Use of the MIDI-FAME technique to characterize groundwater communities

Fatty acid methyl ester (FAME) profiles were identified directly from groun dwater microbial communities concentrated on and extracted with polycarbona te filters. The sensitivity of this direct extraction method was determined using pure cultures of Acinetobacter junii, Pseudomonas putida and Stenotr ophomonas maltophilia. A minimum concentration of 10(7) cells filter(-1) wa s required to identify the predominant fatty acids from each culture. Howev er, at least 3.7 x 10(9) cells filter(-1) were required to obtain fatty aci d profiles that matched the signature profiles for pure cultures in a comme rcial database. While several saturated fatty acids (i.e. 14 : 0, 16 : 0, 1 8 : 0) were extracted from the polycarbonate filters, they were readily sub tracted from microbial fatty acid profiles and did not interfere with the c haracterization of pure cultures or environmental samples. For the environm ental samples, 3 l of groundwater from the Savannah River Site, Aiken, SC, (USA) contained sufficient biomass for direct extraction. A comparative ana lysis of FAME groundwater profiles demonstrated a qualitative difference am ong communities sampled from spatially discrete locations, while a groundwa ter well that was sampled at two time points showed strong similarities ove r time. Concentration of microbial biomass on polycarbonate filters coupled with the MIDI-FAME extraction of both biomass and filter was a useful tech nique to characterize microbial communities from groundwater.