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Not so simple, not so subtle: the interspecies competition between Bacillus simplex and Bacillus subtilis and its impact on the evolution of biofilms.

ABSTRACT: Bacillus subtilis biofilms have a fundamental role in shaping the soil ecosystem. During this process, they unavoidably interact with neighbour bacterial species. We studied the interspecies interactions between biofilms of the soil-residing bacteria B. subtilis and related Bacillus species. We found that proximity between the biofilms triggered recruitment of motile B. subtilis cells, which engulfed the competing Bacillus simplex colony. Upon interaction, B. subtilis secreted surfactin and cannibalism toxins, at concentrations that were inert to B. subtilis itself, which eliminated the B. simplex colony, as well as colonies of Bacillus toyonensis. Surfactin toxicity was correlated with the presence of short carbon-tail length isomers, and synergistic with the cannibalism toxins. Importantly, during biofilm development and interspecies interactions a subpopulation in B. subtilis biofilm lost its native plasmid, leading to increased virulence against the competing Bacillus species. Overall, these findings indicate that genetic programs and traits that have little effect on biofilm development when each species is grown in isolation have a dramatic impact when different bacterial species interact.

SUBMITTER: Rosenberg G

PROVIDER: S-EPMC5515258 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Not so simple, not so subtle: the interspecies competition between Bacillus simplex and Bacillus subtilis and its impact on the evolution of biofilms.

Rosenberg Gili G Steinberg Nitai N Oppenheimer-Shaanan Yaara Y Olender Tsvia T Doron Shany S Ben-Ari Julius J Sirota-Madi Alexandra A Bloom-Ackermann Zohar Z Kolodkin-Gal Ilana I

NPJ biofilms and microbiomes 20160127

Bacillus subtilis biofilms have a fundamental role in shaping the soil ecosystem. During this process, they unavoidably interact with neighbour bacterial species. We studied the interspecies interactions between biofilms of the soil-residing bacteria B. subtilis and related Bacillus species. We found that proximity between the biofilms triggered recruitment of motile B. subtilis cells, which engulfed the competing Bacillus simplex colony. Upon interaction, B ...[more]

PMID: 28721238

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Project description:Biofilms are multispecies communities, in which bacteria constantly compete with one another for resources and niches. Bacteria produce many antibiotics and toxins for competition. However, since biofilm cells exhibit increased tolerance to antimicrobials, their roles in biofilms remain controversial. Here, we showed that Bacillus subtilis produces multiple diverse polymorphic toxins, called LXG toxins, that contain N-terminal LXG delivery domains and diverse C-terminal toxin domains. Each B. subtilis strain possesses a distinct set of LXG toxin-antitoxin genes, the number and variation of which is sufficient to distinguish each strain. The B. subtilis strain NCIB3610 possesses six LXG toxin-antitoxin operons on its chromosome, and five of the toxins functioned as DNase. In competition assays, deletion mutants of any of the six LXG toxin-antitoxin operons were outcompeted by the wild-type strain. This phenotype was suppressed when the antitoxins were ectopically expressed in the deletion mutants. The fitness defect of the mutants was only observed in solid media that supported biofilm formation. Biofilm matrix polymers, exopolysaccharides and TasA protein polymers were required for LXG toxin function. These results indicate that LXG toxin-antitoxin systems specifically mediate intercellular competition between B. subtilis strains in biofilms. Mutual antagonism between some LXG toxin producers drove the spatial segregation of two strains in a biofilm, indicating that LXG toxins not only mediate competition in biofilms, but may also help to avoid warfare between strains in biofilms. LXG toxins from strain NCIB3610 were effective against some natural isolates, and thus LXG toxin-antitoxin systems have ecological impact. B. subtilis possesses another polymorphic toxin, WapA. WapA had toxic effects under planktonic growth conditions but not under biofilm conditions because exopolysaccharides and TasA protein polymers inhibited WapA function. These results indicate that B. subtilis uses two types of polymorphic toxins for competition, depending on the growth mode.

Dataset Information

Not so simple, not so subtle: the interspecies competition between Bacillus simplex and Bacillus subtilis and its impact on the evolution of biofilms.

Publications

Not so simple, not so subtle: the interspecies competition between <i>Bacillus simplex</i> and <i>Bacillus subtilis</i> and its impact on the evolution of biofilms.

Similar Datasets

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