Molecular composition of Rhizobium meliloti when parathion was added at the start of incubation

Rhizobium meliloti 300h13 reached the stationary phase of growth very quickly and died rapidly when parathion was added to broth medium at the start of incubation. After 120 h cells changed their molecular composition. A striking diminution in poly-β-hydroxybutyrate (PHB) accumulation was noticed, it was accompanied neither by increase of its glucan precursors, nor by increase of polysaccharides excretion. Parathion-treated cells had decreased proteins, and augmented phospholipids (PL) and lipopolysaccharides (LPS) contents. The rise in PL was mainly due to increases in phosphatidyl glycerol (PG) and phosphatidyl choline (PC). LPS electrophoresis showed stacks of bands typical of LPS with increasing O-antigen chain lengths. Bacterial fatty acids profiles showed an increase of cis-vaccenic and palmitoleic acids, and a diminution of lactobacillic and palmitic acids.