Variations in the amino acid constituents of the cell extract and culture filtrate of Xanthomonas campestris pv. phaseoli

Abstract

Summary The amino acid pool size and composition of the cells and filtrates of 24 to 120 h growing cultures of Xanthomonas campestris pv. phaseoli varied greatly with age and was also influenced by the nitrogen source of the growth medium. During tropophase of growth, i.e., lag and log phases, the number of amino acids and their quantity was much higher than in the following idiophase. This was uniformly so for cultures grown with all the different sources. There was a vigorous build up of amino acids in 24 h old actively growing cultures of the bacterium, grown with all the different nitrogen sources. However, a large size amino acid pool with fifteen amino acid components was found in 24-hour KNO3-grown cells alone. The organic nitrogen sources contrived the build up of fewer amino acids during active growth phase. In 48-h-old extracts, however, the number of amino acids and their quantities increased greatly in cells, grown with organic nitrogen sources. For specific age-groups of cells each source created its own amino acid pool with a few exclusive amino acids in it. Thus, homoserine was the cell component of KN03- and proteose-peptone-grown cultures. Similarly, proline was the exclusive cell amino acid for alanine-, asparagine- and glutamine-grown cultures and lysine for KNO3-casamino acid- and tryptophan-grown cells. These three, namely homoserine, proline, and lysine, were found in 24–48-h-old actively growing cells along with other amino acids. The number and amount of amino components, excreted in culture filtrate, was much less and their quantity was higher during the stationary phase of growth.