The Phylogeny of Psychrotrophic Bacteria Isolated from Refrigerated Raw Cow Milk Collected in an Arid Area of Algeria

– The present study investigated the phylogeny based on 16S rRNA gene sequences of psychrotrophic bacteria isolated from refrigerated raw cow milk collected in an arid area of Algeria. During cold storage of milk at 4°C, 29 bacterial morpho-physiotypes were selected among 177 isolates and were identified by partial 16S rRNA gene sequencing. The results of the phylogenetic analysis showed five clusters regrouping six genera namely Stenotrophomonas , Acinetobacter , Chryseobacterium , Lactobacillus , Aeromonas and Enterococcus . Enterococcus constituted the largest cluster composed of 9 taxa with E. faecalis being the predominant species and it was the most subclustered group. The comparative genomic analysis based on 16S rRNA gene sequence of E. faecalis isolates, with related strains from different geographies and climates was performed. The observations of the genetic variation showed that seven E. faecalis strains (MH569850, MH569851, MH569854, MH569856, MH569857, MH569859 and MH569860) registered similarities of sequences less than 97%, which lead to the hypothesis that the isolates could represent a novel species of the genus Enterococcus . The minor richness of the milk microbiota analyzed in this arid region may account for the intervention of environmental factors influencing the selection and the evolution of the microflora.