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Curr Microbiol. 2011 Jan;62(1):235-41. doi: 10.1007/s00284-010-9696-0. Epub 2010 Jul 1.

Depressed biofilm production in Bacillus amyloliquefaciens C06 causes γ-polyglutamic acid (γ-PGA) overproduction.

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Department of Plant Pathology, College of Plant Protection, Key Laboratory of Monitoring and Management of Crop Diseases and Pest Insects, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.


Bacillus amyloliquefaciens C06, a potential agent in biological preservation of post-harvest fruit, was found to secrete extra-cellular γ-polyglutamic acid (γ-PGA) in liquid culture. In this work, M306, a transposon mutant of B. amyloliquefaciens C06, defective in forming structured colony and displaying enhanced ability of producing γ-PGA, was obtained. Inverse PCR and quantitative reverse transcription PCR (qRT-PCR) analysis demonstrated that the defective phenotype in M306 was associated with an ORF showing high similarity to RBAM_034550 from B. amyloliquefaciens FZB42. In this paper, the ORF was designated pbrA, standing for γ-PGA production and biofilm formation regulatory factor. qRT-PCR analysis also indicated that pbrA down-regulated mRNA expression of epsD and yqxM, the crucial genes involved in biofilm formation, but affected little on expression of ywtB, the gene directing γ-PGA synthesis. Evaluations in γ-PGA productivity of wild-type C06 and its mutants C06ΔepsA and C06ΔtasA, respectively, deficient in producing exopolysaccharides (EPS) and TasA, revealed that γ-PGA overproduction in M306 was probably due to the redistributed metabolic flux caused by defective production of EPS.

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