Strain-dependent variations in attachment of E. coli to soil particles of different sizes
O. Yu 1
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USDA-ARS Environmental Microbial Safety Laboratory, 10300 Baltimore Ave, Bldg. 173, BARC-EAST, Beltsville, MD 20705, USA
Int. Agrophys. 2008, 22(1): 61-66
Attachment of E. coli to soil particles affects bacteria transport in overland flow and in soil. The objective of this research was to investigate the existence of strain-dependent variations in attachment of manure-borne E. coli to soil particles of different sizes using repetitive sequenced-based PCR techniques. Tyler clay loam soil was fractionated to obtain particles of coarse sand, medium sand, fine sand, silt, and clay sizes. The inoculum for attachment studies was produced by culturing aged manure. Serial dilutions of the fecal coliform suspension (102 and 103 CFU ml-1) were mixed with soil particle fractions. After incubation, soil-bacteria suspensions were centrifuged, and DNA was extracted from supernatants to be used for polymerase chain reaction (PCR) with ERIC primers. The DNA fingerprint analysis was done with pseudo-gel images from electrophoregrams using BioNumerics. Cluster analysis led to identification of five clusters with the similarity level within them higher than 80% and 17 clusters with the similarity level within them higher than 90%. The chi-square test was applied to test the hypothesis that the strain distribution among the clusters does not depend on adsorbent. This hypothesis could be rejected at 0.0001 probability level. The preferential attachment of different strains to particles of different size classes may be attributable to differences in both particle surface and bacteria surface properties. Because the attachment to mineral surfaces for pathogenic E. coli strains may be different from that for non-pathogenic strains, more information on attachment pathogenic E. coli to suspended solids in overland flow attachment needs to be collected, as the differences in attachment may result in differences in overland transport of pathogenic and non-pathogenic E. coli.
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