Tolerance to high osmolality of the lactic acid bacterium Oenococcus oeni and identification of potential osmoprotectants.

International audienceGrowth of the lactic acid bacterium Oenococcus oeni under hyperosmotic constraint was investigated in a chemically defined medium. The bacterium could grow on media with an elevated osmolality, preferably below 1.5 Osm kg(-)(1) H(2)O. At osmolalities comprised between 0.6 and 1.5 Osm kg(-)(1) H(2)O, the growth deficit elicited by the sugars glucose and fructose was slightly more severe than with salts (NaCl or KCl). In contrast to what was observed in other lactic acid bacteria, proline, glycine betaine and related molecules were unable to relieve inhibition of growth of O. oeni under osmotic constraint. This was correlated to the absence of sequences homologous to the genes coding for glycine betaine and/or proline transporters described in Lactococcus lactis and Lactobacillus plantarum. The amino acid aspartate proved to be osmoprotective under electrolyte and non-electrolyte stress. Examination of the role of peptides during osmoregulation showed that proline- and glutamate-containing peptides were protective under salt-induced stress, and not under sugar-induced stress. Under high salt, PepQ a cytoplasmic prolidase that specifically liberated proline from di-peptides increased activity, while PepX (X-prolyl-dipeptidyl aminopeptidase) and PepI (iminopeptidase) activities were unaffected. Our data suggest that proline- and glutamate-containing peptides may contribute to the adaptation of O. oeni to high salt through their intracellular hydrolysis and/or direct accumulation

Characterization of an acquired dps-containing gene island in the lactic acid bacterium Oenococcus oeni

International audienceGenomic surveillance of the two available genome sequences from Oenococcus oeni indicated the presence of a 480-bp ORF, encoding a 18.7-kDa protein named DpsA, whose deduced amino acid sequence was in significant homology with the Dps proteins from Escherichia coli and various lactic acid bacteria. Consistent with the role of Dps proteins as a key component in response to oxydative stress, the cloned dpsA gene complemented the dps- mutant of E. coli and conferred resistance to hydrogen peroxide. More interestingly, the oenococcal gene also protected E. coli from the deleterious effects of wine, copper and ferric ions, three stressors encountered by O. oeni in its environment. The dpsA gene was flanked by IS-related elements. The entire region was characterized by an anomalously high GC content compared to those reported for complete PSU-1 and ATCC-BAA-1163 oenococcal genomes. In the O. oeni species, the dpsA gene was present in 15 of the 38 tested isolates. Positive strains were apparently unrelated, as they originated from different geographical areas and types of wines. No change in tolerance to wine was observed between strains harbouring dpsA and those not harbouring this gene. Our results suggest that some O. oeni have acquired the dpsA gene as part of a mobile element. DpsA probably increases the O. oeni fitness in response to environmental challenges. However, the physiological condition under which it adds a selective advantage to O. oeni during winemaking remains to be found

Characterization of an acquired-dps-containing gene island in the lactic acid bacterium Oenococcus oeni

International audienceAims: To identify novel actors responsible for the marked adaptation of the Oenococcus oeni species to its environment. Methods and Results: Genomic surveillance of the available genome sequences from O. oeni indicated the presence of a small ORF, encoding a protein named DpsA. The cloned gene complemented the dps) mutant of Escherichia coli and conferred resistance to hydrogen peroxide, wine, and metals. The dpsA gene was flanked by IS-related elements. The entire region was characterized by an anomalously high GC content compared to those reported for oenococcal genomes. The dpsA gene was present in 15 of the 38 tested isolates. Positive strains originated from different geographical areas and sources. No change in tolerance to wine or to oxidative stress was observed between O. oeni strains harbouring dpsA and those not harbouring this gene. Conclusions: Some O. oeni have acquired a functional homologue to the dps gene from E. coli as part of a mobile element. Significance and Impact of the Study: DpsA probably increases the bacterial fitness in response to environmental challenges. However, the physiological condition under which it adds a selective advantage to O. oeni during wine-making remains to be found

Biology-oriented synthesis of a natural-product inspired oxepane collection yields a small-molecule activator of the Wnt-pathway

In Biology Oriented Synthesis the scaffolds of biologically relevant compound classes inspire the synthesis of focused compound collections enriched in bioactivity. This criterion is met by the structurally complex scaffolds of natural products (NPs) selected in evolution. The synthesis of NP-inspired compound collections approaching the complexity of NPs calls for the development of efficient synthetic methods. We have developed a one pot 4–7 step synthesis of mono-, bi-, and tricyclic oxepanes that resemble the core scaffolds of numerous NPs with diverse bioactivities. This sequence entails a ring-closing ene-yne metathesis reaction as key step and makes productive use of polymer-immobilized scavenger reagents. Biological profiling of a corresponding focused compound collection in a reporter gene assay monitoring for Wnt-signaling modulation revealed active Wntepanes. This unique class of small-molecule activators of the Wnt pathway modulates the van-Gogh-like receptor proteins (Vangl), which were previously identified in noncanonical Wnt signaling, and acts in synergy with the canonical activator protein (Wnt-3a)

Intraspecific diversity of Oenococcus oeni strains determined by sequence analysis of target genes.

International audienceUsing molecular techniques and sequencing, we studied the intraspecific diversity of Oenococcus oeni, a lactic acid bacterium involved in red winemaking. A relationship between the phenotypic and genotypic characterization of 16 O. oeni strains isolated from wine with different levels of enological potential was shown. The study was based on the comparative genomic analysis by subtractive hybridization between two strains of O. oeni with opposite enological potential. The genomic sequences obtained from subtractive hybridization were amplified by polymerase chain reaction and sequenced for the 16 strains. A considerable diversity among strains of O. oeni was observed