Cell Wall Composition of Lactic Acid Bacteria

Abstract

SUMMARY Cell walls were isolated from thirteen species of lactobacilli grown in defined media. The walls were hydrolyzed and ex- amined qualitatively and quantitatively for phosphorus, am- monia, different reducing sugars and amino sugars, and, in all but a few instances, for sugar alcohols and D- and L-amino acids. The principal aldohexose found was glucose; galactose occurred in fewer cells. Rhamnose was an important component of many of the cell walls and always occurred together with glucose. All of the cell walls contained glucosamine and muramic acid; a few contained galactosamine as well. Ribitol or glycerol was present in walls of all of the organisms tested except L. casei. Absence of any sugar alcohol from the wall of L. casei indicates that the teichoic acids (29), although frequently prominent, are not an obligatory feature of the walls of gram-positive organisms. Glutamic acid, alanine, and either diaminopimelic acid or aspartic acid plus lysine were the principal amino acids present. Most or all of the glutamic acid was present in the n-form; from one- to two-thirds of the alanine was n-alanine, and from two- to four-fifths of the aspartic acid was n-aspartic acid. Only L-lysine was present. Some but not all of the wall hydrolysates contained substantial amounts of e-aminosuccinoyllysine. From two to six additional amino acids were present in smaller, but frequently substantial amounts. No obvious regularities in structure of walls of different organisms became evident from an examination of the mole ratios components determined. Instead, a rather striking divergence in both qualitative and quantitative composition of the walls this rather closely re- lated group of bacteria became evident. Summation of the known components of these walls accounts for only about 60 to 80% of the total wall hydrolyzed, and thus points to presence of presently unrecognized components these structures. Acknowledgment-We are indebted to Mrs. Geraldine Tomlin- son for technical assistance. REFERENCES 1.