Journal Article


A Coffey
C Hill
G F Fitzgerald
D P Twomey
R P Ross
D O' Sullivan



genetics molecular sequence data pathogenicity genetic markers transformation bacterial pharmacology base sequence open reading frames physiology plasmids cobalt bacteriophages mob protein bacteria electroporation introns cadmium drug resistance microbial food microbiology sequence analysis dna virology metabolism lactococcus lactis bacterial proteins repb protein bacteria drug effects

Naturally occurring lactococcal plasmid pAH90 links bacteriophage resistance and mobility functions to a food-grade selectable marker. (2001)

Abstract The bacteriophage resistance plasmid pAH90 (26,490 bp) is a natural cointegrate plasmid formed via homologous recombination between the type I restriction-modification specificity determinants (hsdS) of two smaller lactococcal plasmids, pAH33 (6,159 bp) and pAH82 (20,331 bp), giving rise to a bacteriophage-insensitive mutant following phage challenge (D. O'Sullivan, D. P. Twomey, A. Coffey, C. Hill, G. F. Fitzgerald, and R. P. Ross, Mol. Microbiol. 36:866-876; 2000). In this communication we provide evidence that the recombination event is favored by phage infection. The entire nucleotide sequence of plasmid pAH90 was determined and found to contain 24 open reading frames (ORFs) responsible for phenotypes which include restriction-modification, phage adsorption inhibition, plasmid replication, cadmium resistance, cobalt transport, and conjugative mobilization. The cadmium resistance property, encoded by the cadA gene, which has an associated regulatory gene (cadC), is of particular interest, as it facilitated the selection of pAH90 in other phage-sensitive lactococci after electroporation. In addition, we report the identification of a group II self-splicing intron bounded by two exons which have the capacity to encode a relaxase implicated in conjugation in gram-positive bacteria. The functionality of this intron was evident by demonstrating splicing in vivo. Given that pAH90 encodes potent phage defense systems which act at different stages in the phage lytic cycle, the linkage of these with a food-grade selectable marker on a replicon that can be mobilized among lactococci has significant potential for natural strain improvement for industrial dairy fermentations which are susceptible to phage inhibition.
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Full list of authors on original publication

A Coffey, C Hill, G F Fitzgerald, D P Twomey, R P Ross, D O' Sullivan

Experts in our system

Aidan Coffey
Total Publications: 63
Colin Hill
University College Cork
Total Publications: 351
Gerald F Fitzgerald
Total Publications: 207
R Paul Ross
Total Publications: 441