Role of Extracellular Polymeric Substances in Microbial Reduction of Arsenate to Arsenite by Escherichia coli and Bacillus subtilis

Abstract

We show that arsenate can be readily reduced to arsenite on cell surfaces of common bacteria (E. coli or B. subtilis) or in aqueous dissolved extracellular polymeric substances (EPS) extracted from different microorganisms (E. coli, B. subtilis, P. chrysosporium, D. gigas, and a natural biofilm) in the absence of exogenous electron donors. The efficiency of arsenate reduction by E. coli after a 7-h incubation was only moderately reduced from 51.3% to 32.7% after knocking out the arsenic resistance genes (arsB and arsC). Most (>97%) of the reduced arsenite was present outside the bacterial cells, including for the E. coli blocked mutant lacking arsB and arsC. Thus, extracellular processes dominated arsenate reduction. Arsenate reduction was facilitated by removing EPS attached to E. coli or B. subtilis, which was attributed to enhanced access to reduced extracellular cytochromes. This highlights the role of EPS as a permeability barrier to arsenate reduction. Fourier-transform infrared (FTIR) combined with other chemical analyses implicated some low-molecular weight (<3 kDa) molecules as electron donors (reducing saccharides) and electron transfer mediators (quinones) in arsenate reduction by dissolved EPS alone. These results indicate that EPS act as both reducing agent and permeability barrier for access to reduced biomolecules in bacterial reduction of arsenate.

Effects of extracellular polymeric substances on silver nanoparticle bioaccumulation and toxicity to Triticum aestivum L.

“…5A, two typical peaks of EEM fluorescence spectra were observed in pristine EPS, which were located at Ex/Em (excitation/ emission) wavelengths of 235-280/340 nm and 205-215/225-490 nm, respectively. These peaks indicated that B. subtilis EPS were mainly composed of tryptophan-like substances (peak A) and aromatic proteinlike substances (peak B) (Chen et al, 2003;Zhou et al, 2020), implying that protein-like substances were abundant in B. subtilis EPS fluorescent compounds. The FTIR spectra of pristine B. subtilis EPS, as well as AgNO 3 -EPS, Ag-NPs-EPS and Ag 2 S-NPs-EPS incubated for 48 h were shown in Fig.…”

“…5B). Peaks for the pristine B. subtilis EPS at 3419, 1652, 1411, and 1061 cm − 1 were assigned to -OH/-NH stretching in the hydroxyl group, C--O stretching in amide groups of protein-like substances, the symmetric stretching vibration of C-O from carboxylic group, and the stretching of C-O-C and C-O in polysaccharides, respectively (Chen et al, 2012;Lai et al, 2018;Zhou et al, 2020). The peak at 2935 cm − 1 could be attributed to the asymmetric stretching vibrations of -CH 2 of proteins (Fernando et al, 2020).…”

Spontaneous genomic variation as a survival strategy of nosocomial S. haemolyticus

“…It is thus conceivable that the strong biofilm phenotype might be due to mutations occurring in regions of the chromosome different from oriC environ or new regulatory mechanisms induced by the deletion event. Analysis of SNPs showed mutations in cadD and arsC genes (nonsynonymous substitutions) in strong biofilms producers comparing to biofilm weak producers or non-producers suggesting that the phenotype alteration could alternatively be due to mutation in these genes that have been previously shown to be involved to biofilm formation (Gill et al 2005; Zhou et al 2020; Vernyik et al 2020; Wu et al 2015). Regarding hemolysis no clear alteration in phenotype was observed and the small variations in the hemolysis halo observed were not correlated with any particular deletion variant, gene or mutation.…”

“…shown to be involved to biofilm formation (Gill et al 2005;Zhou et al 2020;Vernyik et al 2020;Wu et al 2015). Regarding hemolysis no clear alteration in phenotype was observed and the small variations in the hemolysis halo observed were not correlated with any particular deletion variant, gene or mutation.…”

Enhancement on the Microbial Extracellular Electron Transfers by Modified Lignin Materials: Application on Decolorization of Azo Dye

“…Extracellular electron transfers (EETs) are mainly involved in anaerobic respiration of quinone-respiring microbial strains, which is of great geochemical and environmental significances [1][2][3][4]. EETs have many applications, including microbiological fuel cell, bio-hydrogen production, reduction and detoxification of heavy metals, anoxic denitrification, and bio-reduction of azo dyes [5][6][7][8][9]. However, this kind of instinctive function of microbes was nonspecific and low efficient, which needed to be improved by addition of exogenous redox mediators (RMs) [10][11][12].…”