title: Over-expression of stress protein-encoding genes helps Clostridium acetobutylicum to rapidly adapt to butanol stress.
abstract: The toxicity of n-butanol in microbial fermentations limits its formation. The stress response of Clostridium acetobutylicum involves various stress proteins and therefore, over-expression of genes encoding stress proteins constitutes an option to improve solvent tolerance. Over-expression of groESL, grpE and htpG, significantly improved butanol tolerance of C. acetobutylicum. Whereas the wild type and vector control strain did not survive 2 % (v/v) butanol for 2 h, the recombinant strains showed 45 % (groESL), 25 % (grpE) and 56 % (htpG), respectively, of the initial c.f.u. after 2 h of butanol exposure. As previously, over-expression of groESL led to higher butanol production rates, but the novel strains over-expressing grpE or htpG produced only 51 and 68 %, respectively, of the wild type butanol concentrations after 72 h clearly differentiating butanol tolerance and production. Not only butanol tolerance but also the adaptation to butanol in successive stress experiments was significantly facilitated by increased levels of GroESL, GrpE and HtpG. Re-transformation and sequence analyses of the plasmids confirmed that not the plasmids, but the host cells evolved to a more robust phenotype.
authors.affiliation: Abteilung Mikrobiologie, Institut für Biowissenschaften, Universität Rostock, Albert-Einstein-Str. 3, 18059 Rostock, Germany. miriam.mann@uni-rostock.de
authors.forename: Miriam S
authors.initials: MS
authors.lastname: Mann
authors.forename: Zdravko
authors.initials: Z
authors.lastname: Dragovic
authors.forename: Georg
authors.initials: G
authors.lastname: Schirrmacher
authors.forename: Tina
authors.initials: T
authors.lastname: Lütke-Eversloh
mesh_terms: D000222:Adaptation, Physiological; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D000440:Butanols / Q000633:toxicity*; D018833:Chaperonins / Q000096:biosynthesis / Q000235:genetics; D046969:Clostridium acetobutylicum / Q000187:drug effects* / Q000235:genetics*; D018628:Gene Dosage; D015870:Gene Expression; D018841:HSP90 Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics; D006360:Heat-Shock Proteins / Q000096:biosynthesis* / Q000235:genetics; D050296:Microbial Viability / Q000187:drug effects; D010957:Plasmids; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D000440:Butanols; C097970:GroESL protein, Bacteria; C068113:GrpE protein, Bacteria; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C066720:HtpG protein, bacteria; D018833:Chaperonins