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Microorganisms
Special Issues
Toxin-Antitoxin Systems I
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Toxin-Antitoxin Systems I

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Molecular Microbiology and Immunology".

Deadline for manuscript submissions: closed (31 December 2020) | Viewed by 11445

Special Issue Editor

Dr. Hisako Masuda

E-Mail Website
Guest Editor
School of Sciences, Indiana University Kokomo, Kokomo, IN 46902, USA
Interests: Cellular Physiology of Bacteria and Environmental Microbiology; elucidation of biodegradation pathways for organic pollutants; isolation of novel organic pollutant degrading bacteria; microbial genome analysis; bacterial stress response; and multicellular behavior of bacteria
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Toxin–antitoxin (TA) systems are genetic loci composed of toxin and cognate antitoxin genes. TA systems are ubiquitously found in bacterial genomes, many of which often carry multiple TA pairs. The largest class of TA toxins are endoribonucleases, which cleave mRNA and/or tRNA in a sequence-specific manner. The degradation of RNA leads to rapid but reversible growth arrest. Other toxins also halt cell growth by inhibiting essential cellular processes such as DNA replication and cell division. In normally growing cells, antitoxins block cognate toxins’ activity or expression. Under stress conditions, antitoxins are preferentially degraded, allowing toxins to exert their toxicity. Despite the prevalence and clear biochemical mechanism of action, the physiological roles of TA systems are still under debate. TA-induced growth arrest is attributed to plasmid stabilization, inhibition of phage propagation, biofilm formation, and stress tolerance. Many recent studies have also investigated if and how each TA system is involved in the formation of persister cells, which are a metabolically quiescent subpopulation with multi-drug tolerance. The future of this research is leading towards solutions to many concerning phenomena, such as chronic and recurrent infections and the spreading of multidrug resistant genes among pathogenic bacteria.

In this Special Issue of Microbiology, devoted to the “Toxin-Antitoxin systems”, we invite current innovative research of any aspects related to TA systems.

Dr. Hisako Masuda
Guest Editor

Manuscript Submission Information

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Keywords

  • Toxin-antitoxin
  • Bacteria
  • Stress tolerance
  • Growth arrest
  • Persister

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Published Papers (3 papers)

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Research

18 pages, 1429 KiB  
Article
Prevalence, Distribution, and Phylogeny of Type Two Toxin-Antitoxin Genes Possessed by Cronobacter Species where C. sakazakii Homologs Follow Sequence Type Lineages
by Samantha Finkelstein, Flavia Negrete, Hyein Jang, Jayanthi Gangiredla, Mark Mammel, Isha R. Patel, Hannah R. Chase, JungHa Woo, YouYoung Lee, Caroline Z. Wang, Leah Weinstein, Ben D. Tall and Gopal R. Gopinath
Microorganisms 2019, 7(11), 554; https://doi.org/10.3390/microorganisms7110554 - 12 Nov 2019
Cited by 10 | Viewed by 3574
Abstract
Cronobacter species are a group of foodborne pathogenic bacteria that cause both intestinal and systemic human disease in individuals of all age groups. Little is known about the mechanisms that Cronobacter employ to survive and persist in foods and other environments. Toxin–antitoxin (TA) [...] Read more.
Cronobacter species are a group of foodborne pathogenic bacteria that cause both intestinal and systemic human disease in individuals of all age groups. Little is known about the mechanisms that Cronobacter employ to survive and persist in foods and other environments. Toxin–antitoxin (TA) genes are thought to play a role in bacterial stress physiology, as well as in the stabilization of horizontally-acquired re-combinatorial elements such as plasmids, phage, and transposons. TA systems have been implicated in the formation of a persistence phenotype in some bacterial species including Escherichia coli and Salmonella. This project’s goal was to understand the phylogenetic relatedness among TA genes present in Cronobacter. Preliminary studies showed that two typical toxin genes, fic and hipA followed species evolutionary lines. A local database of 22 TA homologs was created for Cronobacter sakazakii and a Python version 3 shell script was generated to extract TA FASTA sequences present in 234 C. sakazakii genomes previously sequenced as part of Center for Food Safety and Applied Nutrition’s (CFSAN) GenomeTrakr project. BLAST analysis showed that not every C. sakazakii strain possessed all twenty-two TA loci. Interestingly, some strains contained either a toxin or an antitoxin component, but not both. Five common toxin genes: ESA_00258 (parDE toxin-antitoxin family), ESA_00804 (relBE family), ESA_01887 (relBE family), ESA_03838 (relBE family), and ESA_04273 (YhfG-Fic family) were selected for PCR analysis and the primers were designed to detect these genes. PCR analysis showed that 55 of 63 strains possessed three of these genes Sequence analysis identified homologs of the target genes and some of the strains were PCR-negative for one or more of the genes, pointing to potential nucleotide polymorphisms in those loci or that these toxin genes were absent. Phylogenetic studies using a Cronobacter pan genomic microarray showed that for the most part TAs follow species evolutionary lines except for a few toxin genes possessed by some C. malonaticus and C. universalis strains; this demonstrates that some TA orthologues share a common phylogeny. Within the C. sakazakii strains, the prevalence and distribution of these TA homologs by C. sakazakii strain BAA-894 (a powdered infant formula isolate) followed sequence-type evolutionary lineages. Understanding the phylogeny of TAs among the Cronobacter species is essential to design future studies to realize the physiological mechanisms and roles for TAs in stress adaptation and persistence of Cronobacter within food matrices and food processing environments. Full article
(This article belongs to the Special Issue Toxin-Antitoxin Systems I)
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15 pages, 1467 KiB  
Article
Expression of DinJ-YafQ System of Lactobacillus casei Group Strains in Response to Food Processing Stresses
by Alessia Levante, Claudia Folli, Barbara Montanini, Alberto Ferrari, Erasmo Neviani and Camilla Lazzi
Microorganisms 2019, 7(10), 438; https://doi.org/10.3390/microorganisms7100438 - 11 Oct 2019
Cited by 8 | Viewed by 2734
Abstract
Toxin-antitoxin (TA) systems are widely distributed in bacterial genomes and are involved in the adaptive response of microorganisms to stress conditions. Few studies have addressed TA systems in Lactobacillus and their role in the adaptation to food environments and processes. In this work, [...] Read more.
Toxin-antitoxin (TA) systems are widely distributed in bacterial genomes and are involved in the adaptive response of microorganisms to stress conditions. Few studies have addressed TA systems in Lactobacillus and their role in the adaptation to food environments and processes. In this work, for six strains belonging to L. casei group isolated from dairy products, the expression of DinJ-YafQ TA system was investigated after exposure to various food-related stresses (nutrient starvation, low pH, high salt concentration, oxidative stress, and high temperature), as well as to the presence of antibiotics. In particular, culturability and DinJ-YafQ expression were evaluated for all strains and conditions by plate counts and RT qPCR. Among all the food-related stress conditions, only thermal stress was capable to significantly affect culturability. Furthermore, exposure to ampicillin significantly decreased the culturability of two L. rhamnosus strains. The regulation of DinJ-YafQ TA system resulted strain-specific; however, high temperature was the most significant stress condition able to modulate DinJ-YafQ expression. The increasing knowledge about TA systems activity and regulation might offer new perspectives to understand the mechanisms that L. casei group strains exploit to adapt to different niches or production processes. Full article
(This article belongs to the Special Issue Toxin-Antitoxin Systems I)
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18 pages, 4129 KiB  
Article
In Silico Analysis of Genetic VapC Profiles from the Toxin-Antitoxin Type II VapBC Modules among Pathogenic, Intermediate, and Non-Pathogenic Leptospira
by Alexandre P. Y. Lopes, Bruna O. P. Azevedo, Rebeca C. Emídio, Deborah K. Damiano, Ana L. T. O. Nascimento and Giovana C. Barazzone
Microorganisms 2019, 7(2), 56; https://doi.org/10.3390/microorganisms7020056 - 20 Feb 2019
Cited by 6 | Viewed by 4361
Abstract
Pathogenic Leptospira spp. is the etiological agent of leptospirosis. The high diversity among Leptospira species provides an array to look for important mediators involved in pathogenesis. Toxin-antitoxin (TA) systems represent an important survival mechanism on stress conditions. vapBC modules have been found [...] Read more.
Pathogenic Leptospira spp. is the etiological agent of leptospirosis. The high diversity among Leptospira species provides an array to look for important mediators involved in pathogenesis. Toxin-antitoxin (TA) systems represent an important survival mechanism on stress conditions. vapBC modules have been found in nearly one thousand genomes corresponding to about 40% of known TAs. In the present study, we investigated TA profiles of some strains of Leptospira using a TA database and compared them through protein alignment of VapC toxin sequences among Leptospira spp. genomes. Our analysis identified significant differences in the number of putative vapBC modules distributed in pathogenic, saprophytic, and intermediate strains: four in L. interrogans, three in L. borgpetersenii, eight in L. biflexa, and 15 in L. licerasiae. The VapC toxins show low identity among amino acid sequences within the species. Some VapC toxins appear to be exclusively conserved in unique species, others appear to be conserved among pathogenic or saprophytic strains, and some appear to be distributed randomly. The data shown here indicate that these modules evolved in a very complex manner, which highlights the strong need to identify and characterize new TAs as well as to understand their regulation networks and the possible roles of TA systems in pathogenic bacteria. Full article
(This article belongs to the Special Issue Toxin-Antitoxin Systems I)
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