Characterization of microbial communities of biofilters by phospholipid fatty acid analysis and rRNA targeted oligonucleotide probes

The microbial community of a biofilter for waste gas treatment of an animal rendering plant was characterized by the analyses of the phospholipid fatt y acids (PLFAs) of the filter material. For these analyses five samples of one filter were taken in intervals between one and two months. The main com ponents of the PLFA profiles were straight chain saturated, monounsaturated and cyclopropyl fatty acids. Terminally branched and 10-methyl branched fa tty acids were present in minor amounts. The structure and succession of th e microbial community was interpreted by the presence and quantitative chan ges of diagnostic fatty acids. The stability of diagnostic fatty acids in r elation to varying incubation parameters was tested for a number of bacteri al isolates from biofilters representing different phylogenetic branches. F or two samples, the data from the PLFA-analyses were compared with data obt ained by hybridization with fluorescently labeled, rRNA-targeted oligonucle otide probes specific for the alpha-, beta- and gamma-subclass of the Prote obacteria, the Actinobacteria (Firmicutes with high G+C content) and the Fi rmicutes with low G+C content. These data indicated a dominating number of Proteobacteria (54% and 35% of DAPI-stained cells), in which the gamma-Prot eobacteria represented the main fraction. Actinobacteria were detected in m inor amounts, the number of Firmicutes with low G+C content was near the de tection limit of the method. About half of the cells detected with a probe specific fur Bacteria did not hybridize with the probes specific for the al pha-, beta- and gamma subclass of the Pruteobacteria and the two subgroups of the Firmicutes. The results of both methods, the fluorescence in situ hy bridization (FISH) and the PLFA analyses corresponded well and were best su ited to confirm and complement each other.