Antioxidant enzyme activities of Microcystis aeruginosa in response to nonylphenols and degradation of nonylphenols by M. aeruginosa

Abstract

The aim of this study was to examine the effects of chemical nonylphenols (NPs) on the antioxidant system of Microcystis aeruginosa strains. The degradation and sorption of NPs by M. aeruginosa were also evaluated. High concentrations of NPs (1 and 2 mg/l) were found to cause increases in superoxidase dismutase (SOD) and glutathione-S-transferase (GST) activities and in glutathione (GSH) levels. These results suggest that toxic stress manifested by elevated SOD and GST levels and GSH contents may be responsible for the toxicity of NPs to M. aeruginosa and that the algal cells could improve their antioxidant and detoxification ability through the enhancement of enzymatic and nonenzymatic prevention substances. The observed elevations in GSH levels and GST activities were relatively higher than those in SOD activities, indicating that GSH and GST contributed more in eliminating toxic effects than SOD. Low concentrations of NPs (0.05-0.2 mg/l) enhanced cell growth and decreased GST activity in algal cells of M. aeruginosa, suggesting that NPs may have acted as a protecting factor, such as an antioxidant.The larger portion of the NPs (>60%) disappeared after 12 days of incubation, indicating the strong ability of M. aeruginosa to degrade the moderate persistent NP compounds. The sorption ratio of M. aeruginosa after a 12-day exposure to low nominal concentrations of NPs (0.02-0.5 mg/l) was relatively high (>30%). The fact that M. aeruginosa effectively resisted the toxic effects of NPs and strongly degraded these pollutants indicate that M. aeruginosa cells have a strong ability to adapt to variations in environmental conditions and that low and moderate concentrations of organic compounds may favor its survival. Further studies are needed to provide detailed information on the fate of persistent organic pollutants and the survival of algae and to determine the possible role of organic pollutants in the occurrence of water blooms in eutrophic lakes.

Removal and Biodegradation of Nonylphenol by Four Freshwater Microalgae

“…A similar cell response was also observed in Microcystis aeruginosa and Chlorella species after NP exposure [38,39,40], and Chlorella fusca , Monoraphidium braunii and Stephanodiscus hantzschii after bisphenol-A (BPA) exposure [41,42,43]. The chlorophyll a curves showed that the A. acicularis , C. minutus and S. quadriauda had negative growth under 2.0–2.5 mg·L −1 NP exposure, whereas the C. vulgaris still grew well (Figure 1).…”

“…Such A. acicularis , C. vulgaris and S. quadriauda biodegradation was much faster than the previous results from two M. aeruginosa strains, which exhibited more than 60% NP degradation after 12 days of incubation, with different concentrations of NP [38] and microalgal species from other taxa [34]. These findings suggested that potential use of A. acicularis , C. vulgaris and S. quadriauda in the treatment of waste water containing the compound.…”

Fate and effects of nonylphenol in the presence of the cyanobacteriumMicrocystis aeruginosa

“…Therefore, internalisation of NP, followed by formation of another sub-product (which could not be measured in this study) probably took place. This result is very different from that reported by Wang and Xie [18] for M. aeruginosa binding of NP, at concentrations from 0.09 to 9 μM, who have found binding as high as 61% of the compound. Even so, results similar to ours have been reported in another work in which the amount of oestrogen that partitioned to the algae Chlorella vulgaris did not exceed 9% of the total [3].…”

“…Wang and Xie [18] have found that NP at concentrations ranging from 4.5 to 9.0 μM was biotically removed from cultures of M. aeruginosa by glutathione conjugation. We can hypothesise, but not prove using our data, that a similar mechanism might occur when M. aeruginosa was exposed to the lower NP concentrations used in the current study.…”

Interactions between Microcystis aeruginosa and coexisting amoxicillin contaminant at different phosphorus levels

“…The antioxidant enzyme GST is involved in the degradation of exogenous chemicals in microalgae, which could catalyze the conjugation of exogenous chemicals with glutathione [41]. For instance, Wang and Xie [42] observed the contribution of elevated GST activity to the biodegradation of nonylphenol in M. aeruginosa. In the present study, elevated GST activity was also coupled to the degradation of amoxicillin.…”