RESUMO
A microbial enrichment originating from a pristine aquifer was found to aerobically biodegrade benzene and toluene, but not chloroform. This enrichment culture was used to study changes in pollutant toxicity as affected by biodegradative activity. Two assays for toxicity were used: (1) a 48-h acute toxicity test using the freshwater invertebrate Ceriodaphnia dubia and (2) microbial biodegradation activity as affected by the presence of mixed pollutants. At 20-ppm concentrations, toluene was significantly more toxic (99% mortality) to C. dubia than benzene (48% mortality) or chloroform (40% mortality). Also at 20-ppm concentrations, but before biodegradation, toluene was significantly more toxic (88% mortality) to C. dubia than benzene (33% mortality). After biodegradation of 98% of toluene and benzene, significant residual toxicity still remained in the bacterial supernatant: toluene-degraded supernatant caused 33% mortality in C. dubia and benzene-degraded supernatant caused 24% mortality. In the second toxicity assay, examining the effect of mixed pollutants on biodegradation activity, the presence of benzene slowed the biodegradation of toluene, but chloroform had no effect on either benzene or toluene biodegradation. Results indicate that significant toxicity remain after biodegradation and that halogenated aliphatic hydrocarbons may have little or no effect on aromatic hydrocarbon biodegradation at sites impacted by mixed pollutants.
Assuntos
Benzeno/metabolismo , Benzeno/toxicidade , Clorofórmio/metabolismo , Clorofórmio/toxicidade , Solventes/metabolismo , Solventes/toxicidade , Tolueno/metabolismo , Tolueno/toxicidade , Poluentes Químicos da Água/metabolismo , Poluentes Químicos da Água/toxicidade , Animais , Biodegradação Ambiental , Bioensaio , Cladocera , Interações Medicamentosas , Dose Letal Mediana , Microbiologia da ÁguaRESUMO
Bioluminescent bacteria are widespread in natural environments. Over the years, many researchers have been studying the physiology, biochemistry and genetic control of bacterial bioluminescence. These discoveries have revolutionized the area of Environmental Microbiology through the use of luminescent genes as biosensors for environmental studies. This paper will review the chronology of scientific discoveries on bacterial bioluminescence and the current applications of bioluminescence in environmental studies, with special emphasis on the Microtox toxicity bioassay. Also, the general ecological significance of bioluminescence will be addressed.
Bactérias que emitem bioluminescência são amplamente distribuídas em ambientes naturais. Ao longo dos anos vários pesquisadores vêm estudando a fisiologia, bioquímica e controle genético da bioluminescência. Essas descobertas têm revolucionado a Área de Microbiologia Ambiental através da utilização dos genes lux como biosensores em estudos ambientais. Esta revisão examinará a cronologia de descobertas científicas da bioluminescência bacteriana e as aplicações atuais em estudos ambientais, salientando a utilização do teste de toxicidade Microtox. A significância ecológica da bioluminescência será também examinada.