CLONING AND DNA-SEQUENCE ANALYSIS OF THE REGION CONTAINING ATTP OF THE TEMPERATE PHAGE-PHI-AR29 OF PREVOTELLA-RUMINICOLA-AR29

Phage phi AR29 was shown to exist as a prophage integrated into the ch romosome of Prevotella ruminicola AR29. By DNA hybridization studies, the point of integrative recombination on the phage genome (attP) was located on a 4.5 kb EcoRV fragment. After preliminary mapping with res triction endonucleases, a 2.8 kb EcoRV/HindIII fragment was isolated, cloned in Escherichia coil and sequenced. DNA hybridization localized the attP site to the vicinity of an internal Dral site. Sequence analy sis showed the presence of several direct and inverted repeats around the attP site, with consensus core sequences similar to the integrase binding sites of phage lambda. Two open reading frames are present adj acent to attP (ORF1 and ORF2). The predicted polypeptide product of OR F1 has a region of structural similarity to known integrases. Although the predicted product of ORF2 shows at best weak homology with known excisionases, no other ORFs occur in the sequence upstream from ORF1, leaving ORF2 as the mast likely candidate for this role. However, if O RF2 does represent an xis gene, then this putative integration module would possess a notable difference from that of other temperate phages in the inversion of the positions of int and xis relative to attP. Th e proposed phi AR29 integration module is being used to develop phage- based integrative vector systems for the genetic manipulation of rumen bacteria.