Kälteschockadaptation von Bacillus subtilis: Identifizierung kälteinduzierter Gene und Proteine und Untersuchung ihrer kältespezifischen Funktion und Regulation

Unknown cold-induced proteins and genes of Bacillus subtilis were identified by two-dimensional gelelectrophoresis and genomewide transcriptional analysis. The role of the cold-induced genes in the adaptation to low temperature was investigated. A cold-specific phenotype was observed for a yplP deletion mutant and a yqfR/ydbR double-deletion mutant. The yplP-gene encodes a sigL-dependent transcriptional activators in B. subtilis. The YplP-regulon is currently unknown. The genes yqfR and YdbR encode for DEAD-box mRNA-helicases, which were already identified as cold-induced proteins in several microorganisms. It could be demonstrated by fluorescence-microscopy of helicase-gfp fusions that the RNA helicase co-localize at the cell-poles with coldshock-proteins and ribosomes, depending on active transcription. Based on this experiment the following model was proposed: The RNA-helicases unwind cold-stabilized secondary structures of mRNA. After that the coldshock-proteins bind to the mRNA to prevent refolding of mRNA, resulting in efficient initiation of translation at low temperatures. In addition the regulation of the fatty-acid desaturase Des of Bacillus subtilis was investigated. The desaturase Des maintains the fluidity of the membrane after coldshock by synthesis of unsaturated fatty-acids in the membrane. Genetic studies could show that the transcription of the des-gene is regulated by the temperature-sensitive two-component system DesKR of Bacillus subtilis. The cold-specific regulation of other genes by DesKR could be excluded.