Metabolic Activation of CsgD in the Regulation of Salmonella Biofilms

Abstract

<jats:p>Among human food-borne pathogens, gastroenteritis-causing Salmonella strains have the most real-world impact. Like all pathogens, their success relies on efficient transmission. Biofilm formation, a specialized physiology characterized by multicellular aggregation and persistence, is proposed to play an important role in the Salmonella transmission cycle. In this manuscript, we used luciferase reporters to examine the expression of csgD, which encodes the master biofilm regulator. We observed that the CsgD-regulated biofilm system responds differently to regulatory inputs once it is activated. Notably, the CsgD system became unresponsive to repression by Cpx and H-NS in high osmolarity conditions and less responsive to the addition of amino acids. Temperature-mediated regulation of csgD on agar was altered by intracellular levels of RpoS and cyclic-di-GMP. In contrast, the addition of glucose repressed CsgD biofilms seemingly independent of other signals. Understanding the fine-tuned regulation of csgD can help us to piece together how regulation occurs in natural environments, knowing that all Salmonella strains face strong selection pressures both within and outside their hosts. Ultimately, we can use this information to better control Salmonella and develop strategies to break the transmission cycle.</jats:p>

Transcriptional Profiling of the Effect of Coleus amboinicus L. Essential Oil against Salmonella Typhimurium Biofilm Formation

“…csgD, which is a FixJ/LuxR/UhpA family transcription factor, encodes a transcriptional regulator CsgD protein (Curlin subunit gene D) and regulates the csgBAC and csgDEFG operons responsible for curli component synthesis, secretion, and assembly. The CsgD protein additionally triggers the expression of adrA (a diguanylate cyclase), a crucial element in the synthesis of cellulose required for the formation of biofilms [52,53]. A difference in the expression of adrA was noted between the qRT-PCR and RNA sequencing results, and these differences could potentially arise from variances in sensitivity and specificity inherent to these two methodologies [54].…”

Human Salmonellosis: A Continuous Global Threat in the Farm-to-Fork Food Safety Continuum

“…The biofilm formed by Salmonella is mainly made up of O antigen, curli (amyloid fimbriae), biofilm-associated protein (Bap), cellulose, and extracellular DNA [79,80,85]. Curlin subunit gene D (CsgD), regulated by transcriptional factors, bis-3 -5 -cyclic dimeric guanosine monophosphate (c-di-GMP), and sRNAs, regulates biofilm formation by Salmonella [86]. The biofilm-forming capacity may vary among serovars [87] but largely depends on various extrinsic factors, including temperature, source, and contact surface [88,89].…”

Genetic and phenotypic assessment of the antimicrobial activity of three potential probiotic lactobacilli against human enteropathogenic bacteria

“…These genes are conserved in E. coli and S. enterica , being encoded in two different operons that are regulated by several transcriptional factors. CsgD upregulates the production of fibriae by inducing the csgBA operon, however the expression of both csgBA and csgDEFG is regulated by CpxR ( Prigent-Combaret et al., 2001 ; Sokaribo et al., 2020 ). Treatments with CFCS induced the expression of these genes, possibly alluding to an adaptation mechanism to ensure survival of the remaining cells after the bactericidal activity of metabolites in the CFCS.…”