Abstract
Sulfate-reducing bacteria (SRB) biofilm formed on metal surfaces can change the physicochemical properties of metals and cause metal corrosion. To enhance understanding of differential gene expression in Desulfovibrio vulgaris under planktonic and biofilm growth modes, a single-cell based RT-qPCR approach was applied to determine gene expression levels of 8 selected target genes in four sets of the 31 individual cells isolated from each growth condition (i.e., biofilm formed on a mild steel (SS) and planktonic cultures, exponential and stationary phases). The results showed obvious gene-expression heterogeneity for the target genes among D. vulgaris single cells of both biofilm and planktonic cultures. In addition, an increased gene-expression heterogeneity in the D. vulgaris biofilm when compared with the planktonic culture was also observed for seven out of eight selected genes at exponential phase, and six out of eight selected genes at stationary phase, respectively, which may be contributing to the increased complexity in terms of structures and morphology in the biofilm. Moreover, the results showed up-regulation of DVU0281 gene encoding exopolysaccharide biosynthesis protein, and down-regulation of genes involved in energy metabolism (i.e., DVU0434 and DVU0588), stress responses (i.e., DVU2410) and response regulator (i.e., DVU3062) in the D. vulgaris biofilm cells. Finally, the gene (DVU2571) involved in iron transportation was found down-regulated, and two genes (DVU1340 and DVU1397) involved in ferric uptake repressor and iron storage were up-regulated in D. vulgaris biofilm, suggesting their possible roles in maintaining normal metabolism of the D. vulgaris biofilm under environments of high concentration of iron. This study showed that the single-cell based analysis could be a useful approach in deciphering metabolism of microbial biofilms.
Highlights
Propagation and metabolism of microorganisms on metal surfaces can change the physicochemical properties of these surface and cause the deterioration of metallic materials (Little et al, 1992; Thierry and Sand, 1995; Beech et al, 2000)
To investigate gene-expression levels of selected target genes potentially associated with Sulfate-reducing bacteria (SRB) biofilm formation and metal corrosion, D. vulgaris biofilm was formed on the immersed SS slides in 200 mL serum bottles with lactate (38 mM) as electron donor and sulfate (50 mM) as electron acceptor
When D. vulgaris cells was cultured at 35◦C for 6 days, the SS slides were completely covered by D. vulgaris biofilm with average 1-2 mm in thickness (Supplementary Figure S2)
Summary
Propagation and metabolism of microorganisms on metal surfaces can change the physicochemical properties of these surface and cause the deterioration of metallic materials (Little et al, 1992; Thierry and Sand, 1995; Beech et al, 2000).
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