Hemolysins are important virulence factors for many bacterial pathogens, including Serratia marcescens. The role of the major hemolysin gene in the insect pathogen Serratia sp. SCBI was investigated using both forward and reverse genetics approaches. Introduction of the major hemolysin gene into Escherichia coli resulted in a gain of both virulence and hemolytic activity. Inactivation of this hemolysin in Serratia sp. SCBI resulted in loss of hemolysis, but did not attenuate insecticidal activity. Unexpectedly, inactivation of the hemolysin gene in Serratia sp. SCBI resulted in significantly increased motility as well as increased antimicrobial activity. qRT-PCR analysis of mutants with a disrupted hemolysin gene showed a dramatic increase in mRNA levels of a nonribosomal peptide synthetase gene, swrA, which produces the surfactant serrawettin W2. Mutation of the swrA gene in Serratia sp. SCBI resulted in highly variable antibiotic activity, motility, virulence and hemolysis phenotypes that were dependent on the site of disruption within this 17.75 KB gene. When introduced into E. coli, swrA increases rates of motility and confers antimicrobial activity. While it is unclear how inactivation of the major hemolysin gene influences expression of swrA, these results suggest swrA plays an important role in motility and antimicrobial activity in Serratia sp. SCBI.
Molecular, Cellular and Biomedical Sciences
Journal of Bacteriology
American Society for Microbiology
Digital Object Identifier (DOI)
Petersen, L., K. LaCourse, T. Schöner, H. Bode, and L.S. Tisa. 2017. Inactivation of the major hemolysin gene influences expression of the nonribosomal peptide synthetase gene swrA in the insect pathogen Serratia sp. strain SCBI. J Bacteriol. 199:e00333-17. doi: 10.1128/JB.00333-17
© 2017 American Society for Microbiology.