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

Abstract

Drinking water biofilm communities originated from distribution systems in Hamburg, Berlin, Mainz and Stockholm were subjected to a top-to-bottom in situ analysis with rRNA-targeted, fluorescently labeled oligonucleotide probes including beta1–8, specific for drinking water bacteria within the beta-subclass of Proteobacteria. Independent from the raw water source used, between 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 investigate seasonal fluctuations of the bacterial population composition, polyethylen slides exposed during different times of the year were analyzed. Although changes in the species composition of the biofilms could be observed, A. commune was a dominant community member in all of the investigated biofilms. In situ probing with two oligonucleotide probes specific for A. commune revealed that during distinct sampling times an additional yet unknown species was present in the biofilm. Material induced population shifts were studied using glass, polyethylene low and high density and soft-PVC as biofilm substrata. The community composition on soft-PVC differed significantly from the other materials, the dominant species A. commune was replaced by other beta- Proteobacteria hybridizing to an amount of 66% with the Aquabacterium citratiphilum specific probe beta4.