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Category: Applied and Industrial Microbiology; Environmental Microbiology
Environmental Sources of Fecal Bacteria, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555816865/9781555816087_Chap05-1.gif /docserver/preview/fulltext/10.1128/9781555816865/9781555816087_Chap05-2.gifAbstract:
Despite regulatory requirements for treating wastewater to reduce microbial pollutants prior to release into waterways, frequent beach closures or advisories as a result of elevated fecal indicator bacteria (FIB; e.g., Escherichia coli and enterococci) have been a chronic problem at many recreational locations. This chapter provides a review of the research on environmental occurrences of FIB in a variety of terrestrial and aquatic habitats under different geographic and climatic conditions, and discusses how these external sources may affect surface water quality. FIB are usually retained in the upper layer of soil depending on soil type, temperature, rate of water flow, and other environmental variables. Several microbial source tracking studies have identified wildlife as an important nonpoint source of FIB; however, identifying and partitioning these contaminants by source has been challenging. Future research on colonization potential, growth requirements, microbial interactions, and population genetics, can shed more light on FIB occurrence in natural environments. The persistence and potential growth of indicator bacteria in sediments and soils likely have a serious impact on recreational water quality by elevating bacterial counts through resuspension and surface runoff. Since large quantities of wastes generated from animal husbandry activities, such as poultry, dairy, and swine production, are often spread over the land as a fertilizer, these processes may result in an increase of microbial contaminants in the soil that, in turn, could potentially affect the quality of nearby water bodies.
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Escherichia coli densities (log MPN per g) in soil over time for the six locations within Dunes Creek watershed (northwest Indiana). Samples (n = 66) were collected and analyzed over a period of 8 months (March to October 2003) to determine the ubiquity and persistence of E. coli in temperate forest soils. Adapted from Byappanahalli et al. ( 2006b ).
(A) Multivariate analysis of variance (MANOVA) of horizontal, fluorophore-enhanced rep-PCR DNA fingerprints from E. coli strains obtained from soils (
), deer (
), and birds (geese [
], terns [
], and gulls [
]). The first two discriminants are represented by the distances along the x and y axes (adapted from
Byappanahalli et al., 2006b
). (B) Conceptual representation of E. coli distribution among humans, animal hosts, and environmental reservoirs. Some level of host specificity can be detected in among E. coli, but some strains can be found in multiple hosts. Environmentally adapted “naturalized” E. coli strains are unique and different from those found in humans and other animal hosts. Pathogenic E. coli strains can cause human diseases and can be found in other animal hosts and in the environments. Adapted from Ishii and Sadowsky (
2008
).
Conceptual representation of how various sources may contribute E. coli to beach sand, sediment, and water in beachshed ecosystems. Wave action may carry E. coli originating from humans, waterfowl, and other sources to beach areas. E. coli from waterfowl droppings and naturalized populations in beach sand and sediment may also be released back into water. Thus, sediment and beach sand may act as sinks and sources of this fecal indicator bacterium. Adapted from Ishii et al. ( 2007a ).
E. coli density in deep, saturated sand at a Southern Lake Michigan beach (Dunbar, northwest Indiana) as a function of distance from the shoreline. Error bars represent + /— 1 standard error. Adapted from Byappanahalli et al. ( 2006a ).
Log mean densities (+ 1 standard error) of E. coli and enterococci in Cladophora collected from 10 Lake Michigan beaches in Wisconsin (WI), Illinois (IL), Indiana (IN), and Michigan (MI). Adapted from Whitman et al. ( 2003 ).
Conceptual diagram of E. coli within and between stream and beach watersheds (left and right triangles, respectively). For streams, the model partitions stream inputs as human or nonhuman; the latter might include bacterial inputs originating from growth within riparian soils or long-term storage. Within the stream, major processes include (i) inactivation and reactivation, (ii) deposition (temporary or permanent loss) and resuspension, and (iii) death and direct input (e.g., animal defecation and multiplication). Culturable bacteria are delivered from the stream to the beachshed as surface water or groundwater. Internal inputs of E. coli into the lake include foreshore bacteria resuspension (from storage, defecates, and growth) and wastewater releases. Within the lake, there are dynamic interactions between inactivation/reactivation, deposition/resuspension, and offshore importation/exportation of bacteria. The whole beachshed system eventually yields the net culturable E. coli densities (enumerated) monitored by managers at a targeted beach location. Reprinted from Whitman et al. ( 2006 ).
Competition for available nutrients (carbon and energy sources) may limit E. coli multiplication in natural soil a