A toxin-antitoxin module in Bacillus subtilis can both mitigate and amplify effects of lethal stress

Xiangli Wu, Xiuhong Wang, Karl Drlica, Xilin Zhao

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Background: Bacterial type-2 (protein-protein) toxin-antitoxin (TA) modules are two-gene operons that are thought to participate in the response to stress. Previous work with Escherichia coli has led to a debate in which some investigators conclude that the modules protect from stress, while others argue that they amplify lethal stress and lead to programmed cell death. To avoid ambiguity arising from the presence of multiple TA modules in E. coli, the effect of the sole type-2 toxin-antitoxin module of Bacillus subtilis was examined for several types of lethal stress. Methodology/Principal Findings: Genetic knockout of the toxin gene, ndoA (ydcE), conferred protection to lethal stressors that included kanamycin, moxifloxacin, hydrogen peroxide, and UV irradiation. However, at low doses of UV irradiation the ndoA deficiency increased lethality. Indeed, gradually increasing UV dose with the ndoA mutant revealed a crossover response - from the mutant being more sensitive than wild-type cells to being less sensitive. For high temperature and nutrient starvation, the toxin deficiency rendered cells hypersensitive. The ndoA deficiency also reduced sporulation frequency, indicating a role for toxin-antitoxin modules in this developmental process. In the case of lethal antimicrobial treatment, deletion of the toxin eliminated a surge in hydrogen peroxide accumulation observed in wild-type cells. Conclusions: A single toxin-antitoxin module can mediate two opposing effects of stress, one that lowers lethality and another that raises it. Protective effects are thought to arise from toxin-mediated inhibition of translation based on published work. The enhanced, stress-mediated killing probably involves toxin-dependent accumulation of reactive oxygen species, since a deficiency in the NdoA toxin suppressed peroxide accumulation following antimicrobial treatment. The type and perhaps the level of stress appear to be important for determining whether this toxin will have a protective or detrimental effect.

Original languageEnglish (US)
Article numbere23909
JournalPloS one
Volume6
Issue number8
DOIs
StatePublished - Aug 29 2011

Fingerprint

antitoxins
Antitoxins
Bacilli
Bacillus subtilis
lethal genes
toxins
Hydrogen Peroxide
Escherichia coli
Gene Knockout Techniques
Kanamycin
Bacterial Proteins
Gene Regulatory Networks
Peroxides
Genes
Operon
Irradiation
Starvation
Reactive Oxygen Species
Cell Death
Cell death

All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • General

Cite this

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title = "A toxin-antitoxin module in Bacillus subtilis can both mitigate and amplify effects of lethal stress",
abstract = "Background: Bacterial type-2 (protein-protein) toxin-antitoxin (TA) modules are two-gene operons that are thought to participate in the response to stress. Previous work with Escherichia coli has led to a debate in which some investigators conclude that the modules protect from stress, while others argue that they amplify lethal stress and lead to programmed cell death. To avoid ambiguity arising from the presence of multiple TA modules in E. coli, the effect of the sole type-2 toxin-antitoxin module of Bacillus subtilis was examined for several types of lethal stress. Methodology/Principal Findings: Genetic knockout of the toxin gene, ndoA (ydcE), conferred protection to lethal stressors that included kanamycin, moxifloxacin, hydrogen peroxide, and UV irradiation. However, at low doses of UV irradiation the ndoA deficiency increased lethality. Indeed, gradually increasing UV dose with the ndoA mutant revealed a crossover response - from the mutant being more sensitive than wild-type cells to being less sensitive. For high temperature and nutrient starvation, the toxin deficiency rendered cells hypersensitive. The ndoA deficiency also reduced sporulation frequency, indicating a role for toxin-antitoxin modules in this developmental process. In the case of lethal antimicrobial treatment, deletion of the toxin eliminated a surge in hydrogen peroxide accumulation observed in wild-type cells. Conclusions: A single toxin-antitoxin module can mediate two opposing effects of stress, one that lowers lethality and another that raises it. Protective effects are thought to arise from toxin-mediated inhibition of translation based on published work. The enhanced, stress-mediated killing probably involves toxin-dependent accumulation of reactive oxygen species, since a deficiency in the NdoA toxin suppressed peroxide accumulation following antimicrobial treatment. The type and perhaps the level of stress appear to be important for determining whether this toxin will have a protective or detrimental effect.",
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A toxin-antitoxin module in Bacillus subtilis can both mitigate and amplify effects of lethal stress. / Wu, Xiangli; Wang, Xiuhong; Drlica, Karl; Zhao, Xilin.

In: PloS one, Vol. 6, No. 8, e23909, 29.08.2011.

Research output: Contribution to journalArticle

TY - JOUR

T1 - A toxin-antitoxin module in Bacillus subtilis can both mitigate and amplify effects of lethal stress

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