title: The Interplay Between Predation, Competition, and Nutrient Levels Influences the Survival of Escherichia coli in Aquatic Environments.
abstract: Nutrient levels, competition from autochthonous microorganisms, and protozoan predation may all influence survival of fecal microorganisms as they transition from the gastrointestinal tract to aquatic habitats. Although Escherichia coli is an important indicator of waterborne pathogens, the effects of environmental stressors on its survival in aquatic environments remain poorly understood. We manipulated organic nutrient, predation, and competition levels in outdoor microcosms containing natural river water, sediments, and microbial populations to determine their relative contribution to E. coli survival. The activities of predator (protozoa) and competitor (indigenous bacteria) populations were inhibited by adding cycloheximide or kanamycin. We developed a statistical model of E. coli density over time that fits with the data under all experimental conditions. Predation and competition had significant negative effects on E. coli survival, while higher nutrient levels increased survival. Among the main effects, predation accounted for the greatest variation (40 %) compared with nutrients (25 %) or competition (15 %). The highest nutrient level mitigated the effect of predation on E. coli survival. Thus, elevated organic nutrients may disproportionately enhance the survival of E. coli, and potentially that of other enteric bacteria, in aquatic habitats.
authors.affiliation: Department of Integrative Biology, University of South Florida, 4202 East Fowler Avenue, SCA 110, Tampa, FL, 33620, USA.
authors.forename: P
authors.initials: P
authors.lastname: Wanjugi
authors.affiliation: Department of Integrative Biology, University of South Florida, 4202 East Fowler Avenue, SCA 110, Tampa, FL, 33620, USA.
authors.forename: G A
authors.initials: GA
authors.lastname: Fox
authors.affiliation: Department of Integrative Biology, University of South Florida, 4202 East Fowler Avenue, SCA 110, Tampa, FL, 33620, USA. vharwood@usf.edu.
authors.forename: V J
authors.initials: VJ
authors.lastname: Harwood
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects / Q000254:growth & development; D058448:Biota; D003513:Cycloheximide / Q000494:pharmacology; D017753:Ecosystem; D004783:Environmental Microbiology; D004784:Environmental Monitoring; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D005243:Feces / Q000382:microbiology; D005618:Fresh Water / Q000382:microbiology* / Q000469:parasitology*; D019015:Geologic Sediments / Q000382:microbiology; D007612:Kanamycin / Q000494:pharmacology; D056265:Microbial Interactions; D009747:Nutritional Physiological Phenomena; D011235:Predatory Behavior; D013534:Survival; D014871:Water Microbiology
chemical_list: D000900:Anti-Bacterial Agents; D007612:Kanamycin; D003513:Cycloheximide
keywords: Biotic interactions; Decay; E. coli; Fecal indicator bacteria; Predator–prey