Cation interactions and biochemical composition of the cell envelope of a marine bacterium

Envelopes of a marine isolate, c-A1, and of a terrestrial isolate, 121, were compared for their susceptibility to disintegration in distilled water after exposure to 0.05 m MgCl(2) and to 0.1 and 1.0 m NaCl. After exposure to MgCl(2) alone, both types of envelopes remained intact in distilled water. Envelopes of marine isolate c-A1, but not of the terrestrial isolate, fragmented in distilled water after exposure to 1.0 m NaCl. Partial reaggregation of the c-A1 envelope fragments occurred on addition of MgCl(2). In cation-exchange experiments, bound Mg(++) in the envelopes of both organisms was displaced by Na(+). The envelopes of c-A1 were found to contain lipopolysaccharide, muramic acid, and a variety of phospholipids, of which the major component was phosphatidylethanolamine, accompanied by lesser amounts of phosphatidic acid, diphosphatidylglycerol, and phosphatidylserine. Analyses of envelope acid hydrolysates revealed a similar amino acid distribution in the marine and terrestrial isolates, but envelopes of c-A1 had less than half the total amino acid content of envelopes of 121 per envelope dry weight. Possible relationships between cations and biochemical components of the envelopes are considered in terms of differences in behavior of the two organisms in low ionic environments.