Lactococcus protaetiae sp. nov. and Xylanimonas protaetiae sp. nov., isolated from gut of larvae of Protaetia brevitarsis seulensis

High-yield synthesis of 2-O-α-D-glucosyl-D-glycerate by a bifunctional glycoside phosphorylase

Osmolytes are produced by various microorganisms as a defense mechanism to protect cells and macromolecules from damage caused by external stresses in harsh environments. Due to their useful stabilizing properties, these molecules are applied as active ingredients in a wide range of cosmetics and healthcare products. The metabolic pathways and biocatalytic syntheses of glycosidic osmolytes such as 2-O-α-D-glucosyl-D-glycerate often involve the action of a glycoside phosphorylase. Here, we report the discovery of a glucosylglycerate phosphorylase from carbohydrate-active enzyme family GH13 that is also active on sucrose, which contrasts the strict specificity of known glucosylglycerate phosphorylases that can only use α-D-glucose 1-phosphate as glycosyl donor in transglycosylation reactions. The novel enzyme can be distinguished from other phosphorylases from the same family by the presence of an atypical conserved sequence motif at specificity-determining positions in the active site. The promiscuity of the sucrose-active glucosylglycerate phosphorylase can be exploited for the high-yielding and rapid synthesis of 2-O-α-D-glucosyl-D-glycerate from sucrose and D-glycerate. KEY POINTS: • A Xylanimonas protaetiae glycoside phosphorylase can use both d-glycerate and fructose as glucosyl acceptor with high catalytic efficiency • Biocatalytic synthesis of the osmolyte 2-O-α-d-glucosyl-d-glycerate • Positions in the active site of GH13 phosphorylases act as convenient specificity fingerprints.

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.

Jinshanibacter allomyrinae sp. nov., isolated from larvae of Allomyrina dichotoma, proposal of Insectihabitans xujianqingii gen. nov., comb. nov. and emended descriptions of the genera Jinshanibacter, Limnobaculum and Pragia

Taxonomic positions of four Gram-negative bacterial strains, which were isolated from larvae of two insects in Jeju, Republic of Korea, were determined by a polyphasic approach. Strains CWB-B4, CWB-B41 and CWB-B43 were recovered from larvae of Protaetia brevitarsis seulensis, whereas strain BWR-B9^T was from larvae of Allomyrina dichotoma. All the isolates grew at 10-37 °C, at pH 5.0-9.0 and in the presence of 4 % (w/v) NaCl. The 16S rRNA gene phylogeny showed that the four isolates formed two distinct sublines within the order Enterobacteriales and closely associated with members of the genus Jinshanibacter. The first group represented by strain CWB-B4 formed a tight cluster with Jinshanibacter xujianqingii CF-1111^T (99.3 % sequence similarity), whereas strain BWR-B9^T was most closely related to Jinshanibacter zhutongyuii CF-458^T (99.5 % sequence similarity). The 92 core gene analysis showed that the isolates belonged to the family Budviciaceae and supported the clustering shown in 16S rRNA gene phylogeny. The genomic DNA G+C content of the isolates was 45.2 mol%. A combination of overall genomic relatedness and phenotypic distinctness supported that three isolates from Protaetia brevitarsis seulensis are different strains of Jinshanibacter xujianqingii, whereas one isolate from Allomyrina dichotoma represents a new species of the genus Jinshanibacter. On the basis of results obtained here, Jinshanibacter allomyrinae sp. nov. (type strain BWR-B9^T=KACC 22153^T=NBRC 114879^T) and Insectihabitans xujianqingii gen. nov., comb. nov. are proposed, with the emended descriptions of the genera Jinshanibacter, Limnobaculum and Pragia.

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

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 607^T and L. lactis subsp. tructae L105^T 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 607^T (=ATCC 19257^T=DSM 20069^T=JCM 16167^T=LMG 6897^T=NBRC 100676^T). The type strain of L. cremoris subsp. tructae comb. nov. is L105^T (=NBRC 110453^T=DSM 21502^T=JCM 31125^T=LMG 24662^T).