A temperature‐dependent conformational change of NADH oxidase from Thermus thermophilus HB8

Using molecular dynamics simulations and steady‐state fluorescence spectroscopy, we have identified a conformational change in the active site of a thermophilic flavoenzyme, NADH oxidase from Thermus thermophilus HB8 (NOX). The enzyme's far‐UV circular dichroism spectrum, intrinsic tryptophan fluorescence, and apparent molecular weight measured by dynamic light scattering varied little between 25 and 75°C. However, the fluorescence of the tightly bound FAD cofactor increased approximately fourfold over this temperature range. This effect appears not to be due to aggregation, unfolding, cofactor dissociation, or changes in quaternary structure. We therefore attribute the change in flavin fluorescence to a temperature‐dependent conformational change involving the NOX active site. Molecular dynamics simulations and the effects of mutating aromatic residues near the flavin suggest that the change in fluorescence results from a decrease in quenching by electron transfer from tyrosine 137 to the flavin. Proteins 2012. © 2011 Wiley Periodicals, Inc.     

Granulation in thermophilic upflow anaerobic sludge blanket (UASB) reactors

The state of the art for thermophilic UASB reactors is discussed focusing on the start-up of UASB reactors, the influence of the waste water composition and temperature on the development and maintenance of thermophilic granules, and the microbial composition and structure of thermophilic granules.     

Naegleria lovaniensis tarasca New Subspecies, and the Purepecha Strain, a Morphological Variant of N. I. lovaniensis, Isolated from Natural Thermal Waters in Mexico

Amoebae were isolated from a natural thermal water source in Michoacaan, Mexico, in September 1986. Two 500-ml samples were taken from pools with water at 45°C and 46°C and concentrated at 2,000 g for 15 min. The sediment was seeded on nonnutritive agar plates and incubated at 42°C. The isolates were axenized in bactocasitone-serum medium. The identification of the isolates was based on their morphology, total protein and isoenzyme patterns by agarose isoelectric focusing, serology, fine structure, agglutination with Concanavalin A, sensitivity to trimethoprim, capacity to kill mice, and their cytopathic effect in Vero cells. The results showed several morphophysiological, biochemical and serological differences between the isolates and the type strain Aq/9/1/ 45D of Naegleria lovaniensis. These remarkable differences provide sufficient evidence to consider one of the isolates a new subspecies, and the other one a morphological variant of N. l. lovaniensis, which can be differentiated from other Naegleriae by their morphology, biochemistry, serology and physiology. The authors propose the name tarasca for the subspecies and purepecha for the morphological variant.     

Inhibition of the Bacterial Cell Wall Synthesis in vitro by Enduracidin,a New Polypeptide Antibiotic

Adenosine 5′-phosphosulfate (APS) kinase from a thermophilic bacterium, Bacillus st ear other mophilus, was purified to apparent homogeneity. The apparent molecular weight was 50 kDa, consisting of two 26-kDa subunits. The enzyme was very thermostable and lacked cysteine and methionine residues. Enzyme activity was more stimulated with Mn^{2 +} , Zn^{2 +}, or Co^{2 +} than with Mg^{2 +} and the K_m for ATP and APS were 220 µM and 42 µM, respectively.     

Temperature-Dependent Self-Splicing Group I Introns in the Flagellin Genes of the Thermophilic Bacillus Species

A previous report described the presence of a self-splicing group I intron in a flagellin gene from a thermophilic Bacillus species. Here, we present evidence that the splicing reaction of the flagellin introns is dependent on temperature. Furthermore, a complementation analysis using a Bacillus subtilis flagellin-deficient mutant indicated that the intron-containing flagellin gene significantly restored the motility of the mutant at higher temperatures.     

A Group I Self-Splicing Intron in the Flagellin Gene of the Thermophilic Bacterium Geobacillus stearothermophilus

A group I intron that can be spliced in vivo and in vitro was identified in the flagellin gene of the thermophilic bacterium Geobacillus stearothermophilus. We also found one or two intervening sequences (IVS) of flagellin genes in five additional bacterial species. Furthermore, we report the presence of these sequences in two sites of a highly conserved region in the flagellin gene.     

Formation of metabolites during biodegradation of linear alkylbenzene sulfonate in an upflow anaerobic sludge bed reactor under thermophilic conditions.

Biodegradation of linear alkylbenzene sulfonate (LAS) was shown in an upflow anaerobic sludge blanket reactor under thermophilic conditions. The reactor was inoculated with granular biomass and fed with a synthetic medium and 3 micromol/L of a mixture of LAS with alkylchain length of 10 to 13 carbon atoms. The reactor was operated with a hydraulic retention time of 12 h with effluent recirculation in an effluent to influent ratio of 5 to 1. A sterile reactor operated in parallel revealed that sorption to sludge particles initially accounted for a major LAS removal. After 8 days of reactor operation, the removal of LAS in the reactor inoculated with active granular biomass exceeded the removal in the sterile reactor inoculated with sterile granular biomass. The effect of sorption ceased after 185 to 555 h depending on the LAS homologs. 40% of the LAS was biodegraded, and the removal rate was 0.5 x 10(-6) mol/h/mL granular biomass. Acidified effluent from the reactor was subjected to dichloromethane extraction followed by gas chromatography/mass spectrometry. Benzenesulfonic acid and benzaldehyde were detected in the reactor effluent from the reactor with active granular biomass but not in the sterile and unamended reactor effluent. Benzenesulfonic acid and benzaldehyde are the first identified degradation products in the anaerobic degradation of LAS.     

一个耐高温酵母菌株的tps1基因克隆及序列分析

葡萄汁酵母的菌株YY具有耐高温特性,研究其可能的耐高温机理具有重要的理论和实践意义。其在37℃能正常生长,致死温度为68℃。通过克隆其tps1基因序列,体外扩增后测序,分析蛋白序列的突变。发现在这一菌株的tps1基因序列有13个突变,TPS1蛋白序列存在有三个位点的变异,分别是67位(Gly／Ala)、69位(Glu／Gln)、387位(Val／Leu),这三个变异均增加了海藻糖-6-磷酸合成酶的疏水性,从而增加了酶在高温下的稳定性性。通过这一发现,可以部分解释菌株YY的耐高温机理。     

Density discriminates between thermophilic and mesophilic proteins

Despite an intense interest and a remarkable number of studies on the subject, the relationships between thermostability and (primary, secondary and tertiary) structure of proteins are still not fully understood. Here, comparing the protein density – defined by the ratio between the residue number and protein excluded volume – for a set of thermophilic/mesophilic pairs, we provide evidence that this property is connected to the optimal growth temperature. In particular, our results indicate that thermophilic proteins have – in general – a lower density with respect to the mesophilic counterparts, being such a correlation more pronounced for optimal growth temperature differences greater than 40°C. The effect of the protein thermostability changes on the molecular shape is also presented.