Affiliation:
1. Department of Biochemistry and Microbiology, Faculté des Sciences et de Génie, and Groupe de Recherche en Ecologie Buccale, Faculté de Médecine Dentaire, Université Laval, Québec, Canada G1K 7P4
Abstract
ABSTRACT
Three genetically distinct groups of
Lactococcus lactis
phages are encountered in dairy plants worldwide, namely, the 936, c2, and P335 species. The multiplex PCR method was adapted to detect, in a single reaction, the presence of these species in whey samples or in phage lysates. Three sets of primers, one for each species, were designed based on conserved regions of their genomes. The c2-specific primers were constructed using the major capsid protein gene (
mcp
) as the target. The
mcp
sequences for three phages (eb1, Q38, and Q44) were determined and compared with the two available in the databases, those for phages c2 and bIL67. An 86.4% identity was found over the five
mcp
genes. The gene of the only major structural protein (
msp
) was selected as a target for the detection of 936-related phages. The
msp
sequences for three phages (p2, Q7, and Q11) were also established and matched with the available data on phages sk1, bIL170, and F4-1. The comparison of the six
msp
genes revealed an 82.2% identity. A high genomic diversity was observed among structural proteins of the P335-like phages suggesting that the classification of lactococcal phages within this species should be revised. Nevertheless, we have identified a common genomic region in 10 P335-like phages isolated from six countries. This region corresponded to
orfF17-orf18
of phage r1t and
orf20-orf21
of Tuc2009 and was sequenced for three additional P335 phages (Q30, P270, and ul40). An identity of 93.4% within a 739-bp region of the five phages was found. The detection limit of the multiplex PCR method in whey was 10
4
to 10
7
PFU/ml and was 10
3
to 10
5
PFU/ml with an additional phage concentration step. The method can also be used to detect phage DNA in whey powders and may also detect prophage or defective phage in the bacterial genome.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
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