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Bacteriophage ecology in a small community sewer system related to their indicative role in sewage pollution of drinking water

Gino, Efrat, Starosvetsky, Jeana, Armon, Robert
Environmental microbiology 2007 v.9 no.10 pp. 2407-2416
water pollution, Escherichia coli, soil pollution, sewage, hosts, nutrients, ponds, filtrates, bacteriophages, feces, sewer systems, oxidation, community ecology, temperature, infants, host strains, excretion, detergents
In view of various studies looking for the merit of coliphages as indicators of water pollution with viruses originating from faecal material, a small agricultural community (population of approximately 1500 inhabitants of all ages, 2-3 km from Haifa) was selected in order to understand these bacteriophage ecology (F-RNA and somatic coliphages) in its sewer and oxidation pond system. Along the sewer lines, it was possible to isolate constantly both bacteriophage types (F-RNA and somatic coliphages) at 10²-10⁴ plaque-forming units (pfu) ml⁻¹. The average numbers of somatic and F-RNA phages isolated from oxidation pond were 10³-10⁴ pfu ml⁻¹; however, somatic coliphages were undetectable for several months (April-August). Significant high correlation (0.944 < R² < 0.99) was found between increased anionic detergent concentrations and F-RNA coliphage numbers. Infants less than 1 year old excreted both phage types and few only F-RNA coliphages (at high numbers > 10⁵ pfu g⁻¹) for up to 1 year. The excretion of F-RNA coliphages was highly linked to Escherichia coli F⁺ harborage in the intestinal track as found in their faecal content. Finally, three bacterial hosts E. coli F⁺, F⁻ and CN₁₃ tested for survivability in sewage filtrate revealed that E. coli F⁺ had the highest survivability under these conditions. Presence of somatic and F male-specific phages in sewer lines of a small community are influenced by several factors such as: anionic detergents, nutrients, temperature, source (mainly infants), shedding and survival capability of the host strain. Better understanding of coliphages ecology in sewer systems can enhance our evaluation of these proposed indicator/index microorganisms used in tracking environmental pollution of water, soil and crop contamination with faecal material containing enteric viruses.