High abundance and widespread distribution of the archaeal phylum Bathyarchaeota in marine environment have been recognized recently, but knowledge about Bathyarchaeota in terrestrial settings and their correlation with environmental parameters is fairly limited. Here we reported the abundance of Bathyarchaeota members across different ecosystems and their correlation with environmental factors by constructing 16S rRNA clone libraries of peat from the Dajiuhu Peatland, coupling with bioinformatics analysis of 16S rRNA data available to date in NCBI database. In total, 1456 Bathyarchaeota sequences from 28 sites were subjected to UniFrac analysis based on phylogenetic distance and multivariate regression tree analysis of taxonomy. Both phylogenetic and taxon-based approaches showed that salinity, total organic carbon and temperature significantly influenced the distribution of Bathyarchaeota across different terrestrial habitats. By applying the ecological concept of ‘indicator species’, we identify 9 indicator groups among the 6 habitats with the most in the estuary sediments. Network analysis showed that members of Bathyarchaeota formed the “backbone” of archaeal community and often co-occurred with Methanomicrobia. These results suggest that Bathyarchaeota may play an important ecological role within archaeal communities via a potential symbiotic association with Methanomicrobia. Our results shed light on understanding of the biogeography, potential functions of Bathyarchaeota and environment conditions that influence Bathyarchaea distribution in terrestrial settings.

Caves are nutrient-limited and dark subterranean ecosystems. To date, attention has been focused on geological research of caves in China, whilst indigenous microbial diversity has been insufficiently characterized. Here, we report the fungal diversity in the pristine, oligotrophic, karst Heshang Cave, central China, using a culture-dependent method coupled with the analysis of the fungal rRNA-ITS gene sequences. A total of 194 isolates were obtained with six different media from 14 sampling sites of sediments, weathered rocks, and bat guanos. Phylogenetic analysis clustered the 194 sequenced isolates into 33 genera within 15 orders of three phyla, Ascomycota, Basidiomycota, and Zygomycota, indicating a high degree of fungal diversity in the Heshang Cave. Notably, 16 out of the 36 fungal genera were also frequently observed in solution caves around the world and 23 genera were previously found in carbonate cave, indicating potential similarities among fungal communities in cave ecosystems. However, 10 genera in this study were not reported previously in any solution caves, thus expanding our knowledge about fungal diversity in cave ecosystems. Moreover, culturable fungal diversity varied from one habitat to another within the cave, being the highest in sediments, followed by weathered rocks and bat guanos as indicated by α-diversity indexes. At the genus level, Penicillium accounted for 40, 54, and 52% in three habitats of sediments, weathered rocks, and bat guanos, respectively. Trichoderma, Paecilomyces, and Aspergillus accounted for 9, 22, and 37% in the above habitats, correspondingly. Despite of the dominance of Penicillium in all samples, β-diversity index indicated significant differences between each two fungal communities in the three habitats in view of both the composition and abundance. Our study is the first report on fungal communities in a natural pristine solution cave system in central China and sheds light on fungal diversity and functions in cave ecosystems.

No abstract

Deciphering of the mycobiome in pristine karst caves has been impeded by constraints of remote locations, inaccessibility to specimens and technical limitations, which greatly restricted in-depth understanding of mycobiomes in subterranean ecosystem. Here, mycobiomes of Heshang Cave in south-western karst region of China were investigated by Illumina HiSeq sequencing of fungal rRNA-ITS1 gene across different habitats. In total 793,502 ITS1 reads and 2,179 OTUs from 778 Mb reads after stringent quality control (Q30) and 453 genera, 72 orders and 19 classes within 6 phyla were detected. Ascomycota (42% OTUs) dominated across the five habitats. Shannon-Wiener index varied from 1.25 to 7.62 and community richness was highest in drip waters, followed by weathered rocks, bat guanos, sediments, and air samples. Mycobiomes displayed specificity to five habitats and more distinct OTUs were found in weathered rocks (12%) and drip waters (9%). In contrast, only 6.60% core OTUs were shared by five habitats. Notably, weathered rocks possessed more indicator groups and were revealed for the first time to be dominated by Sordariomycetes (43%). The community richness of air mycobiomes increased from cave entrance to the innermost part and dominated by the indicator groups of Penicillium mallochii (>30%) and P. herquei (>9%). Our work represents the largest attempt to date to a systematical investigation of oligotrophic solution-cave-associated mycobiomes in China. Our discovery of high diversity of mycobiomes in Heshang Cave also suggests that eukaryotic microorganisms may play a crucial role in subsurface environments.

Microbial lipids in stalagmites are increasingly used to reconstruct the paleoclimate change, necessitating the investigations on microbial communities in dripping waters. A pilot molecular survey was conducted on bacterial communities of dripping waters at two sites (1D and 3D) in Heshang Cave of Hubei province in central China for a period of 2008 to 2013. The samples were subjected to genome DNA extraction, 16S rRNA gene amplification, clone library construction and phylogenetic analysis to explore the seasonal variation of bacterial communities and their association with environmental factors including regional air temperature， precipitation, cave temperature, pH, conductivity and dripping rate of the water samples. Seasonal variations were clearly observed in components and diversities of bacterial communities at both sites. Bacterial community was dominated by Gammaproteobacteria in autumn and winter, whereasDownloaded by [FU Berlin] at 04:42 04 July 2015 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2Betaproteobacteria became dominant in samples collected in summer and spring. Among the environmental factors investigated, regional air temperature was found to have a strong impact on bacterial communities indicated by cluster and redundancy analysis. Moreover the bacterial biodiversity was observed to increase with the temperature rising. Bacteria identified in dripping water were either oligotrophs or able to acquire nutrients from minerals under oligotrophic conditions. They may also be able to induce calcite precipitation in cave systems. Our data shed light on the potential of microbes used as a tool for the reconstruction of paleo-temperature as well as on the ecological functions of bacterial communities in oligotrophic caves.