title: Carotenoids play a positive role in the degradation of heterocycles by Sphingobium yanoikuyae.
abstract: BACKGROUND
  Microbial oxidative degradation is a potential way of removing pollutants such as heterocycles from the environment. During this process, reactive oxygen species or other oxidants are inevitably produced, and may cause damage to DNA, proteins, and membranes, thereby decreasing the degradation rate. Carotenoids can serve as membrane-integrated antioxidants, protecting cells from oxidative stress.
  
  
  RESULTS
  Several genes involved in the carotenoid biosynthetic pathway were cloned and characterized from a carbazole-degrading bacterium Sphingobium yanoikuyae XLDN2-5. In addition, a yellow-pigmented carotenoid synthesized by strain XLDN2-5 was identified as zeaxanthin that was synthesized from β-carotene through β-cryptoxanthin. The amounts of zeaxanthin and hydrogen peroxide produced were significantly and simultaneously enhanced during the biodegradation of heterocycles (carbazole < carbazole + benzothiophene < carbazole + dibenzothiophene). These higher production levels were consistent with the transcriptional increase of the gene encoding phytoene desaturase, one of the key enzymes for carotenoid biosynthesis.
  
  
  CONCLUSIONS
  Sphingobium yanoikuyae XLDN2-5 can enhance the synthesis of zeaxanthin, one of the carotenoids, which may modulate membrane fluidity and defense against intracellular oxidative stress. To our knowledge, this is the first report on the positive role of carotenoids in the biodegradation of heterocycles, while elucidating the carotenoid biosynthetic pathway in the Sphingobium genus.
authors: State Key Laboratory of Microbial Metabolism & School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China.
authors: Xiaorui
authors: X
authors: Liu
authors: Zhonghui
authors: Z
authors: Gai
authors: Fei
authors: F
authors: Tao
authors: Hongzhi
authors: H
authors: Tang
authors: Ping
authors: P
authors: Xu
mesh_terms: D002338:Carotenoids / Q000378:metabolism*; D065366:Cryptoxanthins; D006571:Heterocyclic Compounds / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology; D042301:Sphingomonadaceae / Q000378:metabolism*; D024341:Xanthophylls / Q000378:metabolism; D065146:Zeaxanthins; D019207:beta Carotene / Q000378:metabolism
chemical_list: D065366:Cryptoxanthins; D006571:Heterocyclic Compounds; D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene; D002338:Carotenoids