Studies of the cell envelope of Vibrio parahaemolyticus A55: Isolation and purification of bag-shaped peptidoglycan (murein sacculus).

: The peptidoglycan (PG) component of the envelope of Vibrio parahaemolyticus A55 was studied in relation to the salt dependency of the organism. A bag-shaped PG (murein sacculus) was isolated and purified by digestion of freshly harvested intact whole cells with sodium dodecyl sulfate (SDS) and then protease treatment. Whole cells lyze in salt-deficient or hypotonic conditions and this can be measured by turbidometry. Lysis is prevented by addition of 0.35 M NaCl or acidification to below pH 4.5. The isolated PG or murein sacculi did not seem to require salt for structural integrity. The PG obtained by the same method from subcellular fractions, that is, envelope fractions, prepared either with or without NaCl, was extensively fragmented. The main amino acids and amino sugars of the murein sacculus were glucosamine, muramic acid, alanine, glutamic acid, 2, 6-diamnopimelic acid (A2pm) in a molar ratio of 0.4:0.6:1.7:0.9:1.0. A polyglucose, which was only degraded by Pseudomonas isoamylase,and poly-beta-hydroxybutyrate (PHBA) were found in the murein sacculus. The murein sacculus of the organism is discussed in comparison with PG of other gram negative bacteria and marine or halophilic microorganisms.