Biofilm Formation and Dispersal under the Influence of the Global Regulator CsrA of Escherichia coli

Abstract

The predominant mode of growth of bacteria in the environment is within sessile, matrix-enclosed communities known as biofilms. Biofilms often complicate chronic and difficult-to-treat infections by protecting bacteria from the immune system, decreasing antibiotic efficacy, and dispersing planktonic cells to distant body sites. While the biology of bacterial biofilms has become a major focus of microbial research, the regulatory mechanisms of biofilm development remain poorly defined and those of dispersal are unknown. Here we establish that the RNA binding global regulatory protein CsrA (carbon storage regulator) of Escherichia coli K-12 serves as both a repressor of biofilm formation and an activator of biofilm dispersal under a variety of culture conditions. Ectopic expression of the E. coli K-12 csrA gene repressed biofilm formation by related bacterial pathogens. A csrA knockout mutation enhanced biofilm formation in E. coli strains that were defective for extracellular, surface, or regulatory factors previously implicated in biofilm formation. In contrast, this csrA mutation did not affect biofilm formation by a glgA (glycogen synthase) knockout mutant. Complementation studies with glg genes provided further genetic evidence that the effects of CsrA on biofilm formation are mediated largely through the regulation of intracellular glycogen biosynthesis and catabolism. Finally, the expression of a chromosomally encoded csrA-lacZ translational fusion was dynamically regulated during biofilm formation in a pattern consistent with its role as a repressor. We propose that global regulation of central carbon flux by CsrA is an extremely important feature of E. coli biofilm development.

Circuitry Linking the Catabolite Repression and Csr Global Regulatory Systems of Escherichia coli

“…For example, (i) crp and cya mRNAs copurified with the CsrA protein (25), (ii) potential cAMP-CRP binding sites were identified upstream of the csrB gene by bioinformatics analysis (47), and (iii) a number of genes and processes have been reported to be regulated by both CsrA and cAMP-CRP (14,18,21,66) (Fig. 10).…”

“…In Escherichia coli, CsrA activates glycolysis and central carbon pathways (7)(8)(9)(10)(11)(12)(13) and motility (14,15). Conversely, it represses gluconeogenesis (7), glycogen biosynthesis (16)(17)(18)(19)(20), biofilm formation (21)(22)(23)(24), the stringent response (25), and expression of genes involved in other stress resistance and stationary-phase processes, e.g., cstA, hfq, cel, sdiA, and nhaR (24,(26)(27)(28)(29)(30). Its effects on pathogenesis are complex.…”

Sticky Situations: Key Components That Control Bacterial Surface Attachment

“…One would therefore assume that an abundant supply of nutrients fosters attachment and biofilm formation. However, bacteria grown under high-nutrient conditions either fail to form biofilms or form loose, floc-like structures at the substratum that are easily disrupted with fluid shear (27,31,68,97). Instead, bacteria tend to form biofilms under low-nutrient or starvation conditions (17,27,97,130).…”

“…Originally identified as a system to regulate glycogen biosynthesis, CsrA represses numerous genes associated with the stationary phase of growth but activates certain exponential-phase metabolic pathways. In addition, virulence, motility, cell surface properties, and adherence are modulated by CsrA in E. coli (reviewed in references 6 and 135), with CsrA acting as a repressor of biofilm formation (68). Gene expression is controlled by CsrA binding to leader segments of target mRNAs, affecting their translation and stability.…”

Resonadores piezoeléctricos de cizalladura: estudio de la formación de biofilms y caracterización de fluidos magneto‐reológicos

“…No obstante, esta fase de adaptación se produce de forma muy rápida, calculándose que se da aproximadamente en los primeros 60 minutos desde que inoculamos el caldo TSB con las células procedentes del medio sólido El medio de cultivo empleado para la formación de biofilm con las cepas E. coli fue el denominado CFA (Jackson D. et al 2002).…”