Distribution of polycyclic aromatic hydrocarbons degrading bacteria in southern coastal sediments of Puerto Rico

Abstract

Most probable number technique was used for enumeration of heterotrophic bacteria. For enumeration of PAHs, the degrading bacteria overlayer technique was used. Higher numbers of heterotrophic bacteria were observed for all sampling sites during June and November. During the rainy season, higher numbers of naphthalene-degrading bacteria (1.6 x 103 CFU/g) were found in Guayanilla Bay sediments. Possible explanations may be the input of nutrients through the river effluents and mixing of bottom sediments. However, during the dry season, lower number of naphthalene but higher numbers of phenanthrene-degrading bacteria (8.8 x 103 CFU/g) were observed in Guayanilla Bay sediments. That may be due to the absence of the growth factors during the dry season that are necessary for growth of naphthalene-degrading bacteria. Low numbers in hydrocarbon-degrading bacteria were observed in Guánica samples during all sampling periods. Bacterial isolates were identified by 16S rDNA as species from the genera: Alteromonas, Microbulbifer, and Vibrio.

El conteo de bacterias heterotróficas se realizó mediante la técnica del número más probable. La técnica de esparcido en plato se utilizó para la enumeración de bacterias degradadoras de hidrocarburos aromáticos policíclicos (HAPs). Durante los meses de junio y noviembre se observó en todas las áreas bajo estudio, alto conteo de bacterias heterotróficas. En el período de lluvia, los sedimentos de la Bahía de Guayanilla presentaron alto conteo de bacterias degradadoras de naftaleno (1.6 x 103 CFU/g). Esto puede ser causado por el aporte de nutrientes a través de los afluentes del río Guayanilla y la resuspensión del sedimento. Durante eventos de sequía, se observó un alto conteo de degradadoras de fenantreno para las muestras de la Bahía de Guayanilla (8.8 x 103 CFU/g). Este aumento puede ser causado por la ausencia de factores de crecimiento durante períodos de sequía que sean requeridos por las bacterias degradadoras de naftaleno. Las bacterias aisladas fueron identificadas mediante el 16S rDNA como Alteromonas, Microbulbifer y Vibrio sp.