title: The effects of hydrogen peroxide on the circadian rhythms of Microcystis aeruginosa.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou, People's Republic of China.
authors.forename: Haifeng
authors.initials: H
authors.lastname: Qian
authors.forename: Baolan
authors.initials: B
authors.lastname: Hu
authors.forename: Shuqiong
authors.initials: S
authors.lastname: Yu
authors.forename: Xiangjie
authors.initials: X
authors.lastname: Pan
authors.forename: Tao
authors.initials: T
authors.lastname: Wu
authors.forename: Zhengwei
authors.initials: Z
authors.lastname: Fu
mesh_terms: D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D001427:Bacterial Toxins / Q000235:genetics; D002940:Circadian Rhythm / Q000235:genetics*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D052998:Microcystins / Q000235:genetics; D046931:Microcystis / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010788:Photosynthesis / Q000187:drug effects / Q000235:genetics; D015262:Xenobiotics / Q000494:pharmacology
chemical_list: D000891:Anti-Infective Agents, Local; D001427:Bacterial Toxins; D052998:Microcystins; D016877:Oxidants; D015262:Xenobiotics; D006861:Hydrogen Peroxide