Prevalence of Enterobacteriaceae and contaminants survey in sediments of the Atoyac River

We identified the bacterial community in sediments from the Atoyac River within Puebla, Mexico by a 16S rRNA gene clone library. The Enterobacteriaceae, specifically Shigella, Escherichia fergusonii and E. coli species dominate the bacterial community which is consistent with the values obtained for total coliforms. Genes encoding Shiga toxins (stx1 and stx2) were not found. Higher alkanes (C11-C16), esters, organic acids, phenols and phthalates, classified as potential endocrine disruptors were recovered from the sediments, while the presence of coprostanol indicated fecal pollution. Element concentrations were also determined in sediments and they decreased in the following sequence: Ca > Fe > K > Ti > Sr > Ba > Mn > Zr > Zn > Cu > Rb, while As, Mo and Pb were below the detection limit. All element values but Cu are below those permitted by the United States Environmental Protection Agency (USEPA). This study highlights the dominance of Enterobacteriaceae and the low bacterial diversity with the ability to degrade hydrocarbons or persistent organic pollutants (POPs) in sediments of the Atoyac River in an area prior to the water storage in the Avila Camacho (Valsequillo) dam whose waters are used for irrigation in lands above for several crops.