title: A Survey of Escherichia coli and Salmonella in the Hyporheic Zone of a Subtropical Stream: Their Bacteriological, Physicochemical and Environmental Relationships.
abstract: The Hyporheic Zone is among the most important interstitial freshwater habitats, but the relationship between biotic and abiotic factors in this zone remains under-explored. Enterobacteria were expected to be present, but no specific studies had ever confirmed this prediction. The aim of this study was, therefore, to evaluate the total coliforms, Escherichia coli and Salmonella spp. in hyporheic water and to determine the relationship of the physical, chemical and environmental factors at different depths in a rainforest stream. To this end, thirty-six water samples were collected at three depths in sites located in the first, second and third orders in diverse substrates. The total coliforms, Escherichia coli and Salmonella sp. were evaluated in terms of their CFU/ml. In the interstitial samples, coliforms were detected in 100% of the samples. The total coliform counts had higher values at intermediate depths, while E. coli and Salmonella spp. instead had higher values at intermediate and large depths, often reaching or exceeding the values of the surface samples. Our results revealed that Salmonella spp. and the coliforms have different microhabitat preferences. Salmonella spp. and coliform species prefer deposition areas, such as lateral sides of pools, curves and bars, but they have a tendency to distribute into different depths, likely due to temperature differences. Salmonella spp. prefer compact substrata, with fewer fluids passing through and with upwelling areas with lower oxygen inflow. The coliform species showed the opposite preference. Our results suggest that bacterial variation is related to environmental factors and physical-chemical parameters within the HZ and may play a key role in the microbial diversity and distribution in these ecosystems.
authors.affiliation: Laboratorio de Aracnologia, Departamento de Invertebrados Museu Nacional/Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Mugnai
authors.affiliation: Laboratório de Avaliação e Promoção da Saúde Ambiental, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil.
authors.forename: Ana
authors.initials: A
authors.lastname: Sattamini
authors.affiliation: Laboratório de Avaliação e Promoção da Saúde Ambiental, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil.
authors.forename: José Augusto
authors.initials: JA
authors.lastname: Albuquerque dos Santos
authors.affiliation: Laboratório de Epidemiologia Molecular de Doenças Infecciosas/Departamento de Ciências Biológicas, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil.
authors.forename: Adriana Hamond
authors.initials: AH
authors.lastname: Regua-Mangia
mesh_terms: D004926:Escherichia coli / Q000235:genetics / Q000302:isolation & purification*; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology*; D060587:Groundwater / Q000737:chemistry / Q000382:microbiology*; D012475:Salmonella / Q000235:genetics / Q000302:isolation & purification*; D014329:Tropical Climate