Gene organization in a central DNA fragment of Oenococcus oeni bacteriophage fOg44 encoding lytic, integrative and non-essential functions

Abstract The nucleotide sequence of a DNA fragment previously shown to contain the attachment site ( attP ) of Oenococcus oeni phage fOg44 ( Santos et al., 1998 . Arch. Virol . 143 , 523–536) has been determined. Sequence analysis indicated that this 6226 bp Eco RI fragment harbours an integrase gene, in the vicinity of a direct repeat rich region defining attP , as well as genes encoding a muramidase-related lysin (Lys) and a holin polypeptide (Hol). Transcriptional studies suggested that lys and hol are mainly co-expressed, late in the lytic cycle, from a promotor located upstream of lys . Between the lytic cassette and the phage integration elements three additional open reading frames were found: orf217 and orf252 of unknown function and orf72 , the putative product of which bears 32% identity with acidic excisionases from other Gram positive phages. We have established that the first two orf s, as well as the predicted promotor of orf72 , are included in a 2143-bp DNA segment missing from the genome of the deletion mutant fOg44Δ2. Although lysogens of fOg44 and fOg44Δ2 exhibited similar properties, each phage produced two distinguishable types of lysogenic strains, differing in inducibility and immunity to other oenophages.