DIVERSITY OF CALCIUM CARBONATE PRECIPITATING BACTERIA IN FORT STANTON AND LECHUGUILLA CAVES

There is debate among the scientific community as to the role that bacteria play in the development of speleothems, specifically in carbonate speleothems. To shed further light on this debate, we undertook a study of the biodiversity associated with cave carbonate pool precipitates and water flowing over an actively precipitating calcite river (Snowy River) within a cave to look for the presence of known calcium carbonate precipitating bacteria.

In order to determine the diversity among the bacteria found on these calcite speleothems, water and calcite samples were collected aseptically from on or near the carbonate deposits. The samples were then extracted, the 16S gene was amplified, and cloned to create clone libraries for sequencing at the University of Washington High-Throughput Facility. To test whether bacteria were present that possess the capability to precipitate calcite, carbonate surfaces both below and above the water line of pools in Lechuguilla Cave and Snowy River in Fort Stanton were swabs with sterile rayon swabs and inoculated onto ½ R2A and R2A media on site. Cultures were subcultured to produce putatively pure cultures and then transferred to B4 medium to assess calcite production. Approximately 50% of the isolated bacteria that were able to grow on the calcium-rich B4 medium precipitated calcite. Gram-staining showed rods and clustered coccoid-shaped bacteria, suggesting there are a variety of bacteria that precipitate.

Using phylogenetic and community analyses we show that several of the bacteria associated with calcite formations are related to known calcite precipitating bacteria and that differences exist between communities of bacteria associated with the flowing river and standing pool calcite habitats. These results suggest that bacteria are present in caves that can precipitate calcite and that further research into the role that bacteria play in calcite speleothem formation is warranted.