Effect of growth temperature on membrane fatty acid composition and susceptibility to cold shock of Bacillus amyloliquefaciens.

We investigated the fatty acid composition of the membrane of Bacillus amyloliquefaciens grown at different temperatures. A decrease in growth temperature was accompanied by an increase in the ratio of branched- to straight-chain fatty acids and a marked increase in the level of unsaturation of branched-chain fatty acids. When cells of this organism grown at 30 degrees C were cold shocked, viability and ability to secrete extracellular protease were lost. Growth of this organism at lower temperatures or addition of Tween 80 to cells caused the critical temperature zone for cold shocking to be lowered significantly. These results suggest a direct correlation between membrane fluidity and the susceptibility to cold shock.

Isolation and characterization of genomic clones for two chicken phenobarbital-inducible cytochrome P-450 genes.

A cDNA clone specific for a chicken phenobarbital-inducible cytochrome P-450 was used to screen a chicken genomic library. Twenty-nine clones were isolated, restriction mapped, and divided into two non-overlapping groups. The cDNA clone hybridized to 12 kilobases of DNA from both groups. Both groups contained restriction fragments which hybridized to both 5' and 3' fragments of the cDNA clone, and it was concluded that the two groups were derived from two separate genes. Southern transfer analysis of individual chicken DNAs and quantitative hybridization analysis indicated that these two genes are independent and are present as single copies/haploid genome. Comparison of restriction digests of the cloned DNAs and total genomic DNA discounted the possibility that other closely related P-450 genes are present in the chicken genome.