Ten atypical Enterococcus strains were isolated from Italian raw milk cheeses. The 16S rRNA gene, phenylalanyl-tRNA synthase alpha subunit (pheS), RNA polymerase alpha subunit (rpoA) and the 16S-23S rRNA intergenic transcribed spacer (ITS) sequences, randomly amplified polymorphic DNA (RAPD) PCR and the phenotypic properties revealed that the isolates represent a novel enterococcal species. On the basis of 16S rRNA gene sequence analysis, the isolates were closely related to Enterococcus hirae ATCC 8043 T , Enterococcus durans CECT 411 T andEnterococcus faecium ATCC 19434 T , with 98.8, 98.9 and 99.4 % sequence similarity, respectively. On the basis of sequence analysis of the housekeeping gene pheS, the reference strain, BT159T , occupied a position separate from E. faecium LMG 16198. The group of isolates could be easily differentiated from recognized species of the genus Enterococcus by 16S-23S rRNA ITS analysis, RAPD-PCR and phenotypic characteristics. The name Enterococcus lactis sp. nov. is proposed, with BT159 T (5DSM 23655 T 5LMG 25958 T ) as the type strain.Enterococci belong to a group of organisms known as lactic acid bacteria and large numbers are usually present in vegetables, plant material and foodstuffs, especially those of animal origin such as dairy products (Giraffa, 2003;Fisher & Phillips, 2009). Studies on the microbiota of traditional cheeses of Mediterranean countries, produced mainly from raw milk from sheep, goats or cows, indicate that enterococci are a relevant component of the natural cultures involved in fermentation and that they play an important role in cheese ripening, hence contributing to the cheeses' typical taste and flavour (Foulquié Moreno et al., 2006). In addition, enterococci are also used to extend the shelf life and improve the hygienic safety of foodstuffs because they produce antimicrobial substances such as lactic acid, hydrogen peroxide and bacteriocins (enterocins). Bacteriocins have become of great interest as they are frequently active against several Gram-positive, food-borne pathogens such as Listeria monocytogenes, Staphylococcus aureus and Clostridium botulinum and it has been suggested that they should be used as biopreservatives in foods (Franz et al., 2007). Enterococci have also been investigated for their potential as probiotics, a role that is still controversial as some strains isolated from foods and human samples have been associated with human infections, several virulence factors and antibiotic resistance including resistance to glycopeptide antibiotics (vancomycin) (Foulquié Moreno et al., 2006).Since the revival of the genus Enterococcus by Schleifer & Kilpper-Bälz (1984), phylogenetic studies based on 16S rRNA gene sequences have established the presence of some species groups, namely 'faecium', 'faecalis', 'avium', 'gallinarum' and a fifth group comprising Enterococcus columbae and Enterococcus cecorum. Other described enterococci form individual lines of descent (Devriese et al., 1993;Devriese & Pot, 1995;Stiles & Holzapfel, 1997;Fortina et ...