title: Adaptative biochemical pathways and regulatory networks in Klebsiella oxytoca BAS-10 producing a biotechnologically relevant exopolysaccharide during Fe(III)-citrate fermentation.
abstract: BACKGROUND
  A bacterial strain previously isolated from pyrite mine drainage and named BAS-10 was tentatively identified as Klebsiella oxytoca. Unlikely other enterobacteria, BAS-10 is able to grow on Fe(III)-citrate as sole carbon and energy source, yielding acetic acid and CO2 coupled with Fe(III) reduction to Fe(II) and showing unusual physiological characteristics. In fact, under this growth condition, BAS-10 produces an exopolysaccharide (EPS) having a high rhamnose content and metal-binding properties, whose biotechnological applications were proven as very relevant.
  
  
  RESULTS
  Further phylogenetic analysis, based on 16S rDNA sequence, definitively confirmed that BAS-10 belongs to K. oxytoca species. In order to rationalize the biochemical peculiarities of this unusual enterobacteriun, combined 2D-Differential Gel Electrophoresis (2D-DIGE) analysis and mass spectrometry procedures were used to investigate its proteomic changes: i) under aerobic or anaerobic cultivation with Fe(III)-citrate as sole carbon source; ii) under anaerobic cultivations using Na(I)-citrate or Fe(III)-citrate as sole carbon source. Combining data from these differential studies peculiar levels of outer membrane proteins, key regulatory factors of carbon and nitrogen metabolism and enzymes involved in TCA cycle and sugar biosynthesis or required for citrate fermentation and stress response during anaerobic growth on Fe(III)-citrate were revealed. The protein differential regulation seems to ensure efficient cell growth coupled with EPS production by adapting metabolic and biochemical processes in order to face iron toxicity and to optimize energy production.
  
  
  CONCLUSIONS
  Differential proteomics provided insights on the molecular mechanisms necessary for anaeorobic utilization of Fe(III)-citrate in a biotechnologically promising enterobacteriun, also revealing genes that can be targeted for the rational design of high-yielding EPS producer strains.
authors.affiliation: Dipartimento di Scienze e Tecnologie Molecolari e Biomolecolari (STEMBIO), Università di Palermo Viale delle Scienze, ed, 16, Parco d'Orleans II, Palermo, 90128, Italy. giumir@msn.com
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Gallo
authors.forename: Franco
authors.initials: F
authors.lastname: Baldi
authors.forename: Giovanni
authors.initials: G
authors.lastname: Renzone
authors.forename: Michele
authors.initials: M
authors.lastname: Gallo
authors.forename: Antonio
authors.initials: A
authors.lastname: Cordaro
authors.forename: Andrea
authors.initials: A
authors.lastname: Scaloni
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Puglia
mesh_terms: D001709:Biotechnology; D019343:Citric Acid / Q000378:metabolism*; D005285:Fermentation; D005290:Ferric Compounds / Q000378:metabolism*; D053263:Gene Regulatory Networks; D041121:Klebsiella oxytoca / Q000145:classification / Q000378:metabolism*; D053858:Metabolic Networks and Pathways; D010802:Phylogeny; D040901:Proteomics; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D005290:Ferric Compounds; D012336:RNA, Ribosomal, 16S; D019343:Citric Acid