Characterization of Extracellular Polymeric Substances from Acidophilic Microbial Biofilms

Abstract

We examined the chemical composition of extracellular polymeric substances (EPS) extracted from two natural microbial pellicle biofilms growing on acid mine drainage (AMD) solutions. The EPS obtained from a mid-developmental-stage biofilm (DS1) and a mature biofilm (DS2) were qualitatively and quantitatively compared. More than twice as much EPS was derived from DS2 as from DS1 (approximately 340 and 150 mg of EPS per g [dry weight] for DS2 and DS1, respectively). Composition analyses indicated the presence of carbohydrates, metals, proteins, and minor quantities of DNA and lipids, although the relative concentrations of these components were different for the two EPS samples. EPS from DS2 contained higher concentrations of metals and carbohydrates than EPS from DS1. Fe was the most abundant metal in both samples, accounting for about 73% of the total metal content, followed by Al, Mg, and Zn. The relative concentration profile for these metals resembled that for the AMD solution in which the biofilms grew, except for Si, Mn, and Co. Glycosyl composition analysis indicated that both EPS samples were composed primarily of galactose, glucose, heptose, rhamnose, and mannose, while the relative amounts of individual sugars were substantially different in DS1 and DS2. Additionally, carbohydrate linkage analysis revealed multiply linked heptose, galactose, glucose, mannose, and rhamnose, with some of the glucose in a 4-linked form. These results indicate that the biochemical composition of the EPS from these acidic biofilms is dependent on maturity and is controlled by the microbial communities, as well as the local geochemical environment.

Detection Techniques for Extracellular Polymeric Substances in Biofilms: A Review

“…Generally, the production of EPS is significantly increased under so-called adverse conditions. For example, Jiao et al (2010) found that substantially higher carbohydrate-to-protein ratios were observed for the acidophilic microbial biofilms than the previously reported ratios. And more than twice as much EPS was derived from a mature biofilm as from a mid-developmental-stage biofilm (approximately 340 and 150 mg of EPS per g [dry weight] for a mature biofilm and a mid-developmental-stage biofilm, respectively).…”

“…Reichhardt and Cegelski (2013) implemented solid-state NMR to deliver quantitative insights into the composition and structure of biofilm systems. Jiao et al (2010) applied solid-state NMR and linkage analysis to characterize the polysaccharide composition and yielded limited but promising information, such as, they found that solid-state NMR cannot distinguish between the β-O-4 and β-O-3 linkages of glycosidic carbon atoms. Thus, a more in-depth analysis of purified EPS fractions is needed to illuminate the structures molecular distribution of polymers (Reichhardt et al 2015).…”

“…NMR data provide the key quantitative parameters of the intact matrix, including the percentages of EPS components by mass. In order to provide more detailed characterization of the EPS functional groups, the exact chemical mechanism of metal binding should be revealed further (Jiao et al 2010). To date, solid-and liquid-state NMR techniques have been applied to study the chemical composition and molecular mobility of biofilm EPS.…”

“…Even though carbohydrates and proteins have been validated as the main components of EPS, the biochemical characteristics of these compounds remain obscure because of their complex structures and unique linkages (Jiao et al 2010). Moreover, defining the composition of EPS is critical for the elucidation of structure-function relationships that can facilitate the development of chemical strategies to disrupt biofilms.…”

Elevated temperature alters proteomic responses of individual organisms within a biofilm community

“…For instance, GT2 involved in biosynthesis of carbohydrates was upregulated at 46 1C, whereas GH57 involved in hydrolysis of carbohydrates was upregulated at 40 1C. The extracellular polymeric substance in AMD biofilms from the Richmond mine has been shown to contain abundant carbohydrates, including galactose, glucose, heptose, rhamnose and mannose (Jiao et al, 2010). Thus, Leptospirillum group III might act both as a source and sink to the carbohydrate pool in the biofilm matrix.…”