Regulation Of Polyhydroxyalkanoates Biosynthesis In Pseudomonas Fluorescens2P24by Quorum Sensing、gacs/gacaand Rpos

Polyhydroxyalkanoates (PHA) are biopolyesters, which are accumulatedintracellularly in granue as carbon and energy storage materials by many microorganismsunder unbalanced conditions. PHA has drawed much attention due to its good materialproperties, such as biodegradability, biocompatibility and the potential substitutes ofchemical plastic. In recent years, the research and development of PHA was focused on thescreening the high yield strains or inexpensive substrate for biosynthesis of PHA, but theresearch of regulation mechanism about PHA biosynthesis is relatively small. Bacterialquorum sensing(Quorum-sensing, QS) system, two-component regulatory systemGacS/GacA, transcriptional factor RpoS play an important role in regulating bacteria tosense environmental signals. However, little is known about roles of the three regulatorysystem in the bacterial synthesis of PHA. In this study, with Psdeuomnoda fluoerncnet2P24as the research object, the functions of QS, GacS/GacA and RpoS in regulation ofPHA synthesis were explored by molecular genetics, biochemistry and cell biologymethods. It is the first report, to our best knowledge, that Pseudomonas fluorescens2P24can accumulate PHA using sodium gluconate or sodium octanoate as sole carbon source.When sodium gluconate serves as the sole carbon source, the main monomer of PHA is3-hydroxydecanoic acid. When sodium octanoate serves as sole carbon source, the mainmonomer of PHAis3-hydroxyoctanoic.The complementary strains and over-expression strains of regulatory gene have beenconstructed. The double mutant strains of the gacA/rpoS and gacS/rpoS have beenconstructed also. The ability of wild-type strain and related strains to accumulate PHA weredetected. When the bacterium was cultured with sodium octanate as sole carbon source, theaccumulation of PHA of PM201(△GacA), PM202(△GacS) and PM303(△RpoS)decreased significantly when compared with the2P24. In contrast, the PHA accumulationof PM100(△PcoI) has no significant difference with that of wild type. Recovery of gacA orgacS gene can significantly improve the accumulation of PHA. The results revealed thatgacA/gacS and rpoS are involved in the biosynthesis of PHA, and play a positive role. ButpcoI does not participate in PHA biosynthesis when sodium octanate as sole carbon source.The content of PHA of gacA/rpoS and gacS/rpoS double mutant strain are similar with the rpoS mutant. This indicated that rpoS is located downstream of gacA/gacS and plays animportant role in biosynthesis of PHA.In summary, in Pseudomonas fluorescens2P24the rpoS and gacA/gacS involved inregulation of PHA biosynthesis. When sodium octanoate as a carbon source, GacS/GacAsystem may be regulates the biosynthesis of PHAthrough the regulation of rpoS.