characterized endophytes present in Pholiota nameko, focusing on examining the impact of dominant endophyte genera on autolysis. We also conducted a metabolic pathway analysis. Results and discussion The results unveiled 578,414 valid sequences of Pholiota nameko endophytic fungi. At the phylum level, the dominant taxa were Basidiomycota, Ascomycota, Zoopagomycota, and Mucoromycota. At the genus level, the dominant taxa observed were Pholiota, Inocybe, Fusarium, and Hortiboletus. For endophytic bacteria, we obtained 458,475 valid sequences. The dominant phyla were Proteobacteria, TM6, Firmicutes, and Bacteroidetes, while the dominant genera were Edaphobacter, Xanthomonas, Burkholderia, and Pseudomonas. Moreover, we identified the isolated strains in Pholiota nameko using 16S rDNA, and most of them were found to belong to the genus Pseudomonas, with Pseudomonas putida being the most prevalent strain. The findings revealed that the Pseudomonas putida strain has the ability to slow down the breakdown of soluble proteins and partially suppress the metabolic processes that generate superoxide anion radicals in Pholiota nameko, thereby reducing autolysis. Additionally, our results demonstrated that molybdenum enzyme-mediated anaerobic oxidative phosphorylation reactions were the primary energy metabolism pathway in the Pseudomonas putida strain. This suggests that the molybdenum cofactor synthesis pathway might be the main mechanism through which Pholiota nameko adapts to its complex and diverse habitats.
Collapse
Affiliation(s)
| | | | | | - Xiaolong He
- College of Life Sciences, Yan’an University, Yan’an, China
| | | | | |
Collapse
|
3
|
Louie TS, Kumar A, Bini E, Häggblom MM. Mo than meets the eye: genomic insights into molybdoenzyme diversity of Seleniivibrio woodruffii strain S4T. Lett Appl Microbiol 2024; 77:ovae038. [PMID: 38573838 DOI: 10.1093/lambio/ovae038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Revised: 02/12/2024] [Accepted: 04/03/2024] [Indexed: 04/06/2024]
Abstract
Seleniivibrio woodruffii strain S4T is an obligate anaerobe belonging to the phylum Deferribacterota. It was isolated for its ability to respire selenate and was also found to respire arsenate. The high-quality draft genome of this bacterium is 2.9 Mbp, has a G+C content of 48%, 2762 predicted genes of which 2709 are protein-coding, and 53 RNA genes. An analysis of the genome focusing on the genes encoding for molybdenum-containing enzymes (molybdoenzymes) uncovered a remarkable number of genes encoding for members of the dimethylsulfoxide reductase family of proteins (DMSOR), including putative reductases for selenate and arsenate respiration, as well as genes for nitrogen fixation. Respiratory molybdoenzymes catalyze redox reactions that transfer electrons to a variety of substrates that can act as terminal electron acceptors for energy generation. Seleniivibrio woodruffii strain S4T also has essential genes for molybdate transporters and the biosynthesis of the molybdopterin guanine dinucleotide cofactors characteristic of the active centers of DMSORs. Phylogenetic analysis revealed candidate respiratory DMSORs spanning nine subfamilies encoded within the genome. Our analysis revealed the untapped potential of this interesting microorganism and expanded our knowledge of molybdoenzyme co-occurrence.
Collapse
Affiliation(s)
- Tiffany S Louie
- Department of Biochemistry and Microbiology Rutgers, The State University of New Jersey, School of Environmental and Biological Sciences, 76 Lipman Drive, New Brunswick, NJ 08901, United States
| | - Anil Kumar
- Department of Biochemistry and Microbiology Rutgers, The State University of New Jersey, School of Environmental and Biological Sciences,, 76 Lipman Drive, New Brunswick, NJ 08901, United States
| | - Elisabetta Bini
- Department of Biochemistry and Microbiology Rutgers, The State University of New Jersey, School of Environmental and Biological Sciences,, 76 Lipman Drive, New Brunswick, NJ 08901, United States
| | - Max M Häggblom
- Department of Biochemistry and Microbiology Rutgers, The State University of New Jersey, School of Environmental and Biological Sciences,, 76 Lipman Drive, New Brunswick, NJ 08901, United States
| |
Collapse
|
4
|
Kim JS, Liu L, Kant S, Orlicky DJ, Uppalapati S, Margolis A, Davenport BJ, Morrison TE, Matsuda J, McClelland M, Jones-Carson J, Vazquez-Torres A. Anaerobic respiration of host-derived methionine sulfoxide protects intracellular Salmonella from the phagocyte NADPH oxidase. Cell Host Microbe 2024; 32:411-424.e10. [PMID: 38307020 PMCID: PMC11396582 DOI: 10.1016/j.chom.2024.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Revised: 12/06/2023] [Accepted: 01/10/2024] [Indexed: 02/04/2024]
Abstract
Intracellular Salmonella experiencing oxidative stress downregulates aerobic respiration. To maintain cellular energetics during periods of oxidative stress, intracellular Salmonella must utilize terminal electron acceptors of lower energetic value than molecular oxygen. We show here that intracellular Salmonella undergoes anaerobic respiration during adaptation to the respiratory burst of the phagocyte NADPH oxidase in macrophages and in mice. Reactive oxygen species generated by phagocytes oxidize methionine, generating methionine sulfoxide. Anaerobic Salmonella uses the molybdenum cofactor-containing DmsABC enzymatic complex to reduce methionine sulfoxide. The enzymatic activity of the methionine sulfoxide reductase DmsABC helps Salmonella maintain an alkaline cytoplasm that supports the synthesis of the antioxidant hydrogen sulfide via cysteine desulfuration while providing a source of methionine and fostering redox balancing by associated dehydrogenases. Our investigations demonstrate that nontyphoidal Salmonella responding to oxidative stress exploits the anaerobic metabolism associated with dmsABC gene products, a pathway that has accrued inactivating mutations in human-adapted typhoidal serovars.
Collapse
Affiliation(s)
- Ju-Sim Kim
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Lin Liu
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Sashi Kant
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - David J Orlicky
- Department of Pathology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Siva Uppalapati
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Alyssa Margolis
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Bennett J Davenport
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Thomas E Morrison
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | | | - Michael McClelland
- University of California Irvine School of Medicine, Department of Microbiology and Molecular Genetics, Irvine, CA, USA
| | - Jessica Jones-Carson
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Andres Vazquez-Torres
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, CO 80045, USA; Veterans Affairs, Eastern Colorado Health Care System, Aurora, CO 80045, USA.
| |
Collapse
|
5
|
Sun W, Sun X, Häggblom MM, Kolton M, Lan L, Li B, Dong Y, Xu R, Li F. Identification of Antimonate Reducing Bacteria and Their Potential Metabolic Traits by the Combination of Stable Isotope Probing and Metagenomic-Pangenomic Analysis. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:13902-13912. [PMID: 34581566 DOI: 10.1021/acs.est.1c03967] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Microorganisms play an important role in altering antimony (Sb) speciation, mobility, and bioavailability, but the understanding of the microorganisms responsible for Sb(V) reduction has been limited. In this study, DNA-stable isotope probing (DNA-SIP) and metagenomics analysis were combined to identify potential Sb(V)-reducing bacteria (SbRB) and predict their metabolic pathways for Sb(V) reduction. Soil slurry cultures inoculated with Sb-contaminated paddy soils from two Sb-contaminated sites demonstrated the capability to reduce Sb(V). DNA-SIP identified bacteria belonging to the genera Pseudomonas and Geobacter as putative SbRB in these two Sb-contaminated sites. In addition, bacteria such as Lysinibacillus and Dechloromonas may potentially participate in Sb(V) reduction. Nearly complete draft genomes of putative SbRB (i.e., Pseudomonas and Geobacter) were obtained, and the genes potentially responsible for arsenic (As) and Sb reduction (i.e., respiratory arsenate reductase (arrA) and antimonate reductase (anrA)) were examined. Notably, bins affiliated with Geobacter contained arrA and anrA genes, supporting our hypothesis that they are putative SbRB. Further, pangenomic analysis indicated that various Geobacter-associated genomes obtained from diverse habitats also contained arrA and anrA genes. In contrast, Pseudomonas may use a predicted DMSO reductase closely related to sbrA (Sb(V) reductase gene) clade II to reduce Sb(V), which may need further experiments to verify. This current work represents a demonstration of using DNA-SIP and metagenomic-binning to identify SbRB and their key genes involved in Sb(V) reduction and provides valuable data sets to link bacterial identities with Sb(V) reduction.
Collapse
Affiliation(s)
- Weimin Sun
- Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangzhou 510650, China
| | - Xiaoxu Sun
- Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangzhou 510650, China
| | - Max M Häggblom
- Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, New Jersey 08901, United States
| | - Max Kolton
- Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangzhou 510650, China
| | - Ling Lan
- Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangzhou 510650, China
| | - Baoqin Li
- Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangzhou 510650, China
| | - Yiran Dong
- School of Environmental Studies, China University of Geosciences (Wuhan), Wuhan 430070, China
| | - Rui Xu
- Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangzhou 510650, China
| | - Fangbai Li
- Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangzhou 510650, China
| |
Collapse
|
6
|
Sun X, Qiu L, Kolton M, Häggblom M, Xu R, Kong T, Gao P, Li B, Jiang C, Sun W. V V Reduction by Polaromonas spp. in Vanadium Mine Tailings. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:14442-14454. [PMID: 33125214 DOI: 10.1021/acs.est.0c05328] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Vanadium (V) is an important metal with critical industrial and medical applications. Elevated V contamination, however, can be a threat to the environment and human health. Microorganisms can reduce the more toxic and mobile VV to the less toxic and immobile VIV, which could be a detoxification and energy metabolism strategy adopted by V-reducing bacteria (VRB). The limited understanding of microbial responses to V contamination and the mechanisms for VV reduction, however, hamper our capability to attenuate V contamination. This study focused on determining the microbial responses to elevated V concentration and the mechanisms of VV reduction in V tailings. The bacterial communities were characterized and compared between the V tailings and the less contaminated adjacent mineral soils. Further, VV-reducing enrichments indicated that bacteria associated with Polaromonas, a genus belonging to the family Burkholderiaceae, were potentially responsible for VV reduction. Retrieved metagenome-assembled genomes (MAGs) suggested that the Polaromonas spp. encoded genes (cymA, omcA, and narG) were responsible for VV reduction. Additionally, Polaromonas spp. was metabolically versatile and could use both organic and inorganic electron donors. The metabolic versatility of Polaromonas spp. may be important for its ability to flourish in the V tailings.
Collapse
Affiliation(s)
- Xiaoxu Sun
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou 510650, China
| | - Lang Qiu
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou 510650, China
| | - Max Kolton
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou 510650, China
| | - Max Häggblom
- Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, New Jersey 08901, United States
| | - Rui Xu
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou 510650, China
| | - Tianle Kong
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou 510650, China
| | - Pin Gao
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou 510650, China
| | - Baoqin Li
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou 510650, China
| | - Chengjian Jiang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi Research Center for Microbial and Enzyme Engineering Technology, College of Life Science and Technology, Guangxi University, Nanning 530004, China
| | - Weimin Sun
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Institute of Eco-environmental and Soil Sciences, Guangdong Academy of Sciences, Guangzhou 510650, China
- Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou 510650, China
| |
Collapse
|
7
|
Methane, arsenic, selenium and the origins of the DMSO reductase family. Sci Rep 2020; 10:10946. [PMID: 32616801 PMCID: PMC7331816 DOI: 10.1038/s41598-020-67892-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 06/16/2020] [Indexed: 11/16/2022] Open
Abstract
Mononuclear molybdoenzymes of the dimethyl sulfoxide reductase (DMSOR) family catalyze a number of reactions essential to the carbon, nitrogen, sulfur, arsenic, and selenium biogeochemical cycles. These enzymes are also ancient, with many lineages likely predating the divergence of the last universal common ancestor into the Bacteria and Archaea domains. We have constructed rooted phylogenies for over 1,550 representatives of the DMSOR family using maximum likelihood methods to investigate the evolution of the arsenic biogeochemical cycle. The phylogenetic analysis provides compelling evidence that formylmethanofuran dehydrogenase B subunits, which catalyze the reduction of CO2 to formate during hydrogenotrophic methanogenesis, constitutes the most ancient lineage. Our analysis also provides robust support for selenocysteine as the ancestral ligand for the Mo/W atom. Finally, we demonstrate that anaerobic arsenite oxidase and respiratory arsenate reductase catalytic subunits represent a more ancient lineage of DMSORs compared to aerobic arsenite oxidase catalytic subunits, which evolved from the assimilatory nitrate reductase lineage. This provides substantial support for an active arsenic biogeochemical cycle on the anoxic Archean Earth. Our work emphasizes that the use of chalcophilic elements as substrates as well as the Mo/W ligand in DMSORs has indelibly shaped the diversification of these enzymes through deep time.
Collapse
|
8
|
Lavy A, McGrath DG, Matheus Carnevali PB, Wan J, Dong W, Tokunaga TK, Thomas BC, Williams KH, Hubbard SS, Banfield JF. Microbial communities across a hillslope-riparian transect shaped by proximity to the stream, groundwater table, and weathered bedrock. Ecol Evol 2019; 9:6869-6900. [PMID: 31380022 PMCID: PMC6662431 DOI: 10.1002/ece3.5254] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 04/25/2019] [Accepted: 04/26/2019] [Indexed: 01/01/2023] Open
Abstract
Watersheds are important suppliers of freshwater for human societies. Within mountainous watersheds, microbial communities impact water chemistry and element fluxes as water from precipitation events discharge through soils and underlying weathered rock, yet there is limited information regarding the structure and function of these communities. Within the East River, CO watershed, we conducted a depth-resolved, hillslope to riparian zone transect study to identify factors that control how microorganisms are distributed and their functions. Metagenomic and geochemical analyses indicate that distance from the East River and proximity to groundwater and underlying weathered shale strongly impact microbial community structure and metabolic potential. Riparian zone microbial communities are compositionally distinct, from the phylum down to the species level, from all hillslope communities. Bacteria from phyla lacking isolated representatives consistently increase in abundance with increasing depth, but only in the riparian zone saturated sediments we found Candidate Phyla Radiation bacteria. Riparian zone microbial communities are functionally differentiated from hillslope communities based on their capacities for carbon and nitrogen fixation and sulfate reduction. Selenium reduction is prominent at depth in weathered shale and saturated riparian zone sediments and could impact water quality. We anticipate that the drivers of community composition and metabolic potential identified throughout the studied transect will predict patterns across the larger watershed hillslope system.
Collapse
Affiliation(s)
- Adi Lavy
- Earth and Planetary ScienceUniversity of CaliforniaBerkeleyCalifornia
- Earth and Environmental SciencesLawrence Berkeley National LabBerkeleyCalifornia
| | | | | | - Jiamin Wan
- Earth and Environmental SciencesLawrence Berkeley National LabBerkeleyCalifornia
| | - Wenming Dong
- Earth and Environmental SciencesLawrence Berkeley National LabBerkeleyCalifornia
| | - Tetsu K. Tokunaga
- Earth and Environmental SciencesLawrence Berkeley National LabBerkeleyCalifornia
| | - Brian C. Thomas
- Earth and Planetary ScienceUniversity of CaliforniaBerkeleyCalifornia
| | - Kenneth H. Williams
- Earth and Environmental SciencesLawrence Berkeley National LabBerkeleyCalifornia
| | - Susan S. Hubbard
- Earth and Environmental SciencesLawrence Berkeley National LabBerkeleyCalifornia
| | | |
Collapse
|
9
|
Respiratory Selenite Reductase from Bacillus selenitireducens Strain MLS10. J Bacteriol 2019; 201:JB.00614-18. [PMID: 30642986 DOI: 10.1128/jb.00614-18] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 01/03/2019] [Indexed: 11/20/2022] Open
Abstract
The putative respiratory selenite [Se(IV)] reductase (Srr) from Bacillus selenitireducens MLS10 has been identified through a polyphasic approach involving genomics, proteomics, and enzymology. Nondenaturing gel assays were used to identify Srr in cell fractions, and the active band was shown to contain a single protein of 80 kDa. The protein was identified through liquid chromatography-tandem mass spectrometry (LC-MS/MS) as a homolog of the catalytic subunit of polysulfide reductase (PsrA). It was found to be encoded as part of an operon that contains six genes that we designated srrE, srrA, srrB, srrC, srrD, and srrF SrrA is the catalytic subunit (80 kDa), with a twin-arginine translocation (TAT) leader sequence indicative of a periplasmic protein and one putative 4Fe-4S binding site. SrrB is a small subunit (17 kDa) with four putative 4Fe-4S binding sites, SrrC (43 kDa) is an anchoring subunit, and SrrD (24 kDa) is a chaperon protein. Both SrrE (38 kDa) and SrrF (45 kDa) were annotated as rhodanese domain-containing proteins. Phylogenetic analysis revealed that SrrA belonged to the PsrA/PhsA clade but that it did not define a distinct subgroup, based on the putative homologs that were subsequently identified from other known selenite-respiring bacteria (e.g., Desulfurispirillum indicum and Pyrobaculum aerophilum). The enzyme appeared to be specific for Se(IV), showing no activity with selenate, arsenate, or thiosulfate, with a Km of 145 ± 53 μM, a V max of 23 ± 2.5 μM min-1, and a k cat of 23 ± 2.68 s-1 These results further our understanding of the mechanisms of selenium biotransformation and its biogeochemical cycle.IMPORTANCE Selenium is an essential element for life, with Se(IV) reduction a key step in its biogeochemical cycle. This report identifies for the first time a dissimilatory Se(IV) reductase, Srr, from a known selenite-respiring bacterium, the haloalkalophilic Bacillus selenitireducens strain MLS10. The work extends the versatility of the complex iron-sulfur molybdoenzyme (CISM) superfamily in electron transfer involving chalcogen substrates with different redox potentials. Further, it underscores the importance of biochemical and enzymological approaches in establishing the functionality of these enzymes.
Collapse
|
10
|
Schwanhold N, Iobbi-Nivol C, Lehmann A, Leimkühler S. Same but different: Comparison of two system-specific molecular chaperones for the maturation of formate dehydrogenases. PLoS One 2018; 13:e0201935. [PMID: 30444874 PMCID: PMC6239281 DOI: 10.1371/journal.pone.0201935] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 08/21/2018] [Indexed: 11/19/2022] Open
Abstract
The maturation of bacterial molybdoenzymes is a complex process leading to the insertion of the bulky bis-molybdopterin guanine dinucleotide (bis-MGD) cofactor into the apo-enzyme. Most molybdoenzymes were shown to contain a specific chaperone for the insertion of the bis-MGD cofactor. Formate dehydrogenases (FDH) together with their molecular chaperone partner seem to display an exception to this specificity rule, since the chaperone FdhD has been proven to be involved in the maturation of all three FDH enzymes present in Escherichia coli. Multiple roles have been suggested for FdhD-like chaperones in the past, including the involvement in a sulfur transfer reaction from the l-cysteine desulfurase IscS to bis-MGD by the action of two cysteine residues present in a conserved CXXC motif of the chaperones. However, in this study we show by phylogenetic analyses that the CXXC motif is not conserved among FdhD-like chaperones. We compared in detail the FdhD-like homologues from Rhodobacter capsulatus and E. coli and show that their roles in the maturation of FDH enzymes from different subgroups can be exchanged. We reveal that bis-MGD-binding is a common characteristic of FdhD-like proteins and that the cofactor is bound with a sulfido-ligand at the molybdenum atom to the chaperone. Generally, we reveal that the cysteine residues in the motif CXXC of the chaperone are not essential for the production of active FDH enzymes.
Collapse
Affiliation(s)
- Nadine Schwanhold
- Institute of Biochemistry and Biology, Department of Molecular Enzymology, University of Potsdam, Potsdam, Germany
| | | | - Angelika Lehmann
- Institute of Biochemistry and Biology, Department of Molecular Enzymology, University of Potsdam, Potsdam, Germany
| | - Silke Leimkühler
- Institute of Biochemistry and Biology, Department of Molecular Enzymology, University of Potsdam, Potsdam, Germany
- * E-mail:
| |
Collapse
|
11
|
Badilla C, Osborne TH, Cole A, Watson C, Djordjevic S, Santini JM. A new family of periplasmic-binding proteins that sense arsenic oxyanions. Sci Rep 2018; 8:6282. [PMID: 29674678 PMCID: PMC5908839 DOI: 10.1038/s41598-018-24591-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 04/06/2018] [Indexed: 01/21/2023] Open
Abstract
Arsenic contamination of drinking water affects more than 140 million people worldwide. While toxic to humans, inorganic forms of arsenic (arsenite and arsenate), can be used as energy sources for microbial respiration. AioX and its orthologues (ArxX and ArrX) represent the first members of a new sub-family of periplasmic-binding proteins that serve as the first component of a signal transduction system, that’s role is to positively regulate expression of arsenic metabolism enzymes. As determined by X-ray crystallography for AioX, arsenite binding only requires subtle conformational changes in protein structure, providing insights into protein-ligand interactions. The binding pocket of all orthologues is conserved but this alone is not sufficient for oxyanion selectivity, with proteins selectively binding either arsenite or arsenate. Phylogenetic evidence, clearly demonstrates that the regulatory proteins evolved together early in prokaryotic evolution and had a separate origin from the metabolic enzymes whose expression they regulate.
Collapse
Affiliation(s)
- Consuelo Badilla
- Institute of Structural & Molecular Biology, Division of Biosciences, University College London, London, WC1E 6BT, UK
| | - Thomas H Osborne
- Institute of Structural & Molecular Biology, Division of Biosciences, University College London, London, WC1E 6BT, UK
| | - Ambrose Cole
- Institute of Structural & Molecular Biology, Department of Biological Sciences, Birkbeck College, University of London, WC1E 7HX, London, UK
| | - Cameron Watson
- Institute of Structural & Molecular Biology, Division of Biosciences, University College London, London, WC1E 6BT, UK
| | - Snezana Djordjevic
- Institute of Structural & Molecular Biology, Division of Biosciences, University College London, London, WC1E 6BT, UK.
| | - Joanne M Santini
- Institute of Structural & Molecular Biology, Division of Biosciences, University College London, London, WC1E 6BT, UK.
| |
Collapse
|
12
|
Wasmund K, Mußmann M, Loy A. The life sulfuric: microbial ecology of sulfur cycling in marine sediments. ENVIRONMENTAL MICROBIOLOGY REPORTS 2017; 9:323-344. [PMID: 28419734 PMCID: PMC5573963 DOI: 10.1111/1758-2229.12538] [Citation(s) in RCA: 162] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Almost the entire seafloor is covered with sediments that can be more than 10 000 m thick and represent a vast microbial ecosystem that is a major component of Earth's element and energy cycles. Notably, a significant proportion of microbial life in marine sediments can exploit energy conserved during transformations of sulfur compounds among different redox states. Sulfur cycling, which is primarily driven by sulfate reduction, is tightly interwoven with other important element cycles (carbon, nitrogen, iron, manganese) and therefore has profound implications for both cellular- and ecosystem-level processes. Sulfur-transforming microorganisms have evolved diverse genetic, metabolic, and in some cases, peculiar phenotypic features to fill an array of ecological niches in marine sediments. Here, we review recent and selected findings on the microbial guilds that are involved in the transformation of different sulfur compounds in marine sediments and emphasise how these are interlinked and have a major influence on ecology and biogeochemistry in the seafloor. Extraordinary discoveries have increased our knowledge on microbial sulfur cycling, mainly in sulfate-rich surface sediments, yet many questions remain regarding how sulfur redox processes may sustain the deep-subsurface biosphere and the impact of organic sulfur compounds on the marine sulfur cycle.
Collapse
Affiliation(s)
- Kenneth Wasmund
- Department of Microbiology and Ecosystem Science, Division of Microbial Ecology, Research Network “Chemistry meets Microbiology”University of ViennaAlthanstrasse 14ViennaA‐1090Austria
- Austrian Polar Research InstituteViennaAustria
| | - Marc Mußmann
- Department of Microbiology and Ecosystem Science, Division of Microbial Ecology, Research Network “Chemistry meets Microbiology”University of ViennaAlthanstrasse 14ViennaA‐1090Austria
| | - Alexander Loy
- Department of Microbiology and Ecosystem Science, Division of Microbial Ecology, Research Network “Chemistry meets Microbiology”University of ViennaAlthanstrasse 14ViennaA‐1090Austria
- Austrian Polar Research InstituteViennaAustria
| |
Collapse
|