Eubacterium cellulosolvens alters its membrane protein, lipoprotein, and fatty acid composition in response to growth on cellulose

The cellulolytic bacterium, Eubacterium cellulosolvens, altered its cytopla smic membrane protein composition in response to growth on specific energy substrates. Electrophoresis profiles obtained from membrane protein fractio ns of cellulose-grown cells were different from that obtained from cells cu ltivated with other carbohydrates, such as cellobiose or glucose. In additi on, [H-3]palmitic acid labelling of cellulose-grown E. cellulosolvens revea led two lipoproteins. that were not detected in glucose- or cellobiose-grow n cultures. These lipoproteins partitioned with the membrane fraction, indi cating their association with the cytoplasmic membrane. Proteinase K treatm ent of whole cells further suggested that these lipoproteins were exposed t o the surface of the cell envelope. These membrane proteins and lipoprotein s appear to be under some substrate-specific regulatory control with distin ct, but as yet undetermined, roles in cellulose utilization. In addition, c ellulose-grown E. cellulosolvens was found to posses a higher ratio of olei c. acid (C-18:1) to palmitic acid (C-16:0) than cells cultivated on soluble carbohydrates. This change in the ratio of unsaturated to saturated fatty acids was consistent with a comparative increase of membrane fluidity. Furt her analysis of this shift in the fatty acid profile revealed a correlation with the appearance of protruberances on the cell surface. Such a shift of fatty acid composition may indicate that the assembly and function of prot eins for cellulose utilization necessitates an increase of the membrane flu idity. (C) 2001 Academic Press.