Efeitos dos nanomateriais Fulereno e Nanoprata sobre bactérias associadas á superfície corporal do Poliqueto estuarino Laeonereis acuta (Polychaeta, Nereididae)

Abstract

Ambientes estuarinos e costeiros são um dos prováveis destinos finais dos nanomateriais, mesmo havendo ainda uma grande lacuna em relação a estudos que lidem com os efeitos dos nanomateriais sobre organismos estuarinos. Este trabalho analisou o crescimento e respostas bioquímicas de seis colônias expostas aos nanomateriais fulereno (nC60, preparado sem uso de solventes) e nanoprata (nAg; não encapsulada), aplicados individualmente (0,01; 0,1; e 1 mg/L) e conjuntamente (nC60 + nAg: 0,01; 0,1; e 1 mg/L de nanoprata e 1 mg/L de fulereno), sobre colônias de bactérias isoladas do muco do poliqueto estuarino Laeonereis acuta (Nereididae), no escuro. As exposições ocorreram em 24 h, com agitação constante e, em seguida, as amostras foram inoculadas em agar por mais 24 h para analisar a biomassa produzida e as unidades formadoras de colônias (UFC). As UFC foram, então, contadas, e a biomassa úmida foi pesada, sendo este material utilizado para as análises bioquímicas. O crescimento (por biomassa úmida) foi inibido nas concentrações de 0,01 e 0,1 mg/L de nAg e para 0,01 e 0,1 mg/L de nAg + 1 mg/L constantes de nC60 (p < 0,05). O crescimento não foi afetado em termo de número de UFC (p > 0,05). A capacidade antioxidante total contra peroxi-radicais não mostrou diferenças significativas aos controles (p > 0,05). O dano por peroxidação lipídica foi significativo em relação ao controle nas concentrações 0,1 e 0,01 mg/L de nC60 e a atividade da GST foi significativamente maior em relação ao seu controle apenas concentração de 1 mg/L da co-exposição de ambos os nanomateriais (p < 0,05). A nanoprata demonstrou-se tóxica para as colônias bacterianas. Apesar do fulereno não ter inibido o crescimento bacteriano, ele intermediou peroxidação lipídica e induziu aumento nos níveis de GST quando em exposição conjunta com nAg. Tais resultados podem significar que nC60 induziu a produção de algum nível de ERO nos tratamentos, estando tanto em coexposição com nAg ou sozinho, na ausência de luz, mas seu efeito no crescimento bacteriano quando em exposição conjunta com nAg foi inexistente. Por outro lado, nAg foi capaz de inibir o crescimento bacteriano aparentemente sob limitado intermédio de ERO.

Estuarine and coastal environments are likely to become one of the final destinations for nanomaterials, and there is still a great lack of studies that deal with the effects of nanomaterials on estuarine organisms. This work analised growth and biochemical responses of six colonies exposed to the nanomaterials fullerene (nC60, no solvents used in preparation) and nanosilver (nAg, not encapsulated) alone (0.01, 0.1, and 1 mg/L) and together (nC60 + nAg: 0.01, 0.1, and 1 mg/L of nanosilver and 1 mg/L of fullerene), in darkness, on bacterial colonies isolated from the mucus of the estuarine polichaeta Laeonereis acuta (Nereididae). Exposures were performed during 24 h, with constant shaking and then the samples were inoculated on agar during 24 h again to produce biomass or colony forming units (CFU). After growth analysis this material was employed for the biochemical tests. Growth (tested by wet biomass weight) was inhibited at the 0.01 and 0.1 mg/L nAg and 0.01 and 0.1 mg/L nAg + constant 1 mg/L nC60 (p < 0.05). Colonies growth was not affected in terms of CFU number (p > 0.05). Total antioxidant capacity against peroxyl radicals showed no significant variation (p > 0.05). Lipid peroxidation damage was significant from the control for the concentrations of 0.01 and 0.1 mg of nC60/L and GST activity was significant from the control group at the concentration of 1 mg/L of both nanomaterials co-exposed (p < 0.05). Althoug nC60 did not induce inhibition in bacterial growth, it induced lipid peroxidation when alone and increased GST activity when coapled with nAg. These results could mean that nC60 induced some ROS levels in treatments, being alone or coupled with nAg, without light, but it did not induce bacterial growth inhibition when alone or affected nAg bacterial growth inhibition when together with the latter. On the other hand, nAg was capable of bacterial growth inhibition, without the detection of ROS influence by our biochemical tests.

Estuarine and coastal environments are likely to become one of the final destinations for nanomaterials, and there is still a great lack of studies that deal with the effects of nanomaterials on estuarine organisms. This work analised growth and biochemical responses of six bacterial colonies, which were isolated from the mucus of the estuarine polichaeta Laeonereis acuta (Nereididae), after been exposed to the nanomaterials fullerene (nC60, no solvents used in preparation) and colloida nanosilver (nAg) alone (0.01, 0.1, and 1 mg/L) and together (0.01, 0.1, and 1 mg/L of nanosilver and 1 mg/L of fullerene added to each nAg concentration), in darkness. Exposures were performed during 24 h, with constant shaking and then the samples were inoculated on agar during 24 h again to produce biomass or colony forming units (CFU). After growth analysis this material was employed for the biochemical tests. Growth (tested by wet biomass weight) was inhibited at the 0.01 and 0.1 mg/L of nAg and 0.01 and 0.1 mg/L nAg + constant 1 mg/L of nC60 (p < 0.05). Colonies growth was not affected in terms of CFU number (p > 0.05). Total antioxidant capacity against peroxyl radicals showed no significant variation (p > 0.05). Lipid peroxidation damage was significant from the control for the concentrations of 0.01 and 0.1 mg/L of nC60 and GST activity was significant from the control group at the concentration of 1 mg/L of both nanomaterials co-exposed (p < 0.05). Althoug nC60 did not induce inhibition in bacterial growth, it induced lipid peroxidation when alone and increased GST activity when together with nAg. These results could mean that nC60 induced some ROS levels in treatments, being alone or together with nAg, without light, but it did not induce bacterial growth inhibition when alone or affected nAg bacterial growth inhibition when together with the latter. On the other hand, nAg was capable of bacterial growth inhibition, although 18 the biochemical measurements did not suggest that this response is due to ROS generation.