Spent media from cultures of environmental isolates of Escherichia coli can suppress the deficiency of biofilm formation under anoxic conditions of laboratory E. coli strains

Abstract

The prevailing lifestyle of bacteria is sessile and they attach to surfaces in structures known as biofilms. In Escherichia coli, as in many other bacteria, biofilms are formed at the air-liquid interface, suggesting that oxygen has a critical role in the biofilm formation process. It has been reported that anaerobically growing E. coli laboratory strains are unable to form biofilms even after 96 h of incubation on Luria Bertani (LB) medium. After analyzing 22,000 transposon-induced and 26,000 chemically-induced mutants we failed to isolate an E. coli laboratory strain with the ability to form biofilm under anaerobic growth conditions. Notably, seven strains from a collection of E. coli isolated from different hosts and the environment had the ability to form biofilm in the absence of oxygen. Interestingly, spent medium from cultures of one strain, Souza298, can promote biofilm formation of E. coli laboratory strains growing under anaerobic conditions. Our results led us to propose that laboratory E. coli strains do not release (or synthesize) a molecule needed for biofilm formation under anoxic conditions but that they bear all the required machinery needed for this process.

Increased Transfer of a Multidrug Resistance Plasmid in Escherichia coli Biofilms at the Air-Liquid Interface

“…4B). Previous studies have also shown an increased ability of E. coli strains to form biofilms at the air-liquid interface, even in the absence of conjugative plasmids (11,15,22). Thus, the low transfer frequencies in submerged biofilms of E. coli K-12 must be due in part to the poor ability of the plasmid-free strain to adhere and form a biofilm.…”

“…3) and the batch culture reactor (data not shown) and correlated with decreasing cell densities in the biofilms along the glass surface. While the physicochemical conditions of the air-liquid interface may also directly promote adherence of E. coli cells to each other and to the glass surface, the mere presence of more cells in that zone (11,15). Future studies will have to clarify the role of aerobiosis in E. coli biofilm formation and determine if characteristics of the air-liquid interface other than the oxygen level are responsible for enhanced plasmid transfer.…”

Adherence to abiotic surface induces SOS response in Escherichia coli K-12 strains under aerobic and anaerobic conditions

“…Nevertheless, some authors have shown that E. coli K-12 strains are able to form biofilms under anaerobic conditions, depending on the conditions of the experiment (Cabellos-Avelar et al, 2006;Bjergbaek et al, 2007).…”

Released products of pathogenic bacteria stimulate biofilm formation by Escherichia coli K-12 strains

“…Environmental isolates of E. coli were shown to release proteins (Cabellos-Avelar et al 2006) and carbohydrates (Valle et al 2006) capable of modulating the biofilm growth of other strains. For example, the commensal E. coli strain Ec300 released a polysaccharide that prevented biofilm formation by Gram-positive bacteria.…”