Nitrate enrichment does not affect enteropathogenic Escherichia coli in aquatic microcosms but may affect other strains present in aquatic habitats

Davis, Meredith T., Canning, Adam D., Midwinter, Anne C., and Death, Russell G. (2022) Nitrate enrichment does not affect enteropathogenic Escherichia coli in aquatic microcosms but may affect other strains present in aquatic habitats. PeerJ, 10. e13914.

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Abstract

Eutrophication of the planet’s aquatic systems is increasing at an unprecedented rate. In freshwater systems, nitrate—one of the nutrients responsible for eutrophication—is linked to biodiversity losses and ecosystem degradation. One of the main sources of freshwater nitrate pollution in New Zealand is agriculture. New Zealand’s pastoral farming system relies heavily on the application of chemical fertilisers. These fertilisers in combination with animal urine, also high in nitrogen, result in high rates of nitrogen leaching into adjacent aquatic systems. In addition to nitrogen, livestock waste commonly carries human and animal enteropathogenic bacteria, many of which can survive in freshwater environments. Two strains of enteropathogenic bacteria found in New Zealand cattle, are K99 and Shiga-toxin producing Escherichia coli (STEC). To better understand the effects of ambient nitrate concentrations in the water column on environmental enteropathogenic bacteria survival, a microcosm experiment with three nitrate-nitrogen concentrations (0, 1, and 3 mg NO3-N/L), two enteropathogenic bacterial strains (STEC O26—human, and K99—animal), and two water types (sterile and containing natural microbiota) was run. Both STEC O26 and K99 reached 500 CFU/10 ml in both water types at all three nitrate concentrations within 24 hours and remained at those levels for the full 91 days of the experiment. Although enteropathogenic strains showed no response to water column nitrate concentrations, the survival of background Escherichia coli, imported as part of the in-stream microbiota did, surviving longer in 1 and 3 mg NO3-N/L concentrations (P < 0.001). While further work is needed to fully understand how nitrate enrichment and in-stream microbiota may affect the viability of human and animal pathogens in freshwater systems, it is clear that these two New Zealand strains of STEC O26 and K99 can persist in river water for extended periods alongside some natural microbiota.

Item ID: 76145
Item Type: Article (Research - C1)
ISSN: 2167-8359
Keywords: E. coli, Enteropathogenic, Eutrophication, Microcosm, Nitrate, Water quality
Copyright Information: Copyright 2022 Davis et al. Distributed under Creative Commons CC-BY 4.0
Date Deposited: 05 Oct 2022 01:02
FoR Codes: 41 ENVIRONMENTAL SCIENCES > 4104 Environmental management > 410402 Environmental assessment and monitoring @ 20%
41 ENVIRONMENTAL SCIENCES > 4105 Pollution and contamination > 410504 Surface water quality processes and contaminated sediment assessment @ 50%
30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3002 Agriculture, land and farm management > 300204 Agricultural management of nutrients @ 30%
SEO Codes: 10 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 1001 Environmentally sustainable animal production > 100102 Management of liquid waste from animal production (excl. water) @ 30%
18 ENVIRONMENTAL MANAGEMENT > 1803 Fresh, ground and surface water systems and management > 180302 Control of pests, diseases and exotic species in fresh, ground and surface water @ 50%
20 HEALTH > 2004 Public health (excl. specific population health) > 200404 Disease distribution and transmission (incl. surveillance and response) @ 20%
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