title: Chlorpyrifos degradation by the cyanobacterium Synechocystis sp. strain PUPCCC 64.
abstract: OBJECTIVE
  Indiscriminate use of insecticides leads to environmental problems and poses a great threat to beneficial microorganisms. The aim of the present work was to study chlorpyrifos degradation by a rice field cyanobacterium Synechocystis sp. strain PUPCCC 64 so that the organism is able to reduce insecticide pollution in situ.
  
  
  METHODS
  The unicellular cyanobacterium isolated and purified from a rice field was identified by partial 16S rRNA gene sequence as Synechocystis sp. strain PUPCCC 64. Tolerance limit of the organism was determined by studying its growth in graded concentrations (2.5-20 mg/L) of chlorpyrifos. Chlorpyrifos removal was studied by its depletion from the insecticide supplemented growth medium, and its biodegradation products were identified in the cell extract, biomass wash, and growth medium.
  
  
  CONCLUSIONS
  The organism tolerated chlorpyrifos up to 15 mg/L. Major fraction of chlorpyrifos was removed by the organism during the first day followed by slow uptake. Biomass, pH, and temperature influenced the insecticide removal and the organism exhibited maximum chlorpyrifos removal at 100 mg protein/L biomass, pH 7.0, and 30°C. The cyanobacterium metabolized chlorpyrifos producing a number of degradation products as evidenced by GC-MS chromatogram. One of the degradation products was identified as 3,5,6-trichloro-2-pyridinol.
  
  
  CONCLUSIONS
  Present study reports the biodegradation of chlorpyrifos by Synechocystis sp. Biodegradation of the insecticide by the cyanobacterium is significant as it can be biologically removed from the environment. The cyanobacterium may be used for bioremediation of chlorpyrifos-contaminated soils.
authors.affiliation: Department of Botany, Punjabi University, Patiala, 147 002 Punjab, India. dp.khokhar@rediffmail.com
authors.forename: D P
authors.initials: DP
authors.lastname: Singh
authors.forename: J I S
authors.initials: JI
authors.lastname: Khattar
authors.forename: J
authors.initials: J
authors.lastname: Nadda
authors.forename: Y
authors.initials: Y
authors.lastname: Singh
authors.forename: A
authors.initials: A
authors.lastname: Garg
authors.forename: N
authors.initials: N
authors.lastname: Kaur
authors.forename: A
authors.initials: A
authors.lastname: Gulati
mesh_terms: D001673:Biodegradation, Environmental; D018533:Biomass; D004390:Chlorpyrifos / Q000737:chemistry / Q000378:metabolism*; D004785:Environmental Pollutants / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007306:Insecticides / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D012336:RNA, Ribosomal, 16S / Q000737:chemistry; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism*; D013696:Temperature
chemical_list: D004785:Environmental Pollutants; D007306:Insecticides; D012336:RNA, Ribosomal, 16S; D004390:Chlorpyrifos