Abstract
Stress response plays an important role on microbial adaptation under hostile environmental conditions. It is generally unclear how the signaling transduction pathway mediates a stress response in planktonic and biofilm modes of microbial communities simultaneously. Here, we showed that metalloid tellurite (TeO32–) exposure induced the intracellular content of the secondary messenger cyclic di-GMP (c-di-GMP) of Pseudomonas aeruginosa. Two diguanylate cyclases (DGCs), SadC and SiaD, were responsible for the increased intracellular content of c-di-GMP. Enhanced c-di-GMP levels by TeO32– further increased P. aeruginosa biofilm formation and resistance to TeO32–. P. aeruginosa ΔsadCΔsiaD and PAO1/plac-yhjH mutants with low intracellular c-di-GMP content were more sensitive to TeO32– exposure and had low relative fitness compared to the wild-type PAO1 planktonic and biofilm cultures exposed to TeO32–. Our study provided evidence that c-di-GMP level can play an important role in mediating stress response in microbial communities during both planktonic and biofilm modes of growth.
Highlights
Increase synthesis of EPS matrix, resulting in biofilm formation[10,11]
No tellurium-containing precipitates were observed for P. aeruginosa cells growing in medium without TeO32−
PAO1/plac-yhjH was fully outcompeted by PAO1 in biofilm co-cultures supplemented with TeO32− (Fig. 6b). These results suggest that variants with low intracellular c-di-GMP content are unlikely to be protected and maintained by both P. aeruginosa planktonic and biofilm communities when c-di-GMP is required for stress response
Summary
Increase synthesis of EPS matrix, resulting in biofilm formation[10,11]. In contrast, biofilm cells increase their motility and disperse from biofilms when the intracellular c-di-GMP content is low[12,13]. C-di-GMP signaling can be induced by stress conditions such as antimicrobial exposure[14,15]. The toxic effects of metal(oild)s on environmental microorganisms at individual cell levels have been extensively studied[20], little is known about the impacts of metal(loid)s on bacterial social behaviours[21]. We investigated the role of c-di-GMP in mediating stress responses by the opportunistic pathogen Pseudomonas aeruginosa to a toxic metalloid, tellurite (TeO32–). Quantification of intracellular c-di-GMP and proteomic analysis indicated that c-di-GMP levels were induced by TeO32– exposure, which enhanced P. aeruginosa TeO32– resistance and biofilm formation. We showed that mutants with low intracellular c-di-GMP content could be outcompeted by the wild-type strain from biofilm and planktonic cultures under metalloid stress condition
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