Salinity-Mediated Increment in Sulfate Reduction, Biofilm Formation, and Quorum Sensing: A Potential Connection Between Quorum Sensing and Sulfate Reduction?

Abstract

Biocorrosion in marine environment is often associated with biofilms of sulfate reducing bacteria (SRB). However, not much information is available on the mechanism underlying exacerbated rates of SRB-mediated biocorrosion under saline conditions. Using Desulfovibrio (D.) vulgaris and Desulfobacterium (Db.) corrodens as model SRBs, the enhancement effects of salinity on sulfate reduction, N-acyl homoserine lactone (AHL) production and biofilm formation by SRBs were demonstrated. Under saline conditions, D. vulgaris and Db. corrodens exhibited significantly higher specific sulfate reduction and specific AHL production rates as well as elevated rates of biofilm formation compared to freshwater medium. Salinity-induced enhancement traits were also confirmed at transcript level through reverse transcription quantitative polymerase chain reaction (RT-qPCR) approach, which showed salinity-influenced increase in the expression of genes associated with carbon metabolism, sulfate reduction, biofilm formation and histidine kinase signal transduction. In addition, by deploying quorum sensing (QS) inhibitors, a potential connection between sulfate reduction and AHL production under saline conditions was demonstrated, which is most significant during early stages of sulfate metabolism. The findings collectively revealed the interconnection between QS, sulfate reduction and biofilm formation among SRBs, and implied the potential of deploying quorum quenching approaches to control SRB-based biocorrosion in saline conditions.

Discovering, Characterizing, and Applying Acyl Homoserine Lactone-Quenching Enzymes to Mitigate Microbe-Associated Problems Under Saline Conditions

“…However, the inhibitory effect was no longer observed at the stationary phase. This observation is consistent with that reported in an earlier study (Park et al, 2005; Sivakumar et al, 2019), and it was probably due to the accumulation of enzymatic inhibitors in the culture over time, or to a decrease in the metabolic activities of the cultures at the stationary phase. QQ enzymes should therefore be deployed as an environmentally benign approach for controlling microbe-associated problems at the early stages of growth and biofilm formation.…”

Effect of Quorum Sensing on the Ability of Desulfovibrio vulgaris To Form Biofilms and To Biocorrode Carbon Steel in Saline Conditions

“…In particular, homologs of proteins involved in the QS-controlled phosphorylation cascade (LuxR and LuxO) and in the acyl homoserine lactone (AHL) synthesis were found in D. vulgaris (17,18). This is verified by the detection of different carbon chains of AHLs, including C 8 -AHL, C 10 -AHL, and C 12 -AHL, in pure cultures of D. vulgaris (19,20). Furthermore, it was found that exposing SRB to QS inhibitors in saline conditions diminished biofilm formation, sulfate reduction, and AHL production (20).…”

Nonlinear rheological characteristics of single species bacterial biofilms

“…Bacterial biofilms occur in diverse environments, such as aquifers 1 , rivers 2,3 , hydrothermal springs 4 , within sewer pipelines 5 , in bioremediation plants 6 and various other places. Within these environments the biofilms can be subjected to extreme temperatures 4,7 , variation in physical forces 8 , changes in chemical concentrations 9 , changes in salinity 10 and pH 11 . These extreme conditions impact a biofilm's lifecycle, and yet, they are able to thrive by colonising a variety of surfaces.…”