Previously uncultured β-Proteobacteria dominate in biologically active granular activated carbon (BAC) filters

Bacteria colonizing BAC filters used in drinking water purification from lake water were characterized by morphology, physiological tests, whole cell protein profiles and PLFA (phospholipid fatty acid) composition, and identified by partial 16S rRNA gene sequencing. Epifluorescence revealed prothecate bacteria to dominate in BAC. The majority of the isolates belonged to order Burkholderiales of β-Proteobacteria, a few to Comamonadaceae but the majority to an undescribed family and the related sequences belonged mainly to uncultured bacteria. Among the less common α-Proteobacteria the genus Sphingomonas and the genera Afipia, Bosea or Bradyrhizobium of the Bradyrhizobiaceae family were detected. The majority of cultured bacteria persisting in the BAC biofilter were Burkholderiales, which according to ecological information are efficient in the mineralisation of dissolved organic matter in BAC. The biotechnical potential of the previously uncultured dominant bacteria warrants to be further studied.