CHEMICAL-ANALYSIS OF ISOLATED CELL-WALLS OF GRAM-POSITIVE BACTERIA AND DETERMINATION OF THE CELL-WALL TO CELL MASS-RATIO

Cell walls of five Gram-positive bacterial strains, including four cor yneforms and a Bacillus brevis strain were isolated and subsequently c hemically analysed. The wall contribution to the total cell mass is ca lculated from a comparison of D-Lactate concentrations in hydrolysates of whole cells and isolated walls. D-lactate concentrations are measu red 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 ran ge of 26-32% and is about 75% for the B. brevis cells. The peptidoglyc an fraction in the walls of the coryneform bacteria was found to be ra ther 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. bre vis strain forms a thin layer and contributes only about 5% to the cel l wall dry weight. The high amount of proteins in the B. brevis cell w all (>56%) can be attributed to a so called S(urface)-layer. (C) 1997 Elsevier Science B.V.