Characterization and Genomic Analysis of ø SHP3, a New Transposable Bacteriophage Infecting Stenotrophomonas maltophilia.

This study describes a novel transposable bacteriophage, ø SHP3, continuously released by Stenotrophomonas maltophilia strain c31. Morphological observation and genomic analysis revealed that ø SHP3 is a siphovirus with a 37,611-bp genome that encodes 51 putative proteins. Genomic comparisons indicated that ø SHP3 is a B3-like transposable phage. Its genome configuration is similar to that of Pseudomonas phage B3, except for the DNA modification module. Similar to B3-like phages, the putative transposase B of ø SHP3 is a homolog of the type two secretion component ExeA, which is proposed to serve as a potential virulence factor. Moreover, most proteins of ø SHP3 have homologs in transposable phages, but only ø SHP3 carries an RdgC-like protein encoded by gene 3, which exhibits exonuclease activity in vitro. Two genes and their promoters coding for ø SHP3 regulatory proteins were identified and appear to control the lytic-lysogenic switch. One of the proteins represses one promoter activity and confers immunity to ø SHP3 superinfection in vivo. The short regulatory region, in addition to the canonical bacterial promoter sequences, displays one LexA and two CpxR recognition sequences. This suggests that LexA and the CpxR/CpxA two-component system might be involved in the control of the ø SHP3 genetic switch. [ABSTRACT FROM AUTHOR]