RESUMEN
Two bacterial strains were isolated in the presence of naphthalene as the sole carbon and energy source from sediments of the Orbetello Lagoon, Italy, which is highly contaminated with both organic compounds and metals. 16S rRNA gene sequence analysis of the two isolates assigned the strains to the genera Paenibacillus and Pseudomonas. The effect of different contaminants on the growth behaviors of the two strains was investigated. Pseudomonas sp. ORNaP2 showed a higher tolerance to benzene, toluene, and ethylbenzene than Paenibacillus sp. ORNaP1. In addition, the toxicity of heavy metals potentially present as co-pollutants in the investigated site was tested. Here, strain Paenibacillus sp. ORNaP1 showed a higher tolerance towards arsenic, cadmium, and lead, whereas it was far more sensitive towards mercury than strain Pseudomonas sp. ORNaP2. These differences between the Gram-negative Pseudomonas and the Gram-positive Paenibacillus strain can be explained by different general adaptive response systems present in the two bacteria.
Asunto(s)
Sedimentos Geológicos/microbiología , Bacterias Grampositivas/metabolismo , Naftalenos/metabolismo , Pseudomonas/metabolismo , Contaminantes Químicos del Agua/metabolismo , Secuencia de Bases , Biodegradación Ambiental , Cartilla de ADN/genética , ADN Bacteriano/genética , ADN Ribosómico/genética , Bacterias Grampositivas/efectos de los fármacos , Bacterias Grampositivas/genética , Bacterias Grampositivas/aislamiento & purificación , Italia , Metales Pesados/toxicidad , Datos de Secuencia Molecular , Naftalenos/toxicidad , Filogenia , Hidrocarburos Policíclicos Aromáticos/metabolismo , Hidrocarburos Policíclicos Aromáticos/toxicidad , Pseudomonas/efectos de los fármacos , Pseudomonas/genética , Pseudomonas/aislamiento & purificación , ARN Bacteriano/genética , ARN Ribosómico 16S/genética , Contaminantes Químicos del Agua/toxicidadRESUMEN
Bacillus sp. ORAs2 and Pseudomonas sp. ORAs5, two arsenic-resistant bacterial strains previously isolated from sediments of the Orbetello Lagoon, Italy, were tested for their adaptation to mixed contaminants on the level of membrane fatty acid composition. The two bacterial strains were characterized by high levels of arsenic resistance, and Pseudomonas sp. ORAs5 was also shown to be solvent-tolerant. The bacterial strains were exposed to mixtures of two toxic compounds: arsenic at fixed concentrations and toluene in variable amounts or, alternatively, toluene at constant values along with arsenic added at variable concentrations. Both strains react to the contaminants by changing the composition of their membrane fatty acids. Bacillus sp. strain ORAs2 showed a correlation between growth rate decreases and fatty acids degree of saturation increases in both cases, although pointedly in the presence of 1, 2, and 3 mM of toluene and different additions of arsenic, counteracting membranes fluidity induced by toxic compounds. In Pseudomonas sp. ORAs5, adaptive changes in membrane composition was observed both in terms of increases in the degree of saturation and in the trans/cis ratio of unsaturated fatty acids in the presence of varying toluene and constant arsenic concentrations, whereas only minor changes occurred with increasing arsenic and constant toluene concentrations. Thus, on the level of membrane composition, Bacillus sp. ORAs2 showed a higher potential for adaptation to the presence of mixed pollutants, suggesting its probable suitability for bioremediation purposes.
