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Shin M, Chang E, Lee D, Kim N, Cho B, Cha N, Koranteng F, Song JJ, Shim J. Drosophila immune cells transport oxygen through PPO2 protein phase transition. Nature 2024; 631:350-359. [PMID: 38926577 PMCID: PMC11236712 DOI: 10.1038/s41586-024-07583-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 05/17/2024] [Indexed: 06/28/2024]
Abstract
Insect respiration has long been thought to be solely dependent on an elaborate tracheal system without assistance from the circulatory system or immune cells1,2. Here we describe that Drosophila crystal cells-myeloid-like immune cells called haemocytes-control respiration by oxygenating Prophenoloxidase 2 (PPO2) proteins. Crystal cells direct the movement of haemocytes between the trachea of the larval body wall and the circulation to collect oxygen. Aided by copper and a neutral pH, oxygen is trapped in the crystalline structures of PPO2 in crystal cells. Conversely, PPO2 crystals can be dissolved when carbonic anhydrase lowers the intracellular pH and then reassembled into crystals in cellulo by adhering to the trachea. Physiologically, larvae lacking crystal cells or PPO2, or those expressing a copper-binding mutant of PPO2, display hypoxic responses under normoxic conditions and are susceptible to hypoxia. These hypoxic phenotypes can be rescued by hyperoxia, expression of arthropod haemocyanin or prevention of larval burrowing activity to expose their respiratory organs. Thus, we propose that insect immune cells collaborate with the tracheal system to reserve and transport oxygen through the phase transition of PPO2 crystals, facilitating internal oxygen homeostasis in a process that is comparable to vertebrate respiration.
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Affiliation(s)
- Mingyu Shin
- Department of Life Science, College of Natural Science, Hanyang University, Seoul, Republic of Korea
| | - Eunji Chang
- Department of Life Science, College of Natural Science, Hanyang University, Seoul, Republic of Korea
| | - Daewon Lee
- Department of Life Science, College of Natural Science, Hanyang University, Seoul, Republic of Korea
| | - Nayun Kim
- Department of Biological Sciences, KI for BioCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea
| | - Bumsik Cho
- Department of Life Science, College of Natural Science, Hanyang University, Seoul, Republic of Korea
| | - Nuri Cha
- Department of Life Science, College of Natural Science, Hanyang University, Seoul, Republic of Korea
| | - Ferdinand Koranteng
- Department of Life Science, College of Natural Science, Hanyang University, Seoul, Republic of Korea
| | - Ji-Joon Song
- Department of Biological Sciences, KI for BioCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea
| | - Jiwon Shim
- Department of Life Science, College of Natural Science, Hanyang University, Seoul, Republic of Korea.
- Research Institute for Natural Science, Hanyang University, Seoul, Republic of Korea.
- Hanyang Institute of Bioscience and Biotechnology, Hanyang University, Seoul, Republic of Korea.
- Hanyang Institute of Advanced BioConvergence, Hanyang University, Seoul, Republic of Korea.
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2
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Suzuki S, Yokota K, Igimi S, Kajikawa A. Negative chemotaxis of Ligilactobacillus agilis BKN88 against gut-derived substances. Sci Rep 2023; 13:15632. [PMID: 37730901 PMCID: PMC10511705 DOI: 10.1038/s41598-023-42840-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Accepted: 09/15/2023] [Indexed: 09/22/2023] Open
Abstract
Ligilactobacillus agilis is a motile lactic acid bacterium found in the gastrointestinal tracts of animals. The findings of our previous study suggest that the motility of L. agilis BKN88 enables gut colonization in murine models. However, the chemotactic abilities of motile lactobacilli remain unknown. This study aimed to identify the gut-derived chemoeffectors and their corresponding chemoreceptors in L. agilis BKN88. Chemotaxis assays with chemotactic and non-chemotactic (ΔcheA) L. agilis strains revealed that low pH, organic acids, and bile salts served as repellents. L. agilis BKN88 was more sensitive to bile and acid than the gut-derived non-motile lactobacilli, implying that L. agilis might utilize motility and chemotaxis instead of exhibiting stress tolerance/resistance. L. agilis BKN88 contains five putative chemoreceptor genes (mcp1-mcp5). Chemotaxis assays using a series of chemoreceptor mutants revealed that each of the five chemoreceptors could sense multiple chemoeffectors and that these chemoreceptors were functionally redundant. Mcp2 and Mcp3 sensed all tested chemoeffectors. This study provides further insights into the interactions between chemoreceptors and ligands of motile lactobacilli and the unique ecological and evolutionary features of motile lactobacilli, which may be distinct from those of non-motile lactobacilli.
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Affiliation(s)
- Shunya Suzuki
- Department of Agricultural Chemistry, Graduate School of Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya, Tokyo, 156-8502, Japan
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8566, Japan
| | - Kenji Yokota
- Department of Agricultural Chemistry, Graduate School of Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya, Tokyo, 156-8502, Japan
| | - Shizunobu Igimi
- Department of Agricultural Chemistry, Graduate School of Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya, Tokyo, 156-8502, Japan
| | - Akinobu Kajikawa
- Department of Agricultural Chemistry, Graduate School of Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya, Tokyo, 156-8502, Japan.
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Horrocks V, King OG, Yip AYG, Marques IM, McDonald JAK. Role of the gut microbiota in nutrient competition and protection against intestinal pathogen colonization. MICROBIOLOGY (READING, ENGLAND) 2023; 169:001377. [PMID: 37540126 PMCID: PMC10482380 DOI: 10.1099/mic.0.001377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 07/25/2023] [Indexed: 08/05/2023]
Abstract
The human gut microbiota can restrict the growth of pathogens to prevent them from colonizing the intestine ('colonization resistance'). However, antibiotic treatment can kill members of the gut microbiota ('gut commensals') and reduce competition for nutrients, making these nutrients available to support the growth of pathogens. This disturbance can lead to the growth and expansion of pathogens within the intestine (including antibiotic-resistant pathogens), where these pathogens can exploit the absence of competitors and the nutrient-enriched gut environment. In this review, we discuss nutrient competition between the gut microbiota and pathogens. We also provide an overview of how nutrient competition can be harnessed to support the design of next-generation microbiome therapeutics to restrict the growth of pathogens and prevent the development of invasive infections.
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Affiliation(s)
- Victoria Horrocks
- Centre for Bacterial Resistance Biology, Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Olivia G. King
- Centre for Bacterial Resistance Biology, Department of Infectious Disease, Imperial College London, London SW7 2AZ, UK
| | - Alexander Y. G. Yip
- Centre for Bacterial Resistance Biology, Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Inês Melo Marques
- Centre for Bacterial Resistance Biology, Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Julie A. K. McDonald
- Centre for Bacterial Resistance Biology, Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
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4
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Muhammad AY, Amonov M, Murugaiah C, Baig AA, Yusoff M. Intestinal colonization against Vibrio cholerae: host and microbial resistance mechanisms. AIMS Microbiol 2023; 9:346-374. [PMID: 37091815 PMCID: PMC10113163 DOI: 10.3934/microbiol.2023019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Revised: 03/22/2023] [Accepted: 03/27/2023] [Indexed: 04/25/2023] Open
Abstract
Vibrio cholerae is a non-invasive enteric pathogen known to cause a major public health problem called cholera. The pathogen inhabits the aquatic environment while outside the human host, it is transmitted into the host easily through ingesting contaminated food and water containing the vibrios, thus causing diarrhoea and vomiting. V. cholerae must resist several layers of colonization resistance mechanisms derived from the host or the gut commensals to successfully survive, grow, and colonize the distal intestinal epithelium, thus causing an infection. The colonization resistance mechanisms derived from the host are not specific to V. cholerae but to all invading pathogens. However, some of the gut commensal-derived colonization resistance may be more specific to the pathogen, making it more challenging to overcome. Consequently, the pathogen has evolved well-coordinated mechanisms that sense and utilize the anti-colonization factors to modulate events that promote its survival and colonization in the gut. This review is aimed at discussing how V. cholerae interacts and resists both host- and microbe-specific colonization resistance mechanisms to cause infection.
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Affiliation(s)
| | - Malik Amonov
- Faculty of Medicine, Universiti Sultan Zainal Abidin, Malaysia
- * Correspondence: ; Tel: +60189164478
| | | | - Atif Amin Baig
- University Institute of Public Health, Faculty of Allied Health Sciences, The University of Lahore, Pakistan
| | - Marina Yusoff
- Faculty of Medicine, Universiti Sultan Zainal Abidin, Malaysia
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Schwarz J, Schumacher K, Brameyer S, Jung K. Bacterial battle against acidity. FEMS Microbiol Rev 2022; 46:6652135. [PMID: 35906711 DOI: 10.1093/femsre/fuac037] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Revised: 07/11/2022] [Accepted: 07/27/2022] [Indexed: 01/09/2023] Open
Abstract
The Earth is home to environments characterized by low pH, including the gastrointestinal tract of vertebrates and large areas of acidic soil. Most bacteria are neutralophiles, but can survive fluctuations in pH. Herein, we review how Escherichia, Salmonella, Helicobacter, Brucella, and other acid-resistant Gram-negative bacteria adapt to acidic environments. We discuss the constitutive and inducible defense mechanisms that promote survival, including proton-consuming or ammonia-producing processes, cellular remodeling affecting membranes and chaperones, and chemotaxis. We provide insights into how Gram-negative bacteria sense environmental acidity using membrane-integrated and cytosolic pH sensors. Finally, we address in more detail the powerful proton-consuming decarboxylase systems by examining the phylogeny of their regulatory components and their collective functionality in a population.
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Affiliation(s)
- Julia Schwarz
- Faculty of Biology, Microbiology, Ludwig-Maximilians-University München, Großhaderner Str. 2-4, 82152 Martinsried, Germany
| | - Kilian Schumacher
- Faculty of Biology, Microbiology, Ludwig-Maximilians-University München, Großhaderner Str. 2-4, 82152 Martinsried, Germany
| | - Sophie Brameyer
- Faculty of Biology, Microbiology, Ludwig-Maximilians-University München, Großhaderner Str. 2-4, 82152 Martinsried, Germany
| | - Kirsten Jung
- Faculty of Biology, Microbiology, Ludwig-Maximilians-University München, Großhaderner Str. 2-4, 82152 Martinsried, Germany
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6
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Schnizlein MK, Young VB. Capturing the environment of the Clostridioides difficile infection cycle. Nat Rev Gastroenterol Hepatol 2022; 19:508-520. [PMID: 35468953 DOI: 10.1038/s41575-022-00610-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/21/2022] [Indexed: 12/11/2022]
Abstract
Clostridioides difficile (formerly Clostridium difficile) infection is a substantial health and economic burden worldwide. Great strides have been made over the past several years in characterizing the physiology of C. difficile infection, particularly regarding how gut microorganisms and their host work together to provide colonization resistance. As mammalian hosts and their indigenous gut microbiota have co-evolved, they have formed a complex yet stable relationship that prevents invading microorganisms from establishing themselves. In this Review, we discuss the latest advances in our understanding of C. difficile physiology that have contributed to its success as a pathogen, including its versatile survival factors and ability to adapt to unique niches. Using discoveries regarding microorganism-host and microorganism-microorganism interactions that constitute colonization resistance, we place C. difficile within the fiercely competitive gut environment. A comprehensive understanding of these relationships is required to continue the development of precision medicine-based treatments for C. difficile infection.
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Affiliation(s)
- Matthew K Schnizlein
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA
| | - Vincent B Young
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, MI, USA.
- Department of Internal Medicine/Division of Infectious Diseases, University of Michigan Medical School, Ann Arbor, MI, USA.
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7
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Environment Constrains Fitness Advantages of Division of Labor in Microbial Consortia Engineered for Metabolite Push or Pull Interactions. mSystems 2022; 7:e0005122. [PMID: 35762764 PMCID: PMC9426560 DOI: 10.1128/msystems.00051-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fitness benefits from division of labor are well documented in microbial consortia, but the dependency of the benefits on environmental context is poorly understood. Two synthetic Escherichia coli consortia were built to test the relationships between exchanged organic acid, local environment, and opportunity costs of different metabolic strategies. Opportunity costs quantify benefits not realized due to selecting one phenotype over another. The consortia catabolized glucose and exchanged either acetic or lactic acid to create producer-consumer food webs. The organic acids had different inhibitory properties and different opportunity costs associated with their positions in central metabolism. The exchanged metabolites modulated different consortial dynamics. The acetic acid-exchanging (AAE) consortium had a “push” interaction motif where acetic acid was secreted faster by the producer than the consumer imported it, while the lactic acid-exchanging (LAE) consortium had a “pull” interaction motif where the consumer imported lactic acid at a comparable rate to its production. The LAE consortium outperformed wild-type (WT) batch cultures under the environmental context of weakly buffered conditions, achieving a 55% increase in biomass titer, a 51% increase in biomass per proton yield, an 86% increase in substrate conversion, and the complete elimination of by-product accumulation all relative to the WT. However, the LAE consortium had the trade-off of a 42% lower specific growth rate. The AAE consortium did not outperform the WT in any considered performance metric. Performance advantages of the LAE consortium were sensitive to environment; increasing the medium buffering capacity negated the performance advantages compared to WT. IMPORTANCE Most naturally occurring microorganisms persist in consortia where metabolic interactions are common and often essential to ecosystem function. This study uses synthetic ecology to test how different cellular interaction motifs influence performance properties of consortia. Environmental context ultimately controlled the division of labor performance as shifts from weakly buffered to highly buffered conditions negated the benefits of the strategy. Understanding the limits of division of labor advances our understanding of natural community functioning, which is central to nutrient cycling and provides design rules for assembling consortia used in applied bioprocessing.
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The hdeD Gene Represses the Expression of Flagella Biosynthesis via LrhA in Escherichia coli K-12. J Bacteriol 2021; 204:e0042021. [PMID: 34694904 DOI: 10.1128/jb.00420-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli survives under acid stress conditions by the glutamic acid-dependent acid resistance (GAD) system, which enzymatically decreases intracellular protons. We found a linkage between GAD and flagellar systems in E. coli. The hdeD gene, one of the GAD cluster genes, encodes an uncharacterized membrane protein. A reporter assay showed that the hdeD promoter was induced in a GadE-dependent manner when grown in the M9 glycerol medium. Transcriptome analysis revealed that most of the transcripts were from genes involved in flagella synthesis, and cell motility increased not only in the hdeD-deficient mutant but also in the gadE-deficient mutant. Defects in both the hdeD and gadE increased the intracellular level of FliA, an alternative sigma factor for flagella synthesis, activated by the master regulator FlhDC. The promoter activity of the lrhA gene, which encodes repressor for the flhDC operon, was found to decrease in both the hdeD- and gadE-deficient mutants. Transmission electron microscopy showed that the number of flagellar filaments on the hdeD-, gadE-, and lrhA-deficient cells increased, and all three mutants showed higher motility than the parent strain. Thus, HdeD in the GAD system activates the lrhA promoter, resulting in a decrease in flagellar filaments in E. coli cells. We speculated that the synthesis of HdeD, stimulated in E. coli exposed to acid stress, could control the flagella biosynthesis by sensing slight changes in pH at the cytoplasmic membrane. This could help in saving energy through termination of flagella biosynthesis and improve bacterial survival efficiency within the animal digestive system. IMPORTANCE E. coli cells encounter various environments from the mouth down to the intestines within the host animals. The pH of gastric juice is lower than 2.0, and the bacterial must quickly respond and adapt to the following environmental changes before reaching the intestines. The quick response plays a role in cellular survival in the population, whereas adaptation may contribute to species survival. The GAD and flagella systems are important for response to low pH in E. coli. Here, we identified the novel inner membrane regulator HdeD, encoding in the GAD cluster, to repress the synthesis of flagella. These insights provide a deeper understanding of how the bacteria enter the animal digestive system, survive, and form colonies in the intestines.
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Cardoza E, Singh H. Involvement of CspC in response to diverse environmental stressors in Escherichia coli. J Appl Microbiol 2021; 132:785-801. [PMID: 34260797 DOI: 10.1111/jam.15219] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 07/07/2021] [Accepted: 07/12/2021] [Indexed: 12/23/2022]
Abstract
The ability of Escherichia coli surviving a cold shock lies mainly with the induction of a few Csps termed as 'Major cold shock proteins'. Regardless of high sequence similarity among the nine homologous members, CspC appears to be functionally diverse in conferring the cell adaptability to various stresses based on fundamental properties of the protein including nucleic acid binding, nucleic acid melting and regulatory activity. Spanning three different stress regulons of acid, oxidative and heat, CspC regulates gene expression and transcript stability of stress proteins and bestows upon the cell tolerance to lethal-inducing agents ultimately helping it adapt to severe environmental assaults. While its exact role in cellular physiology is still to be detailed, understanding the transcriptional and translational control will likely provide insights into the mechanistic role of CspC under stress conditions. To this end, we review the knowledge on stress protein regulation by CspC and highlight its activity in response to stressors thereby elucidating its role as a major Csp player in response to one too many environmental triggers. The knowledge presented here could see various downstream applications in engineering microbes for industrial, agricultural and research applications in order to achieve high product efficiency and to aid bacteria cope with environmentally harsh conditions.
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Affiliation(s)
- Evieann Cardoza
- Department of Biological Sciences, Sunandan Divatia School of Science, NMIMS Deemed to be University, Mumbai, India
| | - Harinder Singh
- Department of Biological Sciences, Sunandan Divatia School of Science, NMIMS Deemed to be University, Mumbai, India
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Afanzar O, Di Paolo D, Eisenstein M, Levi K, Plochowietz A, Kapanidis AN, Berry RM, Eisenbach M. The switching mechanism of the bacterial rotary motor combines tight regulation with inherent flexibility. EMBO J 2021; 40:e104683. [PMID: 33620739 PMCID: PMC7957414 DOI: 10.15252/embj.2020104683] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 12/17/2020] [Accepted: 01/19/2021] [Indexed: 11/20/2022] Open
Abstract
Regulatory switches are wide spread in many biological systems. Uniquely among them, the switch of the bacterial flagellar motor is not an on/off switch but rather controls the motor’s direction of rotation in response to binding of the signaling protein CheY. Despite its extensive study, the molecular mechanism underlying this switch has remained largely unclear. Here, we resolved the functions of each of the three CheY‐binding sites at the switch in E. coli, as well as their different dependencies on phosphorylation and acetylation of CheY. Based on this, we propose that CheY motor switching activity is potentiated upon binding to the first site. Binding of potentiated CheY to the second site produces unstable switching and at the same time enables CheY binding to the third site, an event that stabilizes the switched state. Thereby, this mechanism exemplifies a unique combination of tight motor regulation with inherent switching flexibility.
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Affiliation(s)
- Oshri Afanzar
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Diana Di Paolo
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK
| | - Miriam Eisenstein
- Department of Chemical Research Support, The Weizmann Institute of Science, Rehovot, Israel
| | - Kohava Levi
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Anne Plochowietz
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK
| | - Achillefs N Kapanidis
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK
| | - Richard Michael Berry
- Biological Physics Research Group, Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK
| | - Michael Eisenbach
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
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Mousavi S, Bereswill S, Heimesaat MM. Murine Models for the Investigation of Colonization Resistance and Innate Immune Responses in Campylobacter Jejuni Infections. Curr Top Microbiol Immunol 2021; 431:233-263. [PMID: 33620654 DOI: 10.1007/978-3-030-65481-8_9] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Human infections with the food-borne pathogen Campylobacter jejuni are progressively increasing worldwide and constitute a significant socioeconomic burden to mankind. Intestinal campylobacteriosis in humans is characterized by bloody diarrhea, fever, abdominal pain, and severe malaise. Some individuals develop chronic post-infectious sequelae including neurological and autoimmune diseases such as reactive arthritis and Guillain-Barré syndrome. Studies unraveling the molecular mechanisms underlying campylobacteriosis and post-infectious sequelae have been hampered by the scarcity of appropriate experimental in vivo models. Particularly, conventional laboratory mice are protected from C. jejuni infection due to the physiological colonization resistance exerted by the murine gut microbiota composition. Additionally, as compared to humans, mice are up to 10,000 times more resistant to C. jejuni lipooligosaccharide (LOS) constituting a major pathogenicity factor responsible for the immunopathological host responses during campylobacteriosis. In this chapter, we summarize the recent progress that has been made in overcoming these fundamental obstacles in Campylobacter research in mice. Modification of the murine host-specific gut microbiota composition and sensitization of the mice to C. jejuni LOS by deletion of genes encoding interleukin-10 or a single IL-1 receptor-related molecule as well as by dietary zinc depletion have yielded reliable murine infection models resembling key features of human campylobacteriosis. These substantial improvements pave the way for a better understanding of the molecular mechanisms underlying pathogen-host interactions. The ongoing validation and standardization of these novel murine infection models will provide the basis for the development of innovative treatment and prevention strategies to combat human campylobacteriosis and collateral damages of C. jejuni infections.
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Affiliation(s)
- Soraya Mousavi
- Institute of Microbiology, Infectious Diseases and Immunology, Gastrointestinal Microbiology Research Group, Charité-University Medicine Berlin, Corporate Member of Free University Berlin, Humboldt-University of Berlin, Berlin Institute of Health, Berlin, Germany
| | - Stefan Bereswill
- Institute of Microbiology, Infectious Diseases and Immunology, Gastrointestinal Microbiology Research Group, Charité-University Medicine Berlin, Corporate Member of Free University Berlin, Humboldt-University of Berlin, Berlin Institute of Health, Berlin, Germany
| | - Markus M Heimesaat
- Institute of Microbiology, Infectious Diseases and Immunology, Gastrointestinal Microbiology Research Group, Charité-University Medicine Berlin, Corporate Member of Free University Berlin, Humboldt-University of Berlin, Berlin Institute of Health, Berlin, Germany.
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12
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The Mechanism of Bidirectional pH Taxis in Bacillus subtilis. J Bacteriol 2020; 202:JB.00491-19. [PMID: 31685537 DOI: 10.1128/jb.00491-19] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 10/30/2019] [Indexed: 01/19/2023] Open
Abstract
We investigated pH taxis in Bacillus subtilis This bacterium was found to perform bidirectional taxis in response to external pH gradients, enabling it to preferentially migrate to neutral environments. We next investigated the chemoreceptors involved in sensing pH gradients. We identified four chemoreceptors involved in sensing pH: McpA and TlpA for sensing acidic environments and McpB and TlpB for sensing alkaline ones. In addition, TlpA was found to also weakly sense alkaline environments. By analyzing chimeras between McpA and TlpB, the principal acid- and base-sensing chemoreceptors, we identified four critical amino acid residues-Thr199, Gln200, His273, and Glu274 on McpA and Lys199, Glu200, Gln273, and Asp274 on TlpB-involved in sensing pH. Swapping these four residues between McpA and TlpB converted the former into a base receptor and the latter into an acid receptor. Based on the results, we propose that disruption of hydrogen bonding between the adjacent residues upon pH changes induces signaling. Collectively, our results further our understanding of chemotaxis in B. subtilis and provide a new model for pH sensing in bacteria.IMPORTANCE Many bacteria can sense the pH in their environment and then use this information to direct their movement toward more favorable locations. In this study, we investigated the pH sensing mechanism in Bacillus subtilis This bacterium preferentially migrates to neutral environments. It employs four chemoreceptors to sense pH. Two are involved in sensing acidic environments, and two are involved in sensing alkaline ones. To identify the mechanism for pH sensing, we constructed receptor chimeras of acid- and base-sensing chemoreceptors. By analyzing the responses of these chimeric receptors, we were able to identify four critical amino acid residues involved in pH sensing and propose a model for the pH sensing mechanism in B. subtilis.
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Lamas A, Regal P, Vázquez B, Cepeda A, Franco CM. Short Chain Fatty Acids Commonly Produced by Gut Microbiota Influence Salmonella enterica Motility, Biofilm Formation, and Gene Expression. Antibiotics (Basel) 2019; 8:E265. [PMID: 31847278 PMCID: PMC6963744 DOI: 10.3390/antibiotics8040265] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 12/09/2019] [Accepted: 12/12/2019] [Indexed: 12/16/2022] Open
Abstract
Short chain fatty acids (SCFAs) are commonly produced by healthy gut microbiota and they have a protective role against enteric pathogens. SCFAs also have direct antimicrobial activity against bacterial pathogens by diffusion across the bacterial membrane and reduction of intracellular pH. Due to this antimicrobial activity, SCFAs have promising applications in human health and food safety. In this study, the minimum inhibitory concentrations (MICs) of four SCFAs (acetic acid, butyric acid, propionic acid, and valeric acid) in Salmonella strains isolated from poultry were determined. The effect of subinhibitory concentrations of SCFAs in Salmonella biofilm formation, motility, and gene expression was also evaluated. Butyric acid, propionic acid, and valeric acid showed a MIC of 3750 µg/mL in all strains tested, while the MIC of acetic acid was between 1875 and 3750 µg/mL. Subinhibitory concentrations of SCFAs significantly (p < 0.05) reduced the motility of all Salmonella strains, especially in the presence of acetic acid. Biofilm formation was also significantly (p < 0.05) lower in the presence of SCFAs in some of the Salmonella strains. Salmonella strain. Salmonella Typhimurium T7 showed significant (p < 0.05) upregulation of important virulence genes, such as invA and hilA, especially in the presence of butyric acid. Therefore, SCFAs are promising substances for the inhibition of the growth of foodborne pathogens. However, it is important to avoid the use of subinhibitory concentrations that could increase the virulence of foodborne pathogen Salmonella.
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Affiliation(s)
- Alexandre Lamas
- Laboratorio de Higiene Inspección y Control de Alimentos, Departamento de Química Analítica, Nutrición y Bromatología, Universidad de Santiago de Compostela, 27002 Lugo, Spain; (P.R.); (B.V.); (A.C.); (C.M.F.)
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Multidrug Resistance Regulators MarA, SoxS, Rob, and RamA Repress Flagellar Gene Expression and Motility in Salmonella enterica Serovar Typhimurium. J Bacteriol 2019; 201:JB.00385-19. [PMID: 31501286 DOI: 10.1128/jb.00385-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 09/03/2019] [Indexed: 12/21/2022] Open
Abstract
Production of flagella is costly and subject to global multilayered regulation, which is reflected in the hierarchical control of flagellar production in many bacterial species. For Salmonella enterica serovar Typhimurium and its relatives, global regulation of flagellar production primarily occurs through the control of flhDC transcription and mRNA translation. In this study, the roles of the homologous multidrug resistance regulators MarA, SoxS, Rob, and RamA (constituting the mar-sox-rob regulon in S Typhimurium) in regulating flagellar gene expression were explored. Each of these regulators was found to inhibit flagellar gene expression, production of flagella, and motility. To different degrees, repression via these transcription factors occurred through direct interactions with the flhDC promoter, particularly for MarA and Rob. Additionally, SoxS repressed flagellar gene expression via a posttranscriptional pathway, reducing flhDC translation. The roles of these transcription factors in reducing motility in the presence of salicylic acid were also elucidated, adding a genetic regulatory element to the response of S Typhimurium to this well-characterized chemorepellent. Integration of flagellar gene expression into the mar-sox-rob regulon in S Typhimurium contrasts with findings for closely related species such as Escherichia coli, providing an example of plasticity in the mar-sox-rob regulon throughout the Enterobacteriaceae family.IMPORTANCE The mar-sox-rob regulon is a large and highly conserved stress response network in the Enterobacteriaceae family. Although it is well characterized in E. coli, the extent of this regulon in related species is unclear. Here, the control of costly flagellar gene expression is connected to the mar-sox-rob regulon of S Typhimurium, contrasting with the E. coli regulon model. These findings demonstrate the flexibility of the mar-sox-rob regulon to accommodate novel regulatory targets, and they provide evidence for its broader regulatory role within this family of diverse bacteria.
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15
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Ducarmon QR, Zwittink RD, Hornung BVH, van Schaik W, Young VB, Kuijper EJ. Gut Microbiota and Colonization Resistance against Bacterial Enteric Infection. Microbiol Mol Biol Rev 2019; 83:e00007-19. [PMID: 31167904 PMCID: PMC6710460 DOI: 10.1128/mmbr.00007-19] [Citation(s) in RCA: 241] [Impact Index Per Article: 48.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The gut microbiome is critical in providing resistance against colonization by exogenous microorganisms. The mechanisms via which the gut microbiota provide colonization resistance (CR) have not been fully elucidated, but they include secretion of antimicrobial products, nutrient competition, support of gut barrier integrity, and bacteriophage deployment. However, bacterial enteric infections are an important cause of disease globally, indicating that microbiota-mediated CR can be disturbed and become ineffective. Changes in microbiota composition, and potential subsequent disruption of CR, can be caused by various drugs, such as antibiotics, proton pump inhibitors, antidiabetics, and antipsychotics, thereby providing opportunities for exogenous pathogens to colonize the gut and ultimately cause infection. In addition, the most prevalent bacterial enteropathogens, including Clostridioides difficile, Salmonella enterica serovar Typhimurium, enterohemorrhagic Escherichia coli, Shigella flexneri, Campylobacter jejuni, Vibrio cholerae, Yersinia enterocolitica, and Listeria monocytogenes, can employ a wide array of mechanisms to overcome colonization resistance. This review aims to summarize current knowledge on how the gut microbiota can mediate colonization resistance against bacterial enteric infection and on how bacterial enteropathogens can overcome this resistance.
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Affiliation(s)
- Q R Ducarmon
- Center for Microbiome Analyses and Therapeutics, Leiden University Medical Center, Leiden, Netherlands
- Experimental Bacteriology, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - R D Zwittink
- Center for Microbiome Analyses and Therapeutics, Leiden University Medical Center, Leiden, Netherlands
- Experimental Bacteriology, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - B V H Hornung
- Center for Microbiome Analyses and Therapeutics, Leiden University Medical Center, Leiden, Netherlands
- Experimental Bacteriology, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - W van Schaik
- Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom
| | - V B Young
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan, USA
- Department of Internal Medicine/Infectious Diseases Division, University of Michigan Medical Center, Ann Arbor, Michigan, USA
| | - E J Kuijper
- Center for Microbiome Analyses and Therapeutics, Leiden University Medical Center, Leiden, Netherlands
- Experimental Bacteriology, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
- Clinical Microbiology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
- Netherlands Donor Feces Bank, Leiden, Netherlands
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16
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Effects of fermentation products of the commensal bacterium Clostridium ramosum on motility, intracellular pH, and flagellar synthesis of enterohemorrhagic Escherichia coli. Arch Microbiol 2019; 201:841-846. [PMID: 30963197 DOI: 10.1007/s00203-019-01656-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 03/31/2019] [Accepted: 04/03/2019] [Indexed: 10/27/2022]
Abstract
The flagellum and motility are crucial virulence factors for many pathogenic bacteria. In general, pathogens invade and translocate through motility and adhere to specific tissue via flagella. Therefore, the motility and flagella of pathogens are effectual targets for attenuation. Here, we show that the fermentation products of Clostridium ramosum, a commensal intestinal bacterium, decrease the intracellular pH of enterohemorrhagic Escherichia coli (EHEC) and influence its swimming motility. Quantifications of flagellar rotation in individual EHEC cells showed an increase in reversal frequency and a decrease in rotation rate in the presence of C. ramosum fermentation products. Furthermore, the C. ramosum fermentation products affected synthesis of flagellar filaments. The results were reproduced by a combination of organic acids under acidic conditions. Short-chain fatty acids produced by microbes in the gut flora are beneficial for the host, e.g. they prevent infection. Thus, C. ramosum could affect the physiologies of other enteric microbes and host tissues.
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17
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Salmonella Typhimurium is Attracted to Egg Yolk and Repelled by Albumen. Curr Microbiol 2019; 76:393-397. [PMID: 30600359 DOI: 10.1007/s00284-018-1619-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 12/18/2018] [Indexed: 10/27/2022]
Abstract
Salmonella Typhimurium is the causative agent of non-typhoidal, foodborne salmonellosis. Contamination of hen eggs by the bacterium is a common source of S. Typhimurium infection. S. Typhimurium is peritrichous, and flagellum-dependent motility and chemotaxis are believed to facilitate egg contamination despite the presence of many antimicrobial egg components. We performed motility and chemotaxis assays to demonstrate that S. Typhimurium cells are attracted to egg yolks and are repelled by albumen. The bacterial flagellar motor shows bidirectional rotation, and counterclockwise-biased rotation allows cells to swim smoothly. A rotation assay for a single flagellum showed that, in comparison with thin albumen, the thick albumen more strongly affected the directional bias of the flagellar rotation, resulting in a remarkable suppression of the migration distance. Nevertheless, the S. Typhimurium cells retained positive chemotaxis toward the yolk in the presence of the albumens, suggesting that motility facilitates the growth of S. Typhimurium and survival in eggs.
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18
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Bi S, Jin F, Sourjik V. Inverted signaling by bacterial chemotaxis receptors. Nat Commun 2018; 9:2927. [PMID: 30050034 PMCID: PMC6062612 DOI: 10.1038/s41467-018-05335-w] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 07/02/2018] [Indexed: 11/09/2022] Open
Abstract
Microorganisms use transmembrane sensory receptors to perceive a wide range of environmental factors. It is unclear how rapidly the sensory properties of these receptors can be modified when microorganisms adapt to novel environments. Here, we demonstrate experimentally that the response of an Escherichia coli chemotaxis receptor to its chemical ligands can be easily inverted by mutations at several sites along receptor sequence. We also perform molecular dynamics simulations to shed light on the mechanism of the transmembrane signaling by E. coli chemoreceptors. Finally, we use receptors with inverted signaling to map determinants that enable the same receptor to sense multiple environmental factors, including metal ions, aromatic compounds, osmotic pressure, and salt ions. Our findings demonstrate high plasticity of signaling and provide further insights into the mechanisms of stimulus sensing and processing by bacterial chemoreceptors. Bacteria use chemotaxis receptors to perceive environmental factors. Here, the authors show that mutations in a chemotaxis receptor can invert the sensory response, e.g. from attractant to repellent, and use these mutants to map regions that enable the receptor to sense multiple environmental factors.
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Affiliation(s)
- Shuangyu Bi
- Max Planck Institute for Terrestrial Microbiology & LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg, 35043, Germany
| | - Fan Jin
- Max Planck Institute for Terrestrial Microbiology & LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg, 35043, Germany
| | - Victor Sourjik
- Max Planck Institute for Terrestrial Microbiology & LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg, 35043, Germany.
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19
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Akkermans S, Van Impe JF. Mechanistic modelling of the inhibitory effect of pH on microbial growth. Food Microbiol 2017; 72:214-219. [PMID: 29407400 DOI: 10.1016/j.fm.2017.12.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 12/14/2017] [Accepted: 12/15/2017] [Indexed: 10/18/2022]
Abstract
Modelling and simulation of microbial dynamics as a function of processing, transportation and storage conditions is a useful tool to improve microbial food safety and quality. The goal of this research is to improve an existing methodology for building mechanistic predictive models based on the environmental conditions. The effect of environmental conditions on microbial dynamics is often described by combining the separate effects in a multiplicative way (gamma concept). This idea was extended further in this work by including the effects of the lag and stationary growth phases on microbial growth rate as independent gamma factors. A mechanistic description of the stationary phase as a function of pH was included, based on a novel class of models that consider product inhibition. Experimental results on Escherichia coli growth dynamics indicated that also the parameters of the product inhibition equations can be modelled with the gamma approach. This work has extended a modelling methodology, resulting in predictive models that are (i) mechanistically inspired, (ii) easily identifiable with a limited work load and (iii) easily extended to additional environmental conditions.
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Affiliation(s)
- Simen Akkermans
- BioTeC, Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Ghent, Belgium; OPTEC, Optimization in Engineering Center-of-Excellence, KU Leuven, Belgium; CPMF(2), Flemish Cluster Predictive Microbiology in Foods, Belgium(1).
| | - Jan F Van Impe
- BioTeC, Chemical and Biochemical Process Technology and Control, Department of Chemical Engineering, KU Leuven, Ghent, Belgium; OPTEC, Optimization in Engineering Center-of-Excellence, KU Leuven, Belgium; CPMF(2), Flemish Cluster Predictive Microbiology in Foods, Belgium(1).
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20
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Machuca MA, Johnson KS, Liu YC, Steer DL, Ottemann KM, Roujeinikova A. Helicobacter pylori chemoreceptor TlpC mediates chemotaxis to lactate. Sci Rep 2017; 7:14089. [PMID: 29075010 PMCID: PMC5658362 DOI: 10.1038/s41598-017-14372-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 10/06/2017] [Indexed: 12/13/2022] Open
Abstract
It is recently appreciated that many bacterial chemoreceptors have ligand-binding domains (LBD) of the dCACHE family, a structure with two PAS-like subdomains, one membrane-proximal and the other membrane-distal. Previous studies had implicated only the membrane-distal subdomain in ligand recognition. Here, we report the 2.2 Å resolution crystal structure of dCACHE LBD of the Helicobacter pylori chemoreceptor TlpC. H. pylori tlpC mutants are outcompeted by wild type during stomach colonisation, but no ligands had been mapped to this receptor. The TlpC dCACHE LBD has two PAS-like subdomains, as predicted. The membrane-distal one possesses a long groove instead of a small, well-defined pocket. The membrane-proximal subdomain, in contrast, had a well-delineated pocket with a small molecule that we identified as lactate. We confirmed that amino acid residues making contact with the ligand in the crystal structure-N213, I218 and Y285 and Y249-were required for lactate binding. We determined that lactate is an H. pylori chemoattractant that is sensed via TlpC with a K D = 155 µM. Lactate is utilised by H. pylori, and our work suggests that this pathogen seeks out lactate using chemotaxis. Furthermore, our work suggests that dCACHE domain proteins can utilise both subdomains for ligand recognition.
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Affiliation(s)
- Mayra A Machuca
- Infection and Immunity Program, Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, 3800, Australia
- Department of Microbiology, Monash University, Clayton, Victoria, 3800, Australia
| | - Kevin S Johnson
- Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, Santa Cruz, CA, 95064, USA
| | - Yu C Liu
- Department of Microbiology, Monash University, Clayton, Victoria, 3800, Australia
| | - David L Steer
- Monash Biomedical Proteomics Facility, Monash University, Clayton, Victoria, 3800, Australia
| | - Karen M Ottemann
- Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, Santa Cruz, CA, 95064, USA.
| | - Anna Roujeinikova
- Infection and Immunity Program, Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, 3800, Australia.
- Department of Microbiology, Monash University, Clayton, Victoria, 3800, Australia.
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, 3800, Australia.
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21
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Abstract
Antipyretics are some of the most commonly used drugs. Since they are often coadministered with antimicrobial therapy, it is important to understand the interactions between these two classes of drugs. Our review is the first to summarize the antimicrobial effects of antipyretic drugs and the underlying mechanisms involved. Antipyretics can inhibit virus replication, inhibit or promote bacterial or fungal growth, alter the expression of virulence factors, change the surface hydrophobicity of microbes, influence biofilm production, affect the motility, adherence, and metabolism of pathogens, interact with the transport and release of antibiotics by leukocytes, modify the susceptibility of bacteria to antibiotics, and induce or reduce the frequency of mutations leading to antimicrobial resistance. While antipyretics may compromise the efficacy of antimicrobial therapy, they can also be beneficial, for example, in the management of biofilm-associated infections, in reducing virulence factors, in therapy of resistant pathogens, and in inducing synergistic effects. In an era where it is becoming increasingly difficult to find new antimicrobial drugs, targeting virulence factors, enhancing the efficacy of antimicrobial therapy, and reducing resistance may be important strategies.
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22
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Bell JC, Kowalczykowski SC. RecA: Regulation and Mechanism of a Molecular Search Engine. Trends Biochem Sci 2016; 41:491-507. [PMID: 27156117 PMCID: PMC4892382 DOI: 10.1016/j.tibs.2016.04.002] [Citation(s) in RCA: 137] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 04/04/2016] [Accepted: 04/05/2016] [Indexed: 11/19/2022]
Abstract
Homologous recombination maintains genomic integrity by repairing broken chromosomes. The broken chromosome is partially resected to produce single-stranded DNA (ssDNA) that is used to search for homologous double-stranded DNA (dsDNA). This homology driven 'search and rescue' is catalyzed by a class of DNA strand exchange proteins that are defined in relation to Escherichia coli RecA, which forms a filament on ssDNA. Here, we review the regulation of RecA filament assembly and the mechanism by which RecA quickly and efficiently searches for and identifies a unique homologous sequence among a vast excess of heterologous DNA. Given that RecA is the prototypic DNA strand exchange protein, its behavior affords insight into the actions of eukaryotic RAD51 orthologs and their regulators, BRCA2 and other tumor suppressors.
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Affiliation(s)
- Jason C Bell
- Department of Microbiology and Molecular Genetics and Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA
| | - Stephen C Kowalczykowski
- Department of Microbiology and Molecular Genetics and Department of Molecular and Cellular Biology, University of California, Davis, CA 95616, USA.
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23
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Ortega-Calvo JJ, Jimenez-Sanchez C, Pratarolo P, Pullin H, Scott TB, Thompson IP. Tactic response of bacteria to zero-valent iron nanoparticles. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2016; 213:438-445. [PMID: 26967351 DOI: 10.1016/j.envpol.2016.01.093] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 01/29/2016] [Accepted: 01/29/2016] [Indexed: 06/05/2023]
Abstract
The microbial assessment of pollutant toxicity rarely includes behavioral responses. In this study, we investigated the tactic response of Pseudomonas putida G7, a representative of soil bacterium, towards engineered zero-valent iron nanoparticles (nZVIs), as a new end-point assessment of toxicity. The study integrated the characterization of size distribution and charge of nZVIs and tactic reaction response by means of inverted capillary assay and computer-assisted motion analysis of motility behavior. Iron nanoparticles (diameter ≤ 100 nm) were prepared in the absence of oxygen to prevent aggregation, and then exposed in aerobic conditions. We first demonstrate that iron nanoparticles can elicit a negative tactic response in bacteria at low but environmentally-relevant, sub-lethal concentrations (1-10 μg/L). Cells were repelled by nZVIs in the concentration gradients created inside the capillaries, and a significant increase in turning events, characteristic of negative taxis, was detected under exposure to nZVIs. These tactic responses were not detectable after sustained exposure of the nanoparticles to oxygen. This new behavioral assessment may be prospected for the design of sensitive bioassays for nanomaterial toxicity.
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Affiliation(s)
- José-Julio Ortega-Calvo
- Department of Engineering Science, University of Oxford, Parks Road OX1 3PJ, United Kingdom; Instituto de Recursos Naturales y Agrobiología, C.S.I.C., Apartado 1052, E-41080-Seville, Spain
| | - Celia Jimenez-Sanchez
- Instituto de Recursos Naturales y Agrobiología, C.S.I.C., Apartado 1052, E-41080-Seville, Spain
| | - Paolo Pratarolo
- Instituto de Recursos Naturales y Agrobiología, C.S.I.C., Apartado 1052, E-41080-Seville, Spain
| | - Huw Pullin
- Interface Analysis Centre, University of Bristol, United Kingdom
| | - Thomas B Scott
- Interface Analysis Centre, University of Bristol, United Kingdom
| | - Ian P Thompson
- Department of Engineering Science, University of Oxford, Parks Road OX1 3PJ, United Kingdom.
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24
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Xu J, Nakamura S, Islam MS, Guo Y, Ihara K, Tomioka R, Masuda M, Yoneyama H, Isogai E. Mannose-Binding Lectin Inhibits the Motility of Pathogenic Salmonella by Affecting the Driving Forces of Motility and the Chemotactic Response. PLoS One 2016; 11:e0154165. [PMID: 27104738 PMCID: PMC4841586 DOI: 10.1371/journal.pone.0154165] [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] [Received: 09/10/2015] [Accepted: 04/08/2016] [Indexed: 01/05/2023] Open
Abstract
Mannose-binding lectin (MBL) is a key pattern recognition molecule in the lectin pathway of the complement system, an important component of innate immunity. MBL functions as an opsonin which enhances the sequential immune process such as phagocytosis. We here report an inhibitory effect of MBL on the motility of pathogenic bacteria, which occurs by affecting the energy source required for motility and the signaling pathway of chemotaxis. When Salmonella cells were treated with a physiological concentration of MBL, their motile fraction and free-swimming speed decreased. Rotation assays of a single flagellum showed that the flagellar rotation rate was significantly reduced by the addition of MBL. Measurements of the intracellular pH and membrane potential revealed that MBL affected a driving force for the Salmonella flagellum, the electrochemical potential difference of protons. We also found that MBL treatment increased the reversal frequency of Salmonella flagellar rotation, which interfered with the relative positive chemotaxis toward an attractive substrate. We thus propose that the motility inhibition effect of MBL may be secondarily involved in the attack against pathogens, potentially facilitating the primary role of MBL in the complement system.
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Affiliation(s)
- Jun Xu
- Department of Animal Microbiology, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi, Japan
- * E-mail: (SN); (JX)
| | - Shuichi Nakamura
- Department of Applied Physics, Graduate School of Engineering, Tohoku University, Sendai, Miyagi, Japan
- * E-mail: (SN); (JX)
| | - Md. Shafiqul Islam
- Department of Applied Physics, Graduate School of Engineering, Tohoku University, Sendai, Miyagi, Japan
| | - Yijie Guo
- Department of Immunobiology and Pathogenic Biology, Medical School of Xi’an Jiaotong University, Xi’an, China
| | - Kohei Ihara
- Department of Animal Microbiology, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi, Japan
| | - Rintaro Tomioka
- Department of Animal Microbiology, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi, Japan
| | - Mizuki Masuda
- Department of Animal Microbiology, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi, Japan
| | - Hiroshi Yoneyama
- Department of Animal Microbiology, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi, Japan
| | - Emiko Isogai
- Department of Animal Microbiology, Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi, Japan
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25
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Hollinshead WD, Rodriguez S, Martin HG, Wang G, Baidoo EEK, Sale KL, Keasling JD, Mukhopadhyay A, Tang YJ. Examining Escherichia coli glycolytic pathways, catabolite repression, and metabolite channeling using Δ pfk mutants. BIOTECHNOLOGY FOR BIOFUELS 2016; 9:212. [PMID: 27766116 PMCID: PMC5057261 DOI: 10.1186/s13068-016-0630-y] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 09/28/2016] [Indexed: 05/09/2023]
Abstract
BACKGROUND Glycolysis breakdowns glucose into essential building blocks and ATP/NAD(P)H for the cell, occupying a central role in its growth and bio-production. Among glycolytic pathways, the Entner Doudoroff pathway (EDP) is a more thermodynamically favorable pathway with fewer enzymatic steps than either the Embden-Meyerhof-Parnas pathway (EMPP) or the oxidative pentose phosphate pathway (OPPP). However, Escherichia coli do not use their native EDP for glucose metabolism. RESULTS Overexpression of edd and eda in E. coli to enhance EDP activity resulted in only a small shift in the flux directed through the EDP (~20 % of glycolysis flux). Disrupting the EMPP by phosphofructokinase I (pfkA) knockout increased flux through OPPP (~60 % of glycolysis flux) and the native EDP (~14 % of glycolysis flux), while overexpressing edd and eda in this ΔpfkA mutant directed ~70 % of glycolytic flux through the EDP. The downregulation of EMPP via the pfkA deletion significantly decreased the growth rate, while EDP overexpression in the ΔpfkA mutant failed to improve its growth rates due to metabolic burden. However, the reorganization of E. coli glycolytic strategies did reduce glucose catabolite repression. The ΔpfkA mutant in glucose medium was able to cometabolize acetate via the citric acid cycle and gluconeogenesis, while EDP overexpression in the ΔpfkA mutant repressed acetate flux toward gluconeogenesis. Moreover, 13C-pulse experiments in the ΔpfkA mutants showed unsequential labeling dynamics in glycolysis intermediates, possibly suggesting metabolite channeling (metabolites in glycolysis are pass from enzyme to enzyme without fully equilibrating within the cytosol medium). CONCLUSIONS We engineered E. coli to redistribute its native glycolytic flux. The replacement of EMPP by EDP did not improve E. coli glucose utilization or biomass growth, but alleviated catabolite repression. More importantly, our results supported the hypothesis of channeling in the glycolytic pathways, a potentially overlooked mechanism for regulating glucose catabolism and coutilization of other substrates. The presence of channeling in native pathways, if proven true, would affect synthetic biology applications and metabolic modeling.
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Affiliation(s)
- Whitney D. Hollinshead
- Department of Energy, Environmental and Chemical Engineering, Washington University, St. Louis, MO USA
| | - Sarah Rodriguez
- Sandia National Laboratory, Livermore, CA USA
- Joint BioEnergy Institute, Emeryville, CA USA
| | - Hector Garcia Martin
- Joint BioEnergy Institute, Emeryville, CA USA
- Lawrence Berkeley National Laboratory, Biological Systems and Engineering Division, Berkeley, CA USA
| | - George Wang
- Joint BioEnergy Institute, Emeryville, CA USA
- Lawrence Berkeley National Laboratory, Biological Systems and Engineering Division, Berkeley, CA USA
| | - Edward E. K. Baidoo
- Joint BioEnergy Institute, Emeryville, CA USA
- Lawrence Berkeley National Laboratory, Biological Systems and Engineering Division, Berkeley, CA USA
| | - Kenneth L. Sale
- Joint BioEnergy Institute, Emeryville, CA USA
- Lawrence Berkeley National Laboratory, Biological Systems and Engineering Division, Berkeley, CA USA
| | - Jay D. Keasling
- Joint BioEnergy Institute, Emeryville, CA USA
- Lawrence Berkeley National Laboratory, Biological Systems and Engineering Division, Berkeley, CA USA
- California Institute of Quantitative Biosciences (QB3), University of California, Berkeley, CA USA
- Department of Bioengineering, University of California, Berkeley, CA USA
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA USA
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kogle Allé, DK2970 Hørsholm, Denmark
| | - Aindrila Mukhopadhyay
- Joint BioEnergy Institute, Emeryville, CA USA
- Lawrence Berkeley National Laboratory, Biological Systems and Engineering Division, Berkeley, CA USA
| | - Yinjie J. Tang
- Department of Energy, Environmental and Chemical Engineering, Washington University, St. Louis, MO USA
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26
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H(+) and Na(+) are involved in flagellar rotation of the spirochete Leptospira. Biochem Biophys Res Commun 2015; 466:196-200. [PMID: 26348776 DOI: 10.1016/j.bbrc.2015.09.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 09/01/2015] [Indexed: 11/20/2022]
Abstract
Leptospira is a spirochete possessing intracellular flagella. Each Leptospira flagellar filament is linked with a flagellar motor composed of a rotor and a dozen stators. For many bacterial species, it is known that the stator functions as an ion channel and that the ion flux through the stator is coupled with flagellar rotation. The coupling ion varies depending on the species; for example, H(+) is used in Escherichia coli, and Na(+) is used in Vibrio spp. to drive a polar flagellum. Although genetic and structural studies illustrated that the Leptospira flagellar motor also contains a stator, the coupling ion for flagellar rotation remains unknown. In the present study, we analyzed the motility of Leptospira under various pH values and salt concentrations. Leptospira cells displayed motility in acidic to alkaline pH. In the presence of a protonophore, the cells completely lost motility in acidic to neutral pH but displayed extremely slow movement under alkaline conditions. This result suggests that H(+) is a major coupling ion for flagellar rotation over a wide pH range; however, we also observed that the motility of Leptospira was significantly enhanced by the addition of Na(+), though it vigorously moved even under Na(+)-free conditions. These results suggest that H(+) is preferentially used and that Na(+) is secondarily involved in flagellar rotation in Leptospira. The flexible ion selectivity in the flagellar system could be advantageous for Leptospira to survive in a wide range of environment.
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27
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Park YJ, Chen J. Control of the Biofilms Formed by Curli- and Cellulose-Expressing Shiga Toxin-Producing Escherichia coli Using Treatments with Organic Acids and Commercial Sanitizers. J Food Prot 2015; 78:990-5. [PMID: 25951395 DOI: 10.4315/0362-028x.jfp-14-382] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Biofilms are a mixture of bacteria and extracellular products secreted by bacterial cells and are of great concern to the food industry because they offer physical, mechanical, and biological protection to bacterial cells. This study was conducted to quantify biofilms formed by different Shiga toxin-producing Escherichia coli (STEC) strains on polystyrene and stainless steel surfaces and to determine the effectiveness of sanitizing treatments in control of these biofilms. STEC producing various amounts of cellulose (n = 6) or curli (n = 6) were allowed to develop biofilms on polystyrene and stainless steel surfaces at 28°C for 7 days. The biofilms were treated with 2% acetic or lactic acid and manufacturer-recommended concentrations of acidic or alkaline sanitizers, and residual biofilms were quantified. Treatments with the acidic and alkaline sanitizers were more effective than those with the organic acids for removing the biofilms. Compared with their counterparts, cells expressing a greater amount of cellulose or curli formed more biofilm mass and had greater residual mass after sanitizing treatments on polystyrene than on stainless steel. Research suggests that the organic acids and sanitizers used in the present study differed in their ability to control biofilms. Bacterial surface components and cell contact surfaces can influence both biofilm formation and the efficacy of sanitizing treatments. These results provide additional information on control of biofilms formed by STEC.
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Affiliation(s)
- Yoen Ju Park
- Department of Food Science and Technology, The University of Georgia, Griffin, Georgia 30223-1797, USA
| | - Jinru Chen
- Department of Food Science and Technology, The University of Georgia, Griffin, Georgia 30223-1797, USA.
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Nakamura S, Morimoto YV, Kudo S. A lactose fermentation product produced by Lactococcus lactis subsp. lactis, acetate, inhibits the motility of flagellated pathogenic bacteria. MICROBIOLOGY-SGM 2015; 161:701-7. [PMID: 25573770 DOI: 10.1099/mic.0.000031] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 01/02/2015] [Indexed: 01/17/2023]
Abstract
Many strains of lactic acid bacteria have been used for the production of probiotics. Some metabolites produced by lactic acid bacteria impair the motilities of pathogenic bacteria. Because bacterial motility is strongly associated with virulence, the metabolic activities of lactic acid bacteria are effective for suppressing bacterial infections. Here we show that lactose fermentation by Lactococcus lactis subsp. lactis inhibits the motility of Salmonella enterica serovar Typhimurium. A single-cell tracking and rotation assay for a single flagellum showed that the swimming behaviour of Salmonella was severely but transiently impaired through disruption of flagellar rotation on exposure to media cultivated with Lac. lactis. Using a pH-sensitive fluorescent protein, we observed that the intracellular pH of Salmonella was decreased because of some fermentation products of Lac. lactis. We identified acetate as the lactose fermentation product of Lac. lactis triggering the paralysis of Salmonella flagella. The motilities of Pseudomonas, Vibrio and Leptospira strains were also severely disrupted by lactose utilization by Lac. lactis. These results highlight the potential use of Lac. lactis for preventing infections by multiple bacterial species.
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Affiliation(s)
- Shuichi Nakamura
- Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aoba-ku, Sendai, Miyagi 980-8579, Japan
| | - Yusuke V Morimoto
- Quantitative Biology Center, RIKEN, 6-2-3 Furuedai, Suita, Osaka 565-0874, Japan
| | - Seishi Kudo
- Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aoba-ku, Sendai, Miyagi 980-8579, Japan
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Acetate availability and utilization supports the growth of mutant sub-populations on aging bacterial colonies. PLoS One 2014; 9:e109255. [PMID: 25275605 PMCID: PMC4183559 DOI: 10.1371/journal.pone.0109255] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2014] [Accepted: 09/08/2014] [Indexed: 11/19/2022] Open
Abstract
When bacterial colonies age most cells enter a stationary phase, but sub-populations of mutant bacteria can continue to grow and accumulate. These sub-populations include bacteria with mutations in rpoB (RNA polymerase β-subunit) or rpoS (RNA polymerase stress-response sigma factor). Here we have identified acetate as a nutrient present in the aging colonies that is utilized by these mutant subpopulations to support their continued growth. Proteome analysis of aging colonies showed that several proteins involved in acetate conversion and utilization were upregulated during aging. Acetate is known to be excreted during the exponential growth phase but can be imported later during the transition to stationary phase and converted to acetyl-CoA. Acetyl-CoA is used in multiple processes, including feeding into the TCA cycle, generating ATP via the glyoxylate shunt, as a source of acetyl groups for protein modification, and to support fatty acid biosynthesis. We showed that deletion of acs (encodes acetyl-CoA synthetase; converts acetate into acetyl-CoA) significantly reduced the accumulation of rpoB and rpoS mutant subpopulations on aging colonies. Measurement of radioactive acetate uptake showed that the rate of conversion decreased in aging wild-type colonies, was maintained at a constant level in the rpoB mutant, and significantly increased in the aging rpoS mutant. Finally, we showed that the growth of subpopulations on aging colonies was greatly enhanced if the aging colony itself was unable to utilize acetate, leaving more acetate available for mutant subpopulations to use. Accordingly, the data show that the accumulation of subpopulations of rpoB and rpoS mutants on aging colonies is supported by the availability in the aging colony of acetate, and by the ability of the subpopulation cells to convert the acetate to acetyl-CoA.
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Abstract
Glucose confers acid resistance on exponentially growing bacteria by repressing formation of the cyclic AMP (cAMP)-cAMP receptor protein (CRP) complex and consequently activating acid resistance genes. Therefore, in a glucose-rich growth environment, bacteria are capable of resisting acidic stresses due to low levels of cAMP-CRP. Here we reveal a second mechanism for glucose-conferred acid resistance. We show that glucose induces acid resistance in exponentially growing bacteria through pyruvate, the glycolysis product. Pyruvate and/or the downstream metabolites induce expression of the small noncoding RNA (sncRNA) Spot42, and the sncRNA, in turn, activates expression of the master regulator of acid resistance, RpoS. In contrast to glucose, pyruvate has little effect on levels of the cAMP-CRP complex and does not require the complex for its effects on acid resistance. Another important difference between glucose and pyruvate is that pyruvate can be produced by bacteria. This means that bacteria have the potential to protect themselves from acidic stresses by controlling glucose-derived generation of pyruvate, pyruvate-acetate efflux, or reversion from acetate to pyruvate. We tested this possibility by shutting down pyruvate-acetate efflux and found that the resulting accumulation of pyruvate elevated acid resistance. Many sugars can be broken into glucose, and the subsequent glycolysis generates pyruvate. Therefore, pyruvate-associated acid resistance is not confined to glucose-grown bacteria but is functional in bacteria grown on various sugars.
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Speed switching of gonococcal surface motility correlates with proton motive force. PLoS One 2013; 8:e67718. [PMID: 23826337 PMCID: PMC3691265 DOI: 10.1371/journal.pone.0067718] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 05/21/2013] [Indexed: 11/29/2022] Open
Abstract
Bacterial type IV pili are essential for adhesion to surfaces, motility, microcolony formation, and horizontal gene transfer in many bacterial species. These polymers are strong molecular motors that can retract at two different speeds. In the human pathogen Neisseria gonorrhoeae speed switching of single pili from 2 µm/s to 1 µm/s can be triggered by oxygen depletion. Here, we address the question how proton motive force (PMF) influences motor speed. Using pHluorin expression in combination with dyes that are sensitive to transmembrane ΔpH gradient or transmembrane potential ΔΨ, we measured both components of the PMF at varying external pH. Depletion of PMF using uncouplers reversibly triggered switching into the low speed mode. Reduction of the PMF by ≈ 35 mV was enough to trigger speed switching. Reducing ATP levels by inhibition of the ATP synthase did not induce speed switching. Furthermore, we showed that the strictly aerobic Myxococcus xanthus failed to move upon depletion of PMF or oxygen, indicating that although the mechanical properties of the motor are conserved, its regulatory inputs have evolved differently. We conclude that depletion of PMF triggers speed switching of gonococcal pili. Although ATP is required for gonococcal pilus retraction, our data indicate that PMF is an independent additional energy source driving the high speed mode.
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Abstract
Microorganisms and specifically motile bacteria have been recently added to the list of micro-actuators typically considered for the implementation of microsystems and microrobots. Such trend has been motivated by the fact these microorganisms are self-powered actuators with overall sizes at the lower end of the micrometer range and which have proven to be extremely effective in low Reynolds number hydrodynamic regime of usually less than 10(-2). Furthermore, the various sensors or taxes in bacteria influencing their movements can also be exploited to perform tasks that were previously considered only for futuristic artificial microrobots. Bacterial implementations and related issues are not only reviewed, but this paper also proposes many techniques and approaches that can be considered as building blocks for the implementations of more sophisticated microsystems and microrobots.
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Hung CC, Garner CD, Slauch JM, Dwyer ZW, Lawhon SD, Frye JG, McClelland M, Ahmer BMM, Altier C. The intestinal fatty acid propionate inhibits Salmonella invasion through the post-translational control of HilD. Mol Microbiol 2013; 87:1045-60. [PMID: 23289537 DOI: 10.1111/mmi.12149] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/31/2012] [Indexed: 11/26/2022]
Abstract
To cause disease, Salmonella must invade the intestinal epithelium employing genes encoded within Salmonella Pathogenicity Island 1 (SPI1). We show here that propionate, a fatty acid abundant in the intestine of animals, repressed SPI1 at physiologically relevant concentration and pH, reducing expression of SPI1 transcriptional regulators and consequently decreasing expression and secretion of effector proteins, leading to reduced bacterial penetration of cultured epithelial cells. Essential to repression was hilD, which occupies the apex of the regulatory cascade within SPI1, as loss of only this gene among those of the regulon prevented repression of SPI1 transcription by propionate. Regulation through hilD, however, was achieved through the control of neither transcription nor translation. Instead, growth of Salmonella in propionate significantly reduced the stability of HilD. Extending protein half-life using a Lon protease mutant demonstrated that protein stability itself did not dictate the effects of propionate and suggested modification of HilD with subsequent degradation as the means of action. Furthermore, repression was significantly lessened in a mutant unable to produce propionyl-CoA, while further metabolism of propionyl-CoA appeared not to be required. These results suggest a mechanism of control of Salmonella virulence in which HilD is post-translationally modified using the high-energy intermediate propionyl-CoA.
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Affiliation(s)
- Chien-Che Hung
- Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
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Sun Y, O'Riordan MXD. Regulation of bacterial pathogenesis by intestinal short-chain Fatty acids. ADVANCES IN APPLIED MICROBIOLOGY 2013; 85:93-118. [PMID: 23942149 PMCID: PMC4029053 DOI: 10.1016/b978-0-12-407672-3.00003-4] [Citation(s) in RCA: 197] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The human gut microbiota is inextricably linked to health and disease. One important function of the commensal organisms living in the intestine is to provide colonization resistance against invading enteric pathogens. Because of the complex nature of the interaction between the microbiota and its host, multiple mechanisms likely contribute to resistance. In this review, we dissect the biological role of short-chain fatty acids (SCFA), which are fermentation end products of the intestinal microbiota, in host-pathogen interactions. SCFA exert an extensive influence on host physiology through nutritional, regulatory, and immunomodulatory functions and can also affect bacterial fitness as a form of acid stress. Moreover, SCFA act as a signal for virulence gene regulation in common enteric pathogens. Taken together, these studies highlight the importance of the chemical environment where the biology of the host, the microbiota, and the pathogen intersects, which provides a basis for designing effective infection prevention and control.
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Affiliation(s)
- Yvonne Sun
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
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Demir M, Salman H. Bacterial thermotaxis by speed modulation. Biophys J 2012; 103:1683-90. [PMID: 23083711 DOI: 10.1016/j.bpj.2012.09.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2012] [Revised: 08/07/2012] [Accepted: 09/05/2012] [Indexed: 11/28/2022] Open
Abstract
Naturally occurring gradients often extend over relatively long distances such that their steepness is too small for bacteria to detect. We studied the bacterial behavior in such thermal gradients. We find that bacteria migrate along shallow thermal gradients due to a change in their swimming speed resulting from the effect of temperature on the intracellular pH, which also depends on the chemical environment. When nutrients are scarce in the environment the bacteria's intracellular pH decreases with temperature. As a result, the swimming speed of the bacteria decreases with temperature, which causes them to slowly drift toward the warm end of the thermal gradient. However, when serine is added to the medium at concentrations >300 μM, the intracellular pH increases causing the swimming speed to increase continuously with temperature, and the bacteria to drift toward the cold end of the temperature gradient. This directional migration is not a result of bacterial thermotaxis in the classical sense, because the steepness of the gradients applied is below the sensing threshold of bacteria. Nevertheless, our results show that the directional switch requires the presence of the bacterial sensing receptors. This seems to be due to the involvement of the receptors in regulating the intracellular pH.
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Affiliation(s)
- Mahmut Demir
- Department of Physics and Astronomy, School of Arts and Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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36
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Lee J, Harshey RM. Loss of FlhE in the flagellar Type III secretion system allows proton influx into Salmonella and Escherichia coli. Mol Microbiol 2012; 84:550-65. [PMID: 22435757 DOI: 10.1111/j.1365-2958.2012.08043.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
flhE belongs to the flhBAE flagellar operon in Enterobacteria, whose first two members function in Type III secretion (T3S). In Salmonella enterica, absence of FlhE affects swarming, but not swimming, motility. Based on a chance observation of a 'green' colony phenotype of flhE mutants on pH indicator plates containing glucose, we have established that this phenotype is associated with lysis of flagellated cells in an acidic environment created by glucose metabolism. The flhE mutant phenotype of Escherichia coli is similar overall to that of S. enterica but is seen in the absence of glucose and, unlike in S. enterica, causes a substantial growth defect. flhE mutants have a lowered cytoplasmic pH in both bacteria, indicative of a proton leak. GFP reporter assays indicate that the leak is dependent on the flagellar system, is present before the T3S system switches to secretion of late substrates, and gets worse after the switch and upon filament assembly, leading to cell lysis. We show that FlhE is a periplasmic protein that co-purifies with flagellar basal bodies. FlhE may act as a plug or a chaperone to regulate proton flow through the flagellar T3S system.
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Affiliation(s)
- Jaemin Lee
- Section of Molecular Genetics and Microbiology & Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
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Abstract
This review focuses on the early years of molecular studies of bacterial chemotaxis and motility, beginning in the 1960s with Julius Adler's pioneering work. It describes key observations that established the field and made bacterial chemotaxis a paradigm for the molecular understanding of biological signaling. Consideration of those early years includes aspects of science seldom described in journals: the accidental findings, personal interactions, and scientific culture that often drive scientific progress.
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Zarbiv G, Li H, Wolf A, Cecchini G, Caplan SR, Sourjik V, Eisenbach M. Energy complexes are apparently associated with the switch-motor complex of bacterial flagella. J Mol Biol 2011; 416:192-207. [PMID: 22210351 DOI: 10.1016/j.jmb.2011.12.027] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 12/12/2011] [Accepted: 12/13/2011] [Indexed: 01/27/2023]
Abstract
Recently, the switch-motor complex of bacterial flagella was found to be associated with a number of non-flagellar proteins, which, in spite of not being known as belonging to the chemotaxis system, affect the function of the flagella. The observation that one of these proteins, fumarate reductase, is essentially involved in electron transport under anaerobic conditions raised the question of whether other energy-linked enzymes are associated with the switch-motor complex as well. Here, we identified two additional such enzymes in Escherichia coli. Employing fluorescence resonance energy transfer in vivo and pull-down assays invitro, we provided evidence for the interaction of F(0)F(1) ATP synthase via its β subunit with the flagellar switch protein FliG and for the interaction of NADH-ubiquinone oxidoreductase with FliG, FliM, and possibly FliN. Furthermore, we measured higher rates of ATP synthesis, ATP hydrolysis, and electron transport from NADH to oxygen in membrane areas adjacent to the flagellar motor than in other membrane areas. All these observations suggest the association of energy complexes with the flagellar switch-motor complex. Finding that deletion of the β subunit in vivo affected the direction of flagellar rotation and switching frequency further implied that the interaction of F(0)F(1) ATP synthase with FliG is important for the function of the switch of bacterial flagella.
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Affiliation(s)
- Gabriel Zarbiv
- Department of Biological Chemistry, The Weizmann Institute of Science, 76100 Rehovot, Israel
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Mu Y, Lin J, Liu R. Interaction of sodium benzoate with trypsin by spectroscopic techniques. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2011; 83:130-135. [PMID: 21890401 DOI: 10.1016/j.saa.2011.07.092] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Revised: 07/22/2011] [Accepted: 07/26/2011] [Indexed: 05/31/2023]
Abstract
The toxicity of sodium benzoate to trypsin was investigated by fluorescence spectroscopy, synchronous fluorescence spectroscopy, UV-visible absorption spectroscopy and circular dichroism (CD) spectroscopy under mimic physiological conditions. Sodium benzoate could unfold trypsin by decreasing the β-sheet structure, which leads to more exposure of internal amino acid groups and the obvious intrinsic fluorescence quenching with the rising concentration of sodium benzoate. The results of spectroscopic measurements indicated that sodium benzoate changed the internal microenvironment of trypsin and induced the alteration of the whole molecule, which were performed toxic effects on the organism. Trypsin and sodium benzoate interacted with each other to produce a substance by van der Waals forces and hydrogen bond, the model of which was shown by AutoDock software.
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Affiliation(s)
- Yue Mu
- Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Shandong Province, Jinan, PR China
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Abstract
After a childhood in Germany and being a youth in Grand Forks, North Dakota, I went to Harvard University, then to graduate school in biochemistry at the University of Wisconsin. Then to Washington University and Stanford University for postdoctoral training in biochemistry and genetics. Then at the University of Wisconsin, as a professor in the Department of Biochemistry and the Department of Genetics, I initiated research on bacterial chemotaxis. Here, I review this research by me and by many, many others up to the present moment. During the past few years, I have been studying chemotaxis and related behavior in animals, namely in Drosophila fruit flies, and some of these results are presented here. My current thinking is described.
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Affiliation(s)
- Julius Adler
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706-1544, USA.
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Phenol sensing by Escherichia coli chemoreceptors: a nonclassical mechanism. J Bacteriol 2011; 193:6597-604. [PMID: 21965561 DOI: 10.1128/jb.05987-11] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The four transmembrane chemoreceptors of Escherichia coli sense phenol as either an attractant (Tar) or a repellent (Tap, Trg, and Tsr). In this study, we investigated the Tar determinants that mediate its attractant response to phenol and the Tsr determinants that mediate its repellent response to phenol. Tar molecules with lesions in the aspartate-binding pocket of the periplasmic domain, with a foreign periplasmic domain (from Tsr or from several Pseudomonas chemoreceptors), or lacking nearly the entire periplasmic domain still mediated attractant responses to phenol. Similarly, Tar molecules with the cytoplasmic methylation and kinase control domains of Tsr still sensed phenol as an attractant. Additional hybrid receptors with signaling elements from both Tar and Tsr indicated that the transmembrane (TM) helices and HAMP domain determined the sign of the phenol-sensing response. Several amino acid replacements in the HAMP domain of Tsr, particularly attractant-mimic signaling lesions at residue E248, converted Tsr to an attractant sensor of phenol. These findings suggest that phenol may elicit chemotactic responses by diffusing into the cytoplasmic membrane and perturbing the structural stability or position of the TM bundle helices, in conjunction with structural input from the HAMP domain. We conclude that behavioral responses to phenol, and perhaps to temperature, cytoplasmic pH, and glycerol, as well, occur through a general sensing mechanism in chemoreceptors that detects changes in the structural stability or dynamic behavior of a receptor signaling element. The structurally sensitive target for phenol is probably the TM bundle, but other behaviors could target other receptor elements.
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Effects of dissolved oxygen availability and culture biomass at induction upon the intracellular expression of monoamine oxidase by recombinant E. coli in fed batch bioprocesses. Process Biochem 2011. [DOI: 10.1016/j.procbio.2010.11.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Evidence for symmetry in the elementary process of bidirectional torque generation by the bacterial flagellar motor. Proc Natl Acad Sci U S A 2010; 107:17616-20. [PMID: 20876126 DOI: 10.1073/pnas.1007448107] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The bacterial flagellar motor can rotate in both counterclockwise (CCW) and clockwise (CW) directions. It has been shown that the sodium ion-driven chimeric flagellar motor rotates with 26 steps per revolution, which corresponds to the number of FliG subunits that form part of the rotor ring, but the size of the backward step is smaller than the forward one. Here we report that the proton-driven flagellar motor of Salmonella also rotates with 26 steps per revolution but symmetrical in both CCW and CW directions with occasional smaller backward steps in both directions. Occasional shift in the stepping positions is also observed, suggesting the frequent exchange of stators in one of the 11-12 possible anchoring positions around the rotor. These observations indicate that the elementary process of torque generation by the cyclic association/dissociation of the stator with every FliG subunit along the circumference of the rotor is symmetric in CCW and CW rotation even though the structure of FliG is highly asymmetric and suggests a 180° rotation of a FliG domain for the rotor-stator interaction to reverse the direction of rotation.
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Srinivasan K, Mahadevan R. Characterization of proton production and consumption associated with microbial metabolism. BMC Biotechnol 2010; 10:2. [PMID: 20089195 PMCID: PMC2831035 DOI: 10.1186/1472-6750-10-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Accepted: 01/20/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Production or consumption of protons in growth medium during microbial metabolism plays an important role in determining the pH of the environment. Such pH changes resulting from microbial metabolism may influence the geochemical speciation of many elements in subsurface environments. Protons produced or consumed during microbial growth were measured by determining the amount of acid or base added in a 5 L batch bioreactor equipped with pH control for different species including Escherichia coli, Geobacter sulfurreducens, and Geobacter metallireducens. RESULTS An in silico model was used to predict the proton secretion or consumption rates and the results were compared with the data. The data was found to confirm predictions of proton consumption during aerobic growth of E. coli with acetate as the carbon source. However, in contrast to proton consumption observed during aerobic growth of E. coli with acetate, proton secretion was observed during growth of Geobacter species with acetate as the donor and Fe(III) as the extracellular electron acceptor. CONCLUSIONS In this study, we have also shown that the final pH of the medium can be either acidic or basic depending on the choice of the electron acceptor for the same electron donor. In all cases, the in silico model could predict qualitatively the proton production/consumption rates obtained from the experimental data. Therefore, measurements of pH equivalents generated or consumed during growth can help characterize the microbial physiology further and can be valuable for optimizing practical applications such as microbial fuel cells, where growth associated pH changes can limit current generation rates.
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Affiliation(s)
- Karthikeyan Srinivasan
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario M5S3E5, Canada
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Lüders S, Fallet C, Franco-Lara E. Proteome analysis of the Escherichia coli heat shock response under steady-state conditions. Proteome Sci 2009; 7:36. [PMID: 19772559 PMCID: PMC2758844 DOI: 10.1186/1477-5956-7-36] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Accepted: 09/21/2009] [Indexed: 11/17/2022] Open
Abstract
In this study a proteomic approach was used to investigate the steady-state response of Escherichia coli to temperature up-shifts in a cascade of two continuously operated bioreactors. The first reactor served as cell source with optimal settings for microbial growth, while in the second chemostat the cells were exposed to elevated temperatures. By using this reactor configuration, which has not been reported to be used for the study of bacterial stress responses so far, it is possible to study temperature stress under well-defined, steady-state conditions. Specifically the effect on the cellular adaption to temperature stress using two-dimensional gel electrophoresis was examined and compared at the cultivation temperatures of 37 degrees C and 47.5 degrees C. As expected, the steady-state study with the double bioreactor configuration delivered a different protein spectrum compared to that obtained with standard batch experiments in shaking flasks and bioreactors. Setting a high cut-out spot-to-spot size ratio of 5, proteins involved in defence against oxygen stress, functional cell envelope proteins, chaperones and proteins involved in protein biosynthesis, the energy metabolism and the amino acid biosynthesis were found to be differently expressed at high cultivation temperatures. The results demonstrate the complexity of the stress response in a steady-state culture not reported elsewhere to date.
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Affiliation(s)
- Svenja Lüders
- Institute of Biochemical Engineering, Technische Universität Braunschweig, Gausstrasse 17, 38106 Braunschweig, Germany
| | - Claas Fallet
- Institute of Biochemical Engineering, Technische Universität Braunschweig, Gausstrasse 17, 38106 Braunschweig, Germany
| | - Ezequiel Franco-Lara
- Institute of Biochemical Engineering, Technische Universität Braunschweig, Gausstrasse 17, 38106 Braunschweig, Germany
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Slonczewski JL, Fujisawa M, Dopson M, Krulwich TA. Cytoplasmic pH measurement and homeostasis in bacteria and archaea. Adv Microb Physiol 2009; 55:1-79, 317. [PMID: 19573695 DOI: 10.1016/s0065-2911(09)05501-5] [Citation(s) in RCA: 289] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Of all the molecular determinants for growth, the hydronium and hydroxide ions are found naturally in the widest concentration range, from acid mine drainage below pH 0 to soda lakes above pH 13. Most bacteria and archaea have mechanisms that maintain their internal, cytoplasmic pH within a narrower range than the pH outside the cell, termed "pH homeostasis." Some mechanisms of pH homeostasis are specific to particular species or groups of microorganisms while some common principles apply across the pH spectrum. The measurement of internal pH of microbes presents challenges, which are addressed by a range of techniques under varying growth conditions. This review compares and contrasts cytoplasmic pH homeostasis in acidophilic, neutralophilic, and alkaliphilic bacteria and archaea under conditions of growth, non-growth survival, and biofilms. We present diverse mechanisms of pH homeostasis including cell buffering, adaptations of membrane structure, active ion transport, and metabolic consumption of acids and bases.
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Nakamura S, Kami-ike N, Yokota JIP, Kudo S, Minamino T, Namba K. Effect of intracellular pH on the torque-speed relationship of bacterial proton-driven flagellar motor. J Mol Biol 2008; 386:332-8. [PMID: 19133273 DOI: 10.1016/j.jmb.2008.12.034] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2008] [Revised: 12/11/2008] [Accepted: 12/12/2008] [Indexed: 11/24/2022]
Abstract
Bacterial flagella responsible for motility are driven by rotary motors powered by the electrochemical potential difference of specific ions across the cytoplasmic membrane. The stator of proton-driven flagellar motor converts proton influx into mechanical work. However, the energy conversion mechanism remains unclear. Here, we show that the motor is sensitive to intracellular proton concentration for high-speed rotation at low load, which was considerably impaired by lowering intracellular pH, while zero-speed torque was not affected. The change in extracellular pH did not show any effect. These results suggest that a high intracellular proton concentration decreases the rate of proton translocation and therefore that of the mechanochemical reaction cycle of the motor but not the actual torque generation step within the cycle by the stator-rotor interactions.
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McLoughlin A, Vallom J. The influence of ionic gradients on flocculation ofBrevibacteriumsp. ACTA ACUST UNITED AC 2008. [DOI: 10.1111/j.1365-2672.1984.tb01414.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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JARVIK JONATHANW, REINHART FREDERICKD, KUCHKA MICHAELR, ADLER SALLYA. Altered Flagellar Size-Control inshf-1Short-Flagella Mutants ofChlamydomonas reinhardtii. ACTA ACUST UNITED AC 2007. [DOI: 10.1111/j.1550-7408.1984.tb02949.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Hosking ER, Vogt C, Bakker EP, Manson MD. The Escherichia coli MotAB Proton Channel Unplugged. J Mol Biol 2006; 364:921-37. [PMID: 17052729 DOI: 10.1016/j.jmb.2006.09.035] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2006] [Revised: 09/08/2006] [Accepted: 09/11/2006] [Indexed: 11/26/2022]
Abstract
The MotA and MotB proteins of Escherichia coli serve two functions. The MotA4MotB2 complex attaches to the cell wall via MotB to form the stator of the flagellar motor. The complex also couples the flow of hydrogen ions across the cell membrane to movement of the rotor. The TM3 and TM4 transmembrane helices of MotA and the single TM of MotB comprise the proton channel, which is inactive until the complex assembles into a motor. Here, we identify a segment of the MotB protein that acts as a plug to prevent premature proton flow. The plug is in the periplasm just C-terminal to the MotB TM. It consists of an amphipathic alpha helix flanked by Pro52 and Pro65. When MotA is over-expressed with MotB deleted for residues 51-70, a massive influx of protons acidifies the cytoplasm without significantly depleting the proton motive force. Either that acidification or some sequela thereof, such as potassium or water efflux from the cells, inhibits growth. The Pro residues and Ile58, Tyr61, and Phe62 are essential for plug function. Cys-substituted MotB proteins form a disulfide bond between the two plugs that hold the channels open, and the plugs function intrans within the MotA4MotB2 complex. We present a model in which the MotA4MotB2 complex forms in the bulk membrane. Before association with a motor, we propose the plugs insert into the cell membrane parallel with its periplasmic face and interfere with channel formation. When a complex incorporates into a motor, the plugs leave the membrane and associate with each other via their hydrophobic faces to hold the proton channel open.
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Affiliation(s)
- Edan R Hosking
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA
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