COMBINED MICROBIAL COMMUNITY-LEVEL ANALYSES FOR QUALITY ASSURANCE OF TERRESTRIAL SUBSURFACE CORES

Bacterial communities from surface soils, groundwater, drilling muds and deep subsurface cores were profiled by sole carbon source utilization and by phospholipid ester-linked fatty acid analysis. The combination of these functional and structural methods successfully distinguished communities from disparate origins. Multivariate analysis of the data showed good agreement between the results of the two methods. Subsurface communities tended to respire amino acids over carbohydrates and demonstrated preferential use of individual compounds such as acetate and Tween as sole carbon sources. PLFA profiles indicated that the groundwaters predominately contained gram negative aerobic heterotrophic populations, the drilling muds and cuttings were populated by gram negative anaerobes and the core communities were composed of anaerobic gram negative bacteria and gram positive bacteria. The utility of this approach as a component of quality assurance of core samples obtained for microbiological analysis during mud rotary coring was demonstrated. Monitoring of controlled bioprocesses, environmental remediation and detection of environmental disturbance are some of the numerous potential applications for these community-level characterization methods. Since combined analyses such as these can simultaneously provide specific information about individual community members and about community-level function, it is hoped that these methods will prove useful in answering fundamental questions in microbial ecology, such as the relationship between in situ community structure and its measurable function.