In situ probing reveals Aquabacterium commune as a widespread and highly abundant bacterial species in drinking water biofilms

Drinking water biofilm communities originated from distribution systems in Hamburg, Berlin, Mainz and Stockholm were subjected to a top-to-bottom in s itu analysis with rRNA-targeted, fluorescently labeled oligonucleotide prob es including: beta1-8. specific for drinking water bacteria within the beta -subclass of Proteobacteria. Independent from the raw water source used, be tween 19 and 77% of the total attached bacterial cell counts on polyethylen slides could be hybridized with probes beta1-8 and 19-53% of the bacteria were affiliated to the autochthonous species Aquabacterium commune. To inve stigate seasonal fluctuations of the bacterial population composition, poly ethylen slides exposed during different times of the year were analyzed. Al though changes in the species composition of the biofilms could be observed , A. commune was a dominant community member in all of the investigated bio films. lit situ probing with two oligonucleotide probes specific for A. com mune revealed that during distinct sampling times an additional yet unknown species was present in the biofilm, Material induced population shifts wer e studied using glass, polyethylene low and high density and soft-PVC as bi ofilm substrata. The community composition on soft-PVC differed significant ly from the other materials, the dominant species A. commune was replaced b y other beta-Proteobacteria hybridizing to an amount of 66% with the Aquaba cterium citratiphilum specific probe beta4. (C) 1999 Elsevier Science Ltd. All rights reserved.