The Autoinducer Synthsis Gene Identification, Expression And PHB Accumulation In Rhodopseudanonas Palustris

Quorum sensing (quorum-sensing, QS) system is the bacteria control gene expression on a community-wide scale by producing, secreting, detecting and responding to extracellular signaling molecules (autoinducers) that accumulate in the environment on proportion to cell density. Quorum sensing controlled behavirors. Gram-negative bacteria mostly use acylated homoserine lactones(AHLs) as quorum sensing signal molecule. Gram-positive bacteria use oligopeptides as autoinducers. Some bacterias producer and detect a second autoinducer, AI-2. This autoinducer is produced by a remarkably wide variety of Gram-negative and Gram-positive bacteria, Some findings have led to the proposal that AI-2 is a 'universal'signal, which functions in interspecies cell-to-cell communication.Rhodopseudanonas palustris is a Gram-negative bacteria, one of member of photosynthetic bacteria, quorum sensing system was found in Rhodobacter sphaeroides that is one of the spherical red photosynthetic bacteria, and quorum sensing system control poly-β-hydroxybutyric acid (PHB) accumulation and photosynthetic hydrogen production. Rhodopseudanonas palustris also accumulated PHB and produce hydrogen in the light of heterotrophoc anaerobic condition. but whether there is quorum sensing system and regulating accumulation of PHB has also been reported.The autoinducer were detected by Colorimetry and the reporter strain Agrobacterium tumefaciens JZA1 [KYC55 (pJZ372) (pJZ384) (pJZ410)] in Rhodopseudanonas palustris CQU01. It founded that the solution turnde brown.Clarify R. palustris CQU01can synthesizing AHL. Designed of a pair of specific primers according to NCBI published five Rhodopseudanonas palustris genome sequence homology comparison. With the genomic DNA of Rhodopseudomonas palustris CQU01 as template, PCR amplified DNA fragments of about 650bp, sequence comparison found that the fragment from the AHL synthase gene Rpal. The amplified DNA fragment was cloned to E. coli DH5a, blue-white screening, induced expression, detected in DH5αthat the bacterium produces AI-1.AHL extracted with ethyl acetata. Rhodopseudomonas palustris CQU01 and Rhodopseudomonas palustris phbC- were culture by different concentrations of extract AHL, and then measuring content of th PHB. It found that the AHL can inhibit PHB accumulation when anaerobic growth of Rhodopseudomonas palustris CQU01. But the content of PHB almost have no change. Note that AHL may be inhibit PHB synthase and then inhibit PHB accumulation.