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Photodynamic antimicrobial chemotherapy (PACT) is a potential antimicrobial therapy that combines light and a photosensitizing drug, promoting a phototoxic effect on the treated cells, in general via oxidative damage. In this work we studied the effect of PACT, using methylene blue (MB), on the permeability of Candida albicans membrane. Our results demonstrated that the combination of MB and laser (684 nm) promoted a decrease in Candida growth. The inhibition was more pronounced in the presence of 0.05 mg/ml MB and with an energy density of 28 J/cm(2). The decrease in Candida growth was associated with an increase in membrane permeabilization. Thus, we suggest that a PACT mechanism using MB can be related to damage in the plasma membranes of the cells.

Resumo -A bioatividade de ácidos húmicos (AH) isolados de lodo da estação de tratamento de esgoto (AHL) e de vermicomposto (AHV) foi avaliada pela ação dessas substâncias sobre o transporte de prótons através da membrana plasmática de células de raízes de café e milho e sua relação com o desenvolvimento dessas espécies. Houve estímulo da área superficial radicular em ambas as espécies cultivadas com ambos AH, mostrando uma concentração ótima em torno de 40 mg L -1 . Nessa condição, os tratamentos com AHL e AHV estimularam a H + -ATPase de membrana plasmática em plântulas de café e milho. Os AHL foram mais efetivos na promoção desses efeitos do que os AHV. A modificação do perfil cromatográfico dos AH em solução antes e após o cultivo das plântulas revelou que a interação planta-AH promoveu uma redistribuição das massas moleculares dessas substâncias, sugerindo uma dinâmica de mobilização de subunidades funcionais dos AH por exsudatos das raízes. A análise estrutural dos AH detectou a presença de grupamentos de auxina. A análise comparativa da ação desses dois AH sobre as espécies representantes de plantas monocotiledôneas (milho) e dicotiledôneas (café) apontam para a ativação da H + -ATPase de plasmalema como possível marcador metabólico de bioatividade dos ácidos húmicos.Termos para indexação: Zea mays, Coffea arabica, lodo residual, ácidos orgânicos, vermicomposto. Humic acids bioactivity: effects on root development and on the plasma membrane proton pumpAbstract -The bioactivity of humic acids (HA) isolated from sludge of the station of sewer treatment (HAL) and from vermicompost (HAV) was evaluated through the action of those substances on primary transport of protons of the plasma membrane of coffee and corn root cells and its relationship with the development of those species. A stimulation in the superficial area of roots was observed for both species cultivated with both humic acids, exhibiting an optimum concentration, about 40 mg L -1 of HA. In this condition the treatment with HAL and HAV stimulated the plasma membrane H + -ATPase of corn and coffee roots. HAL were more effective to promote those effects than HAV. The modification of the chromatographic profile of the HA in solution before and after the cultivation of the seedlings revealed that the interaction plant-HA promoted a rearrangement of the average molecular weight of those substances suggesting a dynamic mobilization of bioactive subunits of the HA by plant exudates. The structural analysis of the HA has detected the presence of auxin groups. A comparative analysis of the action of those HA on the monocotyledonous (corn) and dicotyledonous (coffee) plants indicates to the activation of plasmallema H + -ATPase as a possible metabolic marker for bioactivity of humic acids.

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