Towards the diversification of lactococcal starter and non-starter species in mesophilic dairy culture systems

Lactococcus is one of the earliest identified fermentative bacterial genera and among its member species, the dairy-associated Lactococcus lactis and Lactococcus cremoris are undoubtedly the best studied. These two species are believed to have evolved from plant-associated lactococci and through genome decay and acquisition of plasmids, have adapted to the dairy niche. The past decade has witnessed a surge of activity in novel lactococcal species identification from insect, plant and animal sources. Currently, 22 Lactococcus species are described and in this review, we summarise the genome characteristics of and phylogenetic relationships among these species. Furthermore, we explore the role of mobile elements including plasmids and bacteriophages in the diversification of lactococcal species. The pace of identification of novel lactococcal species suggests that the number of lactococcal species is likely to continue to grow. With additional sequence data for the emerging species, it will be possible to perform pathogenicity/virulence risk evaluations and generate extensive insights into the niche adaptation strategies through which they have evolved.

Lactic Acid Bacteria in Raw-Milk Cheeses: From Starter Cultures to Probiotic Functions

Traditional cheeses produced from raw milk exhibit a complex microbiota, characterized by a sequence of different microorganisms from milk coagulation and throughout maturation. Lactic acid bacteria (LAB) play an essential role in traditional cheese making, either as starter cultures that cause the rapid acidification of milk or as secondary microbiota that play an important role during cheese ripening. The enzymes produced by such dynamic LAB communities in raw milk are crucial, since they support proteolysis and lipolysis as chief drivers of flavor and texture of cheese. Recently, several LAB species have been characterized and used as probiotics that successfully promote human health. This review highlights the latest trends encompassing LAB acting in traditional raw milk cheeses (from cow, sheep, and goat milk), and their potential as probiotics and producers of bioactive compounds with health-promoting effects.

Lactococcus insecticola sp. nov. and Lactococcus hodotermopsidis sp. nov., isolated from the gut of the wood-feeding lower termite Hodotermopsis sjostedti

Two strains of lactic acid bacteria, designated Hs20B0-1^T and Hs30E4-3^T, were isolated from the gut of the damp-wood termite Hodotermopsis sjostedti. These strains were characterized genetically and phenotypically. Strain Hs20B0-1^T was related to Lactococcus piscium DSM 6634^T showing 96.3 and 84.2 % sequence similarity in 16S rRNA gene and rpoB gene sequences, respectively. Strain Hs30E4-3^T was related to Lactococcus plantarum DSM 20686^T showing 94.8 and 82.2 % sequence similarity in 16S rRNA gene and rpoB gene sequences, respectively. The 16S rRNA gene sequence similarity between strains Hs20B0-1^T and Hs30E4-3^T was 95.7 %. Furthermore, genomic comparisons using pairwise average nucleotide identity (ANI) and digital DNA-DNA hybridization (DDH) analyses between strain Hs20B0-1^T and L. piscium DSM 6634^T resulted in values of 73.5 and 20.1 %, respectively. Strain Hs30E4-3^T had 72.8 % ANI similarity and 21.3 % DDH similarity to L. plantarum DSM 20686^T. Strains Hs20B0-1^T and Hs30E4-3^T had 75.4 % ANI similarity and 21.1 % DDH similarity to each other. The cell-wall peptidoglycan types of strains Hs20B0-1^T and Hs30E4-3^T were A4α, Lys-Asp and A3α, Lys-Thr-Ala, respectively. The two strains, Hs20B0-1^T and Hs30E4-3^T, are distinguishable from each other and other established Lactococcus species phylogenetically and phenotypically. In conclusion, two novel species of the genus Lactococcus are proposed, namely Lactococcus insecticola Hs20B0-1^T (=JCM 33485^T=DSM 110147^T) and Lactococcus hodotermopsidis Hs30E4-3^T (=JCM 33486^T=DSM 110148^T), respectively.