Biodiversity Of Mineral-weathering Bacterial Communities On The Surfaces Of Altered Tuff And The Mineral-weathering Mechanisms

Tuff is a kind of volcanic clastic rock rich in Al,Si and K elements,tuff weathering plays important roles in the process of soil formation,fertility maintenance and cycling of the geochemical elements.In this study,less and more altered tuff and the soil samples were collected from Fuzhou in Jiangxi.The bacterial communities and diversity of the altered tuff and soil samples were investigated by Illumina Miseq high-throughput sequencing technology.The correlation between bacterial communities and the geochemical factors was also analyzed.The carbon source utilization ability and mineral weathering ability of the bacteria were evaluated through the BIOLOG micro plate system and the cultured method.Furthermore,genomics and transcriptome were used to study the mechanisms involved in the bacterial adhesion influence on the mineral weathering.High-throughput sequencing results showed that the OTU(the Operational Taxonomic Units)numbers of the soil samples(1097)were more than less(733)and more(801)altered tuff rocks.Phylogenetic analysis showed that less and more altered tuff and the soil samples had 24,26,and 30 phyla,respectively.Acidobacteria,Actinobacteria,Proteobacteria and Chloroflexi were the dominant bacterial populations,accounting for77.3%of all bacterial populations.Candidate_division_OP11,Candidate_division_WS6,SHA-109 and Spirochaetae were specific dominant phyla in the soil samples.The typical analysis of geochemical factors and the bacterial populations showed that the pH,available Fe,Mg and Si contents had correlation with populations.The content of available Si had the highest positive correlation with Candidate_division_WS3(R=0.95,P<0.05)and negative correlation with Cyanobacteria(R=-0.93,P<0.05).The content of available Mg had the highest positive correlation with Euryarchaeota(R=0.97,P<0.05)and negative correlation with Cyanobacteria(R=-0.85,P<0.05).The Acidobacteria was the most dominant population which had a significant positive correlation with the contents of available Si(R=0.90,P<0.05)and Mg(0.93,P<0.05)respectively.BIOLOG ECO plate analysis showed that the microbial Richness,Shannon-Wiener index and McIntosh index of the soil samples were significantly higher than the altered tuff samples.One hundred and fifty bacterial strains were isolated from the altered tuff and soil samples.Rock weathering experiment showed that the tested strains coud weather the rocks and release the Fe,Si,and A1 in the solution.Phylogenetic analysis revealed that the strains belonged to 20 species within five major groups,including Actinobacteria,gamma Proteobacteria,Firmicutes,alpha Proteobacteria and beta Proteobacteria.Bacillus was the predominant in the less and more altered tuff,while Arthrobacter was the predominant in the soil sample.Bacillus,Proteus,Enterobacter,Microbacterium,Moraxella,Arthrobacter and Acinetobacter had the higher ablity to weather tuff than other bacterial populations.Physiological,biochemical and molecular genetics methods were taken to identify strain G19.We found that the 16S rRNA sequence of strain G19 showed similarities of97.1%and 97.4%to Bacillus megaterium IAM13418T and Bacillus aryabhattai B8W22T respectively.The major fatty acids of strain G19 were iso-C14:0(6.6%),iso-C15:0(40.6%)and anteiso-C15:0(40.8%).Strain G19 produced special lipids,including phosphatidyl glycerol,phosphatidyl ethanolamine,phosphatidyl glycerol and unclassified lipid.MK-7was the main isoprenoid quinine.The DNA G + C content of strain G19 was 36.7%.DNA-DNA reassociation values between strain G19 with Bacillus megaterium IAM13418T and Bacillus aryabhattai B8W22T were 49.4%and 55.0%.These results indicated that strain G19 represented a novel species of the genus Bacillus,named Bacillus qingshengii sp.nov was proposed.The mineral-weathering Rhizobium sp.S41 was chosen as the tested strain to study the way how bacterial adhesion influenced the process of mineral weathering.Three genes of polS,cpaC and fliF were related to adhesion of Rhizobium sp.S41 according to the genome analysis.The mutant strains of one gene,two genes and three genes were knocked out by homologous recombination,respectively.The adhesion and mineral-weathering abilities of the three-genes-knockout strain were significantly decreased.Transcriptome sequencing technology was used to compare the differences in gene expression between the wild type and the three-genes-knockout mutant strain at different time pionts in the mineral weathering process.There were 1189 differentially expressed-genes in the wild type strain compared with the mutant at 35 min,among which 586 genes were up-regulated and 603genes were down-regulated.At 7 h,only 361 differentially expressed-genes were observed,among which 158 genes were up-regulated and 203 genes were down-regulated.According to gene function annotations,genes coding Peroxidase,Mn-transportor,and Arsenate reductase were all up-regulated at 35 min and 7 h;Based on the analysis of the genomics and transcriptome,15 possible new genes involved in mineral weathering were predicted.