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Alternative pathways for Escherichia coli biofilm formation revealed by sRNA overproduction.

ABSTRACT: Small regulatory RNAs have major roles in many regulatory circuits in Escherichia coli and other bacteria, including the transition from planktonic to biofilm growth. We tested Hfq-dependent sRNAs in E. coli for their ability, when overproduced, to inhibit or stimulate biofilm formation, in two different growth media. We identify two mutually exclusive pathways for biofilm formation. In LB, PgaA, encoding an adhesion export protein, played a critical role; biofilm was independent of the general stress factor RpoS or CsgD, regulator of curli and other biofilm genes. The PgaA-dependent pathway was stimulated upon overproduction of DsrA, via negative regulation of H-NS, or of GadY, likely by titration of CsrA. In yeast extract casamino acids (YESCA) media, biofilm was dependent on RpoS and CsgD, but independent of PgaA; RpoS appears to indirectly negatively regulate the PgaA-dependent pathway in YESCA medium. Deletions of most sRNAs had very little effect on biofilm, although deletion of hfq, encoding an RNA chaperone, was defective in both LB and YESCA. Deletion of ArcZ, a small RNA activator of RpoS, decreased biofilm in YESCA; only a portion of this defect could be bypassed by overproduction of RpoS. Overall, sRNAs highlight different pathways to biofilm formation.

SUBMITTER: Parker A

PROVIDER: S-EPMC5510166 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature

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Alternative pathways for Escherichia coli biofilm formation revealed by sRNA overproduction.

Parker Ashley A Cureoglu Suanur S De Lay Nicholas N Majdalani Nadim N Gottesman Susan S

Molecular microbiology 20170518 2

Small regulatory RNAs have major roles in many regulatory circuits in Escherichia coli and other bacteria, including the transition from planktonic to biofilm growth. We tested Hfq-dependent sRNAs in E. coli for their ability, when overproduced, to inhibit or stimulate biofilm formation, in two different growth media. We identify two mutually exclusive pathways for biofilm formation. In LB, PgaA, encoding an adhesion export protein, played a critical role; biofilm was independent of the general ...[more]

PMID: 28470798

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Project description:BACKGROUND: sRNAs, which belong to the non-coding RNA family and range from approximately 50 to 400 nucleotides, serve various important gene regulatory roles. Most are believed to be trans-regulating and function by being complementary to their target mRNAs in order to inhibiting translation by ribosome occlusion. Despite this understanding of their functionality, the global properties associated with regulation by sRNAs are not yet understood. Here we use topological analysis of sRNA targets in terms of protein-protein interaction and transcription-regulatory networks in Escherichia coli to shed light on the global correlation between sRNA regulation and cellular control networks. RESULTS: The analysis of sRNA targets in terms of their networks showed that some specific network properties could be identified. In protein-protein interaction network, sRNA targets tend to occupy more central positions (higher closeness centrality, p-val = 0.022) and more cliquish (larger clustering coefficient, p-val = 0.037). The targets of the same sRNA tend to form a network module (shorter characteristic path length, p-val = 0.015; larger density, p-val = 0.019; higher in-degree ratio, p-val = 0.009). Using the transcription-regulatory network, sRNA targets tend to be under multiple regulation (higher indegree, p-val = 0.013) and the targets usually are important to the transfer of regulatory signals (higher betweenness, p-val = 0.012). As was found for the protein-protein interaction network, the targets that are regulated by the same sRNA also tend to be closely knit within the transcription-regulatory network (larger density, p-val = 0.036), and inward interactions between them are greater than the outward interactions (higher in-degree ratio, p-val = 0.023). However, after incorporating information on predicted sRNAs and down-stream targets, the results are not as clear-cut, but the overall network modularity is still evident. CONCLUSIONS: Our results indicate that sRNA targeting tends to show a clustering pattern that is similar to the human microRNA regulation associated with protein-protein interaction network that was observed in a previous study. Namely, the sRNA targets show close interaction and forms a closely knit network module for both the protein-protein interaction and the transcription-regulatory networks. Thus, targets of the same sRNA work in a concerted way toward a specific goal. In addition, in the transcription-regulatory network, sRNA targets act as "multiplexor", accepting regulatory control from multiple sources and acting accordingly. Our results indicate that sRNA targeting shows different properties when compared to the proteins that form cellular networks.

Project description:Biofilm formation is a complex process that requires a number of transcriptional, proteomic, and physiological changes to enable bacterial survival. The lipid membrane presents a barrier to communication between the machinery within bacteria and the physical and chemical features of their extracellular environment, and yet little is known about how the membrane influences biofilm development. We found that depleting the anionic phospholipid cardiolipin reduces biofilm formation in Escherichia coli cells by as much as 50%. The absence of cardiolipin activates the regulation of colanic acid synthesis (Rcs) envelope stress response, which represses the production of flagella, disrupts initial biofilm attachment, and reduces biofilm growth. We demonstrate that a reduction in the concentration of cardiolipin impairs translocation of proteins across the inner membrane, which we hypothesize activates the Rcs pathway through the outer membrane lipoprotein RcsF. Our study demonstrates a molecular connection between the composition of membrane phospholipids and biofilm formation in E. coli and suggests that altering lipid biosynthesis may be a viable approach for altering biofilm formation and possibly other multicellular phenotypes related to bacterial adaptation and survival.IMPORTANCE There is a growing interest in the role of lipid membrane composition in the physiology and adaptation of bacteria. We demonstrate that a reduction in the anionic phospholipid cardiolipin impairs biofilm formation in Escherichia coli cells. Depleting cardiolipin reduced protein translocation across the inner membrane and activated the Rcs envelope stress response. Consequently, cardiolipin depletion produced cells lacking assembled flagella, which impacted their ability to attach to surfaces and seed the earliest stage in biofilm formation. This study provides empirical evidence for the role of anionic phospholipid homeostasis in protein translocation and its effect on biofilm development and highlights modulation of the membrane composition as a potential method of altering bacterial phenotypes related to adaptation and survival.

Dataset Information

Alternative pathways for Escherichia coli biofilm formation revealed by sRNA overproduction.

Publications

Alternative pathways for Escherichia coli biofilm formation revealed by sRNA overproduction.

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