Estimation of cellular and extracellular carbon contents in sulfate-reducing bacteria biofilms by lipopolysaccharide assay and epifluorescence microscopic techni

Abstract

Measurement of cellular and extracellular carbon contents of sulfate-reducing bacteria (SRB) is essential and important in studies of the role of SRB in corrosion and biofouling. An epifluorescence (EPI) microscopic technique and a lipopolysaccharide (LPS) assay were used to quantify cellular and extracellular carbon contents in Desulfovibrio desulfuricans biofilms. The average contents of lipopolysaccharide (LPS) and cellular carbon were 7.3 ± 2.8 (fg LPS) cell−1 and 39.9 ± 9.9 (fg cellular-C) cell−1, respectively, in a D. desulfuricans chemostat culture. A ratio of cellular carbon content to LPS content was 6.5 ± 2.8, and was used to estimate cellular carbon contents in a D. desulfuricans biofilm. The LPS and EPI methods gave comparable results for suspended samples, but not for biofilm samples.