Ganzi Prefecture in Western China is situated geographically at the transition regions between Tibetan Plateau and Sichuan Basin in a highly tectonically active boundary area between the India and Eurasia plates. The region hosts various hot springs that span a wide range of temperature from 30 to 98 °C and are located at high altitude (up to 4200 m above sea level) in the region of large geothermal anomalies and active Xianshuihe slip-fault that has been active since Holocene. The site represents a biodiversity reservoir for thermophiles, yet their diversity and relationship to geochemical parameters are largely unknown. In the present work, bacterial diversity and community structure in 14 hot springs of Ganzi were investigated using Illumina MiSeq sequencing. Bacterial community compositions were evidently distinct among the 14 hot springs, and the bacterial communities in hot springs were majorly abundant in phyla Aquificae, Cyanobacteria and Proteobacteria. Both clustering and PCoA analysis suggested the existence of four bacterial community patterns in these hot springs. Temperature contributed to shaping bacterial community structure of hot springs as revealed by correlation analysis. Abundant unassigned-genus sequences detected in this study strongly implied the presence of novel genera or genetic resources in these hot springs. The diversity of hot springs of Ganzi prefecture in Western Sichuan, China is evidently shaped by temperature. Interestingly disproportionally abundant unassigned-genus sequences detected in this study show indicate potential of novel genera or phylotypes. We hypothesize that frequent earthquakes and rapidly changing environment might have contributed to evolution of these potentially new lineages. Overall, this study provided first insight into the bacterial diversity of hot springs located in Western Sichuan, China and its comparison with other similar communities worldwide.

Marine picocyanobacteria belonging to Synechococcus are major contributors to the global carbon cycle, however the genomic information of its cold-adapted members has been lacking to date. To fill this void the genome of a cold-adapted planktonic cyanobacterium Synechococcus sp. CS-601 (SynAce01) has been sequenced. The genome of the strain contains a single chromosome of approximately 2.75 MBp and GC content of 63.92%. Gene prediction yielded 2984 protein coding sequences and 44 tRNA genes. The genome contained evidence of horizontal gene transfer events during its evolution. CS-601 appears as a transport generalist with some specific adaptation to an oligotrophic marine environment. It has a broad repertoire of transporters of both inorganic and organic nutrients to survive in inhospitable environments. The cold adaptation of the strain exhibited characteristics of a psychrotroph rather than psychrophile. Its salt adaptation strategy is likely to rely on the uptake and synthesis of osmolytes, like glycerol or glycine betaine. Overall, the genome reveals two distinct patterns of adaptation to the inhospitable environment of Antarctica. Adaptation to an oligotrophic marine environment is likely due to an abundance of genes, probably acquired horizontally, that are associated with increased transport of nutrients, osmolytes, and light harvesting. On the other hand, adaptations to low temperatures are likely due to prolonged evolutionary changes.

Aurantiochytrium sp. PKU#SW7 is a thraustochytrid strain that was found to exhibit high potential for docosahexaenoic acid (DHA, C22:6n-3) production. In this work, the transcriptome of Aurantiochytrium sp. PKU#SW7 was analyzed for the study of genes involved in basic metabolic functions and especially in the mechanisms of DHA biosynthesis. Sequence annotation and functional analysis revealed that the strain contains components of fatty acid synthesis (FAS) and polyketide synthase (PKS) pathways. Fatty acid desaturases and elongases were identified as components of FAS pathway, whilst key components of PKS pathway were also found in the cDNA library. The relative contribution of the two pathways to the synthesis of DHA was unknown, as both pathways appeared to be lacking full complement of genes for standalone synthesis of DHA. Further analysis of two putative genes encoding the very-long-chain (3R)-3-hydroxyacyl-CoA dehydratase and dehydrase/isomerase involved in FAS and PKS pathways, respectively, revealed that under various salinity conditions, their relative expression levels changed corresponding to the variation of DHA content in Aurantiochytrium sp. Independent knock outs of these genes in Aurantiochytrium sp. resulted in poor cell growth, probably due to little or no intracellular DHA accumulation. Hence, it can be speculated that both genes are engaged in DHA biosynthesis and DHA in Aurantiochytrium sp. could be produced by jointed actions of both FAS and PKS systems.