Seasonal Variation of Hypolithic Microbiomes in the Gobi Desert : Seasonal Variation of Hypolithic Microbiomes in the Gobi Desert.

Understanding how microbial communities adapt to environmental stresses is critical for interpreting ecological patterns and microbial diversity. In the case of the Gobi Desert, little is known on the environmental factors that explain hypolithic colonization under quartz stones. By analyzing nine hypolithic communities across an arid gradient and the effects of the season of the year in the Hexi Corridor of this desert, we found a significant decrease in hypolithic colonization rates (from 47.24 to 15.73%) with the increasing drought gradient and found two distinct communities in Hot and Cold samples, which survived or proliferated after a hot or a cold period. While Cold communities showed a greater species diversity and a predominance of Cyanobacteria, Hot communities showed a predominance of members of the Proteobacteria and the Firmicutes. In comparison, Cold communities also possessed stronger functions in the photosynthesis and carbon metabolism. Based on the findings of this study, we proposed that the hypolithic communities of the Hexi Corridor of the Gobi Desert might follow a seasonal developmental cycle in which temperature play an important role. Thus after a critical thermal threshold is crossed, heterotrophic microorganisms predominate in the hot period, while Cyanobacteria predominate in the cold period.

Nocardia mangyaensis sp. nov., a novel actinomycete isolated from crude-oil-contaminated soil.

A Gram-stain-positive, aerobic, non-motile and mycolic-acid-containing strain, designated Y48T, was isolated from soil contaminated by crude oil located in the northern margin of the Qaidam Basin. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain Y48T belongs to the genus Nocardia and is closely related to N. cummidelens DSM 44490T (99.0 % similarity), N. soli DSM 44488T (99.0 %), N. lasii 3C-HV12T (98.9 %), N. salmonicida NBRC 13393T (98.6 %), N. ignorata NBRC 108230T (98.6 %) and N. coubleae NBRC 108252T (98.6 %). The average nucleotide identity and DNA-DNA hybridization values between strain Y48T and the reference strains were 75.9-84.5 and 27.5-29.0 %, respectively, values that were below the thresholds for species delineation. Chemotaxonomic analysis indicated that the major fatty acids of strain Y48T were C16 : 0, summed feature 3 (C16 : 1ω6c/C16 : 1ω7c), C18 : 1ω9c and C18 : 0 10-methyl (TBSA). The respiratory quinone was MK-8(H4, ω-cycl). The polar lipid profile was composed of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside, two glycolipids and three unidentified lipids. The cell-wall hydrolysates contained meso-diaminopimelic acid, with ribose, arabinose, glucose and galactose as whole-cell sugars. A combination of 16S rRNA gene sequence analysis, and phenotypic and chemotaxonomic characterizations demonstrated that strain Y48T represents a novel species of the genus Nocardia, for which the name Nocardia mangyaensis sp. nov. is proposed. The type strain is Y48T (=JCM 32795T=CGMCC 4.7494T).