Chemical characterization and biological effect of exopolysaccharides synthesized by Antarctic yeasts Cystobasidium ongulense AL101 and Leucosporidium yakuticum AL102 on murine innate immune cells.

The current study aimed to investigate exopolysaccharides (EPSs) produced by two Antarctic yeasts isolated from soil and penguin feathers samples collected on Livingston Island (Antarctica). The strains were identified as belonging to the species Leucosporidium yakuticum (LY) and Cystobasidium ongulense (CO) based on molecular genetic analysis. The EPS production was investigated using submerged cultivation. Different chemical, chromatographic, and spectral analyses were employed to characterize EPSs. LY accumulated 5.5 g/L biomass and 4.0 g/L EPS after 120 h of cultivation, while CO synthesized 2.1 g/L EPS at the end of cultivation, and the biomass amount reached 5.5 g/L. LY-EPS was characterized by a higher total carbohydrate content (80%) and a lower protein content (18%) by comparison with CO-EPS (62%, 30%). The LY-EPS mainly consisted of mannose (90 mol%), whereas CO-EPS had also glucose, galactose, and small amounts of uronic acids (8-5 mol%). Spectral analyses (FT-IR and 1D, 2D NMR) revealed that LY-EPS comprised a typical ß-(1 → 4)-mannan. Branched (hetero)mannan, together with ß/α-glucans constituted the majority of CO-EPS. Unlike LY-EPS, which had a high percentage of high molecular weight populations, CO-EPS displayed a large quantity of lower molecular weight fractions and a higher degree of heterogeneity. LY-EPS (100 ng/mL) elevated significantly interferon gamma (IFN-γ) production in splenic murine macrophages and natural killer (NK) cells. The results indicated that newly identified EPSs might affect IFN-γ signaling and in turn, might enhance anti-infectious responses. The data obtained also revealed the potential of EPSs and yeasts for practical application in biochemical engineering and biotechnology.

Myroides guanonis sp. nov., isolated from prehistoric paintings.

A novel psychrotolerant, strictly aerobic, non-motile, rod-shaped bacterial strain, designated IM13(T), was isolated from a sample taken from prehistoric guano paintings in Magura Cave, northwest Bulgaria and subjected to a polyphasic taxonomic study. Strain IM13(T) formed yellow colonies on LB agar plates and was Gram-staining-negative, heterotrophic and alkalitolerant. It grew optimally at pH 7.5 and 30 °C in the absence of NaCl. Phylogenetic analysis of the whole 16S rRNA gene revealed that strain IM13(T) branched with representatives of the genus Myroides with sequence similarity of 93-94 % with other species of the genus. The novel isolate contained iso-C15 : 0 (49.1 %), iso-C17 : 1ω9c (18.2 %) and iso-C17 : 0 3-OH (14.0 %) as dominant fatty acids. The DNA G+C content of strain IM13(T) was 33.5 mol%. Based on phylogenetic inference and phenotypic characteristics, it was concluded that strain IM13(T) represents a novel species of the genus Myroides, for which the name Myroides guanonis sp. nov. is proposed. The type strain is IM13(T) ( = DSM 26542(T) = NBIMCC 8736(T)).