title: Isolation and classification of a soil actinomycete capable of sulphur-specific biotransformation of dibenzothiophene, benzothiophene and thianthrene.
abstract: OBJECTIVE
  To isolate actinomycete spp with the ability to desulphurize sulphur-containing heterocyclic compounds present in petroleum.
  
  
  RESULTS
  Enrichment cultures were set up to select and isolate sulphur heterocycle metabolizing soil micro-organisms. Screening of the microbial isolates for the desulphurization property led to isolation of R3. The isolate was characterized by PCR screening of 16S rRNA genes and classical taxonomic investigations. HPLC analysis of the desulphurization assays with R3 showed ~85% transformation of dibenzothiophene (270 μmol l(-1)), present as the sole sulphur source in basal salt medium, in 4 days. Production of the desulphurized dibenzothiophene metabolite, 2-hydroxybiphenyl, was confirmed by GC/MS analyses. GC/MS analyses also established the ability of R3 to transform benzothiophene to benzothiophene-1-oxide and benzothiophene-1, 1-dioxide, and thianthrene to thianthrene-5-oxide. PCR primers computed based on the desulphurization operon (dszABC) of Rhodococcus erythropolis IGTS8 yielded the predicted amplification products with R3 genomic DNA as template. Southern hybridization and restriction endonuclease digestion profiles indicated that R3 amplicons were homologous to dsz AB.
  
  
  CONCLUSIONS
  The enrichment method used in this study yielded an environmental isolate with the ability to transform multiple sulphur heterocycles. The isolate R3 has taxonomic proximity to the Oerskovia sp, order Actinomycetales. The isolate R3 selectively removes sulphur from dibenzothiophene yielding 2-hydroxybiphenyl and sulphate. R3 also transforms benzothiophene and thianthrene in a sulphur-targeted manner. The desulphurization genes in R3 bear similarity to those in R. erythropolis IGTS8.
  
  
  CONCLUSIONS
  The actinomycetes present in soil can remove sulphur from different sulphur heterocycle substrates and have potential as biodesulphurization catalysts.
authors.affiliation: CSIR-National Environmental Engineering Research Institute, Nagpur, Maharashtra, India.
authors.forename: S
authors.initials: S
authors.lastname: Khedkar
authors.forename: R
authors.initials: R
authors.lastname: Shanker
mesh_terms: D039903:Actinobacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000192:Actinomycetales / Q000145:classification; D001711:Biotransformation / Q000235:genetics; D006571:Heterocyclic Compounds / Q000378:metabolism*; D010578:Petroleum / Q000378:metabolism; D012240:Rhodococcus / Q000235:genetics; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*; D013876:Thiophenes / Q000378:metabolism*
chemical_list: D006571:Heterocyclic Compounds; D010578:Petroleum; D012989:Soil Pollutants; D013876:Thiophenes; C088015:benzothiophene; C009449:thianthrene; C016366:dibenzothiophene
keywords: Isolation; actinomycetes; biotransformation; characterization; environmental health; pollutants; sulphur heterocycles