Effect of mixed organic compounds extracted from Rhodobacter sphaeroides on Daphnia magna (water flea)

In this study, the potential for Rhodobacter sphaeroides, a purple nonsulfur photosynthetic strain of bacteria, to act as a physiological activation material for water flea, Daphnia magna, was tested under two different culture conditions: i. e. YTC (a 1:1 mixture of yeast: Tetramin: Ceropyl) as a basal diet with Selenastrum capricormutrum, a green microalga, and YTC with physiologically activating compounds (PACs), which were defined as mixed organic compounds produced in R. sphaeroides. The impact of PACs produced in R. sphaeroides was assessed by the viability, growth and reproduction of D. magna until the third generation. Compared to S. capricormutrum, it was found that the number of baby daphnia increased after addition to D. magna of PACs produced from dark-cultured R. sphaeroides. Also, we demonstrated that PACs produced from dark-cultured R. sphaeroides influenced individual D. magna growth parameters, such as body length, survival and number of broods per female. Here, we also studied the effect of enhanced sensitivity of D. magna to toxic materials, i. e. titanium oxide and methidathion, when D. magna were grown in culture using PACs. The data provide strong evidence that R. sphaeroides has the potential to substantially increase the physiological activity of D. magna.