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Mandel CG, Sanchez SE, Monahan CC, Phuklia W, Omsland A. Metabolism and physiology of pathogenic bacterial obligate intracellular parasites. Front Cell Infect Microbiol 2024; 14:1284701. [PMID: 38585652 PMCID: PMC10995303 DOI: 10.3389/fcimb.2024.1284701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 02/01/2024] [Indexed: 04/09/2024] Open
Abstract
Bacterial obligate intracellular parasites (BOIPs) represent an exclusive group of bacterial pathogens that all depend on invasion of a eukaryotic host cell to reproduce. BOIPs are characterized by extensive adaptation to their respective replication niches, regardless of whether they replicate within the host cell cytoplasm or within specialized replication vacuoles. Genome reduction is also a hallmark of BOIPs that likely reflects streamlining of metabolic processes to reduce the need for de novo biosynthesis of energetically costly metabolic intermediates. Despite shared characteristics in lifestyle, BOIPs show considerable diversity in nutrient requirements, metabolic capabilities, and general physiology. In this review, we compare metabolic and physiological processes of prominent pathogenic BOIPs with special emphasis on carbon, energy, and amino acid metabolism. Recent advances are discussed in the context of historical views and opportunities for discovery.
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Affiliation(s)
- Cameron G. Mandel
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, WA, United States
| | - Savannah E. Sanchez
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, WA, United States
- Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine, Richmond, VA, United States
| | - Colleen C. Monahan
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, WA, United States
| | - Weerawat Phuklia
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, WA, United States
- Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit, Microbiology Laboratory, Mahosot Hospital, Vientiane, Lao People’s Democratic Republic
| | - Anders Omsland
- Paul G. Allen School for Global Health, College of Veterinary Medicine, Washington State University, Pullman, WA, United States
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Narra HP, Alsing J, Sahni A, Montini M, Zafar Y, Sahni SK. A Small Non-Coding RNA Mediates Transcript Stability and Expression of Cytochrome bd Ubiquinol Oxidase Subunit I in Rickettsia conorii. Int J Mol Sci 2023; 24:4008. [PMID: 36835430 PMCID: PMC9960880 DOI: 10.3390/ijms24044008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 02/08/2023] [Accepted: 02/11/2023] [Indexed: 02/19/2023] Open
Abstract
Small regulatory RNAs (sRNAs) are now widely recognized for their role in the post-transcriptional regulation of bacterial virulence and growth. We have previously demonstrated the biogenesis and differential expression of several sRNAs in Rickettsia conorii during interactions with the human host and arthropod vector, as well as the in vitro binding of Rickettsia conorii sRNA Rc_sR42 to bicistronic cytochrome bd ubiquinol oxidase subunits I and II (cydAB) mRNA. However, the mechanism of regulation and the effect of sRNA binding on the stability of the cydAB bicistronic transcript and the expression of the cydA and cydB genes are still unknown. In this study, we determined the expression dynamics of Rc_sR42 and its cognate target genes, cydA and cydB, in mouse lung and brain tissues during R. conorii infection in vivo and employed fluorescent and reporter assays to decode the role of sRNA in regulating cognate gene transcripts. Quantitative RT-PCR revealed significant changes in the expression of sRNA and its cognate target gene transcripts during R. conorii infection in vivo, and a greater abundance of these transcripts was observed in the lungs compared to brain tissue. Interestingly, while Rc_sR42 and cydA exhibited similar patterns of change in their expression, indicating the influence of sRNA on the mRNA target, the expression of cydB was independent of sRNA expression. Further, we constructed reporter plasmids of sRNA and cydAB bicistronic mRNA to decipher the role of sRNA on CydA and CydB expression. We observed increased expression of CydA in the presence of sRNA but detected no change in CydB expression in the presence or absence of sRNA. In sum, our results demonstrate that the binding of Rc_sR42 is required for the regulation of cydA but not cydB. Further studies on understanding the influence of this interaction on the mammalian host and tick vector during R. conorii infection are in progress.
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Affiliation(s)
- Hema P. Narra
- Department of Pathology, Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX 77555, USA
| | | | | | | | | | - Sanjeev K. Sahni
- Department of Pathology, Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX 77555, USA
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Krieger MC, Merritt J, Raghavan R. Genome-Wide Identification of Novel sRNAs in Streptococcus mutans. J Bacteriol 2022; 204:e0057721. [PMID: 35285723 PMCID: PMC9017351 DOI: 10.1128/jb.00577-21] [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: 11/16/2021] [Accepted: 02/10/2022] [Indexed: 11/20/2022] Open
Abstract
Streptococcus mutans is a major pathobiont involved in the development of dental caries. Its ability to utilize numerous sugars and to effectively respond to environmental stress promotes S. mutans proliferation in oral biofilms. Because of their quick action and low energetic cost, noncoding small RNAs (sRNAs) represent an ideal mode of gene regulation in stress response networks, yet their roles in oral pathogens have remained largely unexplored. We identified 15 novel sRNAs in S. mutans and show that they respond to four stress-inducing conditions commonly encountered by the pathogen in human mouth: sugar-phosphate stress, hydrogen peroxide exposure, high temperature, and low pH. To better understand the role of sRNAs in S. mutans, we further explored the function of the novel sRNA SmsR4. Our data demonstrate that SmsR4 regulates the enzyme IIA (EIIA) component of the sorbitol phosphotransferase system, which transports and phosphorylates the sugar alcohol sorbitol. The fine-tuning of EIIA availability by SmsR4 likely promotes S. mutans growth while using sorbitol as the main carbon source. Our work lays a foundation for understanding the role of sRNAs in regulating gene expression in stress response networks in S. mutans and highlights the importance of the underexplored phenomenon of posttranscriptional gene regulation in oral bacteria. IMPORTANCE Small RNAs (sRNAs) are important gene regulators in bacteria, but the identities and functions of sRNAs in Streptococcus mutans, the principal bacterium involved in the formation of dental caries, are unknown. In this study, we identified 15 putative sRNAs in S. mutans and show that they respond to four common stress-inducing conditions present in human mouth: sugar-phosphate stress, hydrogen peroxide exposure, high temperature, and low pH. We further show that the novel sRNA SmsR4 likely modulates sorbitol transport into the cell by regulating SMU_313 mRNA, which encodes the EIIA subunit of the sorbitol phosphotransferase system. Gaining a better understanding of sRNA-based gene regulation may provide new opportunities to develop specific inhibitors of S. mutans growth, thereby improving oral health.
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Affiliation(s)
- Madeline C. Krieger
- Department of Biology, Portland State University, Portland, Oregon, USA
- Department of Restorative Dentistry, School of Dentistry, Oregon Health and Science University, Portland, Oregon, USA
| | - Justin Merritt
- Department of Restorative Dentistry, School of Dentistry, Oregon Health and Science University, Portland, Oregon, USA
| | - Rahul Raghavan
- Department of Biology, Portland State University, Portland, Oregon, USA
- Department of Molecular Microbiology and Immunology, The University of Texas at San Antonio, San Antonio, Texas, USA
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6S-Like scr3559 RNA Affects Development and Antibiotic Production in Streptomyces coelicolor. Microorganisms 2021; 9:microorganisms9102004. [PMID: 34683325 PMCID: PMC8539372 DOI: 10.3390/microorganisms9102004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 09/15/2021] [Accepted: 09/16/2021] [Indexed: 11/17/2022] Open
Abstract
Regulatory RNAs control a number of physiological processes in bacterial cells. Here we report on a 6S-like RNA transcript (scr3559) that affects both development and antibiotic production in Streptomyces coelicolor. Its expression is enhanced during the transition to stationary phase. Strains that over-expressed the scr3559 gene region exhibited a shortened exponential growth phase in comparison with a control strain; accelerated aerial mycelium formation and spore maturation; alongside an elevated production of actinorhodin and undecylprodigiosin. These observations were supported by LC-MS analyses of other produced metabolites, including: germicidins, desferrioxamines, and coelimycin. A subsequent microarray differential analysis revealed increased expression of genes associated with the described morphological and physiological changes. Structural and functional similarities between the scr3559 transcript and 6S RNA, and its possible employment in regulating secondary metabolite production are discussed.
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Brenner AE, Muñoz-Leal S, Sachan M, Labruna MB, Raghavan R. Coxiella burnetii and Related Tick Endosymbionts Evolved from Pathogenic Ancestors. Genome Biol Evol 2021; 13:6278299. [PMID: 34009306 PMCID: PMC8290121 DOI: 10.1093/gbe/evab108] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/12/2021] [Indexed: 12/11/2022] Open
Abstract
Both symbiotic and pathogenic bacteria in the family Coxiellaceae cause morbidity and mortality in humans and animals. For instance, Coxiella-like endosymbionts (CLEs) improve the reproductive success of ticks—a major disease vector, while Coxiella burnetii causes human Q fever, and uncharacterized coxiellae infect both animals and humans. To better understand the evolution of pathogenesis and symbiosis in this group of intracellular bacteria, we sequenced the genome of a CLE present in the soft tick Ornithodoros amblus (CLEOA) and compared it to the genomes of other bacteria in the order Legionellales. Our analyses confirmed that CLEOA is more closely related to C. burnetii, the human pathogen, than to CLEs in hard ticks, and showed that most clades of CLEs contain both endosymbionts and pathogens, indicating that several CLE lineages have evolved independently from pathogenic Coxiella. We also determined that the last common ancestorof CLEOA and C. burnetii was equipped to infect macrophages and that even though horizontal gene transfer (HGT) contributed significantly to the evolution of C. burnetii, most acquisition events occurred primarily in ancestors predating the CLEOA–C. burnetii divergence. These discoveries clarify the evolution of C. burnetii, which previously was assumed to have emerged when an avirulent tick endosymbiont recently gained virulence factors via HGT. Finally, we identified several metabolic pathways, including heme biosynthesis, that are likely critical to the intracellular growth of the human pathogen but not the tick symbiont, and show that the use of heme analog is a promising approach to controlling C. burnetii infections.
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Affiliation(s)
- Amanda E Brenner
- Department of Biology and Center for Life in Extreme Environments, Portland State University, Portland, OR, USA
| | - Sebastián Muñoz-Leal
- Departamento de Patología y Medicina Preventiva, Facultad de Ciencias Veterinarias, Universidad de Concepción, Chillán, Ñuble, Chile
| | - Madhur Sachan
- Department of Biology and Center for Life in Extreme Environments, Portland State University, Portland, OR, USA
| | - Marcelo B Labruna
- Departamento de Medicina Veterinária Preventiva e Saúde Animal, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, Brazil
| | - Rahul Raghavan
- Department of Biology and Center for Life in Extreme Environments, Portland State University, Portland, OR, USA.,Department of Biology and South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, TX, USA
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Samuels DS, Lybecker MC, Yang XF, Ouyang Z, Bourret TJ, Boyle WK, Stevenson B, Drecktrah D, Caimano MJ. Gene Regulation and Transcriptomics. Curr Issues Mol Biol 2020; 42:223-266. [PMID: 33300497 DOI: 10.21775/cimb.042.223] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Borrelia (Borreliella) burgdorferi, along with closely related species, is the etiologic agent of Lyme disease. The spirochete subsists in an enzootic cycle that encompasses acquisition from a vertebrate host to a tick vector and transmission from a tick vector to a vertebrate host. To adapt to its environment and persist in each phase of its enzootic cycle, B. burgdorferi wields three systems to regulate the expression of genes: the RpoN-RpoS alternative sigma factor cascade, the Hk1/Rrp1 two-component system and its product c-di-GMP, and the stringent response mediated by RelBbu and DksA. These regulatory systems respond to enzootic phase-specific signals and are controlled or fine- tuned by transcription factors, including BosR and BadR, as well as small RNAs, including DsrABb and Bb6S RNA. In addition, several other DNA-binding and RNA-binding proteins have been identified, although their functions have not all been defined. Global changes in gene expression revealed by high-throughput transcriptomic studies have elucidated various regulons, albeit technical obstacles have mostly limited this experimental approach to cultivated spirochetes. Regardless, we know that the spirochete, which carries a relatively small genome, regulates the expression of a considerable number of genes required for the transitions between the tick vector and the vertebrate host as well as the adaptation to each.
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Affiliation(s)
- D Scott Samuels
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
| | - Meghan C Lybecker
- Department of Biology, University of Colorado, Colorado Springs, CO 80918, USA
| | - X Frank Yang
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Zhiming Ouyang
- Department of Molecular Medicine, University of South Florida, Tampa, FL 33612, USA
| | - Travis J Bourret
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, NE, 68105 USA
| | - William K Boyle
- Department of Medical Microbiology and Immunology, Creighton University, Omaha, NE, 68105 USA
| | - Brian Stevenson
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky School of Medicine, Lexington, KY 40536, USA
| | - Dan Drecktrah
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
| | - Melissa J Caimano
- Departments of Medicine, Pediatrics, and Molecular Biology and Biophysics, UConn Health, Farmington, CT, USA
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Narra HP, Sahni A, Alsing J, Schroeder CLC, Golovko G, Nia AM, Fofanov Y, Khanipov K, Sahni SK. Comparative transcriptomic analysis of Rickettsia conorii during in vitro infection of human and tick host cells. BMC Genomics 2020; 21:665. [PMID: 32977742 PMCID: PMC7519539 DOI: 10.1186/s12864-020-07077-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 09/17/2020] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Pathogenic Rickettsia species belonging to the spotted fever group are arthropod-borne, obligate intracellular bacteria which exhibit preferential tropism for host microvascular endothelium in the mammalian hosts, resulting in disease manifestations attributed primarily to endothelial damage or dysfunction. Although rickettsiae are known to undergo evolution through genomic reduction, the mechanisms by which these pathogens regulate their transcriptome to ensure survival in tick vectors and maintenance by transovarial/transstadial transmission, in contrast to their ability to cause debilitating infections in human hosts remain unknown. In this study, we compare the expression profiles of rickettsial sRNAome/transcriptome and determine the transcriptional start sites (TSSs) of R. conorii transcripts during in vitro infection of human and tick host cells. RESULTS We performed deep sequencing on total RNA from Amblyomma americanum AAE2 cells and human microvascular endothelial cells (HMECs) infected with R. conorii. Strand-specific RNA sequencing of R. conorii transcripts revealed the expression 32 small RNAs (Rc_sR's), which were preferentially expressed above the limit of detection during tick cell infection, and confirmed the expression of Rc_sR61, sR71, and sR74 by quantitative RT-PCR. Intriguingly, a total of 305 and 132 R. conorii coding genes were differentially upregulated (> 2-fold) in AAE2 cells and HMECs, respectively. Further, enrichment for primary transcripts by treatment with Terminator 5'-Phosphate-dependent Exonuclease resulted in the identification of 3903 and 2555 transcription start sites (TSSs), including 214 and 181 primary TSSs in R. conorii during the infection to tick and human host cells, respectively. Seventy-five coding genes exhibited different TSSs depending on the host environment. Finally, we also observed differential expression of 6S RNA during host-pathogen and vector-pathogen interactions in vitro, implicating an important role for this noncoding RNA in the regulation of rickettsial transcriptome depending on the supportive host niche. CONCLUSIONS In sum, the findings of this study authenticate the presence of novel Rc_sR's in R. conorii, reveal the first evidence for differential expression of coding transcripts and utilization of alternate transcriptional start sites depending on the host niche, and implicate a role for 6S RNA in the regulation of coding transcriptome during tripartite host-pathogen-vector interactions.
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Affiliation(s)
- Hema P Narra
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA.
| | - Abha Sahni
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Jessica Alsing
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Casey L C Schroeder
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - George Golovko
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Anna M Nia
- Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Yuriy Fofanov
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Kamil Khanipov
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Sanjeev K Sahni
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, 77555, USA.
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Diallo I, Provost P. RNA-Sequencing Analyses of Small Bacterial RNAs and their Emergence as Virulence Factors in Host-Pathogen Interactions. Int J Mol Sci 2020; 21:E1627. [PMID: 32120885 PMCID: PMC7084465 DOI: 10.3390/ijms21051627] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2020] [Revised: 02/22/2020] [Accepted: 02/25/2020] [Indexed: 12/14/2022] Open
Abstract
Proteins have long been considered to be the most prominent factors regulating so-called invasive genes involved in host-pathogen interactions. The possible role of small non-coding RNAs (sRNAs), either intracellular, secreted or packaged in outer membrane vesicles (OMVs), remained unclear until recently. The advent of high-throughput RNA-sequencing (RNA-seq) techniques has accelerated sRNA discovery. RNA-seq radically changed the paradigm on bacterial virulence and pathogenicity to the point that sRNAs are emerging as an important, distinct class of virulence factors in both gram-positive and gram-negative bacteria. The potential of OMVs, as protectors and carriers of these functional, gene regulatory sRNAs between cells, has also provided an additional layer of complexity to the dynamic host-pathogen relationship. Using a non-exhaustive approach and through examples, this review aims to discuss the involvement of sRNAs, either free or loaded in OMVs, in the mechanisms of virulence and pathogenicity during bacterial infection. We provide a brief overview of sRNA origin and importance, and describe the classical and more recent methods of identification that have enabled their discovery, with an emphasis on the theoretical lower limit of RNA sizes considered for RNA sequencing and bioinformatics analyses.
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Affiliation(s)
| | - Patrick Provost
- CHUQ Research Center/CHUL, Department of Microbiology-Infectious Disease and Immunity, Faculty of Medicine, Université Laval, Quebec, QC G1V 0A6, Canada;
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Drecktrah D, Hall LS, Brinkworth AJ, Comstock JR, Wassarman KM, Samuels DS. Characterization of 6S RNA in the Lyme disease spirochete. Mol Microbiol 2020; 113:399-417. [PMID: 31742773 PMCID: PMC7047579 DOI: 10.1111/mmi.14427] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 11/05/2019] [Accepted: 11/16/2019] [Indexed: 12/31/2022]
Abstract
6S RNA binds to RNA polymerase and regulates gene expression, contributing to bacterial adaptation to environmental stresses. In this study, we examined the role of 6S RNA in murine infectivity and tick persistence of the Lyme disease spirochete Borrelia (Borreliella) burgdorferi. B. burgdorferi 6S RNA (Bb6S RNA) binds to RNA polymerase, is expressed independent of growth phase or nutrient stress in culture, and is processed by RNase Y. We found that rny (bb0504), the gene encoding RNase Y, is essential for B. burgdorferi growth, while ssrS, the gene encoding 6S RNA, is not essential, indicating a broader role for RNase Y activity in the spirochete. Bb6S RNA regulates expression of the ospC and dbpA genes encoding outer surface protein C and decorin binding protein A, respectively, which are lipoproteins important for host infection. The highest levels of Bb6S RNA are found when the spirochete resides in unfed nymphs. ssrS mutants lacking Bb6S RNA were compromised for infectivity by needle inoculation, but injected mice seroconverted, indicating an ability to activate the adaptive immune response. ssrS mutants were successfully acquired by larval ticks and persisted through fed nymphs. Bb6S RNA is one of the first regulatory RNAs identified in B. burgdorferi that controls the expression of lipoproteins involved in host infectivity.
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Affiliation(s)
- Dan Drecktrah
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
| | - Laura S. Hall
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
| | | | | | - Karen M. Wassarman
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - D. Scott Samuels
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
- Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT 59812, USA
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A CsrA-Binding, trans-Acting sRNA of Coxiella burnetii Is Necessary for Optimal Intracellular Growth and Vacuole Formation during Early Infection of Host Cells. J Bacteriol 2019; 201:JB.00524-19. [PMID: 31451541 DOI: 10.1128/jb.00524-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 08/17/2019] [Indexed: 11/20/2022] Open
Abstract
Coxiella burnetii is an obligate intracellular gammaproteobacterium and zoonotic agent of Q fever. We previously identified 15 small noncoding RNAs (sRNAs) of C. burnetii One of them, CbsR12 (Coxiella burnetii small RNA 12), is highly transcribed during axenic growth and becomes more prominent during infection of cultured mammalian cells. Secondary structure predictions of CbsR12 revealed four putative CsrA-binding sites in stem loops with consensus AGGA/ANGGA motifs. We subsequently determined that CbsR12 binds to recombinant C. burnetii CsrA-2, but not CsrA-1, proteins in vitro Moreover, through a combination of in vitro and cell culture assays, we identified several in trans mRNA targets of CbsR12. Of these, we determined that CbsR12 binds and upregulates translation of carA transcripts coding for carbamoyl phosphate synthetase A, an enzyme that catalyzes the first step of pyrimidine biosynthesis. In addition, CbsR12 binds and downregulates translation of metK transcripts coding for S-adenosylmethionine synthetase, a component of the methionine cycle. Furthermore, we found that CbsR12 binds to and downregulates the quantity of cvpD transcripts, coding for a type IVB effector protein, in mammalian cell culture. Finally, we found that CbsR12 is necessary for expansion of Coxiella-containing vacuoles and affects growth rates in a dose-dependent manner in the early phase of infecting THP-1 cells. This is the first characterization of a trans-acting sRNA of C. burnetii and the first example of a bacterial sRNA that regulates both CarA and MetK synthesis. CbsR12 is one of only a few identified trans-acting sRNAs that interacts with CsrA.IMPORTANCE Regulation of metabolism and virulence in C. burnetii is not well understood. Here, we show that C. burnetii small RNA 12 (CbsR12) is highly transcribed in the metabolically active large-cell variant compared to the nonreplicative small-cell variant. We show that CbsR12 directly regulates several genes involved in metabolism, along with a type IV effector gene, in trans In addition, we demonstrate that CbsR12 binds to CsrA-2 in vitro and induces autoaggregation and biofilm formation when transcribed ectopically in Escherichia coli, consistent with other CsrA-sequestering sRNAs. These results implicate CbsR12 in the indirect regulation of a number of genes via CsrA-mediated regulatory activities. The results also support CbsR12 as a crucial regulatory component early on in a mammalian cell infection.
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Coxiella burnetii RpoS Regulates Genes Involved in Morphological Differentiation and Intracellular Growth. J Bacteriol 2019; 201:JB.00009-19. [PMID: 30745369 DOI: 10.1128/jb.00009-19] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 01/30/2019] [Indexed: 12/19/2022] Open
Abstract
Coxiella burnetii, the etiological agent of Q fever, undergoes a unique biphasic developmental cycle where bacteria transition from a replicating (exponential-phase) large cell variant (LCV) form to a nonreplicating (stationary-phase) small cell variant (SCV) form. The alternative sigma factor RpoS is an essential regulator of stress responses and stationary-phase physiology in several bacterial species, including Legionella pneumophila, which has a developmental cycle superficially similar to that of C. burnetii Here, we used a C. burnetii ΔrpoS mutant to define the role of RpoS in intracellular growth and SCV development. Growth yields following infection of Vero epithelial cells or THP-1 macrophage-like cells with the rpoS mutant in the SCV form, but not the LCV form, were significantly lower than that of wild-type bacteria. RNA sequencing and whole-cell mass spectrometry of the C. burnetii ΔrpoS mutant revealed that a substantial portion of the C. burnetii genome is regulated by RpoS during SCV development. Regulated genes include those involved in stress responses, arginine transport, peptidoglycan remodeling, and synthesis of the SCV-specific protein ScvA. Genes comprising the dot/icm locus, responsible for production of the Dot/Icm type 4B secretion system, were also dysregulated in the rpoS mutant. These data were corroborated with independent assays demonstrating that the C. burnetii ΔrpoS strain has increased sensitivity to hydrogen peroxide and carbenicillin and a thinner cell wall/outer membrane complex. Collectively, these results demonstrate that RpoS is an important regulator of genes involved in C. burnetii SCV development and intracellular growth.IMPORTANCE The Q fever bacterium Coxiella burnetii has spore-like environmental stability, a characteristic that contributes to its designation as a potential bioweapon. Stability is likely conferred by a highly resistant, small cell variant (SCV) stationary-phase form that arises during a biphasic developmental cycle. Here, we define the role of the alternative sigma factor RpoS in regulating genes associated with SCV development. Genes involved in stress responses, amino acid transport, cell wall remodeling, and type 4B effector secretion were dysregulated in the rpoS mutant. Cellular impairments included defects in intracellular growth, cell wall structure, and resistance to oxidants. These results support RpoS as a central regulator of the Coxiella developmental cycle and identify developmentally regulated genes involved in morphological differentiation.
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Wassarman KM. 6S RNA, a Global Regulator of Transcription. Microbiol Spectr 2018; 6:10.1128/microbiolspec.RWR-0019-2018. [PMID: 29916345 PMCID: PMC6013841 DOI: 10.1128/microbiolspec.rwr-0019-2018] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Indexed: 01/06/2023] Open
Abstract
6S RNA is a small RNA regulator of RNA polymerase (RNAP) that is present broadly throughout the bacterial kingdom. Initial functional studies in Escherichia coli revealed that 6S RNA forms a complex with RNAP resulting in regulation of transcription, and cells lacking 6S RNA have altered survival phenotypes. The last decade has focused on deepening the understanding of several aspects of 6S RNA activity, including (i) addressing questions of how broadly conserved 6S RNAs are in diverse organisms through continued identification and initial characterization of divergent 6S RNAs; (ii) the nature of the 6S RNA-RNAP interaction through examination of variant proteins and mutant RNAs, cross-linking approaches, and ultimately a cryo-electron microscopic structure; (iii) the physiological consequences of 6S RNA function through identification of the 6S RNA regulon and promoter features that determine 6S RNA sensitivity; and (iv) the mechanism and cellular impact of 6S RNA-directed synthesis of product RNAs (i.e., pRNA synthesis). Much has been learned about this unusual RNA, its mechanism of action, and how it is regulated; yet much still remains to be investigated, especially regarding potential differences in behavior of 6S RNAs in diverse bacteria.
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Affiliation(s)
- Karen M Wassarman
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53562
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Stead CM, Cockrell DC, Beare PA, Miller HE, Heinzen RA. A Coxiella burnetii phospholipase A homolog pldA is required for optimal growth in macrophages and developmental form lipid remodeling. BMC Microbiol 2018; 18:33. [PMID: 29661138 PMCID: PMC5902883 DOI: 10.1186/s12866-018-1181-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 04/09/2018] [Indexed: 04/05/2023] Open
Abstract
BACKGROUND Many gram-negative bacteria produce an outer membrane phospholipase A (PldA) that plays an important role in outer membrane function and is associated with virulence. RESULTS In the current study, we characterized a pldA mutant of Coxiella burnetii, an intracellular gram-negative pathogen and the agent of human Q fever. The C. burnetti pldA open reading frame directs synthesis of a protein with conserved PldA active site residues. A C. burnetii ΔpldA deletion mutant had a significant growth defect in THP-1 macrophages, but not axenic medium, that was rescued by complementation. Thin layer chromatography was employed to assess whether pldA plays a role in remodeling membrane lipids during C. burnetii morphological differentiation. Extracted lipids were analyzed from replicating, logarithmic phase large cell variants (LCVs), non-replicating, stationary phase small cell variants (SCVs), and a mixture of LCVs and SCVs. Similar to Escherichia coli, all three forms contained cardiolipin (CL), phosphatidylglycerol (PG) and phosphatidylethanolamine (PE). However, PE and PG were present in lower quantities in the SCV while three additional lipid species were present in higher quantities. Co-migration with standards tentatively identified two of the three SCV-enriched lipids as lyso-phosphatidylethanolamine, a breakdown product of PE, and free fatty acids, which are generally toxic to bacteria. Developmental form lipid modifications required the activity of PldA. CONCLUSIONS Collectively, these results indicate developmentally-regulated lipid synthesis by C. burnetii contributes to colonization of macrophages and may contribute to the environmental stability and the distinct biological properties of the SCV.
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Affiliation(s)
- Christopher M. Stead
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana USA
- Department of Chemistry, New Mexico Highlands University, Las Vegas, New Mexico USA
| | - Diane C. Cockrell
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana USA
| | - Paul A. Beare
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana USA
| | - Heather E. Miller
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana USA
| | - Robert A. Heinzen
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana USA
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Wachter S, Raghavan R, Wachter J, Minnick MF. Identification of novel MITEs (miniature inverted-repeat transposable elements) in Coxiella burnetii: implications for protein and small RNA evolution. BMC Genomics 2018; 19:247. [PMID: 29642859 PMCID: PMC5896051 DOI: 10.1186/s12864-018-4608-y] [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] [Received: 11/02/2017] [Accepted: 03/16/2018] [Indexed: 01/05/2023] Open
Abstract
Background Coxiella burnetii is a Gram-negative gammaproteobacterium and zoonotic agent of Q fever. C. burnetii’s genome contains an abundance of pseudogenes and numerous selfish genetic elements. MITEs (miniature inverted-repeat transposable elements) are non-autonomous transposons that occur in all domains of life and are thought to be insertion sequences (ISs) that have lost their transposase function. Like most transposable elements (TEs), MITEs are thought to play an active role in evolution by altering gene function and expression through insertion and deletion activities. However, information regarding bacterial MITEs is limited. Results We describe two MITE families discovered during research on small non-coding RNAs (sRNAs) of C. burnetii. Two sRNAs, Cbsr3 and Cbsr13, were found to originate from a novel MITE family, termed QMITE1. Another sRNA, CbsR16, was found to originate from a separate and novel MITE family, termed QMITE2. Members of each family occur ~ 50 times within the strains evaluated. QMITE1 is a typical MITE of 300-400 bp with short (2-3 nt) direct repeats (DRs) of variable sequence and is often found overlapping annotated open reading frames (ORFs). Additionally, QMITE1 elements possess sigma-70 promoters and are transcriptionally active at several loci, potentially influencing expression of nearby genes. QMITE2 is smaller (150-190 bps), but has longer (7-11 nt) DRs of variable sequences and is mainly found in the 3′ untranslated region of annotated ORFs and intergenic regions. QMITE2 contains a GTAG repetitive extragenic palindrome (REP) that serves as a target for IS1111 TE insertion. Both QMITE1 and QMITE2 display inter-strain linkage and sequence conservation, suggesting that they are adaptive and existed before divergence of C. burnetii strains. Conclusions We have discovered two novel MITE families of C. burnetii. Our finding that MITEs serve as a source for sRNAs is novel. QMITE2 has a unique structure and occurs in large or small versions with unique DRs that display linkage and sequence conservation between strains, allowing for tracking of genomic rearrangements. QMITE1 and QMITE2 copies are hypothesized to influence expression of neighboring genes involved in DNA repair and virulence through transcriptional interference and ribonuclease processing. Electronic supplementary material The online version of this article (10.1186/s12864-018-4608-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Shaun Wachter
- Program in Cellular, Molecular and Microbial Biology, Division of Biological Sciences, University of Montana, Missoula, MT, USA
| | - Rahul Raghavan
- Biology Department and Center for Life in Extreme Environments, Portland State University, Portland, OR, USA
| | - Jenny Wachter
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South 4th St, Hamilton, MT, USA
| | - Michael F Minnick
- Program in Cellular, Molecular and Microbial Biology, Division of Biological Sciences, University of Montana, Missoula, MT, USA.
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Ren J, Sang Y, Qin R, Cui Z, Yao YF. 6S RNA is involved in acid resistance and invasion of epithelial cells in Salmonella enterica serovar Typhimurium. Future Microbiol 2017; 12:1045-1057. [PMID: 28796533 DOI: 10.2217/fmb-2017-0055] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
AIM Acid is an important environmental condition encountered frequently by Salmonella enterica serovar Typhimurium during its pathogenesis, but the role of small-noncoding RNAs (sRNAs) in response to acid stress is poorly understood. METHODS We used RNA sequencing to explore acid-responsive sRNAs in S. Typhimurium. RESULTS It identified that 6S RNA encoded by the ssrS was significantly upregulated at pH 3.0. The 6S RNA knockout strain showed a reduced ability to survive at pH 3.0. Additionally, genes in Salmonella pathogenicity island-1 were downregulated in the 6S RNA knockout strain. The loss of 6S RNA significantly reduced S. Typhimurium invasion ability in HeLa cells and virulence in a mouse model. CONCLUSION These findings demonstrate that 6S RNA plays an important role in S. Typhimurium survival under extremely acid conditions and for invasion of epithelial cells.
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Affiliation(s)
- Jie Ren
- Department of Microbiology & Immunology, Laboratory of Bacterial Pathogenesis, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Yu Sang
- Department of Microbiology & Immunology, Laboratory of Bacterial Pathogenesis, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Ran Qin
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, Department of Microbiology, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Zhongli Cui
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, Department of Microbiology, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Yu-Feng Yao
- Department of Microbiology & Immunology, Laboratory of Bacterial Pathogenesis, Institutes of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China.,Department of Laboratory Medicine, Shanghai East Hospital, Tongji University School of Medicine, Shanghai 200120, China
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Abstract
Bacterial pathogens must endure or adapt to different environments and stresses during transmission and infection. Posttranscriptional gene expression control by regulatory RNAs, such as small RNAs and riboswitches, is now considered central to adaptation in many bacteria, including pathogens. The study of RNA-based regulation (riboregulation) in pathogenic species has provided novel insight into how these bacteria regulate virulence gene expression. It has also uncovered diverse mechanisms by which bacterial small RNAs, in general, globally control gene expression. Riboregulators as well as their targets may also prove to be alternative targets or provide new strategies for antimicrobials. In this article, we present an overview of the general mechanisms that bacteria use to regulate with RNA, focusing on examples from pathogens. In addition, we also briefly review how deep sequencing approaches have aided in opening new perspectives in small RNA identification and the study of their functions. Finally, we discuss examples of riboregulators in two model pathogens that control virulence factor expression or survival-associated phenotypes, such as stress tolerance, biofilm formation, or cell-cell communication, to illustrate how riboregulation factors into regulatory networks in bacterial pathogens.
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Moses AS, Millar JA, Bonazzi M, Beare PA, Raghavan R. Horizontally Acquired Biosynthesis Genes Boost Coxiella burnetii's Physiology. Front Cell Infect Microbiol 2017; 7:174. [PMID: 28540258 PMCID: PMC5423948 DOI: 10.3389/fcimb.2017.00174] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 04/21/2017] [Indexed: 01/21/2023] Open
Abstract
Coxiella burnetii, the etiologic agent of acute Q fever and chronic endocarditis, has a unique biphasic life cycle, which includes a metabolically active intracellular form that occupies a large lysosome-derived acidic vacuole. C. burnetii is the only bacterium known to thrive within such an hostile intracellular niche, and this ability is fundamental to its pathogenicity; however, very little is known about genes that facilitate Coxiella's intracellular growth. Recent studies indicate that C. burnetii evolved from a tick-associated ancestor and that the metabolic capabilities of C. burnetii are different from that of Coxiella-like bacteria found in ticks. Horizontally acquired genes that allow C. burnetii to infect and grow within mammalian cells likely facilitated the host shift; however, because of its obligate intracellular replication, C. burnetii would have lost most genes that have been rendered redundant due to the availability of metabolites within the host cell. Based on these observations, we reasoned that horizontally derived biosynthetic genes that have been retained in the reduced genome of C. burnetii are ideal candidates to begin to uncover its intracellular metabolic requirements. Our analyses identified a large number of putative foreign-origin genes in C. burnetii, including tRNAGlu2 that is potentially required for heme biosynthesis, and genes involved in the production of lipopolysaccharide—a virulence factor, and of critical metabolites such as fatty acids and biotin. In comparison to wild-type C. burnetii, a strain that lacks tRNAGlu2 exhibited reduced growth, indicating its importance to Coxiella's physiology. Additionally, by using chemical agents that block heme and biotin biosyntheses, we show that these pathways are promising targets for the development of new anti-Coxiella therapies.
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Affiliation(s)
- Abraham S Moses
- Department of Biology and Center for Life in Extreme Environments, Portland State UniversityPortland, OR, USA
| | - Jess A Millar
- Department of Biology and Center for Life in Extreme Environments, Portland State UniversityPortland, OR, USA
| | - Matteo Bonazzi
- Centre National de la Recherche Scientifique, Formation de Recherche en Évolution 3689, Centre d'Études d'Agents Pathogènes et Biotechnologies Pour la Santé, Université MontpellierMontpellier, France
| | - Paul A Beare
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institutes of HealthHamilton, MT, USA
| | - Rahul Raghavan
- Department of Biology and Center for Life in Extreme Environments, Portland State UniversityPortland, OR, USA
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Sun Y, Zhang J, Qin L, Yan C, Zhang X, Liu D. Identification and validation of sRNAs in Edwardsiella tarda S08. PLoS One 2017; 12:e0172783. [PMID: 28267754 PMCID: PMC5340389 DOI: 10.1371/journal.pone.0172783] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2016] [Accepted: 02/09/2017] [Indexed: 11/29/2022] Open
Abstract
Bacterial small non-coding RNAs (sRNAs) are known as novel regulators involved in virulence, stress responsibility, and so on. Recently, a lot of new researches have highlighted the critical roles of sRNAs in fine-tune gene regulation in both prokaryotes and eukaryotes. Edwardsiella tarda (E. tarda) is a gram-negative, intracellular pathogen that causes edwardsiellosis in fish. Thus far, no sRNA has been reported in E. tarda. The present study represents the first attempt to identify sRNAs in E. tarda S08. Ten sRNAs were validated by RNA sequencing and quantitative PCR (qPCR). ET_sRNA_1 and ET_sRNA_2 were homolous to tmRNA and GcvB, respectively. However, the other candidate sRNAs have not been reported till now. The cellular abundance of 10 validated sRNA was detected by qPCR at different growth phases to monitor their biosynthesis. Nine candidate sRNAs were expressed in the late-stage of exponential growth and stationary stages of growth (36~60 h). And the expression of the nine sRNAs was growth phase-dependent. But ET_sRNA_10 was almost expressed all the time and reached the highest peak at 48 h. Their targets were predicted by TargetRNA2 and each sRNA target contains some genes that directly or indirectly relate to virulence. These results preliminary showed that sRNAs probably play a regulatory role of virulence in E. tarda.
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Affiliation(s)
- Yuying Sun
- College of Marine Life and Fisheries, Huaihai Institute of Technology, Lianyungang, China
- Jiangsu Marine Resources Development Research Institute, Lianyungang, China
- Co-Innovation Center of Jiangsu Marine Bio-industry Technology, Huaihai Institute of Technology, Lianyungang, China
| | - Jiquan Zhang
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- * E-mail:
| | - Lei Qin
- College of Marine Life and Fisheries, Huaihai Institute of Technology, Lianyungang, China
| | - Cui Yan
- College of Marine Life and Fisheries, Huaihai Institute of Technology, Lianyungang, China
| | - Xiaojun Zhang
- College of Marine Life and Fisheries, Huaihai Institute of Technology, Lianyungang, China
| | - Dandan Liu
- College of Marine Life and Fisheries, Huaihai Institute of Technology, Lianyungang, China
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Analysis of Small RNAs in Streptococcus mutans under Acid Stress-A New Insight for Caries Research. Int J Mol Sci 2016; 17:ijms17091529. [PMID: 27649155 PMCID: PMC5037804 DOI: 10.3390/ijms17091529] [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: 07/14/2016] [Revised: 09/06/2016] [Accepted: 09/07/2016] [Indexed: 11/23/2022] Open
Abstract
Streptococcus mutans (S. mutans) is the major clinical pathogen responsible for dental caries. Its acid tolerance has been identified as a significant virulence factor for its survival and cariogenicity in acidic conditions. Small RNAs (sRNAs) are recognized as key regulators of virulence and stress adaptation. Here, we constructed three libraries of sRNAs with small size exposed to acidic conditions for the first time, followed by verification using qRT-PCR. The levels of two sRNAs and target genes predicted to be bioinformatically related to acid tolerance were further evaluated under different acid stress conditions (pH 7.5, 6.5, 5.5, and 4.5) at three time points (0.5, 1, and 2 h). Meanwhile, bacterial growth characteristics and vitality were assessed. We obtained 1879 sRNAs with read counts of at least 100. One hundred and ten sRNAs were perfectly mapped to reported msRNAs in S. mutans. Ten out of 18 sRNAs were validated by qRT-PCR. The survival of bacteria declined as the acid was increased from pH 7.5 to 4.5 at each time point. The bacteria can proliferate under each pH except pH 4.5 with time. The levels of sRNAs gradually decreased from pH 7.5 to 5.5, and slightly increased in pH 4.5; however, the expression levels of target mRNAs were up-regulated in acidic conditions than in pH 7.5. These results indicate that some sRNAs are specially induced at acid stress conditions, involving acid adaptation, and provide a new insight into exploring the complex acid tolerance for S. mutans.
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Warrier I, Walter MC, Frangoulidis D, Raghavan R, Hicks LD, Minnick MF. The Intervening Sequence of Coxiella burnetii: Characterization and Evolution. Front Cell Infect Microbiol 2016; 6:83. [PMID: 27595093 PMCID: PMC4990558 DOI: 10.3389/fcimb.2016.00083] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 08/02/2016] [Indexed: 11/23/2022] Open
Abstract
The intervening sequence (IVS) of Coxiella burnetii, the agent of Q fever, is a 428-nt selfish genetic element located in helix 45 of the precursor 23S rRNA. The IVS element, in turn, contains an ORF that encodes a hypothetical ribosomal S23 protein (S23p). Although S23p can be synthesized in vitro in the presence of an engineered E. coli promoter and ribosome binding site, results suggest that the protein is not synthesized in vivo. In spite of a high degree of IVS conservation among different strains of C. burnetii, the region immediately upstream of the S23p start codon is prone to change, and the S23p-encoding ORF is evidently undergoing reductive evolution. We determined that IVS excision from 23S rRNA was mediated by RNase III, and IVS RNA was rapidly degraded, thereafter. Levels of the resulting 23S rRNA fragments that flank the IVS, F1 (~1.2 kb) and F2 (~1.7 kb), were quantified over C. burnetii's logarithmic growth phase (1–5 d). Results showed that 23S F1 quantities were consistently higher than those of F2 and 16S rRNA. The disparity between levels of the two 23S rRNA fragments following excision of IVS is an interesting phenomenon of unknown significance. Based upon phylogenetic analyses, IVS was acquired through horizontal transfer after C. burnetii's divergence from an ancestral bacterium and has been subsequently maintained by vertical transfer. The widespread occurrence, maintenance and conservation of the IVS in C. burnetii imply that it plays an adaptive role or has a neutral effect on fitness.
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Affiliation(s)
- Indu Warrier
- Program in Cellular, Molecular and Microbial Biology, Division of Biological Sciences, University of Montana Missoula, MT, USA
| | | | | | - Rahul Raghavan
- Department of Biology and Center for Life in Extreme Environments, Portland State University Portland, OR, USA
| | - Linda D Hicks
- Program in Cellular, Molecular and Microbial Biology, Division of Biological Sciences, University of Montana Missoula, MT, USA
| | - Michael F Minnick
- Program in Cellular, Molecular and Microbial Biology, Division of Biological Sciences, University of Montana Missoula, MT, USA
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Schroeder CLC, Narra HP, Sahni A, Rojas M, Khanipov K, Patel J, Shah R, Fofanov Y, Sahni SK. Identification and Characterization of Novel Small RNAs in Rickettsia prowazekii. Front Microbiol 2016; 7:859. [PMID: 27375581 PMCID: PMC4896933 DOI: 10.3389/fmicb.2016.00859] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 05/23/2016] [Indexed: 12/12/2022] Open
Abstract
Emerging evidence implicates a critically important role for bacterial small RNAs (sRNAs) as post-transcriptional regulators of physiology, metabolism, stress/adaptive responses, and virulence, but the roles of sRNAs in pathogenic Rickettsia species remain poorly understood. Here, we report on the identification of both novel and well-known bacterial sRNAs in Rickettsia prowazekii, known to cause epidemic typhus in humans. RNA sequencing of human microvascular endothelial cells (HMECs), the preferred targets during human rickettsioses, infected with R. prowazekii revealed the presence of 35 trans-acting and 23 cis-acting sRNAs, respectively. Of these, expression of two trans-acting (Rp_sR17 and Rp_sR60) and one cis-acting (Rp_sR47) novel sRNAs and four well-characterized bacterial sRNAs (RNaseP_bact_a, α-tmRNA, 4.5S RNA, 6S RNA) was further confirmed by Northern blot or RT-PCR analyses. The transcriptional start sites of five novel rickettsial sRNAs and 6S RNA were next determined using 5' RLM-RACE yielding evidence for their independent biogenesis in R. prowazekii. Finally, computational approaches were employed to determine the secondary structures and potential mRNA targets of novel sRNAs. Together, these results establish the presence and expression of sRNAs in R. prowazekii during host cell infection and suggest potential functional roles for these important post-transcriptional regulators in rickettsial biology and pathogenesis.
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Affiliation(s)
| | - Hema P. Narra
- Department of Pathology, University of Texas Medical BranchGalveston, TX, USA
| | - Abha Sahni
- Department of Pathology, University of Texas Medical BranchGalveston, TX, USA
| | - Mark Rojas
- Department of Pharmacology, University of Texas Medical BranchGalveston, TX, USA
| | - Kamil Khanipov
- Department of Pharmacology, University of Texas Medical BranchGalveston, TX, USA
| | - Jignesh Patel
- Department of Pathology, University of Texas Medical BranchGalveston, TX, USA
| | - Riya Shah
- Department of Neuroscience, University of Texas at DallasDallas, TX, USA
| | - Yuriy Fofanov
- Department of Pharmacology, University of Texas Medical BranchGalveston, TX, USA
| | - Sanjeev K. Sahni
- Department of Pathology, University of Texas Medical BranchGalveston, TX, USA
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Raghavan R. A repeat motif on a Coxiella effector protein facilitates apoptosis inhibition. Virulence 2016; 7:369-71. [PMID: 26949987 DOI: 10.1080/21505594.2016.1156834] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Affiliation(s)
- Rahul Raghavan
- a Department of Biology and Center for Life in Extreme Environments , Portland State University , Portland , OR , USA
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Sandoz KM, Popham DL, Beare PA, Sturdevant DE, Hansen B, Nair V, Heinzen RA. Transcriptional Profiling of Coxiella burnetii Reveals Extensive Cell Wall Remodeling in the Small Cell Variant Developmental Form. PLoS One 2016; 11:e0149957. [PMID: 26909555 PMCID: PMC4766238 DOI: 10.1371/journal.pone.0149957] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 02/05/2016] [Indexed: 11/19/2022] Open
Abstract
A hallmark of Coxiella burnetii, the bacterial cause of human Q fever, is a biphasic developmental cycle that generates biologically, ultrastructurally, and compositionally distinct large cell variant (LCV) and small cell variant (SCV) forms. LCVs are replicating, exponential phase forms while SCVs are non-replicating, stationary phase forms. The SCV has several properties, such as a condensed nucleoid and an unusual cell envelope, suspected of conferring enhanced environmental stability. To identify genetic determinants of the LCV to SCV transition, we profiled the C. burnetii transcriptome at 3 (early LCV), 5 (late LCV), 7 (intermediate forms), 14 (early SCV), and 21 days (late SCV) post-infection of Vero epithelial cells. Relative to early LCV, genes downregulated in the SCV were primarily involved in intermediary metabolism. Upregulated SCV genes included those involved in oxidative stress responses, arginine acquisition, and cell wall remodeling. A striking transcriptional signature of the SCV was induction (>7-fold) of five genes encoding predicted L,D transpeptidases that catalyze nonclassical 3-3 peptide cross-links in peptidoglycan (PG), a modification that can influence several biological traits in bacteria. Accordingly, of cross-links identified, muropeptide analysis showed PG of SCV with 46% 3-3 cross-links as opposed to 16% 3-3 cross-links for LCV. Moreover, electron microscopy revealed SCV with an unusually dense cell wall/outer membrane complex as compared to LCV with its clearly distinguishable periplasm and inner and outer membranes. Collectively, these results indicate the SCV produces a unique transcriptome with a major component directed towards remodeling a PG layer that likely contributes to Coxiella's environmental resistance.
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Affiliation(s)
- Kelsi M. Sandoz
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - David L. Popham
- Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
| | - Paul A. Beare
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Daniel E. Sturdevant
- Genomics Unit, Research Technologies Branch, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Bryan Hansen
- Electron Microscopy Unit, Research Technologies Branch, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Vinod Nair
- Electron Microscopy Unit, Research Technologies Branch, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Robert A. Heinzen
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
- * E-mail:
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Schroeder CLC, Narra HP, Rojas M, Sahni A, Patel J, Khanipov K, Wood TG, Fofanov Y, Sahni SK. Bacterial small RNAs in the Genus Rickettsia. BMC Genomics 2015; 16:1075. [PMID: 26679185 PMCID: PMC4683814 DOI: 10.1186/s12864-015-2293-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 12/14/2015] [Indexed: 01/02/2023] Open
Abstract
Background Rickettsia species are obligate intracellular Gram-negative pathogenic bacteria and the etiologic agents of diseases such as Rocky Mountain spotted fever (RMSF), Mediterranean spotted fever, epidemic typhus, and murine typhus. Genome sequencing revealed that R. prowazekii has ~25 % non-coding DNA, the majority of which is thought to be either “junk DNA” or pseudogenes resulting from genomic reduction. These characteristics also define other Rickettsia genomes. Bacterial small RNAs, whose biogenesis is predominantly attributed to either the intergenic regions (trans-acting) or to the antisense strand of an open reading frame (cis-acting), are now appreciated to be among the most important post-transcriptional regulators of bacterial virulence and growth. We hypothesize that intergenic regions in rickettsial species encode for small, non-coding RNAs (sRNAs) involved in the regulation of its transcriptome, leading to altered virulence and adaptation depending on the host niche. Results We employed a combination of bioinformatics and in vitro approaches to explore the presence of sRNAs in a number of species within Genus Rickettsia. Using the sRNA Identification Protocol using High-throughput Technology (SIPHT) web interface, we predicted over 1,700 small RNAs present in the intergenic regions of 16 different strains representing 13 rickettsial species. We further characterized novel sRNAs from typhus (R. prowazekii and R. typhi) and spotted fever (R. rickettsii and R. conorii) groups for their promoters and Rho-independent terminators using Bacterial Promoter Prediction Program (BPROM) and TransTermHP prediction algorithms, respectively. Strong σ70 promoters were predicted upstream of all novel small RNAs, indicating the potential for transcriptional activity. Next, we infected human microvascular endothelial cells (HMECs) with R. prowazekii for 3 h and 24 h and performed Next Generation Sequencing to experimentally validate the expression of 26 sRNA candidates predicted in R. prowazekii. Reverse transcriptase PCR was also used to further verify the expression of six putative novel sRNA candidates in R. prowazekii. Conclusions Our results yield clear evidence for the expression of novel R. prowazekii sRNA candidates during infection of HMECs. This is the first description of novel small RNAs for a highly pathogenic species of Rickettsia, which should lead to new insights into rickettsial virulence and adaptation mechanisms. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-2293-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Casey L C Schroeder
- Department of Pathology, the University of Texas Medical Branch, 301 University Blvd, Galveston, TX, 77555, USA.
| | - Hema P Narra
- Department of Pathology, the University of Texas Medical Branch, 301 University Blvd, Galveston, TX, 77555, USA.
| | - Mark Rojas
- Department of Pharmacology, the University of Texas Medical Branch, 301 University Blvd, Galveston, TX, 77555, USA.
| | - Abha Sahni
- Department of Pathology, the University of Texas Medical Branch, 301 University Blvd, Galveston, TX, 77555, USA.
| | - Jignesh Patel
- Department of Pathology, the University of Texas Medical Branch, 301 University Blvd, Galveston, TX, 77555, USA.
| | - Kamil Khanipov
- Department of Pharmacology, the University of Texas Medical Branch, 301 University Blvd, Galveston, TX, 77555, USA.
| | - Thomas G Wood
- Department of Biochemistry and Molecular Biology, the University of Texas Medical Branch, 301 University Blvd, Galveston, TX, 77555, USA.
| | - Yuriy Fofanov
- Department of Pharmacology, the University of Texas Medical Branch, 301 University Blvd, Galveston, TX, 77555, USA.
| | - Sanjeev K Sahni
- Department of Pathology, the University of Texas Medical Branch, 301 University Blvd, Galveston, TX, 77555, USA.
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25
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Oliva G, Sahr T, Buchrieser C. Small RNAs, 5′ UTR elements and RNA-binding proteins in intracellular bacteria: impact on metabolism and virulence. FEMS Microbiol Rev 2015; 39:331-349. [DOI: 10.1093/femsre/fuv022] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023] Open
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26
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Ortega AD, Quereda JJ, Pucciarelli MG, García-del Portillo F. Non-coding RNA regulation in pathogenic bacteria located inside eukaryotic cells. Front Cell Infect Microbiol 2014; 4:162. [PMID: 25429360 PMCID: PMC4228915 DOI: 10.3389/fcimb.2014.00162] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 10/20/2014] [Indexed: 01/06/2023] Open
Abstract
Intracellular bacterial pathogens have evolved distinct lifestyles inside eukaryotic cells. Some pathogens coexist with the infected cell in an obligate intracellular state, whereas others transit between the extracellular and intracellular environment. Adaptation to these intracellular lifestyles is regulated in both space and time. Non-coding small RNAs (sRNAs) are post-transcriptional regulatory molecules that fine-tune important processes in bacterial physiology including cell envelope architecture, intermediate metabolism, bacterial communication, biofilm formation, and virulence. Recent studies have shown production of defined sRNA species by intracellular bacteria located inside eukaryotic cells. The molecules targeted by these sRNAs and their expression dynamics along the intracellular infection cycle remain, however, poorly characterized. Technical difficulties linked to the isolation of “intact” intracellular bacteria from infected host cells might explain why sRNA regulation in these specialized pathogens is still a largely unexplored field. Transition from the extracellular to the intracellular lifestyle provides an ideal scenario in which regulatory sRNAs are intended to participate; so much work must be done in this direction. This review focuses on sRNAs expressed by intracellular bacterial pathogens during the infection of eukaryotic cells, strategies used with these pathogens to identify sRNAs required for virulence, and the experimental technical challenges associated to this type of studies. We also discuss varied techniques for their potential application to study RNA regulation in intracellular bacterial infections.
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Affiliation(s)
- Alvaro D Ortega
- Centro Nacional de Biotecnología - Consejo Superior de Investigaciones Científicas (CNB-CSIC) Madrid, Spain
| | - Juan J Quereda
- Centro Nacional de Biotecnología - Consejo Superior de Investigaciones Científicas (CNB-CSIC) Madrid, Spain
| | - M Graciela Pucciarelli
- Centro Nacional de Biotecnología - Consejo Superior de Investigaciones Científicas (CNB-CSIC) Madrid, Spain ; Departamento de Biología Molecular, Universidad Autónoma de Madrid, Centro de Biología Molecular 'Severo Ochoa' (CBMSO-CSIC) Madrid, Spain
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