ABSTRACT
A physical map of bacteriophage MB78 DNA indicating the cleavage sites for the enzyme Bg/II, ClaI, EcoRI, Pvull, Sa/! and SmaI comprising of a total of 34 cleavage sites have been constructed earlier. The cleavage sites for a few more restriction endonucleasesli ke ApaI, AvaI, Bg/!, Hindlll, KpnI and XhoI have now been mapped. A total of 72 cleavage sites on MB78 DNA are known by now. Relative positions of EcoRI I and J fragments which could not be decided earlier has now been determined.
ABSTRACT
The DNA of bacteriophage 9NA, a virulent phage of Salmonella typhimurium, is linear, double' stranded, circularly permuted and is approximately 56 kilobase pairs long. The 9NA genome is partially methylated. A physical map of the DNA has been constructed using the restriction endonucleasesB amHI, Bgill, SmaI and Pvull. The putative packaging end ('pac' end) and the direction of packaging of the concatemeric DNA has been postulated
ABSTRACT
The fatty acid composition of the membrane of the conditional auxotroph fabB2 can be altered by allowing the cells to grow at non-permissive temperature (37°C) in the presence of a cis-unsaturated fatty acid. The phage 9NA, a virulent phage of Salmonella typhimurium, can not multiply in fabB2. Synthesis and maturation of the phage DNA are differentially affected by variation in the fatty acid composition of the cell membrane. The replicating DNA associates with the membrane complex, the site of DNA synthesis. The association is comparatively weak in oleic, claidic, palmitoleic, palmitelaidic and linolelaidic acid enriched cells. When the cells are grown in the presence of palmitoleic acid, a large pool of concatemeric phage DNA accumulates in the cytoplasm within 10 min of infection. The conversion of concatemeric DNA to monomeric one i.e., mature phage length DNA, is inhibited in such cells. The presence of concatemeric DNA can be visualized by electron microscope. Such a situation is not observed when the cells are grown in media supplemented with other types of unsaturated fatty acids. The mechanism by which the host cell membrane lipid controls phage development is yet to be worked out.