Elevation of Lactococcus lactis subsp. cremoris to the species level as Lactococcus cremoris sp. nov. and transfer of Lactococcus lactis subsp. tructae to Lactococcus cremoris as Lactococcus cremoris subsp. tructae comb. nov.

Abstract

Currently, Lactococcus lactis contains four subspecies: L. lactis subsp. lactis , L. lactis subsp. hordniae , L. lactis subsp. cremoris and L. lactis subsp. tructae . In the study of Pérez et al., these four subspecies could be clearly divided into two groups based on recA sequence analysis: L. lactis subsp. lactis and L. lactis subsp. hordniae ; L. lactis subsp. cremoris and L. lactis subsp. tructae . The two groups had a relatively low DNA–DNA hybridization value (about 60 %). In the present study, the taxonomic position of L. lactis subsp. cremoris and L. lactis subsp. tructae was re-examined based on sequence analyses of 16S rRNA, rpoB, recA and pheS genes, average nucleotide identity (ANI) values and digital DNA–DNA hybridization (dDDH) values. The result of 16S rRNA gene sequence analysis indicated that L. lactis subsp. cremoris NCDO 607T and L. lactis subsp. tructae L105T were phylogenetically related to the type strains of L. lactis subsp. hordniae , L. lactis subsp. lactis , Lactococcus taiwanensis , Lactococcus kimchii , Lactococcus allomyrinae , Lactococcus protaetiae, Lactococcus hircilactis , Lactococcus fujiensis and Lactococcus nasutitermitis . The 16S rRNA gene, rpoB, recA, pheS and concatenated rpoB, recA and pheS sequence similarities, ANI values, and dDDH values between the type strains of L. lactis subsp. cremoris , L. lactis subsp. tructae and phylogenetically related species were 93.5–99.4 %, 83.3–97.6 %, 80.6–92.4 %, 79.7–92.7 %, 83.5–94.3 %, 72.4–86.9 % and 21.4–32.5 %, respectively. Lower than 95–96 % ANI values and lower than 70 % dDDH values confirmed that the type strains of L. lactis subsp. cremoris and L. lactis subsp. tructae represent a novel species in the genus Lactococcus . Because L. lactis subsp. cremoris was proposed and validated before L. lactis subsp. tructae , L. lactis subsp. cremoris is elevated to the species level as Lactococcus cremoris sp. nov. and L. lactis subsp. tructae is transferred to L. cremoris as L. cremoris subsp. tructae comb. nov. The type strain of L. cremoris sp. nov. is NCDO 607T (=ATCC 19257T=DSM 20069T=JCM 16167T=LMG 6897T=NBRC 100676T). The type strain of L. cremoris subsp. tructae comb. nov. is L105T (=NBRC 110453T=DSM 21502T=JCM 31125T=LMG 24662T).

Genetic Dissection of a Prevalent Plasmid-Encoded Conjugation System in Lactococcus lactis

“…Lactococcus lactis and Lactococcus cremoris represent two Gram-positive, non-spore forming bacterial species, and members of the lactic acid bacteria (LAB), a group of micro-aerophilic coccoid and rod-shaped bacteria that produce lactic acid as the main product from hexose fermentation (Makarova et al, 2006;Ainsworth et al, 2014a;Li et al, 2021). L. lactis and L. cremoris are commonly used as a starter cultures in cheese, buttermilk, and quark production, with many technologically relevant traits being plasmid-encoded (Tarazanova et al, 2016), such as growth in milk (i.e., metabolism of lactose, citrate, and/or casein), resistance to environmental stresses and viruses (e.g., bacteriophages or heavy metals), and competitive advantages such as bacteriocin production (Fallico et al, 2012).…”

“…The generally recognized as safe (GRAS) status of LAB combined with their potential probiotic properties (Gurien et al, 2018), absence of endotoxins and inclusion bodies, and availability of a diverse selection of cloning and inducible expression vectors render LAB (bio)technologically interesting (Song et al, 2017). A relatively limited number of L. cremoris and L. lactis strains are currently used in large-scale fermentation processes, and this practice may have contributed to the somewhat narrow flavor diversity among dairy products and emergence of ubiquitous host-specific lytic bacteriophages (Coffey and Ross, 2002;Fallico et al, 2012;Li et al, 2021). This has prompted ongoing studies to identify and/or generate novel strains with improved phageresistance, bacteriocin production or immunity, and/or flavorassociated properties.…”

Physiological roles of short-chain and long-chain menaquinones (vitamin K2) in Lactococcus cremoris

“…Lactococcus cremoris [previous known as Lactococcus lactis ssp. cremoris (Li et al, 2021)] and L. lactis are lactic acid bacterium (LAB) that play important roles in food fermentation processes, especially in the manufacturing of fermented dairy products: they are the main constituent of various dairy starter cultures used all over the world for the production of cheese, butter milk and sour cream (Cavanagh et al, 2015). The essential involvement of L. cremoris and L. lactis in the fermentation of food raw materials highlights the interest in understanding the physiology and lifestyle of this bacterium.…”

Stationary Lactococcus cremoris: Energetic State, Protein Synthesis Without Nitrogen and Their Effect on Survival

“…Lactococcus cremoris [formerly Lactococcus lactis subsp. cremoris (Li et al, 2021)] is well-known for its use in food fermentations like cheese and yogurt (Kelleher et al, 2017;Pereira et al, 2020). During storage and ripening of these fermented products, L. cremoris spends weeks to months in a non-growing state.…”