Biodiversity Of Bacteria In The Profiles Of Yellow-Brown Soil Derived From Different Soil Parent Materials And Their Effects On Potassium-Bearing Mineral Weathering

Soil microbial diversity is the difference related to microbial communities and species, including species diversity, genetic diversity, ecological diversity and functional diversity. Researches on bacterial diversity will further understand microbial resource and biodiversity, enrich pool of microbial resource and gene, clarify the relationship between biodiversity and soil physicochemical factors, obtain efficient strains to weather mineral, and offer the theoretical and experimental basis for mineral weathering and soil formation.16S rRNA gene sequence clone library and denaturing gradient gel electrophoresis (DGGE) were used to analyze bacterial biodiversity of two soil profiles sampled at site A (Longshan) and site B (Houhan Road). The results showed that there were13bacterial communities in site A and the major communities were γ-Proteobacteria, Acidobacteria, Actinobacteria, Firmicutes and Chloroflexi; while at site B, there were9bacterial communities, and the dominant communities were y-Proteobacteria, Actinobacteria, Acidobacteria. Actinobacteria, Acidobacteria and γ-Peoteobacteria were the same dominant phyla in both profiles. The major bacterial communities varied with soil depth. In profile A, clones of y-Proteobacteria mainly distributed layer-L2, and clones affiliated to Acidobacteria decreased with soil depth. The numbers of clone of Chloroflexi and Firmicutes mainly distributes in layer-L3. In profile B, the proportion of Acidobacteria and Verrucomicrobia decreased with soil depth, and the most abundant Actinobacteria was in profile B-H2, while clones of y-Peoteobacteria mainly distributed in H3and H4. The major communities were Proteobacteria, Actinobacteria, Bacteroidetes, Acidobacteria, Firmicutes and Chloroflexi at site A by DGGE, and the dominant genera were Rhodoplanes, Pseudomonas、Serratia and Arthrobacter. While at site B, the major phyla were y-Proteobacteria, Bacteroidetes, Actinobacteria and Acidobacteria, and the dominant genera were Pseudomonas, Serralia and Arthrobacter. Principal component analysis (PCA) suggested soil bacterial biodiversity was affected by soil physical and chemical factors such as soil pH, organic matter, effective Fe and Al, soil rapidly available phosphorus and available potassium. Canonical Correlation Analysis indicated bacteria affiliated to y-Proteobacteria were sensitive to soil available Al (r=-0.8, P<0.05), and bacteria affiliated to Acidobacteria were positive related to effective phosphorus significantly (r=0.99, P<0.05) at site A. At site B, bacteria affiliated to y-Proteobacteria were positive related to effective phosphorus and available potassium significantly (r=0.94, P<0.05; r=0.99, P<0.05). Arthrobacter affiliated to Actinobacteria were reported to have the ability to weather minerals in soil.Thirty-six strains were separated from the two soil profiles by dilution plate method using potassium-limited medium.16S rRNA gene sequences revealed that36strains were grouped to9genera affiliated to3phyla, that is Bacillus, Paenibacillus, Dyella, Pantoea, Burkholderia, Nocardioides, Isoptericola, Microbacterium and Arthrobacter. Bacillus, Paenibacillus, Arthrobacter and Burkholderia were the common genera in both profiles, which showed abundant species diversity.Strain H17had the highest similarities with Isoptericola spp., and showed97.8%-99.6%sequence similarities with the other strains. The cell-wall peptidoglycan type of strain H17is L-Lys-D-Asp. The whole-cell sugars are galactose, xylose and mannose. The major fatty acids (>10%of total) are anteiso-C15:0and iso-C15:0.The total polar lipids are diphosphatidylglycerol, phosphatidylglycerol, phospholipids, phosphatidylinositol, phosphoglycolipid, one unidentified glycolipid and one unidentified lipid. The menaquinone of strain H17T is MK9(H4). Mycolic acids were not detected. The DNA-DNA relatedness studies showed relatively low rates with the type strains of I. variabilis MX5T (45.6%), I. hypogeus HKI0342T(37.9%), I. jiangsuensis CLGT (33.4%), I. dokdonensis DS-3T (33.4%), I. halotolerans YIM70177T (40.9%) and I.chiayiensis06182M-1T (15.2%). The DNA G+C content of the type strain is72.4mol%. These results indicated that strain H17T represents a novel species of the genus Isoptericola, for which the name Isoptericola nanjingensis sp. nov. is proposed.Strains Lll, H5and H15derived from different species were tested to weather potassium feldspar by shaking culture. The concentration of Fe, Si and Al increased27.5-115,1.5-2.2and13-35times than controls, respectively, by inductively coupled plasma optical emission spectrometry (ICP-OES). Scanning electron microscope (SEM) analisis showed that there were many corrosion pits in the surface of potassium feldspar, and spherical and small graininess around the mineral, while there was nothing around controls. These spherical and small graininess were the oxide of Fe and Ca, and were speculated to be secondary minerals. In addition, weathering effects of the strain Q12to micas (biotite, muscovite and phlogopite) were also studied. The concentration of Fe, Si, Al and K increased9-173%,9-18%,10-310%and9-29%compared to the controls according to ICP-AES, respectively. Biofilms were formed in the surface of micas after interactions with strain Q12by SEM. Some cotton-shaped, graininess and acicular materials were found around micas, which were identified to calcite and hematite by X-ray energy dispersive spectrum (EDS). X-ray diffraction (XRD) demonstrated that haematite and Mg-bearing turface were formed after interaction between the strain Q12and biotite. Transmission electron microscope (TEM) revealed small grains were adsorbed by bacterial cells.Sand culture experiment showed the strains L11and H5could accelerate weathering of potassium feldspar, promote the growth of rice plants and increase utilization of potassium by rice plants. SEM indicated strain L11, H5and H15could colonize the surfaces of potassium feldspar and the rhizosphere of rice plants, and spheroidal, cluster-shaped, polyhedron and acicular materials were also found. These materials were speculated to be calcite, calcium oxalate, hematite and magnetite by EDS.