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.
In the past several decades, sulfate concentration and salinity have been considered to be the two essential hydrochemical factors in the formation of dolomite, yet arguments against this hypothesis have existed simultaneously. To clarify the effects of sulfate concentration and salinity in the mineralization of dolomite, we conducted experiments on dolomite precipitation mediated by a halophilic archaeon, Natrinema sp. J7-1with various sulfate concentrations and salinities. This strain was cultured in a series of Modified Growth Media (MGM) with salinities of ¬¬¬140‰, 200‰ and 280‰. Cells in the post-log phase were harvested and used to mediate the formation of dolomite in solutions with various sulfate concentrations of 0 mM, 3 mM, 29.8 mM and 100 mM and salinities of 140‰, 200‰ and 280‰. X-ray Diffraction (XRD) spectra showed that proto-dolomite, monohydrocalcite and aragonite formed in samples with cells, yet only aragonite was detected in samples without cells. Proto-dolomite was found in all biotic samples, regardless of the variation in salinity and sulfate concentration. Moreover, the relative abundances of proto-dolomite in the precipitates were positively correlated with the salinities of the media but were uncorrelated with the sulfate concentrations of the solutions. Scanning Electronic Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) results showed that all the proto-dolomites were sphere or sphere aggregates with a mole ratio of Mg/Ca close to 1.0. No obvious variations in morphology and Mg/Ca were found among samples with various sulfate concentrations or salinities. This work reveals that a variation of sulfate concentration in solution (from 0 mM to 100 mM) does not affect the formation of dolomite mediated by halophilic archaea, but an increase of salinity (from 140‰ to 280‰) enhances this process. Our results indicate that under natural conditions, an increase in salinity may be more significant than the decrease of sulfates in microbe-mediated dolomite formation.
Through the observation of pappi of mature fruits of 6 salicaceous plants(Salix caprea,Salix pentandra,Populus simonii,Populus×canadensis,Populus davidiana,Populus pseudo-simonii),it is founded that these plants in poplar and osier family have similar morpha of pappus.Pappi are hollow and the wall of basal pappi(inserting on placenta) is stoutest in the whole pappus,with placation and transverse.The upper wall of basal plume begins to be fine.The bore of plume are visible enlargement and the biggest in all the diameter of the whole pappus.The adjacent pygidial plate become smaller and smaller,even solid cecum.It is difficult to apply these characters to taxonomic index,but statistical analysis shows visible difference.
Methane (CH 4 ) is a potent greenhouse gas but also an important carbon and energy substrate for some lake food webs. Understanding how CH 4 incorporates into food webs is, therefore, crucial for unraveling CH 4 cycling and its impacts on climate and ecosystems. However, CH 4 -fueled lake food webs from pre-Holocene intervals, particularly during greenhouse climates in Earth history, have received relatively little attention. Here, we present a long-term record of CH 4 -fueled pelagic food webs across the Cretaceous Oceanic Anoxic Event 1a (~120 Mya) that serves as a geological analog to future warming. We show an exceptionally strong expansion of both methanogens and CH 4 -oxidizing bacteria (up to 87% of hopanoid-producing bacteria) during this Event. Grazing on CH 4 -oxidizing bacteria by zooplankton (up to 47% of ciliate diets) within the chemocline transferred substantial CH 4 -derived carbon to the higher trophic levels, representing an important CH 4 sink in the water column. Our findings suggest that as Earth warms, microbial CH 4 cycling could restructure food webs and fundamentally alter carbon and energy flows and trophic pathways in lake ecosystems.
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.
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