Temperate Streptococcus thermophilus phages expressing superinfection exclusion proteins of the Ltp type

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 Ltp(TP-EW) was shown to be identical to that of mature Ltp(TP-J34), whereas the amino acid sequence of mature Ltp(TP-778) was shown to differ from mature Ltp(TP-J34) in eight amino acid positions. Ltp(TP-DSM20617) was shown to differ from Ltp(TP-778) in just one amino acid position. In contrast to Ltp(TP-J34), Ltp(TP-778) did not affect infection of lactococcal phage P008 instead increased activity against phage P001 was noticed.