1
|
Bacterial Membrane Vesicles as a Novel Strategy for Extrusion of Antimicrobial Bismuth Drug in Helicobacter pylori. mBio 2022; 13:e0163322. [PMID: 36154274 PMCID: PMC9601102 DOI: 10.1128/mbio.01633-22] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Bacterial antibiotic resistance is a major threat to human health. A combination of antibiotics with metals is among the proposed alternative treatments. Only one such combination is successfully used in clinics; it associates antibiotics with the metal bismuth to treat infections by Helicobacter pylori. This bacterial pathogen colonizes the human stomach and is associated with gastric cancer, killing 800,000 individuals yearly. The effect of bismuth in H. pylori treatment is not well understood in particular for sublethal doses such as those measured in the plasma of treated patients. We addressed this question and observed that bismuth induces the formation of homogeneously sized membrane vesicles (MVs) with unique protein cargo content enriched in bismuth-binding proteins, as shown by quantitative proteomics. Purified MVs of bismuth-exposed bacteria were strongly enriched in bismuth as measured by inductively coupled plasma optical emission spectrometry (ICP-OES), unlike bacterial cells from which they originate. Thus, our results revealed a novel function of MVs in bismuth detoxification, where secreted MVs act as tool to discard bismuth from the bacteria. Bismuth also induces the formation of intracellular polyphosphate granules that are associated with changes in nucleoid structure. Nucleoid compaction in response to bismuth was established by immunogold electron microscopy and refined by the first chromosome conformation capture (Hi-C) analysis of H. pylori. Our results reveal that even low doses of bismuth induce profound changes in H. pylori physiology and highlight a novel defense mechanism that involves MV-mediated bismuth extrusion from the bacteria and a probable local DNA protective response where polyphosphate granules are associated with nucleoid compaction.
Collapse
|
2
|
Lima S, Matinha-Cardoso J, Giner-Lamia J, Couto N, Pacheco CC, Florencio FJ, Wright PC, Tamagnini P, Oliveira P. Extracellular vesicles as an alternative copper-secretion mechanism in bacteria. JOURNAL OF HAZARDOUS MATERIALS 2022; 431:128594. [PMID: 35259694 DOI: 10.1016/j.jhazmat.2022.128594] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 02/18/2022] [Accepted: 02/24/2022] [Indexed: 06/14/2023]
Abstract
Metal homeostasis is fundamental for optimal performance of cell metabolic pathways. Over the course of evolution, several systems emerged to warrant an intracellular metal equilibrium. When exposed to growth-challenging copper concentrations, Gram-negative bacteria quickly activate copper-detoxification mechanisms, dependent on transmembrane-protein complexes and metallochaperones that mediate metal efflux. Here, we show that vesiculation is also a common bacterial response mechanism to high copper concentrations, and that extracellular vesicles (EVs) play a role in transporting copper. We present evidence that bacteria from different ecological niches release copious amounts of EVs when exposed to copper. Along with the activation of the classical detoxification systems, we demonstrate that copper-stressed cells of the cyanobacterium Synechocystis sp. PCC6803 release EVs loaded with the copper-binding metallochaperone CopM. Under standard growth conditions, CopM-loaded EVs could also be isolated from a Synechocystis strain lacking a functional TolC-protein, which we characterize here as exhibiting a copper-sensitive phenotype. Analyses of Synechocystis tolC-mutant's EVs isolated from cells cultivated under standard conditions indicated the presence of copper therein, in significantly higher levels as compared to those from the wild-type. Altogether, these results suggest that release of EVs in bacteria represent a novel copper-secretion mechanism, shedding light into alternative mechanisms of bacterial metal resistance.
Collapse
Affiliation(s)
- Steeve Lima
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135 Porto, Portugal; IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135 Porto, Portugal; MCbiology Doctoral Program, ICBAS - Instituto de Ciências Biomédicas Abel Salazar, Universidade do Porto, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal
| | - Jorge Matinha-Cardoso
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135 Porto, Portugal; IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135 Porto, Portugal
| | - Joaquín Giner-Lamia
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC C, Américo Vespucio, 49, 41092 Sevilla, Spain; Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM), Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Parque Científico y Tecnológico, UPM Campus de Montegancedo, Ctra, M-40, km 38, 28223 Madrid, Spain; Departamento de Biotecnología-Biología Vegetal, Escuela Técnica Superior de Ingeniería Agronómica, Alimentaria y de Biosistemas, Universidad Politécnica de Madrid (UPM), Campus, Av. Puerta de Hierro, nº 2, 4, 28040 Madrid, Spain
| | - Narciso Couto
- Department of Chemical and Biological Engineering, University of Sheffield, Mappin St, Sheffield City Centre, Sheffield S1 4NL, United Kingdom
| | - Catarina C Pacheco
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135 Porto, Portugal; IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135 Porto, Portugal
| | - Francisco J Florencio
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC C, Américo Vespucio, 49, 41092 Sevilla, Spain; Departamento de Bioquímica Vegetal y Biología Molecular, Facultad de Biología, Universidad de Sevilla, Avenida Reina Mercedes s/n, 41012 Sevilla, Spain
| | - Phillip C Wright
- University of Southampton, Office of the President and Vice Chancellor B37, University Rd, Highfield, Southampton SO17 1BJ, United Kingdom
| | - Paula Tamagnini
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135 Porto, Portugal; IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135 Porto, Portugal; Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto, Portugal
| | - Paulo Oliveira
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135 Porto, Portugal; IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua Alfredo Allen, 208, 4200-135 Porto, Portugal; Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre s/n, 4169-007 Porto, Portugal.
| |
Collapse
|
3
|
Mozaheb N, Mingeot-Leclercq MP. Membrane Vesicle Production as a Bacterial Defense Against Stress. Front Microbiol 2020; 11:600221. [PMID: 33362747 PMCID: PMC7755613 DOI: 10.3389/fmicb.2020.600221] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 11/16/2020] [Indexed: 12/15/2022] Open
Abstract
Membrane vesicles are the nano-sized vesicles originating from membranes. The production of membrane vesicles is a common feature among bacteria. Depending on the bacterial growth phase and environmental conditions, membrane vesicles show diverse characteristics. Various physiological and ecological roles have been attributed to membrane vesicles under both homeostatic and stressful conditions. Pathogens encounter several stressors during colonization in the hostile environment of host tissues. Nutrient deficiency, the presence of antibiotics as well as elements of the host’s immune system are examples of stressors threatening pathogens inside their host. To combat stressors and survive, pathogens have established various defensive mechanisms, one of them is production of membrane vesicles. Pathogens produce membrane vesicles to alleviate the destructive effects of antibiotics or other types of antibacterial treatments. Additionally, membrane vesicles can also provide benefits for the wider bacterial community during infections, through the transfer of resistance or virulence factors. Hence, given that membrane vesicle production may affect the activities of antibacterial agents, their production should be considered when administering antibacterial treatments. Besides, regarding that membrane vesicles play vital roles in bacteria, disrupting their production may suggest an alternative strategy for battling against pathogens. Here, we aim to review the stressors encountered by pathogens and shed light on the roles of membrane vesicles in increasing pathogen adaptabilities in the presence of stress-inducing factors.
Collapse
Affiliation(s)
- Negar Mozaheb
- Université catholique de Louvain (UCL), Louvain Drug Research Institute (LDRI), Cellular & Molecular Pharmacology Unit (FACM), Brussels, Belgium
| | - Marie-Paule Mingeot-Leclercq
- Université catholique de Louvain (UCL), Louvain Drug Research Institute (LDRI), Cellular & Molecular Pharmacology Unit (FACM), Brussels, Belgium
| |
Collapse
|
4
|
Abstract
This chapter covers the progress made in the Leptospira field since the application of mutagenesis techniques and how they have allowed the study of virulence factors and, more generally, the biology of Leptospira. The last decade has seen advances in our ability to perform molecular genetic analysis of Leptospira. Major achievements include the generation of large collections of mutant strains and the construction of replicative plasmids, enabling complementation of mutations. However, there are still no practical tools for routine genetic manipulation of pathogenic Leptospira strains, slowing down advances in pathogenesis research. This review summarizes the status of the molecular genetic toolbox for Leptospira species and highlights new challenges in the nascent field of Leptospira genetics.
Collapse
Affiliation(s)
- Mathieu Picardeau
- Biology of Spirochetes Unit, Institut Pasteur, 28 Rue Du Docteur Roux, 75724, Paris Cedex 15, France.
| |
Collapse
|
5
|
Yoshitani K, Hizukuri Y, Akiyama Y. An in vivo protease activity assay for investigating the functions of the Escherichia coli membrane protease HtpX. FEBS Lett 2019; 593:842-851. [PMID: 30903618 DOI: 10.1002/1873-3468.13368] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 03/14/2019] [Accepted: 03/14/2019] [Indexed: 11/06/2022]
Abstract
Escherichia coli HtpX is an M48 family zinc metalloproteinase located in the cytoplasmic membrane. Previous studies suggested that it is involved in the quality control of membrane proteins. However, its in vivo proteolytic function has not been characterized in detail, mainly because the physiological substrates have not been identified and no model substrate that allows sensitive detection of the protease activity is available. We constructed a new model substrate of HtpX and established an in vivo semiquantitative and convenient protease activity assay system for HtpX. This system enables detection of differential protease activities of HtpX mutants carrying mutations in conserved regions. This system would also be useful for investigating the functions of HtpX and its homologs in other bacteria.
Collapse
Affiliation(s)
- Kohei Yoshitani
- Institute for Frontier Life and Medical Sciences, Kyoto University, Japan
| | - Yohei Hizukuri
- Institute for Frontier Life and Medical Sciences, Kyoto University, Japan
| | - Yoshinori Akiyama
- Institute for Frontier Life and Medical Sciences, Kyoto University, Japan
| |
Collapse
|
6
|
Yamaguchi T, Higa N, Okura N, Matsumoto A, Hermawan I, Yamashiro T, Suzuki T, Toma C. Characterizing interactions of Leptospira interrogans with proximal renal tubule epithelial cells. BMC Microbiol 2018; 18:64. [PMID: 29973159 PMCID: PMC6030750 DOI: 10.1186/s12866-018-1206-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 06/20/2018] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Leptospira interrogans is a pathogenic, spirochetal bacterium that is responsible for leptospirosis, an emerging worldwide zoonosis. Leptospires colonize the renal proximal tubules and chronically infect the kidney. Live bacteria are excreted into urine, contaminating the environment. While it is well known that leptospires can persist in the kidneys without signs of disease for several months, the interactions of leptospires with the proximal renal epithelial tubule cells that allow the chronic renal colonization have not been elucidated yet. In the present study, we compared the interactions between a virulent, low passage (LP) strain and a cultured-attenuated, high passage (HP) strain with renal proximal tubule epithelial cells (RPTECs) to elucidate the strategies used by Leptospira to colonize the kidney. RESULTS Kinetics analysis of kidney colonization in a mouse model of chronic infection performed by quantitative real-time PCR and immunofluorescence, showed that the LP strain reached the kidney by 3 days post infection (pi) and attached to the basal membrane side of the renal epithelial cells. At 10 days pi, some leptospires were attached to the luminal side of the tubular epithelia and the number of colonizing leptospires gradually increased. On the other hand, the HP strain was cleared during hematogenous dissemination and did not colonize the kidney. Transmission electron microscopy analysis of LP-infected kidneys at 25 days pi showed aggregated leptospires and membrane vesicles attached to the epithelial brush border. Leptospiral kidney colonization altered the organization of the RPTEC brush border. An in vitro model of infection using TCMK-1 cells, showed that leptospiral infection induced a host stress response, which is delayed in LP-infected cells. CONCLUSIONS After hematogenous dissemination, leptospires create protective and replicative niches in the base membrane and luminal sides of the RPTECs. During the long-term colonization, leptospires attached to the RPTEC brush borders and membrane vesicles might be involved in the formation of a biofilm-like structure in vivo. Our results also suggested that the virulent strain is able to manipulate host cell stress responses to promote renal colonization.
Collapse
Affiliation(s)
- Takayoshi Yamaguchi
- Department of Bacteriology, Graduate School of Medicine, University of the Ryukyus, Okinawa, 903-0215 Japan
- Present address: Department of Food and Nutrition Science, Junior College, Sagami Women’s University, Sagamihara, Kanagawa 252-0383 Japan
| | - Naomi Higa
- Department of Bacteriology, Graduate School of Medicine, University of the Ryukyus, Okinawa, 903-0215 Japan
| | - Nobuhiko Okura
- Department of Molecular Anatomy, Graduate School of Medicine, University of the Ryukyus, Okinawa, 903-0215 Japan
| | - Arina Matsumoto
- Department of Bacteriology, Graduate School of Medicine, University of the Ryukyus, Okinawa, 903-0215 Japan
- Present address: Okinawa Industrial Technology Center, Okinawa, 904-2234 Japan
| | - Idam Hermawan
- Department of Bacteriology, Graduate School of Medicine, University of the Ryukyus, Okinawa, 903-0215 Japan
| | - Tetsu Yamashiro
- Department of Bacteriology, Graduate School of Medicine, University of the Ryukyus, Okinawa, 903-0215 Japan
| | - Toshihiko Suzuki
- Department of Bacterial Pathogenesis, Infection and Host Response, Graduate School of Medicine and Dental Sciences, Tokyo Medical and Dental University, Tokyo, 113-8510 Japan
| | - Claudia Toma
- Department of Bacteriology, Graduate School of Medicine, University of the Ryukyus, Okinawa, 903-0215 Japan
| |
Collapse
|
7
|
Yu YJ, Wang XH, Fan GC. Versatile effects of bacterium-released membrane vesicles on mammalian cells and infectious/inflammatory diseases. Acta Pharmacol Sin 2018; 39:514-533. [PMID: 28858295 PMCID: PMC5888691 DOI: 10.1038/aps.2017.82] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 05/10/2017] [Indexed: 01/18/2023] Open
Abstract
Gram-negative bacterium-released outer-membrane vesicles (OMVs) and Gram-positive bacterium-released membrane vesicles (MVs) share significant similarities with mammalian cell-derived MVs (eg, microvesicles and exosomes) in terms of structure and their biological activities. Recent studies have revealed that bacterial OMVs/MVs could (1) interact with immune cells to regulate inflammatory responses, (2) transport virulence factors (eg, enzymes, DNA and small RNAs) to host cells and result in cell injury, (3) enhance barrier function by stimulating the expression of tight junction proteins in intestinal epithelial cells, (4) upregulate the expression of endothelial cell adhesion molecules, and (5) serve as natural nanocarriers for immunogenic antigens, enzyme support and drug delivery. In addition, OMVs/MVs can enter the systemic circulation and induce a variety of immunological and metabolic responses. This review highlights the recent advances in the understanding of OMV/MV biogenesis and their compositional remodeling. In addition, interactions between OMVs/MVs and various types of mammalian cells (ie, immune cells, epithelial cells, and endothelial cells) and their pathological/preventive effects on infectious/inflammatory diseases are summarized. Finally, methods for engineering OMVs/MVs and their therapeutic potential are discussed.
Collapse
Affiliation(s)
- You-jiang Yu
- Medical College of Yangzhou Polytechnic College, Yangzhou 225009, China
| | - Xiao-hong Wang
- Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA
| | - Guo-Chang Fan
- Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA
| |
Collapse
|
8
|
Herman HS, Mehta S, Cárdenas WB, Stewart-Ibarra AM, Finkelstein JL. Micronutrients and Leptospirosis: A Review of the Current Evidence. PLoS Negl Trop Dis 2016; 10:e0004652. [PMID: 27387046 PMCID: PMC4936698 DOI: 10.1371/journal.pntd.0004652] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Leptospirosis is one of the most widespread zoonoses and represents a major threat to human health. Due to the high burden of disease, limitations in diagnostics, and limited coverage and availability of effective human and veterinary vaccines, leptospirosis remains an important neglected zoonotic disease. Improved surveillance and identification of modifiable risk factors for leptospirosis are urgently needed to inform preventive interventions and reduce the risk and severity of Leptospira infection. METHODOLOGY/PRINCIPAL FINDINGS This review was conducted to examine the evidence that links micronutrient status and Leptospira infection. A total of 56 studies were included in this review: 28 in vitro, 17 animal, and 11 observational human studies. Findings indicated that Leptospira infection is associated with higher iron and calcium concentrations and hypomagnesemia. CONCLUSIONS/SIGNIFICANCE Few prospective studies and no randomized trials have been conducted to date to examine the potential role of micronutrients in Leptospira infection. The limited literature in this area constrains our ability to make specific recommendations; however, the roles of iron, calcium, and magnesium in leptospirosis represent important areas for future research. The role of micronutrients in leptospirosis risk and severity needs to be elucidated in larger prospective human studies to inform public health interventions.
Collapse
Affiliation(s)
- Heather S. Herman
- Division of Nutritional Sciences, Cornell University, Ithaca, New York, United States of America
| | - Saurabh Mehta
- Division of Nutritional Sciences, Cornell University, Ithaca, New York, United States of America
- St. John's Research Institute, Bangalore, India
| | - Washington B. Cárdenas
- Laboratorio de Biomedicina, Escuela Superior Politécnica del Litoral, ESPOL, Guayaquil, Ecuador
| | - Anna M. Stewart-Ibarra
- Department of Medicine and the Center for Global Health and Translational Science, State University of New York (SUNY) Upstate Medical University, Syracuse, New York, United States of America
| | - Julia L. Finkelstein
- Division of Nutritional Sciences, Cornell University, Ithaca, New York, United States of America
- St. John's Research Institute, Bangalore, India
- * E-mail:
| |
Collapse
|
9
|
Schwechheimer C, Kuehn MJ. Outer-membrane vesicles from Gram-negative bacteria: biogenesis and functions. Nat Rev Microbiol 2015; 13:605-19. [PMID: 26373371 PMCID: PMC5308417 DOI: 10.1038/nrmicro3525] [Citation(s) in RCA: 1085] [Impact Index Per Article: 120.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Outer-membrane vesicles (OMVs) are spherical buds of the outer membrane filled with periplasmic content and are commonly produced by Gram-negative bacteria. The production of OMVs allows bacteria to interact with their environment, and OMVs have been found to mediate diverse functions, including promoting pathogenesis, enabling bacterial survival during stress conditions and regulating microbial interactions within bacterial communities. Additionally, because of this functional versatility, researchers have begun to explore OMVs as a platform for bioengineering applications. In this Review, we discuss recent advances in the study of OMVs, focusing on new insights into the mechanisms of biogenesis and the functions of these vesicles.
Collapse
Affiliation(s)
- Carmen Schwechheimer
- Department of Biochemistry, Box 3711, Duke University Medical Center, Durham, North Carolina 27710, USA
| | - Meta J Kuehn
- Department of Biochemistry, Box 3711, Duke University Medical Center, Durham, North Carolina 27710, USA
| |
Collapse
|
10
|
Abstract
Recent advances in molecular genetics, such as the ability to construct defined mutants, have allowed the study of virulence factors and more generally the biology in Leptospira. However, pathogenic leptospires remain much less easily transformable than the saprophyte L. biflexa and further development and improvement of genetic tools are required. Here, we review tools that have been used to genetically manipulate Leptospira. We also describe the major advances achieved in both genomics and postgenomics technologies, including transcriptomics and proteomics.
Collapse
|
11
|
Schwechheimer C, Kulp A, Kuehn MJ. Modulation of bacterial outer membrane vesicle production by envelope structure and content. BMC Microbiol 2014; 14:324. [PMID: 25528573 PMCID: PMC4302634 DOI: 10.1186/s12866-014-0324-1] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 12/11/2014] [Indexed: 02/14/2023] Open
Abstract
Background Vesiculation is a ubiquitous secretion process of Gram-negative bacteria, where outer membrane vesicles (OMVs) are small spherical particles on the order of 50 to 250 nm composed of outer membrane (OM) and lumenal periplasmic content. Vesicle functions have been elucidated in some detail, showing their importance in virulence factor secretion, bacterial survival, and biofilm formation in pathogenesis. Furthermore, OMVs serve as an envelope stress response, protecting the secreting bacteria from internal protein misfolding stress, as well as external envelope stressors. Despite their important functional roles very little is known about the regulation and mechanism of vesicle production. Based on the envelope architecture and prior characterization of the hypervesiculation phenotypes for mutants lacking the lipoprotein, Lpp, which is involved in the covalent OM-peptidoglycan (PG) crosslinks, it is expected that an inverse relationship exists between OMV production and PG-crosslinked Lpp. Results In this study, we found that subtle modifications of PG remodeling and crosslinking modulate OMV production, inversely correlating with bound Lpp levels. However, this inverse relationship was not found in strains in which OMV production is driven by an increase in “periplasmic pressure” resulting from the accumulation of protein, PG fragments, or lipopolysaccharide. In addition, the characterization of an nlpA deletion in backgrounds lacking either Lpp- or OmpA-mediated envelope crosslinks demonstrated a novel role for NlpA in envelope architecture. Conclusions From this work, we conclude that OMV production can be driven by distinct Lpp concentration-dependent and Lpp concentration-independent pathways. Electronic supplementary material The online version of this article (doi:10.1186/s12866-014-0324-1) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Carmen Schwechheimer
- Department of Biochemistry, Duke University Medical Center, Durham, NC, 27710, USA.
| | - Adam Kulp
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, 27710, USA.
| | - Meta J Kuehn
- Department of Biochemistry, Duke University Medical Center, Durham, NC, 27710, USA.
| |
Collapse
|