New features of the cell wall of the radio-resistant bacterium Deinococcus radiodurans

We have analyzed the cell wall of the radio-resistant bacterium Deinococcus radiodurans. Unexpectedly, the bacterial envelope appears to be organized in different complexes of high molecular weight. Each complex is composed of several proteins, most of which are coded by genes of unknown function and the majority are constituents of the inner/outer membrane system. One of the most abundant complexes is constituted by the gene DR_0774. This protein is a type of secretin which is a known subunit of the homo-oligomeric channel that represents the main bulk of the type IV piliation family. Finally, a minor component of the pink envelope consists of several inner-membrane proteins. The implications of these findings are discussed.     

Isolation of bioactive peptides from tryptone that modulate lipase production in Yarrowia lipolytica

In this work the effect of several organic nitrogen sources on lipase production in Yarrowia lipolytica LgX64.81 overproducing mutant was studied. Among them, tryptone and peptone showed the most prominent stimulatory effect. Interestingly, only tryptic and peptic casein digest were found to highly induce lipase biosynthesis while lipase production was very limited in the presence of casein digest from papain and pronase-catalysed hydrolysis and absent in case of chymotryptic digest. It was also demonstrated that the stimulatory peptides should be present in the culture medium at specific proportions and molecular size to match the physiological requirement of Yarrowia lipolytica strain for lipase biosynthesis.     

Photoactivated disinfection (PAD) of dental root canal system – An ex-vivo study

AimTo investigate the efficacy of photo activated disinfection (PAD) in reducing colony-forming unit (CFU) counts of Enterococcus faecalis (E. faecalis) in infected dental root canals. The study compared the efficacy of PAD with conventional endodontic treatment (CET) and also a combination of CET along with PAD.Material and Methods53 maxillary incisors were taken for the study. Teeth were divided into 3 groups, CET (Group I) (n = 11), PAD (Group II) (n = 21), and a combination of CET and PAD (Group III) which consisted of (n = 21) samples, Group II and Group III were further divided into 2 subgroups, Group IIa, IIb and Group IIIa, IIIb. Strains of E. faecalis were inoculated in all the root canals. CET group samples were treated by chemo-mechanical preparation (CMP) alone, PAD samples were treated with laser alone at 2 different exposure time (4 min and 2 min). In the combination treatment, samples were treated initially by CET and then by PAD for a time period of 4 min and 2 min. Contents of the root canal were aspirated, diluted and plated in Tryptone Soya Broth (TSB) and plates were incubated for 24 h to observe the bacterial regrowth.ResultsShowed PAD used along with CMP reduced the bacterial load of E. faecalis by 99.5% at 4 min and 98.89% at 2 min.ConclusionPAD may be an adjunctive procedure to kill residual bacteria in the dental root canal systems after standard endodontic root canal preparation.     

Efficient experimental design and micro‐scale medium enhancement of 6‐deoxyerythronolide B production through Escherichia coli

The recent use of heterologous hosts to produce natural products has shown significant potential, although limitations still exist regarding optimal production titers. In this study, we utilize micro‐scale cultures and well‐defined screening methods to identify key medium components that influence the heterologous production of the complex polyketide 6‐deoxyerythronolide B (6dEB) through E. coli. It was determined that tryptone had a significant effect on 6dEB production and could supplement substrate requirements and improve recombinant protein levels of the essential deoxyerythronolide B synthase (DEBS) which catalyze 6dEB conversion. As a result, the study (1) demonstrates the feasibility of micro‐scale cultures to study E. coli 6dEB production and effectively model larger‐scale cultures; (2) identifies an enhanced medium which generates over 160 mg L^?1 6dEB (a 22‐fold improvement over current culture media); and (3) provides new insight and understanding related to the heterologous production of 6dEB from E. coli. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

酸解羽毛粉代替蛋白胨研制新型细菌培养基

【目的】从工厂下脚料——酸解羽毛粉氨基酸含量高且种类丰富出发,开发出低成本新型细菌培养基,以期资源化该类废弃物。【方法】将酸解羽毛粉代替常用细菌培养基(LB培养基)中的蛋白胨,进行细菌液体发酵试验,比浊法在波长600 nm处比色测定菌液的吸光值,可培养计数法监测细菌数量。【结果】以LB培养基为对照,酸解羽毛粉完全代替蛋白胨液体发酵供试菌株时,菌株的生物量与对照无显著性差异或显著高于对照。培养模式菌株大肠杆菌和枯草芽孢杆菌24 h后,与对照相比,生物量分别增加了21.59%和27.83%。菌株生长曲线表明,生长初期,菌株在新型培养基中生长稍延迟,但含酸解羽毛粉培养基能延长枯草芽孢杆菌的对数生长期,并且两菌株到达稳定期时的生物量均高于对照。可培养计数法结果同样表明,含酸解羽毛粉培养基所培养活菌数量与对照(LB培养基)相比,差异不显著。【结论】用酸解羽毛粉代替LB培养基中蛋白胨进行细菌培养是可行的,可以大大降低生产成本。