Processing The Interspecies Quorum-Sensing Signal Autoinducer-2 (AI-2) Characterization Of Phospho-(S)-4,5-Dihydroxy-2,3-Pentanedione Isomerization By LsrG Protein

The molecule (S)-4,5-dihydroxy-2,3-pentanedione (DPD) is produced by many different species of bacteria and is the precursor of the signal molecule autoinducer-2 (AI-2). AI-2 mediates interspecies communication and facilitates regulation of bacterial behaviors such as biofilm formation and virulence. A variety of bacterial species have the ability to sequester and process the AI-2 present in their environment, thereby interfering with the cell-cell communication of other bacteria. This process involves the AI-2-regulated lsr operon, comprised of the Lsr transport system that facilitates uptake of the signal, a kinase that phosphorylates the signal to phospho-DPD (P-DPD), and enzymes (like LsrG) that are responsible for processing the phosphorylated signal. Because P-DPD is the intracellular inducer of the lsr operon, enzymes involved in P-DPD processing impact the levels of Lsr expression. Here we show that LsrG catalyzes isomerization of P-DPD into 3,4,4-trihydroxy-2-pentanone-5-phosphate. We present the crystal structure of LsrG, identify potential catalytic residues, and determine which of these residues affects P-DPD processing in vivo and in vitro. We also show that an lsrG deletion mutant accumulates at least 10 times more P-DPD than wild type cells. Consistent with this result, we find that the lsrG mutant has increased expression of the lsr operon and an altered profile of AI-2 accumulation and removal. Understanding of the biochemical mechanisms employed by bacteria to quench signaling of other species can be of great utility in the development of therapies to control bacterial behavior

Isolation and characterization of an exopolysaccharide‐producing Leuconostoc citreum strain from artisanal cheese

peer-reviewedHigh molar mass exopolysaccharides (EPS) produced from sucrose by lactic acid bacteria (LAB) are of great interest as natural additives to use in foods, medical and pharmaceutical industry. This study aimed to identify the EPS produced by Leuconostoc citreum L3C1E7 isolated from Pico cheese and characterize the strain for technological and probiotic potential. Purified EPS was isolated from the culture of L. citreum L3C1E7 by ethanol precipitation, with a yield of 520 mg ml−1. The EPS-producing strain had a mucoid phenotype and average molecular weight of 5·88 × 106 Da. The structural characterization of the purified EPS was determined by 1H, 13C and two-dimensional NMR spectroscopy. EPS was composed of alternating α-(1→6)-linked and α-(1→3)-linked D-glucopyranyl units, suggesting the existence of an alternan. The strain was slow acidifying, produced diacetyl and displayed high esterase/lipase and aminopeptidase activities, which promote the desirable flavours in dairy products. Moreover, L. citreum showed moderate resistance to the adverse conditions of the gastrointestinal (GI) tract and high adhesion to GI cells. This work provides a better understanding of EPS produced by L. citreum and the potential application of EPS-producing strain in food and/or as a probiotic culture.Fuel Cycle Technologie

Backbone and side chain 1H, 15N and 13C assignments for a thiol-disulphide oxidoreductase from the Antarctic bacterium Pseudoalteromonas haloplanktis TAC125

Enzymes produced by psychrophilic organisms have successfully overcome the low temperature challenge and evolved to maintain high catalytic rates in their permanently cold environments. As an initial step in our attempt to elucidate the cold-adaptation strategies used by these enzymes we report here the 1H, 15N and 13C assignments for the reduced form of a thiol-disulphide oxidoreductase from the Antarctic bacterium Pseudoalteromonas haloplanktis TAC125.The NMR spectrometers are part of The National NMR Network (REDE/1517/RMN/2005), supported by ‘‘Programa Operacional Ciência e Inovação (POCTI) 2010’’ and Fundação para a Ciência e a Tecnologia (FCT). This work was funded by FCT, POCTI and FEDER; Projects POCI/BIA-PRO/57263/2004 and PTDC/BIO/70806/2006. TC is holder of a long term EMBO fellowship. MM is thankful to the Fundação para a Ciência e Tecnologia for its support through Programa Ciência 2007.info:eu-repo/semantics/publishedVersio

Production of mannosylglycerate in Saccharomyces cerevisiae by metabolic engineering and bioprocess optimization

Mannosylglycerate (MG) is one of the most widespread compatible solutes among marine microorganisms adapted to hot environments. This ionic solute holds excellent ability to protect proteins against thermal denaturation, hence a large number of biotechnological and clinical applications have been put forward. However, the current prohibitive production costs impose severe constraints towards large-scale applications. All known microbial producers synthesize MG from GDP-mannose and 3-phosphoglycerate via a two-step pathway in which mannosyl-3-phosphoglycerate is the intermediate metabolite. In an early work, this pathway was expressed in Saccharomyces cerevisiae with the goal to confirm gene function (Empadinhas et al. in J Bacteriol 186:4075--4084, 2004), but the level of MG accumulation was low. Therefore, in view of the potential biotechnological value of this compound, we decided to invest further effort to convert S. cerevisiae into an efficient cell factory for MG production.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684), BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020—Programa Operacional Regional do Norte and also by project LISBOA-01-0145-FEDER-007660 (Microbiologia Molecular, Estrutural e Celular) funded by FEDER through COMPETE2020—Programa Operacional Competitividade e Internacionalização (POCI). Cristiana Faria was supported by a Ph.D. Grant from FCT (Ref. SFRH/ BD/79552/2011).info:eu-repo/semantics/publishedVersio

Propagation of atlantic climate native species of the Genus Sedum for use in extensive green roofs

In this study, we evaluated the rooting potential of herbaceous cuttings of Atlantic climate native species of Sedum which can be interesting for use in extensive green roofs. The species are native of Galicia and León (NW Spain), which have an Atlantic climate. The following native species were considered: S. album, S. alpestre, S. anglicum, S. brevifolium, S. hirsutum and S. acre. A commercially available species, S. rupestre (S. reflexum), was used as a control for comparison with the native species. The trial was established in June 2011 in a greenhouse equipped with a fog-system and bottom heat. The cuttings used in the trials were harvested from mother plants established from wild populations collected in coastal and inland areas of Galicia and grown in a growth chamber. The cuttings were inserted directly (i.e. without prior hormonal treatment) into individual cells. The rooting media consisted of a mixture of Sphagnum peat moss, pine bark compost and vermiculite (1:1.5:2.5, v/v/v). A split plot design with 5 replicates per species-origin and evaluating date and 7 cuttings per replicate was used. Rooting percentage, visual rooting score and number of primary roots were determined 15 and 30 days after cutting. The quality of roots was evaluated as total root length and number of root tips, with a Delta-T Scan system. The length and dry weight of the shoots were determined 90 days after cutting. The mean rooting percentage was 87% on the first evaluating date and 95% on the second. The rooting percentage differed significantly between species, with the lowest values obtained for S. hirsutum of coastal origin (68%) 15 days after cutting. For the other species, the rooting percentages were similar, varying between 94 and 100% at 30 days after cutting. Root development also differed significantly between species and origins. In general, S. anglicum (from inland locations), S. album (from inland locations) and the control species (S. rupestre) developed larger root systems within the shortest space of time. The findings showed the propagation performance of Atlantic climate native species of Sedum was good. The plants can be propagated on a commercial scale from cuttings within a short time, varying between 1 and 2 or 3 months depending on the speciesS

Organic solutes in Rubrobacter xylanophilus : the first example of di- myo -inositol-phosphate in a thermophile

Abstract The thermophilic and halotolerant nature of Rubrobacter xylanophilus led us to investigate the accumulation of compatible solutes in this member of the deepest lineage of the Phylum Actinobacteria. Trehalose and mannosylglycerate (MG) were the major compounds accumulated under all conditions examined, including those for optimal growth. The addition of NaCl to a complex medium and a defined medium had a slight or negligible effect on the accumulation of these compatible solutes. Glycine betaine, di-myo-inositol-phosphate (DIP), a new phosphodiester compound, identified as di-N-acetyl-glucosamine phosphate and glutamate were also detected but in low or trace levels. DIP was always present, except at the highest salinity examined (5% NaCl) and at the lowest temperature tested (43°C). Nevertheless, the levels of DIP increased with the growth temperature. This is the first report of MG and DIP in an actinobacterium and includes the identification of the new solute di-N-acetyl-glucosamine phosphate

Pseudovitamin B(12) is the corrinoid produced by Lactobacillus reuteri CRL 1098 under anaerobic conditions

We have reported previously on the ability of Lactobacillus reuteri to produce a compound with vitamin B-12 activity. Here we report on the chemical characterisation of this corrinoid-like molecule. High performance liquid chromatography coupled to an ultraviolet diode array detector, mass spectrometry and nuclear magnetic resonance spectroscopy has enabled us to identify the compound as Co alpha-[alpha-(7-adenyl)]-Co beta-cyanocobamide or pseudovitamin B12. This molecule differs from cobalamin in the alpha-ligand, where it has adenine instead of 5,6-dimethylbenzimidazole bound in a alpha-glycosidic linkage to C-1 of ribose. L. reuteri is the first lactic acid bacterium in which the production of a cobalamin-like molecule has been identified and the first microorganism reported to produce exclusively pseudo-B-12. (c) 2007 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved