Chemical analysis of isolated cell walls of Gram-positive bacteria and determination of the cell wall to cell mass ratio

Abstract

Cell walls of five Gram-positive bacterial strains, including four coryneforms and a Bacillus brevis strain were isolated and subsequently chemically analysed. The wall contribution to the total cell mass is calculated from a comparison of D-Lactate concentrations in hydrolysates of whole cells and isolated walls. D-lactate concentrations are measured enzymatically after purification of the samples with active carbon. The optimum condition for the quantitative elimination of D-lactate from the peptidoglycan appears to be at 120 degrees C and 4 M HCl. The wall fraction for the cells of the coryneform bacteria are in the range of 26-32% and is about 75% for the B. brevis cells. The peptidoglycan fraction in the walls of the coryneform bacteria was found to be rather high and constitutes about 23 to 31% of the cell wall dry weight. The protein content of the cell wall dry weight is somewhat lower and in the range of 7 to 14%. The peptidoglycan in the wall of the B. brevis strain forms a thin layer and contributes only about 5% to the cell wall dry weight. The high amount of proteins in the B. brevis cell wall (>56%) can be attributed to a so called S(urface)-layer. (C) 1997 Elsevier Science B.V.