Effects of sunlight and autochthonous microbiota onEscherichia coli survival in an estuarine environment

Rhodes, Martha W.; Kator, Howard

doi:10.1007/bf02090102

Cited by 21 publications

(12 citation statements)

References 43 publications

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“…This observation indicates that, within the confines of our experimental design, the effect of indigenous microbiota on E. coli survival in the water column is influenced by the water type. While protozoan bacterivory is a recognized contributor to the decline of bacterial populations in aquatic environments (29,(59)(60)(61)(62)(63), the relative magnitudes of impact of protozoan presence on E. coli survival in sunlight-exposed freshwater and seawater systems have not been previously described. Interestingly, in the seawater mesocosms, the matrix (water/ sediment) had a greater effect on the persistence of E. coli than the presence of indigenous microbiota.…”

Section: Discussionmentioning

confidence: 99%

Indigenous Microbiota and Habitat Influence Escherichia coli Survival More than Sunlight in Simulated Aquatic Environments

Korajkic

Wanjugi

Harwood

2013

Appl Environ Microbiol

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The reported fate of Escherichia coli in the environment ranges from extended persistence to rapid decline. Incomplete understanding of factors that influence survival hinders risk assessment and modeling of the fate of fecal indicator bacteria (FIB) and pathogens. FIB persistence in subtropical aquatic environments was explored in outdoor mesocosms inoculated with five E. coli strains. The manipulated environmental factors were (i) presence or absence of indigenous microbiota (attained by natural, disinfected, and cycloheximide treatments), (ii) freshwater versus seawater, and (iii) water column versus sediment matrices. When indigenous microbes were removed (disinfected), E. coli concentrations decreased little despite exposure to sunlight. Conversely, under conditions that included the indigenous microbiota (natural), significantly greater declines in E. coli occurred regardless of the habitat. The presence of indigenous microbiota and matrix significantly influenced E. coli decline, but their relative importance differed in freshwater versus seawater. Cycloheximide, which inhibits protein synthesis in eukaryotes, significantly diminished the magnitude of E. coli decline in water but not in sediments. The inactivation of protozoa and bacterial competitors (disinfected) caused a greater decline in E. coli than cycloheximide alone in water and sediments. These results indicate that the autochthonous microbiota are an important contributor to the decline of E. coli in fresh and seawater subtropical systems, but their relative contribution is habitat dependent. This work advances our understanding of how interactions with autochthonous microbiota influence the fate of E. coli in aquatic environments and provides the framework for studies of the ecology of enteric pathogens and other allochthonous bacteria in similar environments.T he sanitary quality of recreational waters in Florida and across the United States is currently assessed by enumeration of fecal indicator bacteria (FIB) (i.e., fecal coliforms, Escherichia coli, and enterococci), which are also intended to act as pathogen surrogates (1, 2). The validity of this paradigm is the subject of ongoing debate, and it is argued that the current regulatory standards do not adequately protect human health, due mainly to the differences in survival and transport characteristics between the FIB and pathogens (3-9). When the assumed predictive relationship is absent (e.g., FIB not detected but pathogens present), public health may be threatened by exposure of humans to pathogens. On the other hand, FIB that are detected in the absence of pathogens can lead to unnecessary beach and shellfishing area closures, which can pose economic hardships in coastal communities.While the roles of sediments and aquatic vegetation as a refuge and a potential reservoir of FIB are the subjects of many studies (10-16), the relative influence of indigenous microbiota on the persistence and rate of decline of FIB in aquatic environments is less well characterized. Germicidal sunlight r...

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Section: Discussionmentioning

confidence: 99%

Indigenous Microbiota and Habitat Influence Escherichia coli Survival More than Sunlight in Simulated Aquatic Environments

Korajkic

Wanjugi

Harwood

2013

Appl Environ Microbiol

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“…Sunlight exposure is an important inactivation mechanism for all forms of pathogens and microbial indicators in both fresh and saline waters [ Gameson and Saxon , 1967; Mancini , 1978; Fujioka et al , 1981; Gould and Munro , 1981; McCambridge and McMeekin , 1981; Kapuscinski and Mitchell , 1980; Evison , 1988; Rhodes and Kator , 1990; Curtis et al , 1992a; Solic and Krstulovic , 1992; Auer and Niehaus , 1993; Davies‐Colley et al , 1994; Sinton et al , 1994, 1999, 2002; Sarikaya and Saatchi , 1995; Johnson et al , 1997; Burkhardt et al , 2000; Noble et al , 2004; King et al , 2008]. In waters of high clarity, it has long been regarded as the most dominant inactivation mechanism.…”

Section: Literature Review and Model Developmentmentioning

confidence: 99%

A generic, process‐based model of microbial pollution in aquatic systems

Hipsey

Antenucci

Brookes

2008

Water Resources Research

119

140

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[1] Based on a comprehensive synthesis of data available within the literature, a new process-based model of microbial pollution is presented, which is applicable for surface and coastal waters. The model is based on a generic set of parameterisations that describe the dynamics of most protozoan, bacterial and viral organisms of interest, including pathogens and microbial indicator organisms. The parameterisations dynamically account for the effects of temperature, salinity, pH, dissolved oxygen, sunlight, nutrients and turbidity on the growth and mortality of enteric organisms. Parameters for a range of organisms are also presented which are based on collation of literature data. The model has been implemented within an aquatic ecology model, Computational Aquatic Ecosystem Dynamics Model (CAEDYM), which can couple to multidimensional hydrodynamic models. Without adjustment of the literature derived parameter values, a 3-D implementation is validated against observed data from three freshwater systems that differ in their climatic zone, trophic status and operation. The simulations highlight the spatial and temporal variability that may be encountered by operators. Additionally, large differences in the fate and distribution of different species originate from variable rates of growth, mortality and sedimentation and it is emphasized that the use of surrogates for quantifying risk is problematic. The model can be used to help design targeted monitoring programs, explore differences between species, and to support real-time decision-making. Areas where insufficient understanding and data exist are discussed.

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“…The applicability of seawater studies to fresh and estuarine waters is doubtful, because of the likely effects on microbial inactivation of differences in optical characteristics (7,20), salinity (10,34), and autochthonous biota (13,23,24,30,36).…”

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confidence: 99%

Sunlight Inactivation of Fecal Indicator Bacteria and Bacteriophages from Waste Stabilization Pond Effluent in Fresh and Saline Waters

Sinton

Hall

Lynch

et al. 2002

Appl Environ Microbiol

458

372

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Sunlight inactivation in fresh (river) water of fecal coliforms, enterococci, Escherichia coli, somatic coliphages, and F-RNA phages from waste stabilization pond (WSP) effluent was compared. Ten experiments were conducted outdoors in 300-liter chambers, held at 14°C (mean river water temperature). Sunlight inactivation (k S ) rates, as a function of cumulative global solar radiation (insolation), were all more than 10 times higher than the corresponding dark inactivation (k D ) rates in enclosed (control) chambers. The overall k S ranking (from greatest to least inactivation) was as follows: enterococci > fecal coliforms > E. coli > somatic coliphages > F-RNA phages. In winter, fecal coliform and enterococci inactivation rates were similar but, in summer, enterococci were inactivated far more rapidly. In four experiments that included freshwater-raw sewage mixtures, enterococci survived longer than fecal coliforms (a pattern opposite to that observed with the WSP effluent), but there was little difference in phage inactivation between effluents. In two experiments which included simulated estuarine water and seawater, sunlight inactivation of all of the indicators increased with increasing salinity. Inactivation rates in freshwater, as seen under different optical filters, decreased with the increase in the spectral cutoff (50% light transmission) wavelength. The enterococci and F-RNA phages were inactivated by a wide range of wavelengths, suggesting photooxidative damage. Inactivation of fecal coliforms and somatic coliphages was mainly by shorter (UV-B) wavelengths, a result consistent with photobiological damage. Fecal coliform repair mechanisms appear to be activated in WSPs, and the surviving cells exhibit greater sunlight resistance in natural waters than those from raw sewage. In contrast, enterococci appear to suffer photooxidative damage in WSPs, rendering them susceptible to further photooxidative damage after discharge. This suggests that they are unsuitable as indicators of WSP effluent discharges to natural waters. Although somatic coliphages are more sunlight resistant than the other indicators in seawater, F-RNA phages are the most resistant in freshwater, where they may thus better represent enteric virus survival.

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Effects of sunlight and autochthonous microbiota onEscherichia coli survival in an estuarine environment

Cited by 21 publications

References 43 publications

Indigenous Microbiota and Habitat Influence Escherichia coli Survival More than Sunlight in Simulated Aquatic Environments

Indigenous Microbiota and Habitat Influence Escherichia coli Survival More than Sunlight in Simulated Aquatic Environments

A generic, process‐based model of microbial pollution in aquatic systems

Sunlight Inactivation of Fecal Indicator Bacteria and Bacteriophages from Waste Stabilization Pond Effluent in Fresh and Saline Waters

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