RESUMO
El presente trabajo tuvo por objeto determinar el período de supervivencia en sedimentos marinos de bacterias con riesgo biológico o indicadoras. Se tomaron muestras de sedimento marino intermareal en dos playas de la ciudad de Comodoro Rivadavia, Argentina; una sometida a contaminación por efluentes domiciliarios, y otra sin pruebas de contaminación evidente. Sobre éstos se realizó una caracterización inicial por recuento de bacterias en diferentes medios de cultivo (TSA, VRB, VRBG, TCBS, agar bilis esculina y agar cetrimide) y por su identificación. También se realizó un estudio de supervivencia de los microorganismos de interés en microcosmos. Estos fueron monitoreados por conteo de bacterias y por identificación de los integrantes de interés. Los principales resultados indicaron que existe una marcada diferencia en la composición de la comunidad bacteriana entre ambas muestras. Los géneros bacterianos en la muestra contaminada fueron Aeromonas, Salmonella, Pseudomonas, Escherichia, Ochrobactum y Klebsiella, y en la playa no contaminada Bacillus, Paenibacillus, Micrococcus, Photobacterium y Vibrio. El ensayo en microcosmos demostró que, luego de 65 días, la comunidad bacteriana de la playa contaminada fue similar a la del sedimento sin contaminación, indicando que al retirar la fuente de contaminación, es probable la recuperación de la zona afectada.
The present study had the purpose of determining the survival period of bacteria which represent a biological risk and are indicators of contamination. Inter-tide marine sediment samples were taken at two beaches of the Comodoro Rivadavia city in Argentine; one the beaches was submitted to contamination due to household effluents, and the other without proof of evident contamination. These samples were initially characterized by bacterial counts in different culture media (TSA, VRB, TCBS, bile esculin agar and cetrimide agar) and by their identification. A study of the survival of the target bacteria in microcosm was also done, monitored by bacterial counts and identification of these bacteria. The main results indicated that there was a marked difference in the composition of the bacterial community between the two samples. In the contaminated sample the bacterial genus were Aeromonas, Salmonella, Pseudomonas, Escherichia, Ochrobactum and Klebsiella, and in the non-contaminated beach Bacillus, Paenibacillus, Micrococcus, Photobacterium and Vibrio. The microcosm assay showed that after 65 days the bacterial community of the contaminated beach was similar to that of the non-contaminated beach sediment, indicating that by withdrawing the contamination source, the affected zone can probably be recovered.
RESUMO
Electrokinetically stimulated bioremediation of soils (electro-bioremediation) requires that the application of weak electric fields has no negative effect on the contaminant degrading microbial communities. This study evaluated the hypothesis that weak direct electric current (DC) fields per se do not negatively influence the physiology and composition of soil microbial communities given that secondary electrokinetic phenomena such as soil pH changes and temperatures are minimized. Mildly buffered, water-saturated laboratory mesocosms with agricultural soil were subjected for 34 days to a constant electric field (X=1.4 V cm(-1); J approximately 1.0 mA cm(-2)) and the spatiotemporal changes of soil microbial communities assessed by fingerprints of phospholipids fatty acids (PLFA) and terminal restriction fragment length polymorphisms (T-RFLP) of bacterial 16S rRNA genes. DC-induced electrolysis of the pore water led to pH changes (<1.5 pH units) in the immediate vicinity of the electrodes and concomitant distinct soil microbial community changes. By contrast, DC-treated bulk soil distant to the electrodes showed no pH changes and developed similar PLFA- and T-RFLP-fingerprints as control soil in the absence of DC. Our data suggest that the presence of an electric field, if suitably applied, will not influence the composition and physiology of soil microbial communities and hence not affect their potential to biodegrade contaminants.