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Sidarta M, Lorente Martín AI, Monsalve A, Marinho Righetto G, Schäfer AB, Wenzel M. Lipid phase separation impairs membrane thickness sensing by the Bacillus subtilis sensor kinase DesK. Microbiol Spectr 2024; 12:e0392523. [PMID: 38717171 DOI: 10.1128/spectrum.03925-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2023] [Accepted: 04/08/2024] [Indexed: 06/06/2024] Open
Abstract
Membrane fluidity and thickness have emerged as crucial factors for the activity of and resistance to several antimicrobials. However, the lack of tools to study membrane fluidity and, in particular, thickness in living bacteria limits our understanding of this interplay. The Bacillus subtilis histidine kinase/phosphatase DesK is a molecular sensor that directly detects membrane thickness. It controls activity of DesR, which regulates expression of the lipid desaturase Des, known for its role in cold adaptation and daptomycin susceptibility. We hypothesized that this property could be exploited to develop biosensors and reporters for antibiotic-induced changes in membrane fluidity and thickness. To test this, we designed three assays based on the des system: activation of the Pdes promoter as reporter for membrane thickening, localization of DesK-GFP(green-fluorescent protein) as proxy for rigidified membrane domains, and antibiotic sensitivity of des, desK, and desR deletion mutants as readout for the importance of membrane rigidification/thickening under the tested condition. While we could not confirm the suitability of the des system as reporter for antibiotic-induced changes in membrane thickness, we did observe that des expression is only activated by mild temperature shocks, likely due to partitioning of the sensor DesK into fluid membrane domains upon phase separation, precluding effective thickness sensing under harsh cold shock and antibiotic stress conditions. Similarly, we did not observe any sensitivity of the deletion mutants to either temperature or antibiotic stress, raising the question to what extent the des system contributes to fluidity adaptation under these conditions. IMPORTANCE The B. subtilis des system is a prime model for direct molecular membrane thickness sensor and, as such, has been well studied in vitro. Our study shows that our understanding of its function in vivo and its importance under temperature and antibiotic stress is still very limited. Specifically, our results suggest that (i) the des system senses very subtle membrane fluidity changes that escape detection by established fluidity reporters like laurdan; (ii) membrane thickness sensing by DesK is impaired by phase separation due to partitioning of the protein into the fluid phase; and (iii) fluidity adaptations by Des are too subtle to elicit growth defects under rigidifying conditions, raising the question of how much the des system contributes to adaptation of overall membrane fluidity.
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Affiliation(s)
- Margareth Sidarta
- Division of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
- Centre for Antibiotic Resistance Research in Gothenburg (CARe), Gothenburg, Sweden
| | - Ana I Lorente Martín
- Division of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
| | - Anuntxi Monsalve
- Division of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
| | - Gabriela Marinho Righetto
- Division of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
- Centre for Antibiotic Resistance Research in Gothenburg (CARe), Gothenburg, Sweden
| | - Ann-Britt Schäfer
- Division of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
- Centre for Antibiotic Resistance Research in Gothenburg (CARe), Gothenburg, Sweden
| | - Michaela Wenzel
- Division of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
- Centre for Antibiotic Resistance Research in Gothenburg (CARe), Gothenburg, Sweden
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Okouakoua FY, Kayath CA, Mokemiabeka SN, Moukala DCR, Kaya-Ongoto MD, Nguimbi E. Involvement of the Bacillus SecYEG Pathway in Biosurfactant Production and Biofilm Formation. Int J Microbiol 2024; 2024:6627190. [PMID: 38725978 PMCID: PMC11081756 DOI: 10.1155/2024/6627190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 04/02/2024] [Accepted: 04/15/2024] [Indexed: 05/12/2024] Open
Abstract
With Bacillus species, about 30% of extracellular proteins are translocated through the cytoplasmic membrane, coordinated by the Sec translocase. This system mainly consists of the cytoplasmic ATPase SecA and the membrane-embedded SecYEG channel. The purpose of this work was to investigate the effects of the SecYEG export system on the production of industrial biomolecules, such as biosurfactants, proteases, amylases, and cellulases. Fifty-two isolates of Bacillus species were obtained from traditional fermented foods and then characterized using molecular microbiology methods. The isolates secreted exoenzymes that included cellulases, amylases, and proteases. We present evidence that a biosurfactant-like molecule requires the SecA ATPase and the SecYEG membrane channel for its secretion. In addition, we showed that biomolecules involved in biofilm formation required the SecYEG pathway. This work presents a novel seven-target fragment multiplex PCR assay capable of identification at the species level of Bacillus through a unique SecDF chromosomal gene. The bacterial membrane protein SecDF allowed the discrimination of Bacillus subtilis, B. licheniformis, B. amyloliquefaciens, and B. sonorensis. SecA was able to interact with AprE, AmyE, and TasA. The Rose Bengal inhibitor of SecA crucially affected the interaction of AprE, AmyE, TapA, and TasA with recombinant Gst-SecA. The Rose Bengal prevented Bacillus species from secreting and producing proteases, cellulases, amylases, and biosurfactant-like molecules. It also inhibited the formation of biofilm cell communities. The data support, for the first time, that the SecYEG translocon mediates the secretion of a biosurfactant-like molecule.
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Affiliation(s)
- Frédéric Yannick Okouakoua
- Laboratoire de Biologie Cellulaire et Moléculaire (BCM), Faculté des Sciences et Techniques, Université Marien N'GOUABI, BP. 69, Brazzaville, Congo
- Institut National de Recherche en Sciences Exactes et Naturelles (IRSEN), Avenue de l'Auberge Gascogne, B.P 2400, Brazzaville, Congo
| | - Christian Aimé Kayath
- Laboratoire de Biologie Cellulaire et Moléculaire (BCM), Faculté des Sciences et Techniques, Université Marien N'GOUABI, BP. 69, Brazzaville, Congo
- Institut National de Recherche en Sciences Exactes et Naturelles (IRSEN), Avenue de l'Auberge Gascogne, B.P 2400, Brazzaville, Congo
| | - Saturnin Nicaise Mokemiabeka
- Laboratoire de Biologie Cellulaire et Moléculaire (BCM), Faculté des Sciences et Techniques, Université Marien N'GOUABI, BP. 69, Brazzaville, Congo
- Institut National de Recherche en Sciences Exactes et Naturelles (IRSEN), Avenue de l'Auberge Gascogne, B.P 2400, Brazzaville, Congo
| | - David Charles Roland Moukala
- Laboratoire de Biologie Cellulaire et Moléculaire (BCM), Faculté des Sciences et Techniques, Université Marien N'GOUABI, BP. 69, Brazzaville, Congo
- Institut National de Recherche en Sciences Exactes et Naturelles (IRSEN), Avenue de l'Auberge Gascogne, B.P 2400, Brazzaville, Congo
| | - Moïse Doria Kaya-Ongoto
- Laboratoire de Biologie Cellulaire et Moléculaire (BCM), Faculté des Sciences et Techniques, Université Marien N'GOUABI, BP. 69, Brazzaville, Congo
- Institut National de Recherche en Sciences Exactes et Naturelles (IRSEN), Avenue de l'Auberge Gascogne, B.P 2400, Brazzaville, Congo
| | - Etienne Nguimbi
- Laboratoire de Biologie Cellulaire et Moléculaire (BCM), Faculté des Sciences et Techniques, Université Marien N'GOUABI, BP. 69, Brazzaville, Congo
- Institut National de Recherche en Sciences Exactes et Naturelles (IRSEN), Avenue de l'Auberge Gascogne, B.P 2400, Brazzaville, Congo
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Schäfer AB, Sidarta M, Abdelmesseh Nekhala I, Marinho Righetto G, Arshad A, Wenzel M. Dissecting antibiotic effects on the cell envelope using bacterial cytological profiling: a phenotypic analysis starter kit. Microbiol Spectr 2024; 12:e0327523. [PMID: 38289933 PMCID: PMC10913488 DOI: 10.1128/spectrum.03275-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Accepted: 12/19/2023] [Indexed: 02/01/2024] Open
Abstract
Phenotypic analysis assays such as bacterial cytological profiling (BCP) have become increasingly popular for antibiotic mode of action analysis. A plethora of dyes, protein fusions, and reporter strains are available and have been used for this purpose, enabling both rapid mode of action categorization and in-depth analysis of antibiotic mechanisms. However, non-expert researchers may struggle choosing suitable assays and interpreting results. This is a particular problem for antibiotics that have multiple or complex targets, such as the bacterial cell envelope. Here, we set out to curate a minimal set of accessible and affordable phenotypic assays that allow distinction between membrane and cell wall targets, can identify dual-action inhibitors, and can be implemented in most research environments. To this end, we employed BCP, membrane potential, fluidity, and cell wall synthesis assays. To assess specificity and ease of interpretation, we tested three well-characterized and commercially available reference antibiotics: the potassium ionophore valinomycin, the lipid II-binding glycopeptide vancomycin, and the dual-action lantibiotic nisin, which binds lipid II and forms a membrane pore. Based on our experiments, we suggest a minimal set of BCP, a membrane-potentiometric probe, and fluorescent protein fusions to MinD and MreB as basic assay set and recommend complementing these assays with Laurdan-based fluidity measurements and a PliaI reporter fusion, where indicated. We believe that our results can provide guidance for researchers who wish to use phenotypic analysis for mode of action studies but do not possess the specialized equipment or expert knowledge to employ the full breadth of possible techniques.IMPORTANCEPhenotypic analysis assays using specialized fluorescence fusions and dyes have become increasingly popular in antibiotic mode of action analysis. However, it can be difficult to implement these methods due to the need for specialized equipment and/or the complexity of bacterial cell biology and physiology, making the interpretation of results difficult for non-experts. This is especially problematic for compounds that have multiple or pleiotropic effects, such as inhibitors of the bacterial cell envelope. In order to make phenotypic analysis assays accessible to labs, whose primary expertise is not bacterial cell biology, or with limited equipment and resources, a set of simple and broadly accessible assays is needed that is easy to implement, execute, and interpret. Here, we have curated a set of assays and strains that does not need highly specialized equipment, can be performed in most labs, and is straightforward to interpret without knowing the intricacies of bacterial cell biology.
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Affiliation(s)
- Ann-Britt Schäfer
- Division of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
- Center for Antibiotic Resistance Research in Gothenburg (CARe), Gothenburg, Sweden
| | - Margareth Sidarta
- Division of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
- Center for Antibiotic Resistance Research in Gothenburg (CARe), Gothenburg, Sweden
| | - Ireny Abdelmesseh Nekhala
- Division of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
| | - Gabriela Marinho Righetto
- Division of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
- Center for Antibiotic Resistance Research in Gothenburg (CARe), Gothenburg, Sweden
| | - Aysha Arshad
- Division of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
| | - Michaela Wenzel
- Division of Chemical Biology, Department of Life Sciences, Chalmers University of Technology, Gothenburg, Sweden
- Center for Antibiotic Resistance Research in Gothenburg (CARe), Gothenburg, Sweden
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Wang B, van der Kloet F, Hamoen LW. Induction of the CtsR regulon improves Xylanase production in Bacillus subtilis. Microb Cell Fact 2023; 22:231. [PMID: 37946188 PMCID: PMC10633939 DOI: 10.1186/s12934-023-02239-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Accepted: 10/27/2023] [Indexed: 11/12/2023] Open
Abstract
BACKGROUND The bacterium Bacillus subtilis is extensively used for the commercial production of enzymes due to its efficient protein secretion capacity. However, the efficiency of secretion varies greatly between enzymes, and despite many years of research, optimization of enzyme production is still largely a matter of trial-and-error. Genome-wide transcriptome analysis seems a useful tool to identify relevant secretion bottlenecks, yet to this day, only a limited number of transcriptome studies have been published that focus on enzyme secretion in B. subtilis. Here, we examined the effect of high-level expression of the commercially important enzyme endo-1,4-β-xylanase XynA on the B. subtilis transcriptome using RNA-seq. RESULTS Using the novel gene-set analysis tool GINtool, we found a reduced activity of the CtsR regulon when XynA was overproduced. This regulon comprises several protein chaperone genes, including clpC, clpE and clpX, and is controlled by transcriptional repression. CtsR levels are directly controlled by regulated proteolysis, involving ClpC and its cognate protease ClpP. When we abolished this negative feedback, by inactivating the repressor CtsR, the XynA production increased by 25%. CONCLUSIONS Overproduction of enzymes can reduce the pool of Clp protein chaperones in B. subtilis, presumably due to negative feedback regulation. Breaking this feedback can improve enzyme production yields. Considering the conserved nature of Clp chaperones and their regulation, this method might benefit high-yield enzyme production in other organisms.
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Affiliation(s)
- Biwen Wang
- Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, C3.108, 1098 XH, Amsterdam, The Netherlands
| | - Frans van der Kloet
- Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, C3.108, 1098 XH, Amsterdam, The Netherlands
| | - Leendert W Hamoen
- Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, C3.108, 1098 XH, Amsterdam, The Netherlands.
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