title: Soluble proteome investigation of cobalt effect on the carotenoidless mutant of Rhodobacter sphaeroides.
abstract: OBJECTIVE
  To investigate the surviving capability of Rhodobacter sphaeroides under phototrophic conditions in the presence of high cobalt concentration and its influence on the photosynthetic apparatus biosynthesis.
  
  
  RESULTS
  Cells from R. sphaeroides strain R26.1 were grown anaerobically in a medium containing 5.0 mmol l(-1) cobalt ions and in a control medium. Metal toxicity was investigated comparing the soluble proteome of Co(2+)-exposed cells and cells grown in control medium by two-dimensional gel electrophoretic analysis. Significant changes in the expression level were detected for 43 proteins, the majority (35) being up-regulated. The enzyme porphobilinogen deaminase (PBGD) was found down-regulated and its activity was investigated.
  
  
  CONCLUSIONS
  The up-regulated enzymes mainly belong to the general category of proteins and DNA degradation enzymes, suggesting that part of the catabolic reaction products can rescue bacterial growth in photosynthetically impaired cells. Furthermore, the down-regulation of PBGD strongly indicates that this key enzyme of the tetrapyrrole and bacteriochlorophyll synthesis is directly involved in the metabolic response.
  
  
  CONCLUSIONS
  Data and experiments show that the cobalt detrimental effect on the photosynthetic growth of R. sphaeroides is associated with an impaired expression and functioning of PBGD.
authors.affiliation: Dipartimento di Biochimica e Biologia Molecolare, Università degli Studi di Bari, Bari, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Pisani
authors.forename: F
authors.initials: F
authors.lastname: Italiano
authors.forename: F
authors.initials: F
authors.lastname: de Leo
authors.forename: R
authors.initials: R
authors.lastname: Gallerani
authors.forename: S
authors.initials: S
authors.lastname: Rinalducci
authors.forename: L
authors.initials: L
authors.lastname: Zolla
authors.forename: A
authors.initials: A
authors.lastname: Agostiano
authors.forename: L R
authors.initials: LR
authors.lastname: Ceci
authors.forename: M
authors.initials: M
authors.lastname: Trotta
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis*; D003035:Cobalt / Q000494:pharmacology*; D015536:Down-Regulation; D004587:Electrophoresis, Agar Gel; D011163:Hydroxymethylbilane Synthase / Q000378:metabolism; D010788:Photosynthesis / Q000187:drug effects; D020543:Proteome / Q000032:analysis*; D012242:Rhodobacter sphaeroides / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D020543:Proteome; D003035:Cobalt; D011163:Hydroxymethylbilane Synthase