Clone Library Analysis Of The Microbial Community In Dripping Waters Of Karst Cave

Karst is a general term describing surface or subsurface geomorphologic shapes usasualy at carbornate area, which were formed by the corrosion of water. In karst abundant area, the ground surface ususlly is characterized by marvelous peaks. The surface water system are lacking while the ground water systems are comparatively well developed. Cave is one of the subsurface karst landform which could hold different karst depeposits such as stalagmite.The stalagmites, as the products of interactive process among the atmosphere, hydrosphere, biosphere, and lithosphere, well record the climate change. Due to their high resolution in record and highly closed system, stalagmites now have become one of the most valuable geological archives to investigate the continental paleoenvironments and paleoclimates. Recent years, much progress has been made in reconstructing the past climate and environment change through the geochemistry index of cave sediment, such as the sediment character, substance component and isotope composition. The stalagmites are of great significance in the Quaternary research with the following advantages: (1) long time-spin, (2) high sensitivity and (3) rich paleoclimates information. It's found that the trace lipids, which originated from organism, preserved in stalagmites are sensitive and showed good relationship with climate change. Furth more, some of the lipids come from microbe whilst others indicate micribal alteration. Thus, the investigation of cave microbe will have important value to reveal the origin of organic compounds in stalagmites, the function of microorganism in stalagmites formation and the reconstruction of the other organic compounds by microbe, moreover, it will provide microbial index to paleoclimates change.In early period, microbial information in environmental samples maily depended on traditional pure culture method. However, only 0.1 percent to 1 percent microbe can be recovered through the technique. With the rapid development of molecular biological technique, genetic information of most uncultured organism can be obtained through DNA amplification in vitro and thus become a routine work in most research labs. Most ongoing research nowadays of cave microorganisms included the microbial distribution in one or several caves, their function in the formation of minerals and rocks. No research on seasonal changes of microbial community, especially the relationship beween microbial change and global climate change is conducted up tp date. This paper reveals some of the blind region.This study focuses on the HS-4 stalagmite in Heshang cave, Qingjiang, Hubei, using the 16S rDNA clone library analysis method. The purpose is to investigate the bacteria community in the dripping water from HS-3D and construct phylogentic trees. Finally we try to reveal the seasonal changes of the dripping water bacteria community group with time, explore correlation between such changes with climate change, and establish new microbial index in the ancient climate reconstruction.Eleven clones were obtained through 16S ribosome DNA clone library analysis of the HS-3D diripping waters in Feb, May, Aug, Nov, 2006. The NCBI search showed that they respectively had the highest genetic relationship with strains or clones of Acinetobacter,α-proteobacteria, Cytophagales,β- proteobacteria, Acidovorax. A wide view of the microbe in HS-3D, Feb's were rather simple, which all belong to Acinetobacter, Nov's took the second place, May's and Aug's were relatively diverse. Bacteria in each months differed widely and presented a better seasonal transformation.Due to the scarce clones recoved in this study and relative short time period, it is still early to draw any conclusion about the whole picture of the microbial community concerning the seasonal changes. Nevertheless this experiment obtained some of the bacteria that can not be cultured by traditional methods.Thus, the datum got from this method are more comprehensive than from the way of pure culture. If the study can be carried on, and the research methods can be improved, more sequences are obtained from each month, better relations will be interpreted between the microorganisms and the inside environment as well as the climate change response. Moreover, it can provide a reliable source of the molecular microbiology data for the stalagmite inside lipoid, which will also be able to play an important role in reconstruction of the ancient climate.