Abstract
Lipoprotein Ltp encoded by temperate Streptococcus thermophilus phage TP-J34 is the prototype of the wide-spread family of host cell surface-exposed lipoproteins involved in superinfection exclusion (sie). When screening for other S. thermophilus phages expressing this type of lipoprotein, three temperate phages—TP-EW, TP-DSM20617, and TP-778—were isolated. In this communication we present the total nucleotide sequences of TP-J34 and TP-778L. For TP-EW, a phage almost identical to TP-J34, besides the ltp gene only the two regions of deviation from TP-J34 DNA were analyzed: the gene encoding the tail protein causing an assembly defect in TP-J34 and the gene encoding the lysin, which in TP-EW contains an intron. For TP-DSM20617 only the sequence of the lysogeny module containing the ltp gene was determined. The region showed high homology to the same region of TP-778. For TP-778 we could show that absence of the attR region resulted in aberrant excision of phage DNA. The amino acid sequence of mature LtpTP-EW was shown to be identical to that of mature LtpTP-J34, whereas the amino acid sequence of mature LtpTP-778 was shown to differ from mature LtpTP-J34 in eight amino acid positions. LtpTP-DSM20617 was shown to differ from LtpTP-778 in just one amino acid position. In contrast to LtpTP-J34, LtpTP-778 did not affect infection of lactococcal phage P008 instead increased activity against phage P001 was noticed.
Highlights
Superinfection exclusion is generally known as a mechanism by which a prophage residing in a host cell prevents infection of the lysogenic host cell by other phage through blocking DNA injection (Donnelly-Wu et al, 1993)
Sie has been mostly described for prophages of Gram-negative bacteria: P22 residing in Salmonella typhimurium (Hofer et al, 1995), Lambda-like phages in Escherichia coli (Cumby et al, 2012), and kappa-phage K139 in Vibrio cholerae (Nesper et al, 1999)
S. thermophilus temperate phage TP-J34 carrying an ltp gene has been described in some detail (Neve et al, 1998, 2003; Sun et al, 2006)
Summary
Superinfection exclusion (sie) is generally known as a mechanism by which a prophage residing in a host cell prevents infection of the lysogenic host cell by other phage through blocking DNA injection (Donnelly-Wu et al, 1993). This protects the host from being lysed by the infecting and multiplying incoming phage, and the prophage will not be destroyed in the process of phage multiplication (McGrath et al, 2002; Mahony et al, 2008). One exception appears to be the Glo protein of Vibrio cholerae, which has been described to a be soluble periplasmic protein (Nesper et al, 1999)
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