A phage cocktail approach for the control of iron bacteria from biofouled water supply wells

Biofouling refers to the accumulation of biofilm and biogenic precipitates on wetted surfaces and is one of the major problems associated with groundwater production. Groundwaters rich in ferrous iron (Fe(II)) are particularly susceptible to biofouling due to the low energetic yield of Fe(II) oxidation, which forces ironoxidizing bacteria to convert large quantities of soluble Fe(II) to insoluble ferric iron (Fe(III)) to sustain growth. Bacteria-specific viruses, known as bacteriophages or phages, are particularly promising for biofilm control given their specificity and ability to spread from one host cell to another. Phage therapy for biofilm control has been most successful with pure cultures and low-diversity bacterial communities. However, the applicability of phages to control mixed bacterial communities, in particular those of groundwater supply wells, remains largely unexplored. To assess whether phages constitute an effective alternative to treat well biofouling, the microbial communities of two biofouled wells were interrogated by 16S rRNA gene sequencing. Potential key species of iron bacteria (FeB) were identified and enriched by repeated subculturing in vii Modified Wolfe and Winogradsky media. Mixed phage suspensions were extracted by filtration from activated sludge, and this suspension was enriched against bacterial enrichment cultures developed from well water inocula. Batch tests showed a decrease in cell density and an impairment in iron redox cycling on well enrichment cultures when exposed to phage suspensions. Future work includes testing the phage suspensions against mixed biofilms of FeB, characterizing the specificity of these phage suspensions, and evaluating the impact of the phage on iron redox cycling under other culture conditions. Overall, this work is a first step toward a sustainable rehabilitation approach for biofouled wells.