1
|
Kim YY, Kim JC, Kim S, Yang JE, Kim HM, Park HW. Heterotypic stress-induced adaptive evolution enhances freeze-drying tolerance and storage stability of Leuconostoc mesenteroides WiKim33. Food Res Int 2024; 175:113731. [PMID: 38128991 DOI: 10.1016/j.foodres.2023.113731] [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: 08/31/2023] [Revised: 11/15/2023] [Accepted: 11/22/2023] [Indexed: 12/23/2023]
Abstract
Lactic acid bacteria (LAB) are currently being investigated for their potential use as probiotics and starter cultures. Researchers have developed powdering processes for the commercialization of LAB. Previous studies have focused on identifying innovative cryoprotective agents and freeze-drying (FD) techniques to enhance the stability of LAB. In this study, adaptive laboratory evolution (ALE) was employed to develop a strain with high FD tolerance and enhanced storage stability. Leuconostoc mesenteroids WiKim33 was subjected to heterotypic shock (heat and osmosis shock) to induce the desired phenotype and genotype. An FD-tolerant enhanced Leu. mesenteroides WiKim33 strain (ALE50) was obtained, which harbored a modified fatty acid composition and cell envelope characteristics. Specifically, ALE50 showed a lower unsaturated fatty acid (UFA)/saturated fatty acid (SFA) ratio and a higher cyclic fatty acid (CFA) composition. Moreover, the exopolysaccharide (EPS) thickness increased significantly by 331% compared to that of the wild type (WT). FD tolerance, which was evaluated using viability testing after FD, was enhanced by 33.4%. Overall, we demonstrated the feasibility of ALE to achieve desirable characteristics and provided insights into the mechanisms underlying increased FD tolerance.
Collapse
Affiliation(s)
- Yeong Yeol Kim
- Technology Innovation Research Division, World Institute of Kimchi, Gwangju 61755, Republic of Korea; Department of Integrative Food, Bioscience and Biotechnology, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Jong-Cheol Kim
- Technology Innovation Research Division, World Institute of Kimchi, Gwangju 61755, Republic of Korea
| | - Seulbi Kim
- Technology Innovation Research Division, World Institute of Kimchi, Gwangju 61755, Republic of Korea; Division of Applied Bioscience & Biotechnology, Chonnam National University, Gwangju 61186, Republic of Korea
| | - Jung Eun Yang
- Technology Innovation Research Division, World Institute of Kimchi, Gwangju 61755, Republic of Korea
| | - Ho Myeong Kim
- Technology Innovation Research Division, World Institute of Kimchi, Gwangju 61755, Republic of Korea.
| | - Hae Woong Park
- Technology Innovation Research Division, World Institute of Kimchi, Gwangju 61755, Republic of Korea.
| |
Collapse
|
2
|
Characterization of the oxidative stress response regulatory network in Bacteroides fragilis: An interaction between BmoR and OxyR regulons promotes abscess formation in a model of intra-abdominal infection. Anaerobe 2022; 78:102668. [DOI: 10.1016/j.anaerobe.2022.102668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 10/31/2022] [Accepted: 11/01/2022] [Indexed: 11/10/2022]
|
3
|
Alves JA, Previato-Mello M, Barroso KCM, Koide T, da Silva Neto JF. The MarR family regulator OsbR controls oxidative stress response, anaerobic nitrate respiration, and biofilm formation in Chromobacterium violaceum. BMC Microbiol 2021; 21:304. [PMID: 34736409 PMCID: PMC8567585 DOI: 10.1186/s12866-021-02369-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 10/26/2021] [Indexed: 12/16/2022] Open
Abstract
Background Chromobacterium violaceum is an environmental opportunistic pathogen that causes rare but deadly infections in humans. The transcriptional regulators that C. violaceum uses to sense and respond to environmental cues remain largely unknown. Results Here, we described a novel transcriptional regulator in C. violaceum belonging to the MarR family that we named OsbR (oxidative stress response and biofilm formation regulator). Transcriptome profiling by DNA microarray using strains with deletion or overexpression of osbR showed that OsbR exerts a global regulatory role in C. violaceum, regulating genes involved in oxidative stress response, nitrate reduction, biofilm formation, and several metabolic pathways. EMSA assays showed that OsbR binds to the promoter regions of several OsbR-regulated genes, and the in vitro DNA binding activity was inhibited by oxidants. We demonstrated that the overexpression of osbR caused activation of ohrA even in the presence of the repressor OhrR, which resulted in improved growth under organic hydroperoxide treatment, as seem by growth curve assays. We showed that the proper regulation of the nar genes by OsbR ensures optimal growth of C. violaceum under anaerobic conditions by tuning the reduction of nitrate to nitrite. Finally, the osbR overexpressing strain showed a reduction in biofilm formation, and this phenotype correlated with the OsbR-mediated repression of two gene clusters encoding putative adhesins. Conclusions Together, our data indicated that OsbR is a MarR-type regulator that controls the expression of a large number of genes in C. violaceum, thereby contributing to oxidative stress defense (ohrA/ohrR), anaerobic respiration (narK1K2 and narGHJI), and biofilm formation (putative RTX adhesins). Supplementary Information The online version contains supplementary material available at 10.1186/s12866-021-02369-x.
Collapse
Affiliation(s)
- Júlia A Alves
- Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Maristela Previato-Mello
- Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Kelly C M Barroso
- Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Tie Koide
- Departamento de Bioquímica e Imunologia, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - José F da Silva Neto
- Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
| |
Collapse
|
4
|
Kotecka K, Kawalek A, Kobylecki K, Bartosik AA. The MarR-Type Regulator PA3458 Is Involved in Osmoadaptation Control in Pseudomonas aeruginosa. Int J Mol Sci 2021; 22:ijms22083982. [PMID: 33921535 PMCID: PMC8070244 DOI: 10.3390/ijms22083982] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 04/08/2021] [Accepted: 04/09/2021] [Indexed: 12/13/2022] Open
Abstract
Pseudomonas aeruginosa is a facultative human pathogen, causing acute and chronic infections that are especially dangerous for immunocompromised patients. The eradication of P. aeruginosa is difficult due to its intrinsic antibiotic resistance mechanisms, high adaptability, and genetic plasticity. The bacterium possesses multilevel regulatory systems engaging a huge repertoire of transcriptional regulators (TRs). Among these, the MarR family encompasses a number of proteins, mainly acting as repressors, which are involved in response to various environmental signals. In this work, we aimed to decipher the role of PA3458, a putative MarR-type TR from P. aeruginosa. Transcriptional profiling of P. aeruginosa PAO1161 overexpressing PA3458 showed changes in the mRNA level of 133 genes; among them, 100 were down-regulated, suggesting the repressor function of PA3458. Concomitantly, ChIP-seq analysis identified more than 300 PA3458 binding sites in P. aeruginosa. The PA3458 regulon encompasses genes involved in stress response, including the PA3459–PA3461 operon, which is divergent to PA3458. This operon encodes an asparagine synthase, a GNAT-family acetyltransferase, and a glutamyl aminopeptidase engaged in the production of N-acetylglutaminylglutamine amide (NAGGN), which is a potent bacterial osmoprotectant. We showed that PA3458-mediated control of PA3459–PA3461 expression is required for the adaptation of P. aeruginosa growth in high osmolarity. Overall, our data indicate that PA3458 plays a role in osmoadaptation control in P. aeruginosa.
Collapse
|
5
|
Yekani M, Baghi HB, Vahed SZ, Ghanbari H, Hosseinpur R, Azargun R, Azimi S, Memar MY. Tightly controlled response to oxidative stress; an important factor in the tolerance of Bacteroides fragilis. Res Microbiol 2021; 172:103798. [PMID: 33485914 DOI: 10.1016/j.resmic.2021.103798] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 01/07/2021] [Accepted: 01/08/2021] [Indexed: 12/01/2022]
Abstract
The exposure of Bacteroides fragilis to highly oxygenated tissues induces an oxidative stress due to a shift from the reduced condition of the gastrointestinal tract to an aerobic environment of host tissues. The potent and effective responses to reactive oxygen species (ROS) make the B. fragilis tolerant to atmospheric oxygen for several days. The response to oxidative stress in B. fragilis is a complicated event that is induced and regulated by different agents. In this review, we will focus on the B. fragilis response to oxidative stress and present an overview of the regulators of responses to oxidative stress in this bacterium.
Collapse
Affiliation(s)
- Mina Yekani
- Department of Microbiology, Faculty of Medicine, Kashan University of Medical Sciences, Kashan, Iran; Student Research Committee, Kashan University of Medical Sciences, Kashan, Iran
| | - Hossein Bannazadeh Baghi
- Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Immunology Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | | | - Hadi Ghanbari
- Department of Pharmacognosy, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Rasul Hosseinpur
- Immunology Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Robab Azargun
- Department of Microbiology, Faculty of Medicine, Maragheh University of Medical Sciences, Maragheh, Iran
| | - Somayeh Azimi
- Immunology Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Mohammad Yousef Memar
- Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Microbiology Department, School of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
| |
Collapse
|
6
|
Valguarnera E, Wardenburg JB. Good Gone Bad: One Toxin Away From Disease for Bacteroides fragilis. J Mol Biol 2019; 432:765-785. [PMID: 31857085 DOI: 10.1016/j.jmb.2019.12.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 11/27/2019] [Accepted: 12/05/2019] [Indexed: 02/06/2023]
Abstract
The human gut is colonized by hundreds of trillions of microorganisms whose acquisition begins during early infancy. Species from the Bacteroides genus are ubiquitous commensals, comprising about thirty percent of the human gut microbiota. Bacteroides fragilis is one of the least abundant Bacteroides species, yet is the most common anaerobe isolated from extraintestinal infections in humans. A subset of B. fragilis strains carry a genetic element that encodes a metalloprotease enterotoxin named Bacteroides fragilis toxin, or BFT. Toxin-bearing strains, or Enterotoxigenic B. fragilis (ETBF) cause acute and chronic intestinal disease in children and adults. Despite this association with disease, around twenty percent of the human population appear to be asymptomatic carriers of ETBF. BFT damages the colonic epithelial barrier by inducing cleavage of the zonula adherens protein E-cadherin and initiating a cell signaling response characterized by inflammation and c-Myc-dependent pro-oncogenic hyperproliferation. As a consequence, mice harboring genetic mutations that predispose to colonic inflammation or tumor formation are uniquely susceptible to toxin-mediated injury. The recent observation of ETBF-bearing biofilms in colon biopsies from humans with colon cancer susceptibility loci strongly suggests that ETBF is a driver of colorectal cancer. This article will address ETBF biology from a host-pathobiont perspective, including clinical data, analysis of molecular mechanisms of disease, and the complex ecological context of the human gut.
Collapse
Affiliation(s)
- Ezequiel Valguarnera
- Department of Pediatrics, Washington University School of Medicine, 660 S. Euclid Ave. Box 8208, St. Louis, MO 63110
| | - Juliane Bubeck Wardenburg
- Department of Pediatrics, Washington University School of Medicine, 660 S. Euclid Ave. Box 8208, St. Louis, MO 63110.
| |
Collapse
|
7
|
Teixeira FL, Pauer H, Costa SB, Smith CJ, Domingues RMCP, Rocha ER, Lobo LA. Deletion of BmoR affects the expression of genes related to thiol/disulfide balance in Bacteroides fragilis. Sci Rep 2018; 8:14405. [PMID: 30258073 PMCID: PMC6158253 DOI: 10.1038/s41598-018-32880-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 09/10/2018] [Indexed: 01/03/2023] Open
Abstract
Bacteroides fragilis, an opportunistic pathogen and commensal bacterium in the gut, is one the most aerotolerant species among strict anaerobes. However, the mechanisms that control gene regulation in response to oxidative stress are not completely understood. In this study, we show that the MarR type regulator, BmoR, regulates the expression of genes involved in the homeostasis of intracellular redox state. Transcriptome analysis showed that absence of BmoR leads to altered expression in total of 167 genes. Sixteen of these genes had a 2-fold or greater change in their expression. Most of these genes are related to LPS biosynthesis and carbohydrates metabolism, but there was a significant increase in the expression of genes related to the redox balance inside the cell. A pyridine nucleotide-disulfide oxidoreductase located directly upstream of bmoR was shown to be repressed by direct binding of BmoR to the promoter region. The expression of two other genes, coding for a thiosulphate:quinone-oxidoreductase and a thioredoxin, are indirectly affected by bmoR mutation during oxygen exposure. Phenotypic assays showed that BmoR is important to maintain the thiol/disulfide balance in the cell, confirming its relevance to B. fragilis response to oxidative stress.
Collapse
Affiliation(s)
- Felipe L Teixeira
- Departamento de Microbiologia Médica, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC, USA.
| | - Heidi Pauer
- Departamento de Microbiologia Médica, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC, USA
| | - Scarlathe B Costa
- Departamento de Microbiologia Médica, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - C Jeffrey Smith
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC, USA
| | - Regina M C P Domingues
- Departamento de Microbiologia Médica, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Edson R Rocha
- Department of Microbiology and Immunology, Brody School of Medicine, East Carolina University, Greenville, NC, USA
| | - Leandro A Lobo
- Departamento de Microbiologia Médica, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
| |
Collapse
|
8
|
Silva CMG, Silva DNDS, Costa SBD, Almeida JSDS, Boente RF, Teixeira FL, Domingues RMCP, Lobo LA. Inactivation of MarR gene homologs increases susceptibility to antimicrobials in Bacteroides fragilis. Braz J Microbiol 2017; 49:200-206. [PMID: 28847541 PMCID: PMC5790583 DOI: 10.1016/j.bjm.2017.05.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 04/18/2017] [Accepted: 05/06/2017] [Indexed: 01/05/2023] Open
Abstract
Bacteroides fragilis is the strict anaerobic bacteria most commonly found in human infections, and has a high mortality rate. Among other virulence factors, the remarkable ability to acquire resistance to a variety of antimicrobial agents and to tolerate nanomolar concentrations of oxygen explains in part their success in causing infection and colonizing the mucosa. Much attention has been given to genes related to multiple drug resistance derived from plasmids, integrons or transposon, but such genes are also detected in chromosomal systems, like the mar (multiple antibiotic resistance) locus, that confer resistance to a range of drugs. Regulators like MarR, that control expression of the locus mar, also regulate resistance to organic solvents, disinfectants and oxygen reactive species are important players in these events. Strains derived from the parental strain 638R, with mutations in the genes hereby known as marRI (BF638R_3159) and marRII (BF638R_3706) were constructed by gene disruption using a suicide plasmid. Phenotypic response of the mutant strains to hydrogen peroxide, cell survival assay against exposure to oxygen, biofilm formation, resistance to bile salts and resistance to antibiotics was evaluated. The results showed that the mutant strains exhibit statistically significant differences in their response to oxygen stress, but no changes were observed in survival when exposed to bile salts. Biofilm formation was not affected by either gene disruption. Both mutant strains however, became more sensitive to multiple antimicrobial drugs tested. This indicates that as observed in other bacterial species, MarR are an important resistance mechanism in B. fragilis.
Collapse
Affiliation(s)
| | | | | | | | - Renata Ferreira Boente
- Universidade Federal do Rio de Janeiro, Medical Microbiology Department, Rio de Janeiro, RJ, Brazil
| | - Felipe Lopes Teixeira
- Universidade Federal do Rio de Janeiro, Medical Microbiology Department, Rio de Janeiro, RJ, Brazil
| | | | - Leandro Araujo Lobo
- Universidade Federal do Rio de Janeiro, Medical Microbiology Department, Rio de Janeiro, RJ, Brazil.
| |
Collapse
|
9
|
Li L, Krause L, Somerset S. Associations between micronutrient intakes and gut microbiota in a group of adults with cystic fibrosis. Clin Nutr 2016; 36:1097-1104. [PMID: 27595636 DOI: 10.1016/j.clnu.2016.06.029] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Revised: 06/23/2016] [Accepted: 06/30/2016] [Indexed: 12/18/2022]
Abstract
BACKGROUND Cystic fibrosis (CF) involves chronic inflammation and oxidative stress affecting mainly the respiratory and digestive systems. Survival rates for CF have improved with advances in treatment including nutritional interventions such as micronutrient supplementation. Diet can modulate gut microbiota in the general population with consequences on local and systemic immunity, and inflammation. The gut microbiota appears disrupted and may associate with pulmonary status in CF. This study investigated associations between micronutrient intakes and gut microbiota variations in a group of adults with CF. METHODS Faecal microbiota of sixteen free-living adults with CF was profiled by 16ss rDNA sequencing on the GS-FLX platform. Associations were tested between UniFrac distances of faecal microbiota and time-corresponding micronutrient intakes. Associations between relative abundances of bacterial taxa and micronutrient intakes (those showing significant associations with UniFrac distances) were examined by Spearman correlation. RESULTS Unweighted UniFrac distances were associated with intakes of potassium and antioxidant vitamins C, E and beta-carotene equivalents, whereas weighted UniFrac distances were associated with antioxidant vitamins riboflavin, niacin equivalents, beta-carotene equivalents and vitamin A equivalents. Intakes of beta-carotene equivalents, vitamin C, vitamin E, niacin equivalents and riboflavin correlated negatively with Bacteroides and/or its corresponding higher level taxa. Intakes of beta-carotene equivalents and vitamin E also positively correlated with Firmicutes and specific taxa belonging to Firmicutes. CONCLUSION Some micronutrients, particularly antioxidant vitamins, correlated with gut microbiota variations in the studied cohort. Further research is required to clarify whether antioxidant vitamin intakes can influence CF gut microbiota and potential clinical/therapeutic implications in CF.
Collapse
Affiliation(s)
- Li Li
- School of Medicine, Griffith University, Brisbane, Queensland, Australia
| | - Lutz Krause
- The University of Queensland, Diamantina Institute, Translational Research Institute, Woolloongabba 4102, Brisbane, Queensland, Australia
| | - Shawn Somerset
- School of Medicine, Griffith University, Brisbane, Queensland, Australia; School of Allied Health, Faculty of Health Sciences, Australian Catholic University, Brisbane, Queensland, Australia.
| |
Collapse
|
10
|
Multidrug Efflux Systems in Microaerobic and Anaerobic Bacteria. Antibiotics (Basel) 2015; 4:379-96. [PMID: 27025630 PMCID: PMC4790292 DOI: 10.3390/antibiotics4030379] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 08/11/2015] [Accepted: 08/13/2015] [Indexed: 12/13/2022] Open
Abstract
Active drug efflux constitutes an important mechanism of antibiotic and multidrug resistance in bacteria. Understanding the distribution, expression, and physiological functions of multidrug efflux pumps, especially under physiologically and clinically relevant conditions of the pathogens, is the key to combat drug resistance. In animal hosts, most wounded, infected and inflamed tissues display low oxygen tensions. In this article, we summarize research development on multidrug efflux pumps in the medicinally relevant microaerobic and anaerobic pathogens and their implications in the effort to combat drug-resistant infections.
Collapse
|
11
|
The Bacillus subtilis tyrZ gene encodes a highly selective tyrosyl-tRNA synthetase and is regulated by a MarR regulator and T box riboswitch. J Bacteriol 2015; 197:1624-31. [PMID: 25733610 DOI: 10.1128/jb.00008-15] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 02/19/2015] [Indexed: 02/02/2023] Open
Abstract
UNLABELLED Misincorporation of D-tyrosine (D-Tyr) into cellular proteins due to mischarging of tRNA(Tyr) with D-Tyr by tyrosyl-tRNA synthetase inhibits growth and biofilm formation of Bacillus subtilis. Furthermore, many B. subtilis strains lack a functional gene encoding D-aminoacyl-tRNA deacylase, which prevents misincorporation of D-Tyr in most organisms. B. subtilis has two genes that encode tyrosyl-tRNA synthetase: tyrS is expressed under normal growth conditions, and tyrZ is known to be expressed only when tyrS is inactivated by mutation. We hypothesized that tyrZ encodes an alternate tyrosyl-tRNA synthetase, expression of which allows the cell to grow when D-Tyr is present. We show that TyrZ is more selective for L-Tyr over D-Tyr than is TyrS; however, TyrZ is less efficient overall. We also show that expression of tyrZ is required for growth and biofilm formation in the presence of D-Tyr. Both tyrS and tyrZ are preceded by a T box riboswitch, but tyrZ is found in an operon with ywaE, which is predicted to encode a MarR family transcriptional regulator. Expression of tyrZ is repressed by YwaE and also is regulated at the level of transcription attenuation by the T box riboswitch. We conclude that expression of tyrZ may allow growth when excess D-Tyr is present. IMPORTANCE Accurate protein synthesis requires correct aminoacylation of each tRNA with the cognate amino acid and discrimination against related compounds. Bacillus subtilis produces D-Tyr, an analog of L-Tyr that is toxic when incorporated into protein, during stationary phase. Most organisms utilize a D-aminoacyl-tRNA deacylase to prevent misincorporation of D-Tyr. This work demonstrates that the increased selectivity of the TyrZ form of tyrosyl-tRNA synthetase may provide a mechanism by which B. subtilis prevents misincorporation of D-Tyr in the absence of a functional D-aminoacyl-tRNA deacylase gene.
Collapse
|