Composition and Corrosivity of Extracellular Polymeric Substances from the Hydrocarbon-Degrading Sulfate-Reducing Bacterium Desulfoglaeba alkanexedens ALDC.

Irene A Davidova,Joseph M Suflita,Tiffany R Lenhart,Mark A Nanny

doi:10.3390/microorganisms9091994

Irene A Davidova, Joseph M Suflita + Show 2 more

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https://doi.org/10.3390/microorganisms9091994

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Journal: Microorganisms	Publication Date: Sep 21, 2021
Citations: 4	License type: CC BY 4.0

Affiliation: University of Oklahoma

Abstract

Sulfate-reducing bacteria (SRB) often exist as cell aggregates and in biofilms surrounded by a matrix of extracellular polymeric substances (EPSs). The chemical composition of EPSs may facilitate hydrophobic substrate biodegradation and promote microbial influenced corrosion (MIC). Although EPSs from non-hydrocarbon-degrading SRB have been studied; the chemical composition of EPSs from hydrocarbon-degrading SRBs has not been reported. The isolated EPSs from the sulfate-reducing alkane-degrading bacterium Desulfoglaeba alkanexedens ALDC was characterized with scanning and fluorescent microscopy, nuclear magnetic resonance spectroscopy (NMR), and by colorimetric chemical assays. Specific fluorescent staining and 1H NMR spectroscopy revealed that the fundamental chemical structure of the EPS produced by D. alkanexedens is composed of pyranose polysaccharide and cyclopentanone in a 2:1 ratio. NMR analyses indicated that the pyranose ring structure is bonded by 1,4 connections with the cyclopentanone directly bonded to one pyranose ring. The presence of cyclopentanone presumably increases the hydrophobicity of the EPS that may facilitate the accessibility of hydrocarbon substrates to aggregating cells or cells in a biofilm. Weight loss and iron dissolution experiments demonstrated that the EPS did not contribute to the corrosivity of D. alkanexedens cells.

Highlights

Planktonic and biofilm-associated anaerobes, most notably sulfate-reducing bacteria (SRB), have long been implicated in metal biocorrosion processes [1,2]
When individual clumps were imaged at a high magnification by FE-scanning electron microscopy (SEM), biofilms containing D. alkanexedens cells surrounded by and imbedded in extracellular material could be observed (Figure 1b,c)
Specific fluorescent staining and 1 H nuclear magnetic resonance spectroscopy (NMR) spectroscopy revealed that the fundamental chemical structure of D. alkanexedens extracellular polymeric substances (EPSs) was composed of a pyranose polysaccharide and cyclopentanone in a 2:1 ratio

Summary

Introduction

Planktonic and biofilm-associated anaerobes, most notably sulfate-reducing bacteria (SRB), have long been implicated in metal biocorrosion processes [1,2]. Many microorganisms, including SRB, exist as cell aggregates, or biofilms, surrounded by a matrix of extracellular polymeric substances (EPSs). Among their many functions, EPSs provide cell protection, allow for biofilm stabilization and substratum attachments, and are a source of microbial nutrition [4,5,6]. The structural integrity of EPSs critically depends on the extracellular material produced by the biofilm-associated cells [5,7]. Extracellular material can account for more than 90% of the dry weight of a biofilm and may contain a combination of modified polysaccharides, proteins, nucleic acids, lipids, and bacterial metabolites, all of which determine the architecture of the matrix as well as its interaction with a substratum or surface [4,5,6,11]

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