RESUMO
Hydrocarbon contamination of groundwater resources has become a major environmental and human health concern in many parts of the world. Our objectives were to employ both culture and culture-independent techniques to characterize the dynamics of microbial community structure within a fluidized bed reactor used to bioremediate a diesel-contaminated groundwater in a tropical environment. Under normal operating conditions, 97 to 99% of total hydrocarbons were removed with only 14 min hydraulic retention time. Over 25 different cultures were isolated from the treatment unit (96% which utilized diesel constituents as sole carbon source). Approximately 20% of the isolates were also capable of complete denitrification to nitrogen gas. Sequence analysis of 16S rDNA demonstrated ample diversity with most belonging to the infinity, beta and gamma subdivision of the Proteobacteria, Bacilli, and Actinobacteria groups. Moreover, the genetic constitution of the microbial community was examined at multiple time points with a Functional Gene Array (FGA) containing over 12,000 probes for genes involved in organic degradation and major biogeochemical cycles. Total community DNA was extracted and amplified using an isothermal phi29 polymerase-based technique, labeled with Cy5 dye, and hybridized to the arrays in 50% formimide overnight at 50 degrees C. Cluster analysis revealed comparable profiles over the course of treatment suggesting the early selection of a very stable microbial community. A total of 270 genes for organic contaminant degradation (including naphthalene, toluene [aerobic and anaerobic], octane, biphenyl, pyrene, xylene, phenanthrene, and benzene); and 333 genes involved in metabolic activities (nitrite and nitrous oxide reductases [nirS, nirK, and nosZ], dissimilatory sulfite reductases [dsrAB], potential metal reducing C-type cytochromes, and methane monooxygenase [pmoA]) were repeatedly detected. Genes for degradation of MTBE, nitroaromatics and chlorinated compounds were also present, indicating a broad catabolic potential of the treatment unit. FGA's demonstrated the early establishment of a diverse community with concurrent aerobic and anaerobic processes contributing to the bioremediation process.
Assuntos
Bactérias/metabolismo , Recuperação e Remediação Ambiental , Hidrocarbonetos/metabolismo , Microbiologia da Água , Poluentes Químicos da Água/metabolismo , Bactérias/classificação , Sequência de Bases , Biofilmes , Primers do DNARESUMO
Plants are good environmental sensors of the soil conditions in which they are growing. They also respond directly to the state of air. The tops of plants are collectors of air pollutants, and their chemical composition may be a good indicator for contaminated-areas when it is assessed against background values obtained for unpolluted vegetation. Both, aquatic and terrestrial plants are known to bioaccumulate heavy metals and therefore represent a potential source of these contaminants to the human food chain. An evaluation of heavy metals was conducted from vegetation samples collected at the Atlantic Fleet Weapons Training Facilities (AFWTF) in Vieques, Puerto Rico. In order to understand the potential risks associated to heavy metal mobilization through biological systems, it is first necessary to establish background values obtained from reference locations. This information allows a better interpretation of the significance of anthropogenic factors in changing trace elements status in soil and plants. Since Guánica State Forest is located at a similar geoclimatic zone as the AFWTF, samples at this site were used as a standard reference material and as experimental controls. Both sampling and analysis were conducted as previously described in standardized protocols using acid digestion of dry ashes. Then, levels of heavy metals were obtained by air-acetylene flame detection in an atomic absorption spectrophotometer. Our results from the samples taken at the AFWTF indicate mobilization of undesirable trace elements through the marine and terrestrial food web. Since plants naturally remove heavy metals from soils, they could be employed for the restoration of this and similarly contaminated sites.