The impact of environmental perturbation on microbial community structure and dynamics: factors affecting growth of Clonothrix fusca in groundwater

In a previous work temporal succession of two sheathed, filamentous methanotrophic g-Proteobacteria, Crenothrix polyspora and Clonothrix fusca, was observed by analyzing the microbial community of an artesian well. Although a correlation between physical-chemical environmental parameters and growth of these microorganisms was suggested, the link with the microbial physiology remained elusive. In this study we demonstrate that phosphatidylethanolamine and cardiolipin, generally abundant in most g-Proteobacteria, could not be detected in C. fusca membranes by thin-layer chromatography. The absence of cardiolipin was supported by results of enzymatic assay of cardiolipin synthase activity and by Southern blot analysis that failed to detect cls homologous sequences in the genomic DNA of this microorganism. The absence of phosphatidylethanolamine and cardiolipin might account for requirement of millimolar concentrations of magnesium and calcium for growth, and for massive over-growth of this microorganism during the winter season when the water levels of magnesium and calcium increased in the artesian well.