Potassic Trachyte-Associated Bacterial Communities And Their Involvement In Rock Weathering

Potassic trachyte, mostly consisting of alkali feldspar, is a kind of widely distributed volcanic rock. Interaction between bacteria and rock (mineral) is one of the most important phenomenons occurred at earth’s surface and its vicinity. It plays an impotant role in rock or mineral weathering, the biogeochemical cycling of elements, the formation of soil, and the maintenance of soil fertility. In a long time scale, rock (mineral) weathering will have an important impact on soil environment and the concentration of carbo dioxide.In the study of the weathering process of potassic tracyte in situ, we found that the coverage of lichen and moss on the surface of potassic tracyte accleate the weathering process significantly. However there is no study about the influence of lichen and moss on the bacterial communities of potassic tracyte and their rock weathering efficacy. In this study, we used pyrosequencing and culture-dependent methodology to characterize bacterial populations of potassic trachyte samples in different microhabitats and their involvement in rock weathering. Sample Ⅰ and sample Ⅲ were covered by lichen and moss, repectively. While, the surface of sample Ⅱ was bare. Canonical correlation analysis was used to analyze the correlations between the relative abundance of bacterial groups and physiochemical characterizations of potassic trachyte samples. Strain JN53, with the ability of dissolving potassic trachyte, was identified as a new species of Chitinophaga. This isolate was used to study the influence of nutrient limitation on bacterial weathering efficacy of different minerals.Sequences provided by 454 pyrosequencing revealed that the numbers of Operational Taxonomic Unit of both sample Ⅰ and sample Ⅲ were almost twice of the OTU number of sample Ⅱ. The diversities of bacterial community of both sample Ⅰ and sample Ⅲ were significantly higher than those of sample Ⅱ, and the evenness of bacterial community of sample Ⅲ was higher than that of sample Ⅰ. Phylogenetic analysis showed that the bacterial groups of potassic tracyte samples belong to 16 phyla and a few unknown bacterial groups (2.25%). Actinobacteria took up the largest proportion (72.3% of sample I,77.8% of sample Ⅱ, and 62% of sample Ⅲ), and then were Proteobacteria and Acidobacteria. Among all of these phyla, Chlamydiae and Verrucomicrobia were detected both in sample Ⅰ and sample Ⅲ, Fusobacteria and Spirochaetes were detected both in sample Ⅱ and sample Ⅲ, Planctomycetes was only detected in sample Ⅱ, and Deinococcus-Thermus was only detected in sample Ⅲ.Principle coordinate analysis and UPGMA clustering analysis were used to compare the bacterial communities of the three samples. The results indicated that potassic trycate samples covered by linchen and moss share similar bacterial community compared with bacterial community of the exposed potassic trycate. Correlation analysis indicated that the contents of available K, Si and A1 of the potassic tracyte samples significantly affected the abundances of the 3 dominant bacterial groups (Actinobacteria, Proteobacteria and Acidobacteria). The significantly positive correlations were found between the contents of available Al, Si and Acidobacteria (r= 0.623-0.724, p< 0.01). Another significantly positive correlation was found between the content of available K and Actinobacteria (r= 0.621, p< 0.01). The significantly negative correlation was found between content of available K and Acidobacteria, Proteobacteria (r=-0.591--0.574, p< 0.01). Another significantly negative correlation was found between the content of available Si and Actinobacteria (r=-0.560,P< 0.01).With the culture-dependent methodology,270 bacterial isolates were obtained from the surfaces of different samples. All of these 270 bacterial isolates showed the ability of dissolving potassic tracyte in situ. The proportion of tested strains which released Fe, Si, Al and K significantly were 67%,93%,95% and 65%, respectively. Take into account the number of isolates which had the ability of releasing Fe, Si and A1 at the same time, and amount of available elements released by rock weathering bacteria, the rock dissolution ability of the bacterial isolates from sample Ⅲ was significantly greater than that of bacterial isolates from sample Ⅰ, and the mineral dissolution ability of the bacterial isolates from sample Ⅰ was significantly greater than that of bacterial isolates from sample Ⅱ. The acids-production ability of tested bacterial isolates showed the same trend, and the significantly negative correlations were found between the pH value and the concentrations of Fe, Si, Al and K in culture solutions (r=-0.855～-0.488, p< 0.01). Phylogenetic analysis showed that all of these rock wethering bacteria were affiliated with 25 genera, which belong to Proteobacteria, Actinobacteria and Bacteroidetes. Among all these genera, Bacillus (52.6%), Arthrobacter (9.2%) and Sinomonas (5.6%) were dominant genera, which detected in all the samples.10 genera were only dectected in sample Ⅰ, Janthinobacterium was only detected in sample Ⅱ, Cohnella、Sphingomonas、Dyella and Enterobacter were only detected in sample Ⅲ. Rock weathering bacteria belong to Burkholderia, Mesorhizobium, Dyella, and Ralstonia showed stronger ability of dissolving potassic tracyte in situ. Study on the kinetics of the dissolution of potassic tracyte in situ and the pattern of elements release, indicated that the release patterns of Fe, Si, Al and K of strain JN197 was qutite different from those of strain JN73 and strain JN111.The rock weathering bacterial strain JN53 was related most closely to Chitinophaga terrae KP01T (97.3% 16S r RNA gene sequence similarity), Chitinophaga eiseniae YC6729T (96.3%). It contained MK-7 as the major menaquinone and homospermidine as the major polymine. The main fatty acids of strain JN53T were iso-C15:0, C16:1ω5c, C16:1ω7c and/or C16:1ω6c, iso-C17:0 3-OH, C16:0, iso-C15:0 3-OH, and C16:0 3-OH. The polar lipid profile contained phosphatidylethanolamine, unknown aminolipids and unknown lipids. The total DNA G+ C content of strain JN53T was 49.7 mol%. The low level of DNA-DNA relatedness to other species of the genus Chitinophaga and the many phenotypic properties that distinguished strain JN53T from recognized species of this genus demonstrated that isolate JN53T should be classified as representing a novel species of the genus Chitinophaga. The name Chitinophaga Jiangningensis sp. nov. is proposed for this novel species. Bacterial isolates belong to Chitinophaga have not been reported for their mineral weathering ability.Strain JN53 was used to study the influence of nutrient limitation on the weathering efficacy of different minerals, such as biotite, feldspar and quartz. The results indicated that, when in SSKM (with limited K), the contents of dissolved Fe and Al form biotite were increased by 34-and 91-fold respectively compared to the no-inoculated control, and the contents of dissolved Fe and Al from feldspar were increased by 2-and 93-fold respectively. When in BHm (lack of Fe and K), the content of dissolved K from biotite was increased by 13-fold compared to the no-inoculated control. However, strain JN53 did not show the ability of dissolving quartz.