Research On The Mechanism Of Carbonate Minerals Induced By Bacillus Subtilis YXY1 And Characteristics Of Biominerals

Period of sea was divided calcite sea period and aragonite sea period according to whether it was benefied for calcite precipitation or aragonite precipitation by former researchers,the important difference of them is Mg/Ca molar ratio of the sea water,besides,microorganism,as the important factor widely distributed on the earthy plays an important role in the precipitation of carbonate minerals in the sea,and the mechanism of process and the mineralogical characteristics of mineral need more exploration.Bacillus subtilis YXY1 saved in our laboratory was used to induce.carbonate minerals in the liquid culture medium with 10%salinity,five Mg/Ca molar ratios(0,2,4,6,8)to simulate sea water,and the control group without bacteria was set as well as preparation of inorganogenic calcite at the same time.In order to research the mechanism of carbonate minerals induced by microbe,growth curve,pH curve,NH32-and HCO3-concentration and carbonic anhydrase activity curve for bacterial suspension were measured.XRD,SEM(EDX),polarizing microscope and FTIR were used to analyze minerals induced by Bacillus subtilis YXY1,the microbiogenic stromatolite,abiogenic wormkalk formed in the geologic history and inorganogenic calcite were analyzed to research the mineralogical characteristics of carbonate minerals induced by microbe.The result of research demonstrates that:Bacillus subtilis YXY1 has good ability to induce carbonate mineral precipitate by means of the physiological and biochemical results.In the experimental group,when the Mg/Ca molar ratio is 0,the induced precipitate is calcite and infinitesimal vaterite after 14 days of culture,and after 24 days of culture,the induced precipitate is calcite,the crystallinity of calcite increases with the extension of culture time;when the Mg/Ca molar ratio is 2,the induced precipitate is calcite whether 14 days of culture or 24 days,the crystallinity of calcite decreases with the extension of culture time,for the calcite formed at Mg/Ca molar ratio 0 and 2,its crystallinity decreases with the increasing of Mg/Ca molar ratio,so Mg2+ can destroy the crystal structure of calcite;Calcite,Mg-rich formed at Mg/Ca molar ratio 4,the phase did not change but crystallinity reduced and the content of magnesium carbonate increased from 10.90%to 13.04%with the extension of culture time.When the Mg/Ca molar ratio is 6 and 8,the induced precipitate is aragonite,yet the phase did not change,the crystallinity of aragonite decrease with the increasing of Mg/Ca molar ratio and the extension of culture time.All of this demonstrates that bacillus subtilis YXY1 facilitates to form some kinds of typical carbonate minerals,and the minerals induced by bacillus subtilis have many kinds of morphologies and obvious microbial traces including microorganism attached to the mineral surface,microbial remains on the mineral surface,biomarker elements and lots of organic functional groups contained in minerals.The analysis result of field samples and inorganogenic calcite shows that stromatolite in comparison to wormkalk formed in the geologic history has organic functional groups,and the former has bigger crystallinity for calcite,in accord with the characteristics of calcite formed at Mg/Ca molar ratio 0 and inorganogenic calcite.The thesis is not only to provide some reference for the characteristics and mechanism of microbial induced carbonate minerals in the laboratory,but also to provide some reference for the research of carbonate mineral precipitate in the calcite sea and aragonite sea and field limestone sample.