Nisin-triggered activity of Lys44, the secreted endolysin from Oenococcus oeni phage fOg44.

The intrinsic resistance of Oenococcus oeni cells to the secreted endolysin from oenophage fOg44 (Lys44) was investigated. Experiments with several antimicrobials support the hypothesis that the full activity of Lys44 requires sudden ion-nonspecific dissipation of the proton motive force, an event undertaken by the fOg44 holin in the phage infection context.

The ectodomain of the viral receptor YueB forms a fiber that triggers ejection of bacteriophage SPP1 DNA.

The irreversible binding of bacteriophages to their receptor(s) in the host cell surface triggers release of the naked genome from the virion followed by transit of viral DNA to the host cell cytoplasm. We have purified, for the first time, a receptor from a Gram-positive bacterium that is active to trigger viral DNA ejection in vitro. This extracellular region ("ectodomain") of the Bacillus subtilis protein YueB (YueB780) was a 7 S elongated dimer forming a 36.5-nm-long fiber. YueB780 bound to the tail tip of bacteriophage SPP1. Although a stable receptor-phage interaction occurred between 0 and 37 degrees C, complete blocking of phage DNA release or partial ejection events were observed at temperatures below 15 degrees C. We also showed that the receptor was exposed to the B. subtilis surface. YueB differed structurally from phage receptors from Gram-negative bacteria. Its properties revealed a fiber spanning the full length of the 30-nm-thick peptidoglycan layer. The fiber is predicted to be anchored in the cell membrane through transmembrane segments. These features, highly suitable for a virus receptor in Gram-positive bacteria, are very likely shared by a large number of phage receptors.

Diversity in the lysis-integration region of oenophage genomes and evidence for multiple tRNA loci, as targets for prophage integration in Oenococcus oeni.

The central genomic regions of Oenococcus oeni phages fOg30 and fOgPSU1 have been compared with the equivalent regions of oenophages fOg44 and phi 10MC. In all cases, an almost identical endolysin gene was followed by one of two orfs, encoding putative holins (orf117 and orf163). The fOg44 endolysin was established as a secretory protein when expressed in Lactococcus lactis. Orf117 (from fOg44) promoted lysis of Escherichia coli cultures upon induction of a defective lambda Sam7 prophage, but Orf163 (from fOg30) failed to elicit a lysis response in this system. fOg44 and fOgPSU1 were shown to integrate at the 3' end of a tRNA(Glu) and a tRNA(Lys), respectively. Searching the available sequence of the O. oeni MCW genome for attP-like elements, two other tRNA targets could be proposed for prophage establishment. Between the lysis and integration elements, a diverse cluster of genes (absent in phi 10MC) was observed. One common gene in this "lysogenic conversion cluster" was experimentally confirmed as a transcriptional repressor, affecting the expression of a putative permease gene.