Abstract
S-ribosylhomocysteine lyase (LuxS) has been shown to regulate bacterial multicellular behaviors, typically biofilm formation. However, the mechanisms for the regulation are still mysterious. We previously identified a malonylation modification on K124 and K130 of the LuxS in the plant growth-promoting rhizobacterium B. velezensis (FZB42). In this work, we investigated the effects of the two malonylation sites on biofilm formation and other biological characteristics of FZB42. The results showed that the K124R mutation could severely impair biofilm formation, swarming, and sporulation but promote AI-2 production, suggesting inhibitory effects of high-level AI-2 on the features. All mutations (K124R, K124E, K130R, and K130E) suppressed FZB42 sporulation but increased its antibiotic production. The double mutations generally had a synergistic effect or at least equal to the effects of the single mutations. The mutation of K130 but not of K124 decreased the in vitro enzymatic activity of LuxS, corresponding to the conservation of K130 among various Bacillus LuxS proteins. From the results, we deduce that an alternative regulatory circuit may exist to compensate for the roles of LuxS upon its disruption. This study broadens the understanding of the biological function of LuxS in bacilli and underlines the importance of the two post-translational modification sites.
Highlights
Lysine malonylation is a type of dynamic and reversible protein post-translational modifications (PTM), which can affect many biological processes by regulating activities, localizations, and/or interactions of proteins involved in glycolysis and fatty acids metabolism pathways, malonic aciduria, type II diabetes, and other genetic diseases [1,2,3,4,5].At present, studies on malonylation are mainly performed with eukaryotes, whereas only a few reports were focused on bacteria such as B. velezensis (FZB42) [1]
Studies on malonylation are mainly performed with eukaryotes, whereas only a few reports were focused on bacteria such as B. velezensis (FZB42) [1]
B. velezensis (FZB42) is a prototype of plant growth-promoting rhizobacteria (PGPR), which have been the subject of extensive investigations in the past decade due to their enormous economic values [6,7]
Summary
Lysine malonylation is a type of dynamic and reversible protein post-translational modifications (PTM), which can affect many biological processes by regulating activities, localizations, and/or interactions of proteins involved in glycolysis and fatty acids metabolism pathways, malonic aciduria, type II diabetes, and other genetic diseases [1,2,3,4,5]. While SRH is a member of the activated methyl cycle (AMC), AI-2 serves as the signaling molecule in quorum sensing and is generally regarded as a universal language by bacteria to in mediate their intra-and andisinterspecific communication [12,13,14]. LuxS regulate bacterial including in B. subtilis, serve as athat novel typecan of AI-2 receptors [25].multicellular behaviorPrevious such as reports biofilmhave formation [26], of the effect have notbehavbeen established that LuxS mechanisms can regulate bacterial multicellular fully elucidated. Some suggested of a central metabolic role of LuxS in in biofilm formation apart from the participation. The crystal structure of LuxS in B.three subtilis has been determined [24,30].His, The active sites of this LuxS include Cys-4, Glu-57, Fe2+.
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