Encystment and polymer production by Azotobacter vinelandii in the presence of beta-hydroxybutyrate

Abstract

Cells of Azotobacter vinelandii encysted in Burk's nitrogen-free liquid media which had been supplemented with n-butyl alcohol, beta-hydroxybutyrate, or crotonate. Butyraldehyde and butyrate did not influence the extent of encystment. In the absence of glucose, beta-hydroxybutyrate enhanced the rate and extent of encystment. In the presence of glucose, it promoted abortive encystment, which was manifested by the disorganization of the exine and the release of a highly viscous material into the medium. The soluble, viscous polymer was separated from the medium by a series of ethyl alcohol precipitations and identified as a mucopeptide. It was cleaved by treatment with lysozyme and lysostaphin with a concomitant increase in reducing power. It contained 13.9% N; 56% amino acids, as alanine (alanine, lysine, and glutamic acids); and 42% hexosamines. The polymer appeared to be similar to a noncross-linked peptidoglycan.