Biomedical subjects
Publications and source records attributed to N Sar.
The EtOAc extract of the whole culture medium of Vibrio parahaemolyticus, which inhabits the toxic mucus of the box fish Ostracion cubicus, afforded a new indole-derived natural product, vibrindole A [1], along with some known cyclic dipeptides and indoles. The structure of 1 was determined by analysis of its physicochemical characteristics.
Vibrio parahaemolyticus synthesizes two distinct flagellar organelles, the polar flagellum (Fla), which propels the bacterium in a liquid environment (swimming), and the lateral flagella (Laf), which are responsible for movement over surfaces (swarming). Chemotactic control of each of these flagellar systems was evaluated separately by analyzing the behavioral responses of strains defective in either motility system, i.e., Fla+ Laf- (swimming only) or Fla- Laf+ (swarming only) mutants. Capillary assays, modified by using viscous solutions to measure swarming motility, were used to quantitate chemotaxis by the Fla+ Laf- or Fla- Laf+ mutants. The behavior of the mutants was very similar with respect to the attractant compounds and the concentrations which elicited responses. The effect of chemotaxis gene defects on the operation of the two flagellar systems was also examined. A locus previously shown to encode functions required for chemotactic control of the polar flagellum was cloned and mutated by transposon Tn5 insertion in Escherichia coli, and the defects in this locus, che-4 and che-5, were then transferred to the Fla+ Laf- or Fla- Laf+ strains of V. parahaemolyticus. Introduction of the che mutations into these strains prevented chemotaxis into capillary tubes and greatly diminished movement of bacteria over the surface of agar media or through semisolid media. We conclude that the two flagellar organelles, which consist of independent motor-propeller structures, are directed by a common chemosensory control system.
The encapsulated bacterium Acinetobacter calcoaceticus BD4 at a density of 3.6 X 10(9) cells per ml reduced the friction of turbulent water in a narrow pipe by 55%. This drag reduction was due to the tightly bound polysaccharide capsules (0.4 mg per ml) of culture. Capsule-deficient mutants of BD4 failed to reduce drag. The cell-bound polysaccharide demonstrated a threefold-higher drag-reducing activity than the polymer which was free in solution.
PhoS64 is a mutation in the Phosphate Specific Transport (PST) region on the E. coli chromosome which lacks the periplasmic phosphate binding protein. In contrast to other phoS mutations (which have the same phenotype) it complements the mutations in phoT and pstB. A detailed genetic map of the PST region constructed by three point transductional crosses has revealed that phoS64 is located distally from other phoS mutations. The genetic order obtained was phoS64-phoU35-pstB401-phoT-phoS-ilvC. The data indicate that phoS64 belongs to a different complementation unit in the PST region not known hitherto. We propose to name it phoV.