VARIABILITY OF TYPE 021N IN ACTIVATED-SLUDGE AS DETERMINED BY IN-SITUSUBSTRATE UPTAKE PATTERN AND IN-SITU HYBRIDIZATION WITH FLUORESCENT RIBOSOMAL-RNA-TARGETED PROBES

Bulking sludges were investigated in seven industrial or municipal act ivated sludge treatment plants from Denmark Germany and Australia. The dominating filaments were all identified as type 021N according to th e Eikelboom key. The extent of variability in the filament taxonomy wa s assessed using fluorescence in situ hybridization (FISH) with rRNA-t argeted nucleic acid probes specific for type 021N, Thiothrix and Leuc othrix. Not all of the filaments morphologically identified as type 02 1N hybridized with the 021N probe. In one treatment plant the predomin ant filament hybridized with the probe for Thiothrix and in one treatm ent plant the predominant filament did not hybridize with any of these probes. In none of the plants did filaments hybridize with the probe for Leucothrix. A study of the in situ uptake of different organic sub strates by the various filaments was also conducted using microautogra diography. The uptake of 6 different organic substrates under aerobic conditions was studied by providing C-14 or H-3 labeled substrates (ac etate, glucose, ethanol, glycine, leucine and oleic acid) in incubatio ns of a period of 3 hours. No filaments took up all the tested substra tes, and type 021N from the various treatment plants varied in their u ptake abilities. The study demonstrated that strain differences with r egard to substrate utilization are likely to occur among bacteria with in the same genera and designated types which are indistinguishable on the basis of morphological observations alone and by the molecular pr obes used in this study for identification. Whether there is a clear c orrelation between type of wastewater and the capability of taking up the various organic substrates for the filaments remains to be elucida ted. (C) 1998 LAWQ. Published by Elsevier Science Ltd.