Growth of acetotrophic,methane-producing bacteria in a pH auxostat

Three acetotrophicMethanosarcina species, which included marine, nonmarine, and thermophilic strains, were grown on acetate in a 10-liter pH auxostat. Specific growth rates and molar growth yields were constant throughout growth. Cell yields were up to 18-fold greater than previously reported. These properties of the pH auxostat indicate that it is a preferred culture method for the biochemical study of methanogenesis from acetate.     

Links between global taxonomic diversity,ecological diversity and the expansion of vertebrates on land

Tetrapod biodiversity today is great; over the past 400 Myr since vertebrates moved onto land, global tetrapod diversity has risen exponentially, punctuated by losses during major extinctions. There are links between the total global diversity of tetrapods and the diversity of their ecological roles, yet no one fully understands the interplay of these two aspects of biodiversity and a numerical analysis of this relationship has not so far been undertaken. Here we show that the global taxonomic and ecological diversity of tetrapods are closely linked. Throughout geological time, patterns of global diversity of tetrapod families show 97 per cent correlation with ecological modes. Global taxonomic and ecological diversity of this group correlates closely with the dominant classes of tetrapods (amphibians in the Palaeozoic, reptiles in the Mesozoic, birds and mammals in the Cenozoic). These groups have driven ecological diversity by expansion and contraction of occupied ecospace, rather than by direct competition within existing ecospace and each group has used ecospace at a greater rate than their predecessors.     

Locations of the hydrogenases of Methanobacterium formicicum after subcellular fractionation of cell extract.

The F420 hydrogenase of Methanobacterium formicicum was associated with membranes isolated by sucrose density gradient ultracentrifugation of cell extract. The methyl viologen hydrogenase was present in the soluble fractions. Column chromatography with phenyl-Sepharose CL-4B revealed that the F420 hydrogenase was strongly hydrophobic, suggesting that it associates with isolated membranes through hydrophobic interactions.     

Small-angle X-ray scattering studies of fibrin film: comparisons of fine and coarse films prepared with thrombin and ancrod

Measurements of small-angle x-ray scattering have been made on films prepared from fine and coarse (i.e., formed at high and low, respectively, pH and ionic strength) clots of bovine fibrin by osmotic shrinkage or compression in one dimension. Intensity profiles were obtained with pinhole geometry on films stretched up to a stretch ratio of 1.43. In unstretched coarse films, repeat spacings were seen at about 245, 120, and 77-80 A. These peaks can probably be identified with the first, second, and third orders of the well-known fibrin repeat of 225 A. In unstretched fine films, only the 77-80 A spacing was seen. In this case, the first two orders may be weak because the half-staggered arrangement of monomer units giving rise to the 225 A reflection is not reinforced by lateral aggregation of protofibrils; the third order may be strong since the molecular subdomains appear to divide the repeat roughly into thirds. After stretching, the 77-80 A spacing persisted in the meridional direction but almost disappeared in the equatorial. Experiments on unstretched films prepared with ancrod substituted for thrombin gave similar results.     

Ligation of fibrinogen by factor XIIIa with dithiothreitol: mechanical properties of ligated fibrinogen gels

Human fibrinogen (concentration 8.4 mg/mL) was ligated (cross-linked) with factor XIIIa and dithiothreitol (DTT) at pH 8.5, ionic strength 0.45. With 7.5 μg/mL of factor XIIIa alone, there was almost no γ-γ ligation, but with 2 mM DTT added, oligomers appeared, and γ-γ and Aα-Aα ligation was nearly complete after 3 days. At 38 μg/mL of factor XIIIa, some γ-γ and Aα-Aα ligation occurred even without DTT. For fibrinogen concentrations of 4.0 and 8.4 mg/mL, 38 μ/mL factor XIIIa, 2.0 mM DTT, clot-like gels formed and the shear modulus of elasticity increased slowly over several days to a constant value. The final modulus was similar in magnitude to those of ligated clots of α-fibrin (clotted by thrombin) and α-fibrin (clotted by batroxobin) under the same conditions. However, the opacity was somewhat higher; whereas in fine fibrin clots there is minimal lateral association of the protofibrils, in fibrinogen gels at the same pH and ionic strength the protofibrils (which are presumably single chains of fibrinogen monomers joined end to end at their D domains) are evidently associated in bundles (although not to the degree seen in coarse fibrin clots). Creep and creep recovery measurements showed almost perfect elastic behavior, with essentially no creep under stress and complete recovery after removal of stress. The modulus was scarcely affected by introduction of lithium bromide by diffusion to a concentration of 0.6M, which in unligated fibrin clots causes substantial softening. Whereas in fine fibrin clots (both αβ-fibrin and α-fibrin) factor XIIIa causes only γ-γ ligation, addition of 2 mM DTT produced some α-α ligation in these also.     

gamma-Glutamyl transpeptidase: a single copy gene in the rat and a multigene family in the human genome

gamma-Glutamyl transpeptidase (GGT) genomic sequences were isolated from rat and human libraries using a rat GGT cDNA as a cross-species hybridization probe. Characterization of the human GGT clones by restriction mapping clearly establishes that at least four different GGT genes or pseudogenes are present in the human genome. All the rat genomic clones cover a 12.5-kilobase sequence and exhibit a unique restriction pattern. A precise quantitation of the rat GGT gene copy number by Southern blot analysis demonstrates that this sequence is present as a single copy/rat haploid genome. Therefore, the GGT gene organization is different between rat and human species; this raises the possibility of different regulatory mechanisms in the two species.     

Nucleotide sequence and glucocorticoid regulation of the mRNAs for the isoenzymes of rat aspartate aminotransferase

Cytosolic and mitochondrial aspartate aminotransferase cDNAs were cloned from a lambda gt11 rat liver cDNA library. The complete coding sequence and the 3' non-coding sequence of the cytosolic isozyme mRNA were obtained from two overlapping cDNA clones. Partial sequences of the mitochondrial enzyme cDNAs were found to be identical to the recently published complete sequence (Mattingly, J. R., Jr., Rodriguez-Berrocal, F. J., Gordon, J., Iriarte, A., and Martinez-Carrion, M. (1987) Biochem. Biophys. Res. Commun. 149, 859-865). A single mRNA (2.4 kb (kilobase pair] hybridizing to the mitochondrial cDNA probe was detected by Northern blot analysis, whereas the cytosolic cDNA probe labeled one major (2.1 kb) and two minor (1.8 and 4 kb) mRNAs. The 1.8-kb and the 2.1-kb cytosolic aspartate aminotransferase mRNAs differ in their 3' ends and probably result from the use of either of the two polyadenylation signals present in the 3' noncoding region of the major cytosolic aspartate aminotransferase mRNA. Glucocorticoid hormones increased the activity of cytosolic but not mitochondrial aspartate aminotransferase in both liver and kidney. The increase in the enzyme activity was accompanied by an increase in the amount of the three corresponding mRNAs, while the mitochondrial enzyme mRNA was not significantly modified.