These observations indicated that increased adherence might be mediated by putative F pili expressed by EAEC strains. Endorsing our assumption, inhibition of the putative F pili by zinc significantly reduced the bacterial aggregation and mixed biofilms produced by EAFC 205 and traA-positive EAEC strains. SEM images showed that enhanced biofilms formed by cocultures of EACF 205 and traA-positive EAEC strains were mediated by pili that promoted bacteria-to-bacteria interactions in addition to adhesion to inert surface. Conversely, biofilms formed by the coculture of EACF 205 and traA-negative EAEC strain 17-2 did not display pili and therefore were resistant to zinc treatment.
Selleck Bucladesine With regard to biofilms formed by traA-positive
EAEC strains (Figure 6A), our results are in agreement with a previous report showing that natural F plasmids promoted single biofilm formation by generating cell-to-cell connections mediated by F pili even in F+-bacteria populations. Endorsing this idea, it was shown that biofilm formation is also induced by transfer-deficient F plasmids Caspase Inhibitor VI supplier indicating that the phenomenon does not require conjugative DNA transfer itself . Curli fiber displayed by Enterobacteriaceae species is an unstable phenotype that is responsive to many environmental conditions. In C. freundii and E. coli strains, it has been shown that curli fibers mediate the biofilm formation at liquid-solid interfaces . Additionally, the presence of natural F conjugative plasmids in E. coli strains was shown to induce the development of mature single biofilms by stimulating the expression of curli fibers after appearance of F pili and following
cell-to-cell contact . Based on previously published SEM images [21, 25], we were unable to detected curli fibers in single biofilms formed by EACF 205 despite the extensive SPTBN5 analysis. Concerning E. coli strains, although curli fibers were detected in traA-positive EAEC 340-1, their expression was infrequent and incipient either in single biofilms (Figure 6D) or in mixed biofilms formed in the presence of EACF 205 (Figure 6B). Taken together our PF-6463922 concentration findings corroborate with previous studies showing the central role of the F pilus in the initial steps of the biofilm formation by E. coli strains. Adding to this model, now it is shown that expression of F pili may engage E. coli pathotypes in microbial consortia associated with diarrhea. Zinc is a vital micronutrient in humans and its dietary deficiency occurs worldwide, particularly in developing countries. Numerous studies have suggested that zinc-deficient populations presented an increased risk of contracting diarrhea. Consequently, the zinc administration has been recommended as an additional approach for the prevention and management of diarrhea, being more efficient in treating persistent diarrhea rather than acute cases [38, 39].