title: A low-GC Gram-positive Thermoanaerobacter-like bacterium isolated from an Indian hot spring contains Cr(VI) reduction activity both in the membrane and cytoplasm.
abstract: OBJECTIVE
  Characterization of an anaerobic thermophilic bacterium and subcellular localization of its Cr(VI)-reducing activity for potential bioremediation applications.
  
  
  RESULTS
  16S rRNA gene sequence-based analyses of bacterial strains isolated from sediment samples of a Bakreshwar (India) hot spring, enriched anaerobically in iron-reducing medium, found them to be 86-96% similar to reported Thermoanaerobacter strains. The most efficient iron reducer among these, BSB-33, could also reduce Cr(VI) at an optimum temperature of 60 degrees C and pH 6.5. Filtered culture medium could reduce Cr(VI) but not Fe(III). Cell-free extracts reduced Cr(VI) inefficiently under aerobic conditions but efficiently anaerobically. Fractionation of the cell-free extracts showed that chromium reduction activity was present in both the cytoplasm and membrane.
  
  
  CONCLUSIONS
  BSB-33 reduced Fe(III) and Cr(VI) anaerobically at 60 degrees C optimally. After fractionation, the reducing activity of Cr(VI) was found in both cytoplasmic and membrane fractions.
  
  
  CONCLUSIONS
  To the best of our knowledge, this is the first systematic study of anaerobic Cr(VI) reduction by a gram-positive thermophilic micro-organism and, in contrast to our results, none of the earlier reports has mentioned Cr(VI)-reducing activity to be present both in the cytoplasm and membrane of an organism. The strain may offer itself as a potential candidate for bioremediation.
authors.affiliation: Department of Life Science and Biotechnology, Jadavpur University, Kolkata.
authors.forename: D C
authors.initials: DC
authors.lastname: Bhowmick
authors.forename: B
authors.initials: B
authors.lastname: Bal
authors.forename: N S
authors.initials: NS
authors.lastname: Chatterjee
authors.forename: A N
authors.initials: AN
authors.lastname: Ghosh
authors.forename: S
authors.initials: S
authors.lastname: Pal
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D002857:Chromium / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D004275:DNA, Ribosomal / Q000235:genetics; D045482:Hot Springs; D006358:Hot Temperature; D007194:India; D007501:Iron / Q000378:metabolism; D008854:Microscopy, Electron; D010088:Oxidoreductases / Q000032:analysis; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*; D046968:Thermoanaerobacter / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*
chemical_list: D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D012989:Soil Pollutants; D002857:Chromium; D007501:Iron; D010088:Oxidoreductases; C063243:chromate reductase