This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ike, Y Articles by Clewell, D B Search for Related Content PubMed PubMed Citation Articles by Ike, Y Articles by Clewell, D B

research-article

Hyperhemolytic phenomena associated with insertions of Tn916 into the hemolysin determinant of Enterococcus faecalis plasmid pAD1.

Department of Microbiology, School of Medicine, Gunma University, Maebashi, Japan.

ABSTRACT

Members of the Tn916 family of conjugative transposons are able to insert themselves into Enterococcus faecalis hemolysin/bacteriocin plasmid pAD1 (and related elements) in such a way as to generate hyperexpression of the hemolysin/bacteriocin. To examine this phenomenon in more detail, E. faecalis (pAD1::Tn916) derivatives defective or altered in hemolysin expression were isolated and characterized with respect to production of the L (lytic) or A (activator) component (also known as CylA) and the specific location of the transposon. The mutants fell into five classes. Class 1 strains were nonhemolytic, and the related insertions mapped in a location known to affect expression of the L component. The other four classes varied from an inability to express hemolysin (class 2) to different degrees of hyperhemolytic expression (classes 3 to 5); the insertions in these classes mapped in a similar place within cylA, near the 3' end of the determinant. A previous study provided evidence that CylA is also necessary for bacteriocin immunity; however, these insertions did not destroy this function. (A Tn917 insertion in the 5' half of the determinant eliminates immunity.) In mutant classes 3 to 5, the presence of tetracycline enhanced hemolysin expression. In late-exponential-phase broth cultures, hemolysin could not be detected in supernatants of classes 2 to 5, in contrast to a wild-type control strain; however, different amounts of the L component could be detected, with the lowest in class 2 and greater-than-normal amounts in classes 3 to 5. Although nucleotide sequencing showed that the Tn916 insertions in classes 2 to 5 were at identical sites, the transposon junction sequences differed in some cases. The data indicated that cylA translation into the transposon would result in different truncation sites, and these differences were probably related to phenotype differences.

This article has been cited by other articles:

• Tomita, H., Kamei, E., Ike, Y. (2008). Cloning and Genetic Analyses of the Bacteriocin 41 Determinant Encoded on the Enterococcus faecalis Pheromone-Responsive Conjugative Plasmid pYI14: a Novel Bacteriocin Complemented by Two Extracellular Components (Lysin and Activator). J. Bacteriol. 190: 2075-2085 [Abstract] [Full Text]  
• Semedo, T., Almeida Santos, M., Martins, P., Silva Lopes, M. F., Figueiredo Marques, J. J., Tenreiro, R., Barreto Crespo, M. T. (2003). Comparative Study Using Type Strains and Clinical and Food Isolates To Examine Hemolytic Activity and Occurrence of the cyl Operon in Enterococci. J. Clin. Microbiol. 41: 2569-2576 [Abstract] [Full Text]  
• Coburn, P. S., Hancock, L. E., Booth, M. C., Gilmore, M. S. (1999). A Novel Means of Self-Protection, Unrelated to Toxin Activation, Confers Immunity to the Bactericidal Effects of the Enterococcus faecalis Cytolysin. Infect. Immun. 67: 3339-3347 [Abstract] [Full Text]  
• Marra, D., Smith, J. G., Scott, J. R. (1999). Excision of the Conjugative Transposon Tn916 in Lactococcus lactis. Appl. Environ. Microbiol. 65: 2230-2231 [Abstract] [Full Text]  
• Rice, L. B. (1998). Tn916 Family Conjugative Transposons and Dissemination of Antimicrobial Resistance Determinants. Antimicrob. Agents Chemother. 42: 1871-1877 [Full Text]