Evidence for Occurrence, Persistence, and Growth Potential of Escherichia coli and Enterococci in Hawaii’s Soil Environments

• Published in: Microbes and Environments Vol. 27; no. 2; pp. 164 - 170
• Main Authors: Byappanahalli, Muruleedhara N., Roll, Bruce M., Fujioka, Roger S.
• Format: Journal Article
• Language: English
• Published: Japan Japanese Society of Microbial Ecology / Japanese Society of Soil Microbiology / Taiwan Society of Microbial Ecology / Japanese Society of Plant Microbe Interactions / Japanese Society for Extremophiles 2012; Japan Science and Technology Agency; Japanese Society of Microbial Ecology/The Japanese Society of Soil Microbiology
• Subjects: autochthonous population; Bacterial Load; Bacterial Typing Techniques; dehydrogenase; Enterobacteriaceae - classification; Enterobacteriaceae - isolation & purification; Enterococcus; Enterococcus - classification; Enterococcus - isolation & purification; Enterococcus faecalis; Enterococcus faecium; Escherichia coli; Fecal coliforms; fecal indicator bacteria; Freshwater environments; Hawaii; Islands; Mesocosms; Most probable number; nonpoint source contamination; Nutrients; recreational water quality; Regular Paper; Rivers; Soil; Soil Microbiology; soil microbiota; Soil microorganisms; Streams; Hawaii
• ISSN: 1342-6311; 1347-4405
• DOI: 10.1264/jsme2.ME11305

High densities of Escherichia coli and enterococci are common in freshwaters on Oahu and other Hawaiian Islands. Soil along stream banks has long been suspected as the likely source of these bacteria; however, the extent of their occurrence and distribution in a wide range of soils remained unknown until the current investigation. Soil samples representing the seven major soil associations were collected on the island of Oahu and analyzed for fecal coliforms, E. coli, and enterococci by the most probable number method. Fecal coliforms, E. coli, and enterococci were found in most of the samples analyzed; log mean densities (MPN ± SE g soil−1) were 1.96±0.18, n=61; 1.21±0.17, n=57; and 2.99±0.12, n=62, respectively. Representative, presumptive cultures of E. coli and enterococci collected from the various soils were identified and further speciated using the API scheme; at least six species of Enterococcus, including Enterococcus faecalis and Enterococcus faecium, were identified. In mesocosm studies, E. coli and enterococci increased by 100-fold in 4 days, after mixing sewage-spiked soil (one part) with autoclaved soil (nine parts). E. coli remained metabolically active in the soil and readily responded to nutrients, as evidenced by increased dehydrogenase activity. Collectively, these findings indicate that populations of E. coli and enterococci are part of the natural soil microflora, potentially influencing the quality of nearby water bodies.