Fagos de lactococcus

APPLIED AND ENVIRONMENTAL MICROBIOLOGY, June 2006, p. 4338–4346 0099-2240/06/$08.00 0 doi:10.1128/AEM.02517-05 Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Vol. 72, No. 6

Biodiversity and Classification of Lactococcal Phages
Helene Deveau,1,2 Simon J. Labrie,1,2 Marie-Christine Chopin,3 and Sylvain Moineau1,2,4* ´`
Departement de Biochimie et de Microbiologie,Faculte des Sciences et de Genie, Universite Laval, Quebec City, Quebec, ´ ´ ´ ´ ´ Canada G1K 7P41; Groupe de Recherche en Ecologie Buccale (GREB), Faculte de Medecine Dentaire, ´ ´ Universite Laval, Quebec City, Quebec, Canada G1K 7P42; Laboratoire de Genetique Microbienne, ´ ´ ´ INRA, 78352 Jouy-en-Josas, France3; and Felix d’Herelle Reference Center for Bacterial Viruses, ´ ´ Universite Laval,Quebec City, Quebec, Canada G1K 7P44 ´
Received 25 October 2005/Accepted 26 March 2006

For this study, an in-depth review of the classification of Lactococcus lactis phages was performed. Reference phages as well as unclassified phages from international collections were analyzed by stringent DNA-DNA hybridization studies, electron microscopy observations, and sequence analyses. A newclassification scheme for lactococcal phages is proposed that reduces the current 12 groups to 8. However, two new phages (Q54 and 1706), which are unrelated to known lactococcal phages, may belong to new emerging groups. The multiplex PCR method currently used for the rapid identification of phages from the three main lactococcal groups (936, c2, and P335) was improved and tested against the other groups, noneof which gave a PCR product, confirming the specificity of this detection tool. However, this method does not detect all members of the highly diverse P335 group. The lactococcal phages characterized here were deposited in the Felix d’Herelle Reference Center ´ ´ for Bacterial Viruses and represent a highly diverse viral community from the dairy environment. Strains of the gram-positive bacteriumLactococcus lactis are used by the dairy industry to acidify milk during the manufacture of fermented products, such as cheese, buttermilk, and sour cream. The use of various L. lactis strains is essential for controlling virulent phages that are responsible for most milk fermentation collapses (40). Lactococcal phages are ubiquitous in the dairy environment, as they are found in raw milk andsurvive pasteurization (14, 36). Due to their negative effects on fermentation as well as their biodiversity within this ecological niche, numerous lactococcal phages have been isolated and characterized, with the overall aim of improving phage control strategies. Currently, only coliphages have received more attention than lactococcal phages (1, 2). All known L. lactis phages have a double-strandedgenome and a noncontractile tail. According to the International Committee on Taxonomy of Viruses, L. lactis phages are members of the Caudovirales order, an extremely large, morphologically and genetically diverse group that encompasses over 95% of all known phages (37). This order contains three families, namely, the Myoviridae (with long, contractile tails), the Siphoviridae (with long,noncontractile tails), and the Podoviridae (with short tails). Lactococcal phages are mainly members of the Siphoviridae family, with a few members from the Podoviridae family. Over a decade ago, a classification scheme which was mainly based on phage morphology and DNA homology criteria was developed for lactococcal phages (3, 4, 7, 25, 32). It is made up of 12 lactococcal phage groups and has been usedsuccessfully for comparing lactococcal phages isolated from around the world. It rapidly became obvious that the vast majority of lactococcal phages belong to one of three main groups, the 936, c2, and P335 groups. Consequently, most studies of lactococcal phages have dealt with these groups. For example, a multiplex PCR method is now available to rapidly assign newly isolated phages to one of...