Cloning, Expression And Characterization Of The Gene Encoding Autoinducer Syntheticase Gene CerI In Rhodobacter Sphaeroides

Many species of bacteria exhibit quorum sensing (QS), the ability to release and respond to signal molecules.Typically, cells produce an extracellular autoinducer molecule often a peptide (in Gram+species) or an acylhomoserine lactone (in Gram' strains),once the concentration exceeds a threshold,the cell is induced to undertake some action,for example, expressing genes leading to the excretion of specific enzymes, toxins,or other functional products. This type of regulation has been named"quorum sensing".Rhodobacter sphaeroides is a free-living, one of the most important member of photosynthetic bacteria, and also is a photosynthetic bacteria with hydrogen-producing capacity, it will produce hydrogen in the light of heterotrophic anaerobic conditions. It is Gram-negative bacteria, founding it can generate 7,8-cis-N-(tetradecenoyl) homoserine lactone, which was named cer quorum sensing system.In this study, the coding sequence for R.sp cerl was cloned into the prokaryotic expression vector pET28a(+) and expressed in Escherichia coli BL21(DE3). A major band corresponding to a protein of 23kDa was detected on SDS-PAGE.we analyzed secondary structure and characteristics of Cerl by bioinformatics and a primary 3D structure model of Cerl protein was constructed by molecular modeling method.The signal molecules of R. sp can promote the bacteria scattered growth in logarithmic phase. The bacterial growth was inhibited by adding recombinant bacteria induced by IPTG.Adding recombinant bacteria induced by IPTG in R.sp by detection of PHB contents and hydrogen production volume,comprehensively analyzed the relationship between the quorum sensing,PHB contents and hydrogen production. The results showed that signal molecules in hydrogen production can inhibit the formation of PHB, making it has more reducing power for the production of hydrogen.