Effect of nonylphenol on response of physiology and photosynthesis-related gene transcription of Chlorella vulgaris.

Nonylphenol (NP) is regarded as a kind of persistent organic pollutant which exists ubiquitously in the environment. The objective of this study was to evaluate the effects of NP on Chlorella vulgaris physiological indices and gene transcription. The results showed that NP stress inhibited algal growth in short-term bioassay. NP also decreased chlorophyll content, including chl a, chl b, and total chlorophyll. NP caused oxidant hurt by overproducing reactive oxygen species (ROS), which might destroy the overall membrane system to cause malondialdehyde content increase. NP inhibited photosynthesis-related gene transcription in C. vulgaris after 24 to 48 h exposure. The lowest transcript levels of psaB, psbA, and rbcL in C. vulgaris decreased to only 18.5%, 7%, and 4% of the control, respectively. Taken together, our results demonstrate that NP is toxic to fresh algae growth by affecting the photosynthesis-related genes transcription and overproducing ROS to disrupt cell structure in a short period.

The effects of hydrogen peroxide on the circadian rhythms of Microcystis aeruginosa.

BACKGROUND: The cyanobacterium Microcystis aeruginosa is one of the principal bloom-forming cyanobacteria present in a wide range of freshwater ecosystems. M. aeruginosa produces cyanotoxins, which can harm human and animal health. Many metabolic pathways in M. aeruginosa, including photosynthesis and microcystin synthesis, are controlled by its circadian rhythms. However, whether xenobiotics affect the cyanobacterial circadian system and change its growth, physiology and biochemistry is unknown. We used real-time PCR to study the effect of hydrogen peroxide (H(2)O(2)) on the expression of clock genes and some circadian genes in M. aeruginosa during the light/dark (LD) cycle. RESULTS: The results revealed that H(2)O(2) changes the expression patterns of clock genes (kaiA, kaiB, kaiC and sasA) and significantly decreases the transcript levels of kaiB, kaiC and sasA. H(2)O(2) treatment also decreased the transcription of circadian genes, such as photosynthesis-related genes (psaB, psbD1 and rbcL) and microcystin-related genes (mcyA, mcyD and mcyH), and changed their circadian expression patterns. Moreover, the physiological functions of M. aeruginosa, including its growth and microcystin synthesis, were greatly influenced by H(2)O(2) treatment during LD. These results indicate that changes in the cyanobacterial circadian system can affect its physiological and metabolic pathways. CONCLUSION: Our findings show that a xenobiotic can change the circadian expression patterns of its clock genes to influence clock-controlled gene regulation, and these influences are evident at the level of cellular physiology.

Effects of copper sulfate, hydrogen peroxide and N-phenyl-2-naphthylamine on oxidative stress and the expression of genes involved photosynthesis and microcystin disposition in Microcystis aeruginosa.

Algal blooms have been increasing in prevalence all over the world, destroying ecosystems and placing other organisms at risk. Chemical remediation is one of most important methods of controlling algal bloom formation. The effects of copper sulfate, hydrogen peroxide (H(2)O(2)) and N-phenyl-2-naphthylamine on photosynthesis-related and microcystin-related gene transcription and physiological changes of Microcystis aeruginosa were analyzed. The results suggest that transcription of psaB, psbD1 and rbcL was inhibited by the three algaecides, which blocked the electron transport chain, significantly enhanced reactive oxygen species (ROS) accumulation and overwhelmed the antioxidant system. The increase in ROS destroyed pigment synthesis and membrane integrity, which inhibited or killed the algal cells. Furthermore, H(2)O(2) treatment down-regulated mcyD transcription, which indicated a decrease in the microcystin level in the cells. Our results demonstrate that H(2)O(2) has the greatest potential as an algaecide because it not only inhibits algae growth but may reduce microcystin synthesis.