Bacteriophage-encoded functions engaged in initiation of homologous recombination events.

Recombination plays a significant role in bacteriophage biology. Functions promoting recombination are involved in key stages of phage multiplication and drive phage evolution. Their biological role is reflected by the great variety of phages existing in the environment. This work presents the role of recombination in the phage life cycle and highlights the discrete character of phage-encoded recombination functions (anti-RecBCD activities, 5' --> 3' DNA exonucleases, single-stranded DNA binding proteins, single-stranded DNA annealing proteins, and recombinases). The focus of this review is on phage proteins that initiate genetic exchange. Importance of recombination is reviewed based on the accepted coli-phages T4 and lambda models, the recombination system of phage P22, and the recently characterized recombination functions of Bacillus subtilis phage SPP1 and mycobacteriophage Che9c. Key steps of the molecular mechanisms involving phage recombination functions and their application in molecular engineering are discussed.

Biodiversity of Lactococcus lactis bacteriophages in Polish dairy environment.

We present here the results of an exploration of the bacteriophage content of dairy wheys collected from milk plants localized in various regions of Poland. Thirty-three whey samples from 17 regions were analyzed and found to contain phages active against L. lactis strains. High phage titer in all whey samples suggested phage-induced lysis to be the main cause of fermentation failures. In total, over 220 isolated phages were examined for their restriction patterns, genome sizes, genetic groups of DNA homology, and host ranges. Based on DNA digestions the identified phages were classified into 34 distinct DNA restriction groups. Phage genome sizes were estimated at 14-35 kb. Multiplex PCR analysis established that the studied phages belong to two out of the three main lactococcal phage types--c2 and 936, while P335-type phages were not detected. Yet, analyses of bacterial starter strains revealed that the majority of them are lysogenic and carry prophages of P335-type in their chromosome. Phage geographical distribution and host range are additionally discussed.

A distinct single-stranded DNA-binding protein encoded by the Lactococcus lactis bacteriophage bIL67.

Single-stranded binding proteins (SSBs) are found to participate in various processes of DNA metabolism in all known organisms. We describe here a SSB protein encoded by the Lactococcus lactis phage bIL67 orf14 gene. It is the first noted attempt at characterizing a SSB protein from a lactococcal phage. The purified Orf14(bIL67) binds unspecifically to ssDNA with the same high affinity as the canonical Bacillus subtilis SSB. Electrophoretic mobility-shift assays performed with mutagenized Orf14(bIL67) protein derivatives suggest that ssDNA-binding occurs via a putative OB-fold structure predicted by three-dimensional modeling. The native Orf14(bIL67) forms homotetramers as determined by gel filtration studies. These results allow distinguishing the first lactococcal phage protein with single-strand binding affinity, which defines a novel cluster of phage SSBs proteins. The possible role of Orf14(bIL67) in phage multiplication cycle is also discussed.