Spatial Distribution Of Bacterial On The Potassic Trachyte And Their Effects On Rock Weathering

Microbes exist in various environments, and their effects on the mineral and rock weathering is one of the most important geochemical phenomena. The spatial distribution of bacterial communities on the surfaces of potassic trachyte and bacterial effects on rock weathering were investigated in this study. This work can not only evaluate the changes in bacterial community from rocks to soils but also provide the theoretical basis for understanding the interaction mechamism of bacteria and rocks. Meanwhile, it can enrich the library of mineral weathering bacterial species.Potassic trachyte located at different sites and soil samples were collected from Nanjing Longshan Mountain. The three different sites were2,8, and16m from the bottom of the mountain and were designed as L, M, and H samples respectively, meanwhile the soil samples were designed as S sample. Denaturing gradient gel electrophoresis (DGGE) technology and16S rRNA sequences analysis were used to study the bacterial community sturctures of rock and soil samples. The results showed that bacterial communities from the samples belonged to10order within five phyla:Acidobacteria. Actinobacteria, Chloroflexi, Alphaproteobacteria, Gammaproteobacteria and uncultured bacteria. The Ktedonobacterales populations were common bacterial communities of the four samples and accounted for75%,59%,71%and64%, respectively(H、M、L、S). The unclassified Actinobacteria were only found on the surfaces of M sample. The Chromatiales were only detected in the soil sample.Two hundred of rock-weathering bacteria were isolated from the above potassic trachyte and soil samples. In rock-weathering expexperiment, Fe concentration in solution changed from0.019to7.06mg/L、Si concentration in solution changed from1.701to8.39mg/L、Al concentration in solution changed from0.579to3.77mg/L. The strains which have ability of Fe dissolution accounted for74%,44%,58%and92%, respectively(H、M、 L、S); The strains which have ability of Si dissolution accounted for62%,100%,30%and98%, respectively(H、M、L、S); The strains which have ability of Al dissolution accounted for48%,66%,50%and86%, respectively(H、M、L、S);These strains which have higher ability of Fe. Si、Al dissolution accounted for26%,4%and15%of the total rock weathering bacteria, respectively; The strains of highly siderophore-producing accounted for16%of the total rock weathering bacteria; The strains of effciently acid-producing(pH<3.5) accounted for28%of the total rock weathering bacteria.16S rRNA sequences and phylogenetic analyses revealed that200rock-weathering bacteria belonged to15genera within five phyla:Firmicutes, Actinobacteria, Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria. The genera that occurred most frequently were Bacillus and Arthrobacter. The cellulosimicrobium, Acinetobacte, Curtobacterium, Sphingomonas, Leifsonia, Erwinia and Sinomonas isolates were specific to H sample; The Pseudomonas and Rhizobium were only found on the surfaces of M sample; The Bacillus and Arthrobacter were only detected in the soil sampleIn order to study the elements release with time from rocks in the presence of bacteria, we selected strains H87, M55, L17and S2for15day-shake flask experiment. The elements dissolution (Fe、Si、Al) were in a rising trend in strains M55, L17and S2, as the bacteria entered the decline phase, the element concentrations in solution decreased gradually. Strain H87showed a clear distinction on the behavior of releasing these there elements. The Fe dissolution experienced rising-steady-rising-decreasing process. In Si, Al dissolution, dissolution-precipitation appeared in0-3days, the rate of elements release increased continuously in3-5days; element concentrations in solution were in a downward trend in5-15days. So the behaviors of elements release among four strains were not only in common but also at different patterns.