1.[Research advances in the virulence factors of Klebsiella pneumoniae--A review].
Kang Y, Tian P, Tan T. Wei Sheng Wu Xue Bao. 2015 Oct 4;55(10):1245-52.
Klebsiella pneumoniae is of great attractiveness because it naturally produces a series of bulk chemicals such as 1,3-propanediol, 2,3-butanediol and 3-hydroxypropionic acid. Although this species has been fueled in recent years, its pathogenicity is considered an obstacle hindering industrial applications. Here we portray a picture of the virulence factors, including pili, receptors, capsular polysaccharides, lipopolysaccharides, and newly identified virulence factors. This review covers aspects of virulence genes, proteins, metabolic activities, as well as the mechanisms underlying infection and immune responses. Based on state-of-the-art advances in metabolic engineering and synthetic biology, the strategies for eliminating or attenuating the virulence of K. pneumoniae were proposed, and the feasibilities for these protocols were also briefly discussed.
2.Aroma compounds generation in citrate metabolism of Enterococcus faecium: Genetic characterization of type I citrate gene cluster.
Martino GP1, Quintana IM1, Espariz M1, Blancato VS1, Magni C2. Int J Food Microbiol. 2016 Feb 2;218:27-37. doi: 10.1016/j.ijfoodmicro.2015.11.004. Epub 2015 Nov 14.
Enterococcus is one of the most controversial genera belonging to Lactic Acid Bacteria. Research involving this microorganism reflects its dual behavior as regards its safety. Although it has also been associated to nosocomial infections, natural occurrence of Enterococcus faecium in food contributes to the final quality of cheese. This bacterium is capable of fermenting citrate, which is metabolized to pyruvate and finally derives in the production of the aroma compounds diacetyl, acetoin and 2,3 butanediol. Citrate metabolism was studied in E. faecium but no data about genes related to these pathways have been described. A bioinformatic approach allowed us to differentiate cit(-) (no citrate metabolism genes) from cit(+) strains in E. faecium. Furthermore, we could classify them according to genes encoding for the transcriptional regulator, the oxaloacetate decarboxylase and the citrate transporter. Thus we defined type I organization having CitI regulator (DeoR family), CitM cytoplasmic soluble oxaloacetate decarboxylase (Malic Enzyme family) and CitP citrate transporter (2-hydroxy-carboxylate transporter family) and type II organization with CitO regulator (GntR family), OAD membrane oxaloacetate decarboxylase complex (Na(+)-transport decarboxylase enzyme family) and CitH citrate transporter (CitMHS family).
3.Enantioselective Synthesis of Vicinal (R,R)-Diols by Saccharomyces cerevisiae Butanediol Dehydrogenase.
Calam E1, González-Roca E1, Fernández MR1, Dequin S2, Parés X1, Virgili A3, Biosca JA4. Appl Environ Microbiol. 2016 Jan 4;82(6):1706-21. doi: 10.1128/AEM.03717-15.
Butanediol dehydrogenase (Bdh1p) from Saccharomyces cerevisiae belongs to the superfamily of the medium-chain dehydrogenases and reductases and converts reversibly R-acetoin and S-acetoin to (2R,3R)-2,3-butanediol and meso-2,3-butanediol, respectively. It is specific for NAD(H) as a coenzyme, and it is the main enzyme involved in the last metabolic step leading to (2R,3R)-2,3-butanediol in yeast. In this study, we have used the activity of Bdh1p in different forms-purified enzyme, yeast extracts, permeabilized yeast cells, and as a fusion protein (with yeast formate dehydrogenase, Fdh1p)-to transform several vicinal diketones to the corresponding diols. We have also developed a new variant of the delitto perfetto methodology to place BDH1 under the control of the GAL1 promoter, resulting in a yeast strain that overexpresses butanediol dehydrogenase and formate dehydrogenase activities in the presence of galactose and regenerates NADH in the presence of formate.
4.Engineering Corynebacterium glutamicum for the production of 2,3-butanediol.
Radoš D1, Carvalho AL2,3, Wieschalka S4,5, Neves AR6,7, Blombach B8, Eikmanns BJ9, Santos H10,11. Microb Cell Fact. 2015 Oct 29;14(1):171. doi: 10.1186/s12934-015-0362-x.
BACKGROUND: 2,3-Butanediol is an important bulk chemical with a wide range of applications. In bacteria, this metabolite is synthesised from pyruvate via a three-step pathway involving α-acetolactate synthase, α-acetolactate decarboxylase and 2,3-butanediol dehydrogenase. Thus far, the best producers of 2,3-butanediol are pathogenic strains, hence, the development of more suitable organisms for industrial scale fermentation is needed. Herein, 2,3-butanediol production was engineered in the Generally Regarded As Safe (GRAS) organism Corynebacterium glutamicum. A two-stage fermentation process was implemented: first, cells were grown aerobically on acetate; in the subsequent production stage cells were used to convert glucose into 2,3-butanediol under non-growing and oxygen-limiting conditions.
