Growth and metabolic responses to methyl viologen (1,1′-dimethyl - 4,4′-bipyridinium dichloride) on Chlorella vulgaris.

Aquatic environments are especially susceptible to being contaminated by pesticides used in agricultural fields. Methyl viologen (MV) is an herbicide with high effectiveness for the control of unwanted land plants; however, it also has a high toxicity towards the algae in the aquatic environment. The objective of this work was to describe the effect of MV on photosynthetic metabolism and its relationship with respiration, growth and the content of photosynthetic pigments of Chlorella vulgaris. The cultures of C. vulgaris were exposed for 72 h at different concentrations of methyl viologen. The results show that growth, pigment content and metabolic activity decrease as the concentration of MV increases. Analysis of the photochemical activity indicates that MV produces an inhibition of electron transport between quinone A and quinone B of photosystem II. The inhibition of photosynthetic electron transport is directly related to the reduction of metabolic activity and cell growth. The results found in this research show that methyl viologen can be a toxic pollutant for primary producers in aquatic environments. [Display omitted] •Exposure to methyl viologen (MV) reduce growth in Chlorella vulgaris. •Photosynthetic activity is more sensitive than cellular respiration to methyl viologen. •Exposure to MV significantly reduces the electron flow in PSII, specifically between QA and QB. •Exposure to MV significantly reduces the content of chlorophylls and carotenoids. • Micromolar concentrations of MV can affect the metabolism and growth of C. vulgaris in 72 h. [ABSTRACT FROM AUTHOR]