Involvement of the global regulators GrrS, RpoS, and SplIR in formation of biofilms in Serratia plymuthica

• Published in: Russian journal of genetics Vol. 46; no. 5; pp. 541 - 545
• Main Authors: Zaitseva, J. V, Voloshina, P. V, Liu, X, Ovadis, M. I, Berg, G, Chernin, L. S, Khmel, I. A
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : SP MAIK Nauka/Interperiodica 01-05-2010; SP MAIK Nauka/Interperiodica
• Subjects: Animal Genetics and Genomics; Biomedical and Life Sciences; Biomedicine; Genetics of Microorganisms; Human Genetics; Microbial Genetics and Genomics; Serratia plymuthica; Global Regulator; Quorum Sense; Quorum Sense System; Luria Broth; Homoserine Lactone
• ISSN: 1022-7954; 1608-3369
• DOI: 10.1134/S1022795410050054

Most bacteria exist in the natural environment as biofilms, multicellular communities attached to various surfaces. Biofilms have a characteristic architecture and are enclosed in the exopolymer matrix. Bacterial cells in biofilms are extremely resistant to antibacterial factors. It was shown in this work that the GrrA/GrrS system of global regulators of gene expression and the sigma S subunit of RNA polymerase (RpoS) play a significant role in positive regulation of biofilm formation in the rhizospheric bacterium Serratia plymuthica IC1270. Inactivation of grrS and rpoS genes resulted in an up to six-to-sevenfold and four-to-fivefold reduction in biofilm formation, respectively. Mutation in the grrS gene decreased the capacity of the bacterium for swarming motility. The splIR Quorum Sensing (QS) system was shown to negatively influence the biofilm formation. Transfer of the recombinant plasmid containing cloned genes splI/splR of S. plymuthica HRO-C48 into S. plymuthica IC1270 cells led to a twofold decrease of their ability to form biofilms. Inactivation of the splI gene coding for the synthase of N-acyl-homoserine lactones in S. plymuthica HRO-C48 resulted in a 2-2.5-fold increase in the level of biofilm formation, whereas the transfer of plasmid carrying the cloned splI/splR genes into these mutant cells restored the biofilm formation to the normal level. The results obtained demonstrate that the formation of biofilms in S. plymuthica is positively regulated by the GrrA/GrrS and RpoS global regulators and is negatively regulated by the SplIR QS system.