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KMID : 0364820180540010009
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Korean Journal of Microbiology
2018 Volume.54 No. 1 p.9 ~ p.17
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Cold shock sensitive growth of Bacillus subtilis mutants deleted for genes involved in fatty acid synthesis
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Kim Do-Hyung
Lee Sang-Soo
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Abstract
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To investigate the role of bkdR, sigL, yplP, and des genes which were known to be involved in fatty acid synthesis and sensitive at low temperature, deletion mutants of Bacillus subtilis CU1065 and JH642 were constructed. To determine the low temperature sensitivity of these genes, we compared the growth curves of cells at 37°C and 15°C. At 37°C, wild type and deletion mutants showed almost similar growth but only bkdR deletion strain at 15°C showed very slow growing compared with wild type. At 15°C sigL and yplP deletions were somewhat slower or similar to those of wild type strain. Double and triple mutants for bkdR, sigL, yplP deletions were constructed and grown at 20°C in LB agar to investigate cold sensitive growth. Double or triple deletions including bkdR deletion showed cold sensitive growing. In order to identify more clearly cold sensitive growth, the experiments were carried out under cold shock conditions in which the temperature was lowered from 37°C to 15°C at the point of 0.4 optical densities at 600 nm. In these cold shock experiments, only bkdR deletion showed significantly lower growing and additional des deletion increases cold sensitivity. The bkdR activates the bkd operon, which catabolized isoleucine, valine and leucine, amino acids and produce precursors for the synthesis of branched fatty acids. At cold shock growing of bkdR deletion strain, isoleucine recovered cold sensitivity of bkdR deletion but valine did not restore cold sensitivity. Isoleucine is used as a precursor for the synthesis of anteiso-branched fatty acids. On the other hand, valine is used as a precursor for the synthesis of iso-branched fatty acids. This indicates that anteisobranched fatty acid plays an important role at the cold shock condition.
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KEYWORD
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Bacillus subtilis, branched-chain fatty acid, cold shock, fatty acid synthesis, isoleucine, leucine, valine
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