E. coli as sole indicator of water pollution questioned

However, new research investigating pathogen survival in Irish soils conducted by Teagasc Johnstown Castle Environment Research Centre and NUI Galway has found that E. coli can become integrated into the indigenous microbial community in soils and survive for more than nine years, considerably longer than scientists initially thought.

"This has important implications for the indicator status of E. coli, suggesting that the presence of E. coli in surface or groundwaters may not be indicative of recent faecal contamination," explains researcher Fiona Brennan in TResearch, the Teagasc Research and Innovation magazine.

"It also suggests that E. coli persistence may be favoured in some soil types and these soils may represent a greater risk of bacterial leaching," she explains. Research conducted at Johnstown Castle has investigated bacterial transport in grassland soils both in situ at field sites and in field lysimeter (soil monolith) units.

In conjunction with NUI Galway, Teagasc researchers are now using proteomics to investigate the unique properties of E. coli that allow it to persist in the soil for such long periods. Initial findings have found that the environmentally persistent E. coli produce specialised proteins, including 'cold shock' and 'stress response' proteins, which may assist in the survival and growth of the organism at lower temperatures. E. coli's ability to survive for prolonged periods of time in soil may compromise its use as the sole indicator of faecal contamination of water.