1
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Zhang G, Li B, Yang Y, Zhang Z, Cheng D, Wang F, Wei Z, Mao N, Wang S, Liu X, Sun Y. Biodegradation of humic acids by Streptomyces rochei to promote the growth and yield of corn. Microbiol Res 2024; 286:127826. [PMID: 38964074 DOI: 10.1016/j.micres.2024.127826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 06/28/2024] [Accepted: 06/29/2024] [Indexed: 07/06/2024]
Abstract
Humic acids (HAs) are organic macromolecules that play an important role in improving soil properties, plant growth and agronomic parameters. However, the feature of relatively complex aromatic structure makes it difficult to be degraded, which restricts the promotion to the crop growth. Thus, exploring microorganisms capable of degrading HAs may be a potential solution. Here, a HAs-degrading strain, Streptomyces rochei L1, and its potential for biodegradation was studied by genomics, transcriptomics, and targeted metabolomics analytical approaches. The results showed that the high molecular weight HAs were cleaved to low molecular aliphatic and aromatic compounds and their derivatives. This cleavage may be associated with the laccase (KatE). In addition, the polysaccharide deacetylase (PdgA) catalyzes the removal of acetyl groups from specific sites on the HAs molecule, resulting in structural changes. The field experiment showed that the degraded HAs significantly promote the growth of corn seedlings and increase the corn yield by 3.6 %. The HAs-degrading products, including aromatic and low molecular weight aliphatic substances as well as secondary metabolites from S. rochei L1, might be the key components responsible for the corn promotion. Our findings will advance the application of HAs as soil nutrients for the green and sustainable agriculture.
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Affiliation(s)
- Guangming Zhang
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Provincial Key Laboratory of Biotechnology, College of Life Sciences, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi 710069, China
| | - Baolei Li
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Provincial Key Laboratory of Biotechnology, College of Life Sciences, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi 710069, China
| | - Yong Yang
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Provincial Key Laboratory of Biotechnology, College of Life Sciences, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi 710069, China
| | - Zhen Zhang
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Provincial Key Laboratory of Biotechnology, College of Life Sciences, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi 710069, China
| | - Dujuan Cheng
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Provincial Key Laboratory of Biotechnology, College of Life Sciences, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi 710069, China
| | - Furong Wang
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Provincial Key Laboratory of Biotechnology, College of Life Sciences, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi 710069, China
| | - Ziyi Wei
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Provincial Key Laboratory of Biotechnology, College of Life Sciences, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi 710069, China
| | - Ning Mao
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Provincial Key Laboratory of Biotechnology, College of Life Sciences, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi 710069, China
| | - Shiwei Wang
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Provincial Key Laboratory of Biotechnology, College of Life Sciences, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi 710069, China.
| | - Xiaobo Liu
- Key Laboratory of Metabolic Engineering and Biosynthesis Technology, Ministry of Industry and Information Technology, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094, China.
| | - Yanmei Sun
- Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Provincial Key Laboratory of Biotechnology, College of Life Sciences, Northwest University, 229 Taibai North Road, Xi'an, Shaanxi 710069, China.
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2
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Bollinger KW, Müh U, Ocius KL, Apostolos AJ, Pires MM, Helm RF, Popham DL, Weiss DS, Ellermeier CD. Identification of a family of peptidoglycan transpeptidases reveals that Clostridioides difficile requires noncanonical cross-links for viability. Proc Natl Acad Sci U S A 2024; 121:e2408540121. [PMID: 39150786 DOI: 10.1073/pnas.2408540121] [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: 04/30/2024] [Accepted: 07/12/2024] [Indexed: 08/18/2024] Open
Abstract
Most bacteria are surrounded by a cell wall that contains peptidoglycan (PG), a large polymer composed of glycan strands held together by short peptide cross-links. There are two major types of cross-links, termed 4-3 and 3-3 based on the amino acids involved. 4-3 cross-links are created by penicillin-binding proteins, while 3-3 cross-links are created by L,D-transpeptidases (LDTs). In most bacteria, the predominant mode of cross-linking is 4-3, and these cross-links are essential for viability, while 3-3 cross-links comprise only a minor fraction and are not essential. However, in the opportunistic intestinal pathogen Clostridioides difficile, about 70% of the cross-links are 3-3. We show here that 3-3 cross-links and LDTs are essential for viability in C. difficile. We also show that C. difficile has five LDTs, three with a YkuD catalytic domain as in all previously known LDTs and two with a VanW catalytic domain, whose function was until now unknown. The five LDTs exhibit extensive functional redundancy. VanW domain proteins are found in many gram-positive bacteria but scarce in other lineages. We tested seven non-C. difficile VanW domain proteins and confirmed LDT activity in three cases. In summary, our findings uncover a previously unrecognized family of PG cross-linking enzymes, assign a catalytic function to VanW domains, and demonstrate that 3-3 cross-linking is essential for viability in C. difficile, the first time this has been shown in any bacterial species. The essentiality of LDTs in C. difficile makes them potential targets for antibiotics that kill C. difficile selectively.
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Affiliation(s)
- Kevin W Bollinger
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242
| | - Ute Müh
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242
| | - Karl L Ocius
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904
| | - Alexis J Apostolos
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904
| | - Marcos M Pires
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904
| | - Richard F Helm
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061
| | - David L Popham
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061
| | - David S Weiss
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242
- Graduate Program in Genetics, University of Iowa, Iowa City, IA 52242
| | - Craig D Ellermeier
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242
- Graduate Program in Genetics, University of Iowa, Iowa City, IA 52242
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3
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Inostroza O, Fuentes JA, Yáñez P, Espinoza G, Fica O, Queraltó C, Rodríguez J, Flores I, González R, Soto JA, Calderón IL, Gil F. Characterization of Clostridioides difficile Persister Cells and Their Role in Antibiotic Tolerance. Microorganisms 2024; 12:1394. [PMID: 39065162 PMCID: PMC11279270 DOI: 10.3390/microorganisms12071394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2024] [Revised: 07/04/2024] [Accepted: 07/06/2024] [Indexed: 07/28/2024] Open
Abstract
Clostridioides difficile is a Gram-positive pathogen known for its toxin production and spore formation. It is primarily responsible for most cases of antibiotic-associated diarrhea. Bacterial persisters are a small subset of the population that exhibits transient tolerance to bactericidal substances, and they are of significant medical concern due to their association with the emergence of antibiotic resistance and difficult-to-treat chronic or recurrent infections. Vancomycin, the predominant antibiotic utilized in the management of C. difficile infection, is extensively applied in the realm of clinical practice. Previous studies have demonstrated a persister-like phenotype with treatments involving this antibiotic. However, the mechanism in C. difficile remains largely unknown, primarily due to the challenge of isolating this small population at any given time. To better characterize C. difficile persister cells, we present a study that enables the enrichment and characterization of persister cells from bacterial cultures in both the exponential and stationary phases. Moreover, we could differentiate between triggered (induced using antibiotics such as vancomycin) and spontaneous (stochastic) persister cells. Additionally, we observed the involvement of toxin-antitoxin systems and Clp proteases in persister cell formation.
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Affiliation(s)
- Osvaldo Inostroza
- Microbiota-Host Interactions and Clostridia Research Group, Departamento de Ciencias Biológicas, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago 8370186, Chile; (O.I.); (P.Y.); (G.E.); (O.F.); camilabelen.-@hotmail.com (C.Q.); (J.R.); (I.F.); (R.G.)
| | - Juan A. Fuentes
- Laboratorio de Genética y Patogénesis Bacteriana, Departamento de Ciencias Biológicas, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago 8370186, Chile;
| | - Paulina Yáñez
- Microbiota-Host Interactions and Clostridia Research Group, Departamento de Ciencias Biológicas, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago 8370186, Chile; (O.I.); (P.Y.); (G.E.); (O.F.); camilabelen.-@hotmail.com (C.Q.); (J.R.); (I.F.); (R.G.)
| | - Giovanni Espinoza
- Microbiota-Host Interactions and Clostridia Research Group, Departamento de Ciencias Biológicas, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago 8370186, Chile; (O.I.); (P.Y.); (G.E.); (O.F.); camilabelen.-@hotmail.com (C.Q.); (J.R.); (I.F.); (R.G.)
| | - Omar Fica
- Microbiota-Host Interactions and Clostridia Research Group, Departamento de Ciencias Biológicas, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago 8370186, Chile; (O.I.); (P.Y.); (G.E.); (O.F.); camilabelen.-@hotmail.com (C.Q.); (J.R.); (I.F.); (R.G.)
| | - Camila Queraltó
- Microbiota-Host Interactions and Clostridia Research Group, Departamento de Ciencias Biológicas, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago 8370186, Chile; (O.I.); (P.Y.); (G.E.); (O.F.); camilabelen.-@hotmail.com (C.Q.); (J.R.); (I.F.); (R.G.)
| | - José Rodríguez
- Microbiota-Host Interactions and Clostridia Research Group, Departamento de Ciencias Biológicas, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago 8370186, Chile; (O.I.); (P.Y.); (G.E.); (O.F.); camilabelen.-@hotmail.com (C.Q.); (J.R.); (I.F.); (R.G.)
| | - Isidora Flores
- Microbiota-Host Interactions and Clostridia Research Group, Departamento de Ciencias Biológicas, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago 8370186, Chile; (O.I.); (P.Y.); (G.E.); (O.F.); camilabelen.-@hotmail.com (C.Q.); (J.R.); (I.F.); (R.G.)
| | - Ruth González
- Microbiota-Host Interactions and Clostridia Research Group, Departamento de Ciencias Biológicas, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago 8370186, Chile; (O.I.); (P.Y.); (G.E.); (O.F.); camilabelen.-@hotmail.com (C.Q.); (J.R.); (I.F.); (R.G.)
| | - Jorge A. Soto
- Millennium Institute on Immunology and Immunotherapy, Departamento de Ciencias Biológicas, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago 8370186, Chile;
| | - Iván L. Calderón
- Laboratorio de RNAs Bacterianos, Departamento de Ciencias Biológicas, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago 8370186, Chile
| | - Fernando Gil
- Microbiota-Host Interactions and Clostridia Research Group, Departamento de Ciencias Biológicas, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago 8370186, Chile; (O.I.); (P.Y.); (G.E.); (O.F.); camilabelen.-@hotmail.com (C.Q.); (J.R.); (I.F.); (R.G.)
- ANID-Millennium Science Initiative Program-Millennium Nucleus in the Biology of the Intestinal Microbiota, Santiago 8370186, Chile
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4
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Zbylicki BR, Murphy CE, Petsche JA, Müh U, Dobrila HA, Ho TD, Daum MN, Pannullo AG, Weiss DS, Ellermeier CD. Identification of Clostridioides difficile mutants with increased daptomycin resistance. J Bacteriol 2024; 206:e0036823. [PMID: 38376203 PMCID: PMC10955854 DOI: 10.1128/jb.00368-23] [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: 11/10/2023] [Accepted: 01/20/2024] [Indexed: 02/21/2024] Open
Abstract
Daptomycin is a cyclic lipopeptide antibiotic used to treat infections caused by some Gram-positive bacteria. Daptomycin disrupts synthesis of the peptidoglycan (PG) cell wall by inserting into the cytoplasmic membrane and binding multiple forms of the undecaprenyl carrier lipid required for PG synthesis. Membrane insertion requires phosphatidylglycerol, so studies of daptomycin can provide insight into assembly and maintenance of the cytoplasmic membrane. Here, we studied the effects of daptomycin on Clostridioides difficile, the leading cause of healthcare-associated diarrhea. We observed that growth of C. difficile strain R20291 in the presence of sub-MIC levels of daptomycin resulted in a chaining phenotype, minicell formation, and lysis-phenotypes broadly consistent with perturbation of membranes and PG synthesis. We also selected for and characterized eight mutants with elevated daptomycin resistance. The mutations in these mutants were mapped to four genes: cdsA (cdr20291_2041), ftsH2 (cdr20291_3396), esrR (cdr20291_1187), and draS (cdr20291_2456). Of these four genes, only draS has been characterized previously. Follow-up studies indicate these mutations confer daptomycin resistance by two general mechanisms: reducing the amount of phosphatidylglycerol in the cytoplasmic membrane (cdsA) or altering the regulation of membrane processes (ftsH2, esrR, and draS). Thus, the mutants described here provide insights into phospholipid synthesis and identify signal transduction systems involved in cell envelope biogenesis and stress response in C. difficile. IMPORTANCE C. difficile is the leading cause of healthcare-associated diarrhea and is a threat to public health due to the risk of recurrent infections. Understanding biosynthesis of the atypical cell envelope of C. difficile may provide insight into novel drug targets to selectively inhibit C. difficile. Here, we identified mutations that increased daptomycin resistance and allowed us to better understand phospholipid synthesis, cell envelope biogenesis, and stress response in C. difficile.
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Affiliation(s)
- Brianne R. Zbylicki
- Department of Microbiology and Immunology, The University of Iowa, Iowa City, Iowa, USA
| | - Claire E. Murphy
- Department of Microbiology and Immunology, The University of Iowa, Iowa City, Iowa, USA
| | - Jennifer A. Petsche
- Interdisciplinary Graduate Program in Molecular Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Ute Müh
- Department of Microbiology and Immunology, The University of Iowa, Iowa City, Iowa, USA
| | - Horia A. Dobrila
- Department of Microbiology and Immunology, The University of Iowa, Iowa City, Iowa, USA
| | - Theresa D. Ho
- Department of Microbiology and Immunology, The University of Iowa, Iowa City, Iowa, USA
| | - Mikaela N. Daum
- Department of Microbiology and Immunology, The University of Iowa, Iowa City, Iowa, USA
| | - Anthony G. Pannullo
- Department of Microbiology and Immunology, The University of Iowa, Iowa City, Iowa, USA
| | - David S. Weiss
- Department of Microbiology and Immunology, The University of Iowa, Iowa City, Iowa, USA
| | - Craig D. Ellermeier
- Department of Microbiology and Immunology, The University of Iowa, Iowa City, Iowa, USA
- Graduate Program in Genetics, University of Iowa, Iowa City, Iowa, USA
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5
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Bollinger KW, Müh U, Ocius KL, Apostolos AJ, Pires MM, Helm RF, Popham DL, Weiss DS, Ellermeier CD. Identification of a new family of peptidoglycan transpeptidases reveals atypical crosslinking is essential for viability in Clostridioides difficile. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.14.584917. [PMID: 38559057 PMCID: PMC10980060 DOI: 10.1101/2024.03.14.584917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Clostridioides difficile, the leading cause of antibiotic-associated diarrhea, relies primarily on 3-3 crosslinks created by L,D-transpeptidases (LDTs) to fortify its peptidoglycan (PG) cell wall. This is unusual, as in most bacteria the vast majority of PG crosslinks are 4-3 crosslinks, which are created by penicillin-binding proteins (PBPs). Here we report the unprecedented observation that 3-3 crosslinking is essential for viability in C. difficile. We also report the discovery of a new family of LDTs that use a VanW domain to catalyze 3-3 crosslinking rather than a YkuD domain as in all previously known LDTs. Bioinformatic analyses indicate VanW domain LDTs are less common than YkuD domain LDTs and are largely restricted to Gram-positive bacteria. Our findings suggest that LDTs might be exploited as targets for antibiotics that kill C. difficile without disrupting the intestinal microbiota that is important for keeping C. difficile in check.
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Affiliation(s)
- Kevin W. Bollinger
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Ute Müh
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Karl L. Ocius
- Department of Chemistry, University of Virginia, Charlottesville, VA, USA
| | - Alexis J. Apostolos
- Department of Chemistry, University of Virginia, Charlottesville, VA, USA
- Present address: Haleon, 1211 Sherwood Ave, Richmond, VA 23220
| | - Marcos M. Pires
- Department of Chemistry, University of Virginia, Charlottesville, VA, USA
| | - Richard F. Helm
- Department of Biochemistry, Virginia Tech, Blacksburg, VA, USA
| | - David L. Popham
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA
| | - David S. Weiss
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
- Graduate Program in Genetics, University of Iowa, Iowa City, IA USA
| | - Craig D. Ellermeier
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
- Graduate Program in Genetics, University of Iowa, Iowa City, IA USA
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6
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Pannullo AG, Zbylicki BR, Ellermeier CD. Identification of DraRS in Clostridioides difficile, a Two-Component Regulatory System That Responds to Lipid II-Interacting Antibiotics. J Bacteriol 2023; 205:e0016423. [PMID: 37439672 PMCID: PMC10601625 DOI: 10.1128/jb.00164-23] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Accepted: 06/27/2023] [Indexed: 07/14/2023] Open
Abstract
Clostridioides difficile is a Gram-positive opportunistic pathogen that results in 220,000 infections, 12,000 deaths, and upwards of $1 billion in medical costs in the United States each year. C. difficile is highly resistant to a variety of antibiotics, but we have a poor understanding of how C. difficile senses and responds to antibiotic stress and how such sensory systems affect clinical outcomes. We have identified a spontaneous C. difficile mutant that displays increased daptomycin resistance. We performed whole-genome sequencing and found a nonsense mutation, S605*, in draS, which encodes a putative sensor histidine kinase of a two-component system (TCS). The draSS605* mutant has an ~4- to 8-fold increase in the daptomycin MIC compared to the wild type (WT). We found that the expression of constitutively active DraRD54E in the WT increases daptomycin resistance 8- to 16-fold and increases bacitracin resistance ~4-fold. We found that a selection of lipid II-inhibiting compounds leads to the increased activity of the luciferase-based reporter PdraR-slucopt, including vancomycin, bacitracin, ramoplanin, and daptomycin. Using RNA sequencing (RNA-seq), we identified the DraRS regulon. Interestingly, we found that DraRS can induce the expression of the previously identified hex locus required for the synthesis of a novel glycolipid produced in C. difficile. Our data suggest that the induction of the hex locus by DraR explains some, but not all, of the DraR-induced daptomycin and bacitracin resistance. IMPORTANCE Clostridioides difficile is a major cause of hospital-acquired diarrhea and represents an urgent concern due to the prevalence of antibiotic resistance and the rate of recurrent infections. C. difficile encodes ~50 annotated two-component systems (TCSs); however, only a few have been studied. The function of these unstudied TCSs is not known. Here, we show that the TCS DraRS plays a role in responding to a subset of lipid II-inhibiting antibiotics and mediates resistance to daptomycin and bacitracin in part by inducing the expression of the recently identified hex locus, which encodes enzymes required for the production of a novel glycolipid in C. difficile.
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Affiliation(s)
- Anthony G. Pannullo
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Brianne R. Zbylicki
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Craig D. Ellermeier
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
- Graduate Program in Genetics, University of Iowa, Iowa City, Iowa, USA
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7
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Dong Q, Lin H, Allen MM, Garneau JR, Sia JK, Smith RC, Haro F, McMillen T, Pope RL, Metcalfe C, Burgo V, Woodson C, Dylla N, Kohout C, Sundararajan A, Snitkin ES, Young VB, Fortier LC, Kamboj M, Pamer EG. Virulence and genomic diversity among clinical isolates of ST1 (BI/NAP1/027) Clostridioides difficile. Cell Rep 2023; 42:112861. [PMID: 37523264 PMCID: PMC10627504 DOI: 10.1016/j.celrep.2023.112861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 05/01/2023] [Accepted: 07/07/2023] [Indexed: 08/02/2023] Open
Abstract
Clostridioides difficile produces toxins that damage the colonic epithelium, causing colitis. Variation in disease severity is poorly understood and has been attributed to host factors and virulence differences between C. difficile strains. We test 23 epidemic ST1 C. difficile clinical isolates for their virulence in mice. All isolates encode a complete Tcd pathogenicity locus and achieve similar colonization densities. However, disease severity varies from lethal to avirulent infections. Genomic analysis of avirulent isolates reveals a 69-bp deletion in the cdtR gene, which encodes a response regulator for binary toxin expression. Deleting the 69-bp sequence in virulent R20291 strain renders it avirulent in mice with reduced toxin gene transcription. Our study demonstrates that a natural deletion within cdtR attenuates virulence in the epidemic ST1 C. difficile isolates without reducing colonization and persistence. Distinguishing strains on the basis of cdtR may enhance the specificity of diagnostic tests for C. difficile colitis.
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Affiliation(s)
- Qiwen Dong
- Department of Medicine, University of Chicago, Chicago, IL 60637, USA; Duchossois Family Institute, University of Chicago, Chicago, IL 60637, USA.
| | - Huaiying Lin
- Duchossois Family Institute, University of Chicago, Chicago, IL 60637, USA
| | - Marie-Maude Allen
- Department of Microbiology and Infectious Diseases, Université de Sherbrooke, Sherbrooke, QC J1E 4K8, Canada
| | - Julian R Garneau
- Department of Microbiology and Infectious Diseases, Université de Sherbrooke, Sherbrooke, QC J1E 4K8, Canada
| | - Jonathan K Sia
- Immunology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Rita C Smith
- Duchossois Family Institute, University of Chicago, Chicago, IL 60637, USA
| | - Fidel Haro
- Duchossois Family Institute, University of Chicago, Chicago, IL 60637, USA
| | - Tracy McMillen
- Infection Control, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Rosemary L Pope
- Duchossois Family Institute, University of Chicago, Chicago, IL 60637, USA; Committee on Immunology, University of Chicago, Chicago, IL 60637, USA
| | - Carolyn Metcalfe
- Duchossois Family Institute, University of Chicago, Chicago, IL 60637, USA
| | - Victoria Burgo
- Duchossois Family Institute, University of Chicago, Chicago, IL 60637, USA
| | - Che Woodson
- Duchossois Family Institute, University of Chicago, Chicago, IL 60637, USA
| | - Nicholas Dylla
- Duchossois Family Institute, University of Chicago, Chicago, IL 60637, USA
| | - Claire Kohout
- Duchossois Family Institute, University of Chicago, Chicago, IL 60637, USA
| | | | - Evan S Snitkin
- Division of Infectious Diseases, Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA
| | - Vincent B Young
- Division of Infectious Diseases, Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA; Department of Microbiology & Immunology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Louis-Charles Fortier
- Department of Microbiology and Infectious Diseases, Université de Sherbrooke, Sherbrooke, QC J1E 4K8, Canada
| | - Mini Kamboj
- Infection Control, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Eric G Pamer
- Department of Medicine, University of Chicago, Chicago, IL 60637, USA; Duchossois Family Institute, University of Chicago, Chicago, IL 60637, USA; Committee on Immunology, University of Chicago, Chicago, IL 60637, USA
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8
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Zou S, Li X, Huang Y, Zhang B, Tang H, Xue Y, Zheng Y. Properties and biotechnological applications of microbial deacetylase. Appl Microbiol Biotechnol 2023:10.1007/s00253-023-12613-1. [PMID: 37326683 DOI: 10.1007/s00253-023-12613-1] [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: 03/10/2023] [Revised: 05/25/2023] [Accepted: 05/31/2023] [Indexed: 06/17/2023]
Abstract
Deacetylases, a class of enzymes that can catalyze the hydrolysis of acetylated substrates to remove the acetyl group, used in producing various products with high qualities, are one of the most influential industrial enzymes. These enzymes are highly specific, non-toxic, sustainable, and eco-friendly biocatalysts. Deacetylases and deacetylated compounds have been widely applicated in pharmaceuticals, medicine, food, and the environment. This review synthetically summarizes deacetylases' sources, characterizations, classifications, and applications. Moreover, the typical structural characteristics of deacetylases from different microbial sources are summarized. We also reviewed the deacetylase-catalyzed reactions for producing various deacetylated compounds, such as chitosan-oligosaccharide (COS), mycothiol, 7-aminocephalosporanic acid (7-ACA), glucosamines, amino acids, and polyamines. It is aimed to expound on the advantages and challenges of deacetylases in industrial applications. Moreover, it also serves perspectives on obtaining promising and innovative biocatalysts for enzymatic deacetylation. KEYPOINTS: • The fundamental properties of microbial deacetylases of various microorganisms are presented. • The biochemical characterizations, structures, and catalyzation mechanisms of microbial deacetylases are summarized. • The applications of microbial deacetylases in food, pharmaceutical, medicine, and the environment were discussed.
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Affiliation(s)
- Shuping Zou
- National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China
| | - Xia Li
- National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China
| | - Yinfeng Huang
- National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China
| | - Bing Zhang
- National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China
| | - Heng Tang
- National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China
| | - Yaping Xue
- National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China.
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China.
| | - Yuguo Zheng
- National and Local Joint Engineering Research Center for Biomanufacturing of Chiral Chemicals, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, 310014, People's Republic of China
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9
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Kristensen SS, Diep DB, Kjos M, Mathiesen G. The role of site-2-proteases in bacteria: a review on physiology, virulence, and therapeutic potential. MICROLIFE 2023; 4:uqad025. [PMID: 37223736 PMCID: PMC10202637 DOI: 10.1093/femsml/uqad025] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 04/21/2023] [Accepted: 05/02/2023] [Indexed: 05/25/2023]
Abstract
Site-2-proteases are a class of intramembrane proteases involved in regulated intramembrane proteolysis. Regulated intramembrane proteolysis is a highly conserved signaling mechanism that commonly involves sequential digestion of an anti-sigma factor by a site-1- and site-2-protease in response to external stimuli, resulting in an adaptive transcriptional response. Variation of this signaling cascade continues to emerge as the role of site-2-proteases in bacteria continues to be explored. Site-2-proteases are highly conserved among bacteria and play a key role in multiple processes, including iron uptake, stress response, and pheromone production. Additionally, an increasing number of site-2-proteases have been found to play a pivotal role in the virulence properties of multiple human pathogens, such as alginate production in Pseudomonas aeruginosa, toxin production in Vibrio cholerae, resistance to lysozyme in enterococci and antimicrobials in several Bacillus spp, and cell-envelope lipid composition in Mycobacterium tuberculosis. The prominent role of site-2-proteases in bacterial pathogenicity highlights the potential of site-2-proteases as novel targets for therapeutic intervention. In this review, we summarize the role of site-2-proteases in bacterial physiology and virulence, as well as evaluate the therapeutic potential of site-2-proteases.
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Affiliation(s)
- Sofie S Kristensen
- Faculty of Chemistry, Biotechnology, and Food Science, Norwegian University of Life Sciences (NMBU), 1433 Ås, Norway
| | | | - Morten Kjos
- Corresponding author. NMBU, P.O. Box 5003, 1433 Ås, Norway. E-mail:
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HexSDF Is Required for Synthesis of a Novel Glycolipid That Mediates Daptomycin and Bacitracin Resistance in C. difficile. mBio 2023; 14:e0339722. [PMID: 36786594 PMCID: PMC10128005 DOI: 10.1128/mbio.03397-22] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023] Open
Abstract
Clostridioides difficile is a Gram-positive opportunistic pathogen responsible for 250,000 hospital-associated infections, 12,000 hospital-associated deaths, and $1 billion in medical costs in the United States each year. There has been recent interest in using a daptomycin analog, surotomycin, to treat C. difficile infections. Daptomycin interacts with phosphatidylglycerol and lipid II to disrupt the membrane and halt peptidoglycan synthesis. C. difficile has an unusual lipid membrane composition, as it has no phosphatidylserine or phosphatidylethanolamine, and ~50% of its membrane is composed of glycolipids, including the unique C. difficile lipid aminohexosyl-hexosyldiradylglycerol (HNHDRG). We identified a two-component system (TCS), HexRK, that is required for C. difficile resistance to daptomycin. Using transcriptome sequencing (RNA-seq), we found that HexRK regulates expression of hexSDF, a three-gene operon of unknown function. Based on bioinformatic predictions, hexS encodes a monogalactosyldiacylglycerol synthase, hexD encodes a polysaccharide deacetylase, and hexF encodes an MprF-like flippase. Deletion of hexRK leads to a 4-fold decrease in daptomycin MIC, and that deletion of hexSDF leads to an 8- to 16-fold decrease in daptomycin MIC. The ΔhexSDF mutant is also 4-fold less resistant to bacitracin but no other cell wall-active antibiotics. Our data indicate that in the absence of HexSDF, the phospholipid membrane composition is altered. In wild-type (WT) C. difficile, the unique glycolipid HNHDRG makes up ~17% of the lipids in the membrane. However, in a ΔhexSDF mutant, HNHDRG is completely absent. While it is unclear how HNHDRG contributes to daptomycin resistance, the requirement for bacitracin resistance suggests it has a general role in cell membrane biogenesis. IMPORTANCE Clostridioides difficile is a major cause of hospital-acquired diarrhea and represents an urgent concern due to the prevalence of antibiotic resistance and the rate of recurrent infections. Little is understood about C. difficile membrane lipids, but a unique glycolipid, HNHDRG, has been previously identified in C. difficile and, currently, has not been identified in other organisms. Here, we show that HexSDF and HexRK are required for synthesis of HNHDRG and that production of HNHDRG impacts resistance to daptomycin and bacitracin.
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11
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Liu P, Dong X, Cao X, Xie Q, Huang X, Jiang J, Dai H, Tang Z, Lin Y, Feng S, Luo K. Identification of Three Campylobacter Lysins and Enhancement of Their Anti-Escherichia coli Efficacy Using Colicin-Based Translocation and Receptor-Binding Domain Fusion. Microbiol Spectr 2023; 11:e0451522. [PMID: 36749047 PMCID: PMC10100823 DOI: 10.1128/spectrum.04515-22] [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: 11/06/2022] [Accepted: 01/24/2023] [Indexed: 02/08/2023] Open
Abstract
The emergence of multidrug-resistant Escherichia coli, which poses a major threat to public health, has motivated the development of numerous alternative antimicrobials. Lysins are bacteriophage- and bacterium-derived peptidoglycan hydrolases that represent a new antibiotic treatment targeting bacterial cell walls. However, the bactericidal effect of native lysins on Gram-negative bacteria is restricted by the presence of an outer membrane. Here, we first evaluated the antibacterial activity of three Campylobacter-derived lysins (Clysins) against E. coli. To improve their transmembrane ability and antibacterial activities, six engineered Clysins were constructed by fusing with the translocation and receptor-binding (TRB) domains from two types of colicins (colicin A [TRBA] and colicin K [TRBK]), and their biological activities were determined. Notably, engineered lysin TRBK-Cly02 exhibited the highest bactericidal activity against the E. coli BL21 strain, with a reduction of 6.22 ± 0.34 log units of cells at a concentration of 60.1 μg/mL, and formed an observable inhibition zone even at a dose of 6.01 μg. Moreover, TRBK-Cly02 killed E. coli dose dependently and exhibited the strongest bactericidal activity at pH 6. It also exhibited potential bioactivity against multidrug-resistant E. coli clinical isolates. In summary, this study identified three lysins from Campylobacter strains against E. coli, and the enhancement of their antibacterial activities by TRB domains fusion may allow them to be developed as potential alternatives to antibiotics. IMPORTANCE Three lysins from Campylobacter, namely, Clysins, were investigated, and their antibacterial activities against E. coli were determined for the first time. To overcome the restriction of the outer membrane of Gram-negative bacteria, we combined the TRB domains of colicins with these Clysins. Moreover, we discovered that the Clysins fused with TRB domains from colicin K (TRBK) killed E. coli more effectively, and this provides a new foundation for the development of novel bioengineered lysins by employing TRBK constructs that target outer membrane receptor/transport systems. One of the designed lysins, TRBK-Cly02, exhibited potent bactericidal efficacy against E. coli strains and may be used for control of multidrug-resistant clinical isolates. The results suggest that TRBK-Cly02 can be considered a potential antibacterial agent against pathogenic E. coli.
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Affiliation(s)
- Peiqi Liu
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Xinying Dong
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Xuewei Cao
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Qianmei Xie
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Xiuqin Huang
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Jinfei Jiang
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Huilin Dai
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Zheng Tang
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Yizhen Lin
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Saixiang Feng
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Kaijian Luo
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
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12
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Dong Q, Lin H, Allen MM, Garneau JR, Sia JK, Smith RC, Haro F, McMillen T, Pope RL, Metcalfe C, Burgo V, Woodson C, Dylla N, Kohout C, Sundararajan A, Snitkin ES, Young VB, Fortier LC, Kamboj M, Pamer EG. Virulence and genomic diversity among clinical isolates of ST1 (BI/NAP1/027) Clostridioides difficile. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.12.523823. [PMID: 36711955 PMCID: PMC9882218 DOI: 10.1101/2023.01.12.523823] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Clostridioides difficile (C. difficile) , a leading cause of nosocomial infection, produces toxins that damage the colonic epithelium and results in colitis that varies from mild to fulminant. Variation in disease severity is poorly understood and has been attributed to host factors (age, immune competence and intestinal microbiome composition) and/or virulence differences between C. difficile strains, with some, such as the epidemic BI/NAP1/027 (MLST1) strain, being associated with greater virulence. We tested 23 MLST1(ST1) C. difficile clinical isolates for virulence in antibiotic-treated C57BL/6 mice. All isolates encoded a complete Tcd pathogenicity locus and achieved similar colonization densities in mice. Disease severity varied, however, with 5 isolates causing lethal infections, 16 isolates causing a range of moderate infections and 2 isolates resulting in no detectable disease. The avirulent ST1 isolates did not cause disease in highly susceptible Myd88 -/- or germ-free mice. Genomic analysis of the avirulent isolates revealed a 69 base-pair deletion in the N-terminus of the cdtR gene, which encodes a response regulator for binary toxin (CDT) expression. Genetic deletion of the 69 base-pair cdtR sequence in the highly virulent ST1 R20291 C. difficile strain rendered it avirulent and reduced toxin gene transcription in cecal contents. Our study demonstrates that a natural deletion within cdtR attenuates virulence in the epidemic ST1 C. difficile strain without reducing colonization and persistence in the gut. Distinguishing strains on the basis of cdtR may enhance the specificity of diagnostic tests for C. difficile colitis.
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Affiliation(s)
- Qiwen Dong
- Department of Medicine, University of Chicago, Chicago, Illinois, USA
- Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA
| | - Huaiying Lin
- Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA
| | - Marie-Maude Allen
- Department of Microbiology and Infectious Diseases, Universite de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Julian R. Garneau
- Department of Microbiology and Infectious Diseases, Universite de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Jonathan K. Sia
- Immunology Program, Memorial Sloan Kettering Cancer Center, New York City, New York, USA
| | - Rita C. Smith
- Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA
| | - Fidel Haro
- Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA
| | - Tracy McMillen
- Infection Control, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Rosemary L. Pope
- Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA
- Committee on Immunology, University of Chicago, Chicago, Illinois, USA
| | - Carolyn Metcalfe
- Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA
| | - Victoria Burgo
- Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA
| | - Che Woodson
- Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA
| | - Nicholas Dylla
- Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA
| | - Claire Kohout
- Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA
| | | | - Evan S Snitkin
- Division of Infectious Diseases, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Vincent B. Young
- Division of Infectious Diseases, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
- Department of Microbiology & Immunology, University of Michigan, Ann Arbor, MI, USA
| | - Louis-Charles Fortier
- Department of Microbiology and Infectious Diseases, Universite de Sherbrooke, Sherbrooke, Quebec, Canada
| | - Mini Kamboj
- Infection Control, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, New York, USA
| | - Eric G. Pamer
- Department of Medicine, University of Chicago, Chicago, Illinois, USA
- Duchossois Family Institute, University of Chicago, Chicago, Illinois, USA
- Committee on Immunology, University of Chicago, Chicago, Illinois, USA
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Harvey DJ. Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2019-2020. MASS SPECTROMETRY REVIEWS 2022:e21806. [PMID: 36468275 DOI: 10.1002/mas.21806] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2020. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. The review is basically divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of arrays. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other areas such as medicine, industrial processes and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. The reported work shows increasing use of incorporation of new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented nearly 40 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show little sign of diminishing.
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Affiliation(s)
- David J Harvey
- Nuffield Department of Medicine, Target Discovery Institute, University of Oxford, Oxford, UK
- Department of Chemistry, University of Oxford, Oxford, Oxfordshire, United Kingdom
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Abstract
Clostridioides difficile spores are the infective form for this endospore-forming organism. The vegetative cells are intolerant to oxygen and poor competitors with a healthy gut microbiota. Therefore, in order for C. difficile to establish infection, the spores have to germinate in an environment that supports vegetative growth. To initiate germination, C. difficile uses Csp-type germinant receptors that consist of the CspC and CspA pseudoproteases as the bile acid and cogerminant receptors, respectively. CspB is a subtilisin-like protease that cleaves the inhibitory propeptide from the pro-SleC cortex lytic enzyme, thereby activating it and initiating cortex degradation. Though several locations have been proposed for where these proteins reside within the spore (i.e., spore coat, outer spore membrane, cortex, and inner spore membrane), these have been based, mostly, on hypotheses or prior data in Clostridium perfringens. In this study, we visualized the germination and outgrowth process using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) and used immunogold labeling to visualize key germination regulators. These analyses localize these key regulators to the spore cortex region for the first time. IMPORTANCE Germination by C. difficile spores is the first step in the establishment of potentially life-threatening C. difficile infection (CDI). A deeper understanding of the mechanism by which spores germinate may provide insight for how to either prevent spore germination into a disease-causing vegetative form or trigger germination prematurely when the spore is either in the outside environment or in a host environment that does not support the establishment of colonization/disease.
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The WalRK Two-Component System Is Essential for Proper Cell Envelope Biogenesis in Clostridioides difficile. J Bacteriol 2022; 204:e0012122. [PMID: 35575581 PMCID: PMC9210968 DOI: 10.1128/jb.00121-22] [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
The WalR-WalK two-component regulatory system (TCS) is found in all Firmicutes, in which it regulates the expression of multiple genes required for remodeling the cell envelope during growth and division. Unlike most TCSs, WalRK is essential for viability, so it has attracted interest as a potential antibiotic target. In this study, we used overexpression of WalR and CRISPR interference to investigate the Wal system of Clostridioides difficile, a major cause of hospital-associated diarrhea in high-income countries. We confirmed that the wal operon is essential and identified morphological defects and cell lysis as the major terminal phenotypes of altered wal expression. We also used transcriptome sequencing (RNA-seq) to identify over 150 genes whose expression changes in response to WalR levels. This gene set is enriched in cell envelope genes and includes genes encoding several predicted PG hydrolases and proteins that could regulate PG hydrolase activity. A distinct feature of the C. difficile cell envelope is the presence of an S-layer, and we found that WalR affects expression of several genes which encode S-layer proteins. An unexpected finding was that some Wal-associated phenotypic defects were inverted in comparison to what has been reported for other Firmicutes. For example, downregulation of Wal signaling caused C. difficile cells to become longer rather than shorter, as in Bacillus subtilis. Likewise, downregulation of Wal rendered C. difficile more sensitive to vancomycin, whereas reduced Wal activity is linked to increased vancomycin resistance in Staphylococcus aureus. IMPORTANCE The WalRK two-component system (TCS) is essential for coordinating synthesis and turnover of peptidoglycan in Firmicutes. We investigated the WalRK TCS in Clostridioides difficile, an important bacterial pathogen with an atypical cell envelope. We confirmed that WalRK is essential and regulates cell envelope biogenesis, although several of the phenotypic changes we observed were opposite to what has been reported for other Firmicutes. We also identified over 150 genes whose expression is controlled either directly or indirectly by WalR. Overall, our findings provide a foundation for future investigations of an important regulatory system and potential antibiotic target in C. difficile.
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Activation of the Extracytoplasmic Function σ Factor σ V in Clostridioides difficile Requires Regulated Intramembrane Proteolysis of the Anti-σ Factor RsiV. mSphere 2022; 7:e0009222. [PMID: 35317618 PMCID: PMC9044953 DOI: 10.1128/msphere.00092-22] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Clostridioides (Clostridium) difficile is one of the leading causes of nosocomial diarrhea. Lysozyme is a common host defense against many pathogenic bacteria. C. difficile exhibits high levels of lysozyme resistance, which is due in part to the extracytoplasmic functioning (ECF) σ factor, σV. It has been previously demonstrated that genes regulated by σV are responsible for peptidoglycan modifications that provide C. difficile with high lysozyme resistance. σV is not unique to C. difficile however, and its role in lysozyme resistance and its mechanism of activation has been well characterized in Bacillus subtilis where the anti-σ, RsiV, sequesters σV until lysozyme directly binds to RsiV, activating σV. However, it remains unclear if the mechanism of σV activation is similar in C. difficile. Here, we investigated how activation of σV is controlled in C. difficile by lysozyme. We found that C. difficile RsiV was degraded in the presence of lysozyme. We also found that disruption of a predicted signal peptidase cleavage site blocked RsiV degradation and σV activation, indicating that the site-1 protease is likely a signal peptidase. We also identified a conserved site-2 protease, RasP, that was required for site-2 cleavage of RsiV and σV activation in response to lysozyme. Combined with previous work showing RsiV directly binds lysozyme, these data suggested that RsiV directly binds lysozyme in C. difficile, which leads to RsiV destruction via cleavage at site-1 by signal peptidase and then at site-2 by RasP, ultimately resulting in σV activation and increased resistance to lysozyme. IMPORTANCE Clostridioides difficile is a major cause of hospital-acquired diarrhea and represents an urgent concern due to the prevalence of antibiotic resistance and the rate of recurrent infections. We previously showed that σV and the regulon under its control were involved in lysozyme resistance. We have also shown in B. subtilis that the anti-σ RsiV acts as a direct sensor for lysozyme. which results in the destruction of RsiV and activation of σV. Here, we described the proteases required for degradation of RsiV in C. difficile in response to lysozyme. Our data indicated that the mechanism is highly conserved between B. subtilis and C. difficile.
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17
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Ho TD, Ellermeier CD. Activation of the extracytoplasmic function σ factor σ V by lysozyme in Clostridioides difficile. Curr Opin Microbiol 2022; 65:162-166. [PMID: 34894542 PMCID: PMC8792214 DOI: 10.1016/j.mib.2021.11.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 11/12/2021] [Accepted: 11/18/2021] [Indexed: 02/03/2023]
Abstract
Clostridioides difficile is naturally resistant to high levels of lysozyme an important component of the innate immune defense system. C. difficile encodes both constitutive as well as inducible lysozyme resistance genes. The inducible lysozyme resistance genes are controlled by an alternative σ factor σV that belongs to the Extracytoplasmic function σ factor family. In the absence of lysozyme, the activity of σV is inhibited by the anti-σ factor RsiV. In the presence of lysozyme RsiV is destroyed via a proteolytic cascade that leads to σV activation and increased lysozyme resistance. This review highlights how activity of σV is controlled.
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Affiliation(s)
- Theresa D. Ho
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, 431 Newton Rd, Iowa City, IA 52242
| | - Craig D. Ellermeier
- Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, 431 Newton Rd, Iowa City, IA 52242,Graduate Program in Genetics, University of Iowa, Iowa City, IA 52242, USA,Corresponding author: , 319-384-4565
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18
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Noori Goodarzi N, Fereshteh S, Azizi O, Rahimi H, Bolourchi N, Badmasti F. Subtractive genomic approach toward introduction of novel immunogenic targets against Clostridioides difficile: Thinking out of the box. Microb Pathog 2021; 162:105372. [PMID: 34954046 DOI: 10.1016/j.micpath.2021.105372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 12/17/2021] [Accepted: 12/20/2021] [Indexed: 10/19/2022]
Abstract
Clostridioides difficile is one of the major causatives of nosocomial infections worldwide. Antibiotic-associated diarrhea, pseudomembranous colitis, and toxic megacolon are the most common forms of C. difficile infection (CDI). Considering the high antibiotic resistance of C. difficile isolates and the low efficacy of immunization with toxin-related vaccines, we suggested that surface-exposed and secreted proteins could be considered as potential immunogenic targets against CDI. Various immuninformatics databases were used to predict antigenicity, allergenicity, B-cell epitopes, MHC-II binding sites, conserved domains, prevalence and conservation of proteins among the most common sequence types, molecular docking, and immunosimulation of immunogenic targets. Finally, 16 proteins belonging to three functional groups were identified, including proteins involved in the cell wall and peptidoglycan layer (nine proteins), flagellar assembly (five proteins), spore germination (one protein), and a protein with unknown function. Molecular docking results showed that among all the mentioned proteins, WP_009892971.1 (Acd) and WP_009890599.1 (a C40 family peptidase) had the strongest interactions with human Toll-like receptor 2 (TLR-2) and TLR-4. This study proposes a combination of C. difficile toxoid (Tcd) and surface-exposed proteins such as Acd as a promising vaccine formulation for protection against circulating clinical strains of C. difficile.
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Affiliation(s)
- Narjes Noori Goodarzi
- Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | | | - Omid Azizi
- Health Sciences Research Center, Torbat Heydariyeh University of Medical Sciences, Torbat Heydariyeh, Iran
| | - Hamzeh Rahimi
- Department of Molecular Medicine, Biotechnology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | - Negin Bolourchi
- Department of Bacteriology, Pasteur Institute of Iran, Tehran, Iran
| | - Farzad Badmasti
- Department of Bacteriology, Pasteur Institute of Iran, Tehran, Iran; Microbiology Research Center (MRC), Pasteur Institute of Iran, Tehran, Iran.
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Coullon H, Candela T. Clostridioides difficile peptidoglycan modifications. Curr Opin Microbiol 2021; 65:156-161. [PMID: 34883390 DOI: 10.1016/j.mib.2021.11.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 11/13/2021] [Accepted: 11/17/2021] [Indexed: 11/29/2022]
Abstract
The cortex and peptidoglycan of Clostridioides difficile have been poorly investigated. This last decade, the interest increased because these two structures are highly modified and these modifications may be involved in antimicrobial resistance. For example, C. difficile peptidoglycan deacetylation was recently reported to be involved in lysozyme resistance. Modifications may also be important for spore cortex synthesis or spore germination, which is essential in C. difficile pathogenesis. As such, the enzymes responsible for modifications of the peptidoglycan and/or cortex could be new drug target candidates or used as anti-C. difficile agents, as seen for the CD11 autolysin. In this review, we focus on C. difficile peptidoglycan and cortex and compare their structures with those of other well studied bacteria.
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Affiliation(s)
- Héloise Coullon
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France; Division of Infectious Diseases, Dept. of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Thomas Candela
- Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, Jouy-en-Josas, France.
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Parthasarathy S, Wang X, Carr KR, Varahan S, Hancock EB, Hancock LE. SigV Mediates Lysozyme Resistance in Enterococcus faecalis via RsiV and PgdA. J Bacteriol 2021; 203:e0025821. [PMID: 34370556 PMCID: PMC8459761 DOI: 10.1128/jb.00258-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Enterococcus faecalis is a gut commensal but transitions to a pathogenic state as a consequence of intestinal dysbiosis and/or the presence of indwelling medical devices, causing a wide range of infections. One of the unique features of E. faecalis is its ability to display high level resistance to lysozyme, an important host defense of the innate immune response. Lysozyme resistance in E. faecalis is known to be mediated by the extracytoplasmic function (ECF) sigma factor SigV. PgdA and RsiV expression is directly regulated by SigV, but pgdA and rsiV mutants display nominal changes in lysozyme resistance, suggesting that additional gene products in the SigV regulon contribute to lysozyme resistance. Using transcriptome sequencing (RNA-seq) analysis, we compared the transcriptional profile of the parental strain to that of an isogenic sigV mutant and show that apart from sigV, only rsiV and pgdA expression was induced upon lysozyme exposure. The combined deletion mutant of both rsiV and pgdA rendered E. faecalis sensitive to lysozyme at a level comparable to that of the sigV mutant, highlighting the limited SigV regulon. Several additional genes were also induced upon lysozyme exposure, but in a SigV-independent fashion. Overexpression of pgdA from a SigV-independent promoter restored lysozyme resistance in a sigV deletion mutant and also induced cell chaining. Overexpression of rsiV from a SigV-independent promoter only partially restored lysozyme resistance in a sigV mutant. Overall, we provide evidence for a simple adaptation to lysozyme stress, in which SigV controls the expression of rsiV and pgdA, and that both gene products contribute to lysozyme resistance. IMPORTANCE Enterococcus faecalis causes health care-associated infections and displays resistance to a variety of antibiotics and molecules of the innate immune system. SigV has been shown to play an important role in enterococcal lysozyme resistance. Even though several proteins have been implicated in enterococcal lysozyme resistance, a complete SigV-dependent regulon has not been functionally characterized as being responsible for the dramatic increase in lysozyme susceptibility displayed by a sigV mutant. Using RNA-seq, we have identified the SigV regulon to be comprised of two gene loci, sigV-rsiV and pgdA. Deletion of both rsiV and pgdA renders E. faecalis susceptible to lysozyme on par with a sigV mutant. We also demonstrate that overproduction of rsiV and pgdA contributes to lysozyme resistance in susceptible strains.
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Affiliation(s)
- Srivatsan Parthasarathy
- Department of Molecular Biosciences, University of Kansasgrid.266515.3, Lawrence, Kansas, USA
| | - Xiaofei Wang
- Department of Molecular Biosciences, University of Kansasgrid.266515.3, Lawrence, Kansas, USA
| | - Kristen R. Carr
- Department of Molecular Biosciences, University of Kansasgrid.266515.3, Lawrence, Kansas, USA
| | - Sriram Varahan
- Department of Molecular Biosciences, University of Kansasgrid.266515.3, Lawrence, Kansas, USA
| | - Elyssa B. Hancock
- Department of Molecular Biosciences, University of Kansasgrid.266515.3, Lawrence, Kansas, USA
| | - Lynn E. Hancock
- Department of Molecular Biosciences, University of Kansasgrid.266515.3, Lawrence, Kansas, USA
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Planas A. Peptidoglycan Deacetylases in Bacterial Cell Wall Remodeling and Pathogenesis. Curr Med Chem 2021; 29:1293-1312. [PMID: 34525907 DOI: 10.2174/0929867328666210915113723] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 07/24/2021] [Accepted: 07/26/2021] [Indexed: 11/22/2022]
Abstract
The bacterial cell wall peptidoglycan (PG) is a dynamic structure that is constantly synthesized, re-modeled and degraded during bacterial division and growth. Post-synthetic modifications modulate the action of endogenous autolysis during PG lysis and remodeling for growth and sporulation, but also they are a mechanism used by pathogenic bacteria to evade the host innate immune system. Modifica-tions of the glycan backbone are limited to the C-2 amine and the C-6 hydroxyl moieties of either Glc-NAc or MurNAc residues. This paper reviews the functional roles and properties of peptidoglycan de-N-acetylases (distinct PG GlcNAc and MurNAc deacetylases) and recent progress through genetic stud-ies and biochemical characterization to elucidate their mechanism of action, 3D structures, substrate specificities and biological functions. Since they are virulence factors in pathogenic bacteria, peptidogly-can deacetylases are potential targets for the design of novel antimicrobial agents.
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Affiliation(s)
- Antoni Planas
- Laboratory of Biochemistry, Institut Químic de Sarrià. University Ramon Llull, 08017 Barcelona. Spain
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Nerber HN, Sorg JA. The small acid-soluble proteins of Clostridioides difficile are important for UV resistance and serve as a check point for sporulation. PLoS Pathog 2021; 17:e1009516. [PMID: 34496003 PMCID: PMC8452069 DOI: 10.1371/journal.ppat.1009516] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 09/20/2021] [Accepted: 09/01/2021] [Indexed: 12/17/2022] Open
Abstract
Clostridioides difficile is a nosocomial pathogen which causes severe diarrhea and colonic inflammation. C. difficile causes disease in susceptible patients when endospores germinate into the toxin-producing vegetative form. The action of these toxins results in diarrhea and the spread of spores into the hospital and healthcare environments. Thus, the destruction of spores is imperative to prevent disease transmission between patients. However, spores are resilient and survive extreme temperatures, chemical exposure, and UV treatment. This makes their elimination from the environment difficult and perpetuates their spread between patients. In the model spore-forming organism, Bacillus subtilis, the small acid-soluble proteins (SASPs) contribute to these resistances. The SASPs are a family of small proteins found in all endospore-forming organisms, C. difficile included. Although these proteins have high sequence similarity between organisms, the role(s) of the proteins differ. Here, we investigated the role of the main α/β SASPs, SspA and SspB, and two annotated putative SASPs, CDR20291_1130 and CDR20291_3080, in protecting C. difficile spores from environmental insults. We found that SspA is necessary for conferring spore UV resistance, SspB minorly contributes, and the annotated putative SASPs do not contribute to UV resistance. In addition, the SASPs minorly contribute to the resistance of nitrous acid. Surprisingly, the combined deletion of sspA and sspB prevented spore formation. Overall, our data indicate that UV resistance of C. difficile spores is dependent on SspA and that SspA and SspB regulate/serve as a checkpoint for spore formation, a previously unreported function of SASPs.
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Affiliation(s)
- Hailee N. Nerber
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
| | - Joseph A. Sorg
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
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23
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Abstract
Clostridioides difficile is a leading cause of health care-associated infections worldwide. These infections are transmitted by C. difficile′s metabolically dormant, aerotolerant spore form. Functional spore formation depends on the assembly of two protective layers, a thick layer of modified peptidoglycan known as the cortex layer and a multilayered proteinaceous meshwork known as the coat. We previously identified two spore morphogenetic proteins, SpoIVA and SipL, that are essential for recruiting coat proteins to the developing forespore and making functional spores. While SpoIVA and SipL directly interact, the identities of the proteins they recruit to the forespore remained unknown. Here, we used mass spectrometry-based affinity proteomics to identify proteins that interact with the SpoIVA-SipL complex. These analyses identified the Peptostreptococcaceae family-specific, sporulation-induced bitopic membrane protein CD3457 (renamed SpoVQ) as a protein that interacts with SipL and SpoIVA. Loss of SpoVQ decreased heat-resistant spore formation by ∼5-fold and reduced cortex thickness ∼2-fold; the thinner cortex layer of ΔspoVQ spores correlated with higher levels of spontaneous germination (i.e., in the absence of germinant). Notably, loss of SpoVQ in either spoIVA or sipL mutants prevented cortex synthesis altogether and greatly impaired the localization of a SipL-mCherry fusion protein around the forespore. Thus, SpoVQ is a novel regulator of C. difficile cortex synthesis that appears to link cortex and coat formation. The identification of SpoVQ as a spore morphogenetic protein further highlights how Peptostreptococcaceae family-specific mechanisms control spore formation in C. difficile. IMPORTANCE The Centers for Disease Control has designated Clostridioides difficile as an urgent threat because of its intrinsic antibiotic resistance. C. difficile persists in the presence of antibiotics in part because it makes metabolically dormant spores. While recent work has shown that preventing the formation of infectious spores can reduce C. difficile disease recurrence, more selective antisporulation therapies are needed. The identification of spore morphogenetic factors specific to C. difficile would facilitate the development of such therapies. In this study, we identified SpoVQ (CD3457) as a spore morphogenetic protein specific to the Peptostreptococcaceae family that regulates the formation of C. difficile’s protective spore cortex layer. SpoVQ acts in concert with the known spore coat morphogenetic factors, SpoIVA and SipL, to link formation of the protective coat and cortex layers. These data reveal a novel pathway that could be targeted to prevent the formation of infectious C. difficile spores.
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Jones JB, Liu L, Rank LA, Wetzel D, Woods EC, Biok N, Anderson SE, Lee MR, Liu R, Huth S, Sandhu BK, Gellman SH, McBride SM. Cationic Homopolymers Inhibit Spore and Vegetative Cell Growth of Clostridioides difficile. ACS Infect Dis 2021; 7:1236-1247. [PMID: 33739823 PMCID: PMC8130196 DOI: 10.1021/acsinfecdis.0c00843] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A wide range of synthetic polymers have been explored for antimicrobial activity. These materials usually contain both cationic and hydrophobic subunits because these two characteristics are prominent among host-defense peptides. Here, we describe a series of nylon-3 polymers containing only cationic subunits and their evaluation against the gastrointestinal, spore-forming pathogen Clostridioides difficile. Despite their highly hydrophilic nature, these homopolymers showed efficacy against both the vegetative and spore forms of the bacterium, including an impact on C. difficile spore germination. The polymer designated P34 demonstrated the greatest efficacy against C. difficile strains, along with low propensities to lyse human red blood cells or intestinal epithelial cells. To gain insight into the mechanism of P34 action, we evaluated several cell-surface mutant strains of C. difficile to determine the impacts on growth, viability, and cell morphology. The results suggest that P34 interacts with the cell wall, resulting in severe cell bending and death in a concentration-dependent manner. The unexpected finding that nylon-3 polymers composed entirely of cationic subunits display significant activities toward C. difficile should expand the range of other polymers considered for antibacterial applications.
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Affiliation(s)
- Joshua B. Jones
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Lei Liu
- Department of Chemistry and Department of Medicine, University of Wisconsin, Madison, WI, USA
| | | | - Daniela Wetzel
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Emily C. Woods
- Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA
| | - Naomi Biok
- Department of Chemistry and Department of Medicine, University of Wisconsin, Madison, WI, USA
| | | | - Myung-ryul Lee
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, USA
| | - Runhui Liu
- State Key Laboratory of Bioreactor Engineering, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai, China
| | - Sean Huth
- Department of Chemistry, Princeton University, Princeton, NJ, USA
| | - Brindar K. Sandhu
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Samuel H. Gellman
- Department of Chemistry and Department of Medicine, University of Wisconsin, Madison, WI, USA
| | - Shonna M. McBride
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
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Signal Peptidase-Mediated Cleavage of the Anti-σ Factor RsiP at Site 1 Controls σ P Activation and β-Lactam Resistance in Bacillus thuringiensis. mBio 2021; 13:e0370721. [PMID: 35164554 PMCID: PMC8844934 DOI: 10.1128/mbio.03707-21] [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: 12/04/2022] Open
Abstract
In Bacillus thuringiensis, β-lactam antibiotic resistance is controlled by the extracytoplasmic function (ECF) σ factor σP. σP activity is inhibited by the anti-σ factor RsiP. In the presence of β-lactam antibiotics, RsiP is degraded and σP is activated. Previous work found that RsiP degradation requires cleavage of RsiP at site 1 by an unknown protease, followed by cleavage at site 2 by the site 2 protease RasP. The penicillin-binding protein PbpP acts as a sensor for β-lactams. PbpP initiates σP activation and is required for site 1 cleavage of RsiP but is not the site 1 protease. Here, we describe the identification of a signal peptidase, SipP, which cleaves RsiP at a site 1 signal peptidase cleavage site and is required for σP activation. Finally, many B. anthracis strains are sensitive to β-lactams yet encode the σP-RsiP signal transduction system. We identified a naturally occurring mutation in the signal peptidase cleavage site of B. anthracis RsiP that renders it resistant to SipP cleavage. We find that B. anthracis RsiP is not degraded in the presence of β-lactams. Altering the B. anthracis RsiP site 1 cleavage site by a single residue to resemble B. thuringiensis RsiP results in β-lactam-dependent degradation of RsiP. We show that mutation of the B. thuringiensis RsiP cleavage site to resemble the sequence of B. anthracis RsiP blocks degradation by SipP. The change in the cleavage site likely explains many reasons why B. anthracis strains are sensitive to β-lactams. IMPORTANCE β-Lactam antibiotics are important for the treatment of many bacterial infections. However, resistance mechanisms have become increasingly more prevalent. Understanding how β-lactam resistance is conferred and how bacteria control expression of β-lactam resistance is important for informing the future treatment of bacterial infections. σP is an alternative σ factor that controls the transcription of genes that confer β-lactam resistance in Bacillus thuringiensis, Bacillus cereus, and Bacillus anthracis. Here, we identify a signal peptidase as the protease required for initiating activation of σP by the degradation of the anti-σ factor RsiP. The discovery that the signal peptidase SipP is required for σP activation highlights an increasing role for signal peptidases in signal transduction, as well as in antibiotic resistance.
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