Isoformes of Malate Dehydrogenase from <Emphasis Type="Italic">Rhodovulum Steppense</Emphasis> A-20s Grown Chemotrophically under Aerobic Conditions

Three malate dehydrogenase isoforms (65-, 60-, and 71-fold purifications) with specific activities of 4.23, 3.88, and 4.56 U/mg protein were obtained in an electrophoretically homogenous state from Rhodоvulum steppense bacteria strain A-20s chemotrophically grown under aerobic conditions. The physicochemical and kinetic properties of malate dehydrogenase isoforms were determined. The molecular weight and the Michaelis constants were determined; the effect of hydrogen ions on the forward and reverse MDH reaction was studied. The results of the study demonstrated that the enzyme consists of subunits; the molecular weight of subunits was determined by SDS-PAGE.     

Comparative study of the fatty acid composition of some groups of purple nonsulfur bacteria

The fatty acid composition (FAC) of 43 strains of purple nonsulfur bacteria belonging to six genera--Rubrivivax, Rhodopseudomonas, Rhodoplanes, Blastochloris, Rhodobium, and Rhodomicrobium--was studied by capillary gas chromatography. The cultures were grown on standard medium under standard conditions. Automatic identification of the fatty acid methyl esters and statistical processing of the results were performed by the computerized Microbial Identification System (M.I.S). Significant differences between the FACs of different genera, species, and, sometimes, strains were revealed. 16S rRNA genes of some of the new isolates, primarily those having a specific FAC, were sequenced. The taxonomic status of a number of the strains in question was determined using the FAC characteristics as one of the criteria. It was shown that the FAC characteristics may be used both for affiliating the isolates to known species and for revealing new taxa.     

Purification and Investigation of Physicochemical and Regulatory Properties of Homogeneous L-Lactate: Cytochrom <Emphasis Type="Italic">c</Emphasis> Oxidoreductase Obtained from the Nonsulfur Purple Bacterium <Emphasis Type="Italic">Rhodovulum steppense</Emphasis>

L-Lactate: cytochrome c oxidoreductase activity was detected in cells of strain A-20s of the nonsulfur haloalkalophilic purple bacterium Rhodovulum steppense. An electrophoretically homogeneous preparation of the enzyme was obtained by purification. The enzyme had a specific activity of 4.75 U/mg protein, a 81.9-fold purification degree, and a 2.2% yield. The kinetic and physicochemical characteristics were determined. The value of the Michaelis constant with lactate was 15 μM. The temperature optimum for the studied enzyme was 31°C; optimum of pH was 8.2. It was found that the enzyme was a homodimer with a molecular weight of ~140 kDa; the mass of individual subunit was 68 kDa.     

Interaction of the haloalkaliphilic purple bacteria <Emphasis Type="Italic">Rhodovulum steppense</Emphasis> with aluminosilicate minerals

The interaction was investigated between the haloalkaliphilic nonsulfur purple bacteria Rhodovulum steppense A-20s^T and layered aluminosilicates: micas (biotite, phlogopite, and muscovite) and clay minerals (montmorillonite and kaolinite). The interaction between all components of this system (minerals, water, medium, and bacteria) resulted in the changes in the chemical composition of the minerals and solutions. These changes were especially significant in the presence of bacteria. By using some elements for growth and promoting their transfer into the exchange pool of the minerals, bacteria removed these elements from the medium. The content of exchange bases in the aluminosilicates incubated in the presence of bacteria was several times higher than in the minerals incubated in sterile medium. The observed saturation of the mineral phase with potassium and magnesium may be considered the initial phase of diagenesis of the aluminosilicates under study.     

Varied diet and opportunistic foraging in the Ethiopian Bush-crow Zavattariornis stresemanni,an Endangered generalist

The Ethiopian Bush-crow Zavattariornis stresemanni is an endangered, co-operatively breeding southern Ethiopian endemic with a remarkably restricted range (c. 6 000 km²). The species’ range was recently found to be almost perfectly predicted by an envelope of cooler, drier and more seasonal climate than surrounding areas, but the proximate determinants of this range restriction remain unclear. We assessed whether specialisation in diet or foraging may restrict the range of the species by conducting foraging watches to determine prey composition, augmented by observations of opportunistic foraging techniques, and by comparing our results to previously published information on diet. Prey composition comprised a range of arthropods, such as insect larvae (62.7%), beetles (Coleoptera) (15.6%), and grasshoppers and crickets (Orthoptera) (11.8%). Prey was primarily obtained by pecks above ground (74.2%) but also frequently dug up (23.8%). Prey capture was most successful during pecks and we also found chicks were preferentially fed larger prey items over smaller ones by adults. We documented opportunistic behaviours such as nest-raiding and ox-pecking. Diet and foraging are varied and unspecialised, and therefore do not appear to explain the restricted range of the Ethiopian Bush-crow.     

Experimental Articles

Volcanic ash (Karymskii Volcano, Kamchatka) stimulated growth of the bacterium Rhodovulum sp. A-20s. The interaction between ash, water, media, and bacteria resulted in changes in the chemical composition of the solutions and ash. The ash-water interaction resulted in release of calcium to the solution, as well as in an increase in the proportions of sodium and calcium among the exchange cations of ash. As a result of the ash-medium interaction, calcium and copper were released to the solution; the exchange sodium cations were substituted by calcium and potassium. As a result of the ash-bacteria interaction, the content of copper in the solution decreased, and the exchange cations of calcium and sodium were actively substituted by potassium and magnesium. An increase in the magnesium content among the exchange cations of ash was especially apparent. The products of bacterial metabolism formed mineral-organic complexes with the ash substrate. The data obtained indicate the biogenic transformation of ash, which may lead to the initial phase of formation of clay minerals from volcanic ashes.     

红腹锦鸡肺的组织结构与微血管构筑

为了了解红腹锦鸡(Chroysolophus pictus)肺的微细结构和微血管构筑特征,为呼吸生物学研究提供形态学依据,用组织学方法和微血管铸型技术在光镜和扫描电镜下观察研究了红腹锦鸡肺的组织结构与微血管构筑情况。结果表明,红腹锦鸡肺主要由各级支气管构成,从三级支气管上呈辅射状分出许多呼吸毛细管(微气管),并相互吻合成网状,呼吸毛细管外面包围有丰富的毛细血管;红腹锦鸡肺毛细血管垂直围绕在各微气管外,并相互吻合成密集的立体微血管网;毛细血管管径4.5~7.0μm,微气管直径11~50μm。并对肺微血管构筑情况与呼吸效率的关系作了探讨。