Ratios between Alpha-, Beta- and Gamma-proteobacteria in tap water determined by the ProteoQuant assay

Proteobacteria are widespread on earth. Recently, it has been discovered that a diverse repertoire of proteobacteria are also dominant in tap water. It is therefore important to use high-throughput monitoring tools for tap water. Here, the high-throughput assay ProteoQuant was developed to quantify the main proteobacterial phyla in tap water. The principle of ProteoQuant is proteobacterial-selective 23S rRNA gene PCR amplification, with multiple competitive TaqMan probes for quantifying the phyla Alpha-, Beta- and Gamma-proteobacteria. The ProteoQuant assay was evaluated, analysing both designed proteobacterial mixes and rRNA gene clone libraries from tap water. These evaluations showed a good coverage and accuracy of the ProteoQuant assay. Large-scale tap water screening using ProteoQuant revealed a dominance of Beta-proteobacteria and a potential interaction between Alpha- and Beta-proteobacteria. Gamma-proteobacteria, on the other hand, seemed independent of the two other phyla. The ProteoQuant assay will potentially be important for future understanding of the ecological forces shaping the tap water microbiota.