Isolation Of Mineral Weathering Bacteria And The Inhibitory Effect Of Glutamine On Biotite Weathering By Strain S71 And Its Mechanism

As a common phenomenon occurred on the earth's surface,mineral weathering plays an important role in the mineral elements cycling and natural environments.Recently,researchers have focused on the exploitation of microbial resources,mechanism of mineral weathering,preservation of stone cultural relics and improvement of soils quality by mineral-weathering bacteria,but the molecular mechanisms of bacterial-enhanced mineral weathering need to be further investigated.This research aimed at isolating the bacteria which has high potential to dissolute biotite,studying the mechanisms of mineral weathering,and exploring the molecular mechanisms of glutamine on biotite weathering by bacteria.Total 121 strains were isolated from the rhizospheric soils,roots and stems of Rumex acetosa,the potentials to weather biotite of these isolates were studied.Based on amplified rDNA restriction analysis(ARDRA),the bacterial isolates from the rhizospheric soils,roots and stems of Rumex acetosa could be devided into 18 ARDRA types,11 ARDRA types and 6 ARDRA types,respectively.Bacterial isolates from the rhizospheric soils,roots and stems were grouped into 9,7,and 4 genera,respectively.Based on 16S rDNA and rpoB gene sequences analysis,phylogenetic analysis and biochemical characteristics,the efficient mineral-weathering strain S71 was identified as Enterobacter cloacae.About lg/L acetate was produced by strain S71 under the condition of modified BHm medium during the mineral weathering process.Similarity of 16S rDNA sequence of strain Myroides TH-19 was 98.7%-97.5%with the closest type strains Myroides odoratimimus JCM 7460,Myroides profundi D25T and Myroides marinus JS-08.Strain TH-19T contained menaquinone-6 as the predominant menaquinone,and its dominant fatty acids were iso-C15:0 and iso-C17:03-OH.The DNA G+C content of strain TH-19T was 37.2 mol%.The DNA-DNA relatedness values berween strain TH-19T and Myroides odoratimimus JCM 7460T,Myroides profundi D25T and Myroides marinus JS-08T were below 70%.These results indicate that strain TH-19represents a novel species of Myroides genus,for which the name Myroides xuanwuensis sp.nov.was proposed.The potential to weather biotite by strain S71 was strongly inhibited by glutamine.The addition of glutamine could significantly(p<0.05)increase the pH and NH4+-N in the culture solution,but inhibite the acetate production by strain S71 in the culture solution.Furthermore,glutamine could also significantly(p<0.05)inhibite the mineral weathering ability of the bacteria belonged to Enterobacter,Bacillus,Burkholderia,Arthrobacter,Klebsiella and Myroides.Intracellular metabolites of strain S71 were determined by GC-MS.Results showed that contents of intracellular Ala,Val,Gly,Leu,malic acid and succinic acid produced by strain S71 were increased by glutamine.These results indicated that metabolites of pyruvate of strain S71 were influenced by glutamine.The 3-phosphoglycerate and pyruvate were transformed towards to Ala,Val,Gly and Leu in the treatments with Gln,while without Gln,3-phosphoglycerate and pyruvate were transformed toward acetate.The ackA,pta and poxB gene mutants of strain S71 were constructed.There was no significant difference in the mineral weathering ability between the strain S71 and the poxB and pta gene mutants.However,significant differences in the production of acetate and the mineral weathering ability were observed between the strain S71 and ackA gene mutant.