ABSTRACT
During certain environmental conditions, the floating aquatic vegetation, mainly represented by Eichhornia crassipes (water hyacinth) invade and even cover water courses assigned to recreational activities or to the supply of drinkable water. The rhizosphere of these plants constitutes an unknown biotope of bacteria of sanitary interest, possibly different from waters without vegetation and of the sediment of the same aquatic system. To verify such possibility, 206 isolated strains in MacConkey Agar (Difco) were typified and identified (78 from water, 65 from sediment and 63 from rhizosphere) using the API 20 E system (v. 4.0) and Apilab plus software (v 3.3.3), both of bioMÚrieux (Marcy-l'Etoile, France, 1998). Nineteen different biochemical phenotypes from E. coli were found. The 79 of the population belonged to only 7 phenotypes; the 21 remaining, to the other 12 phenotypes. Twelve phenotypes did not share the biotopes, while only 4 were in the three. These results (and those obtained by other authors who used the API 20 E system in other biotopes) suggest that it would be possible to characterize the rhizosphere using those phenotypes that are found in smaller proportion. The greatest index of diversity (H) and evenness (E) were found in the rhizosphere (H = 2.903; E = 0.874). The dendrogram (average distances and UPGMA method) reaffirms the dissimilarity in biochemical phenotypes of E. coli populations of the rhizosphere with regard to the other biotopes. The most abundant bacterial species in the three biotopes were E. coli, Klebsiella terrigena and K. pneumoniae, corresponding to 75.2 of the community. The rhizosphere differed from Serratia odorifera and from Klebsiella spp. because of its higher rate of isolation.
Subject(s)
Escherichia coli , Water Microbiology , Argentina , Bacterial Typing Techniques , Ecosystem , Escherichia coli , Species Specificity , Klebsiella , Phenotype , Plants , Plant Roots/microbiology , Geologic Sediments/microbiology , Serratia , Soil MicrobiologyABSTRACT
There are no standards accepted by all the countries to fix top concentrations of microbiological indicators in recreational waters. Even now there is still a considerable discussion either in USA as in Europe. The universal application of a bacteriological quality criterion is hard due to several environmental factors that affect the relation between the indicator, the exposition and the health risks. Our purpose was to present a case study as an example of the influence of the climatic conditions in the application of the most known standards (Environmental Protection Agency of USA, Council of European Communities, World Organization of Health, and others from Canada, South Africa and Hong Kong). The pluvial rainfall increased the number of E. coli, thermotolerant coliforms (C Te), and total coliforms (CT) 6-10 fold, in comparison to the number registered during the steady-state conditions of the system. However, not all the standards included that factor. In Summer, hourly, daily and weekly variations were proved, therefore the standards that suggest fortnightly sampling frequencies would not be convenient in that system. Although the main source of variation was time, spatial variability was also detected. The percentage of E. coli among the C Te was very variable, but the average resulted low (26) compared to the levels in temperate regions of other countries (> 90). According to the directives proposed by the Commission of European Communities, the parameter has been changed (C Te for E. coli), but the standard has remained (2000/100 ml). Thus, the directive would be more permissive.
Subject(s)
Fresh Water/microbiology , Enterobacteriaceae , Water Microbiology , Argentina , Escherichia coli , Quality Control , Recreation , United States , United States Environmental Protection Agency , World Health OrganizationABSTRACT
Durante enero 1993 - diciembre 1996 se recolectaron 85 muestras de agua y 40 de plancton en la cuenca inferior del río Salado. En el 69,4 o/o de las muestras de agua en el 75 o/o de las muestras de plancton se detectó Vibrio cholerae. Ninguna de las cepas de V. cholerae aisladas pertenecieron a los subgrupos O1 y O139. No se comprobó estacionalidad en la frecuencia de los aislamientos de V. cholerae aplicando la prueba de comparación de proporciones múltiples (p>0,05). Se registraron diferencias significativas (p<0,05) entre la frecuencia de aislamiento de V. cholerae en el río Salado (85 muestras, 69,4 o/o) y la hallada en ambientes del río Paraná (16 muestras, 25 o/o) y en efluentes municipales (18 muestras, 33,3 o/o)