Mechanism Of QS System Involved In Temperature Adaptation In Bacillus Cereus MYB41-22

Because of the long-term living in the cold environment,low-temperature microorganisms form a unique cell structures and molecular mechanisms that adapt to the low-temperature environment under the action of natural selection.This mechanism is called low-temperature adaptation.During bacterial growth,specific signal molecules can be released.These signal molecules can be perceived by bacteria and used to regulate the expression of many of their genes to adapt to changes in the surrounding environment.This phenomenon is called quorum sensing(Quorum Sensing,QS).At present,there is no report on whether quorum sensing systems are involved in low-temperature adaptation.In this study,a low-temperature bacterium Bacillus cereus MYB41-22 isolated by our laboratory was used as the research materials.The growth temperature range of the strain was determined to be 4℃~37℃,and the optimal growth temperature was 28℃.The whole genomic DNA of 41-22 sequencing was completed.The sequencing results showed that the genome size was 4,428,864 bp,the GC content was 36.06%,the number of ORFs was 5,481,and the proportion of coding genes was 84.38%;two groups of PlcR-PapR and Lux S were identified.The sensory system exists in its genome,and related genes of codY and hblA that regulate the quorum sensing system are found,and desR and cspA genes related to low temperature adaptation are also found.Secondly,according to the characteristics of its quorum sensing system,the signal molecule pentapeptide and heptapeptide were synthesized.Results have shown that synthetic signal molecules have a definite effect with a minimum concentration of 20 nM.At 15℃,the addition of signaling molecules increased the ability of MYB41-22 to increase by 19.5%,while that at 37℃ resulted in a 24.4% decrease in the growth of MYB41-22.This result indicates that activation of the quorum sensing system affects the cells at different temperatures.The transcriptal levels of quorum sensing system and related genes were also tested.The results showed that the transcription levels of plcR and papR at 15℃ were significantly higher than those at 37℃.In addtion,at presence of signal molecules at 15℃,the transcription levels of genes cod Y,desR and cspA were down-regulated and hblA was up-regulated,in contract,the transcription levels of quorum-sensing genes codY,desR and cspA was up-regulated,and hblA was down-regulated at 37℃.The signal molecules is likely to active the quorum sensing system mechanism first,and then lead to the bacterial cell membrane structure,cold shock protein content change,and finally affect the bacterial growth state.In this paper,Bacillus cereus MYB41-22 was used as model to study the bacterial QS involved in temperature adaptation.The physicochemical properties,quorum sensing,and temperature adaptational genes were investigated in presence or abcence of signal molecules.All results demonstrated that bacterial QS involved in temperature adaptation.