Amino acid and lactate catabolism in trimethylamine oxide respiration of Alteromonas putrefaciens NCMB 1735

The nonfermentative Alteromonas putrefaciens NCMB 1735 grew anaerobically in defined media with trimethylamine oxide as external electron acceptor. All amino acids tested, except taurine and those with a cyclic or aromatic side chain, were utilized during trimethylamine oxide-dependent anaerobic growth. Lactate, serine, and cysteine (which are easily converted to pyruvate) and glutamate and aspartate (which are easily converted to tricarboxylic acid cycle intermediates) were metabolized at the fastest rate. Growth with lactate as growth-limiting substrate gave rise to the formation of 40 mol% acetate, whereas serine and cysteine were nearly completely oxidized to CO2. Molar growth yields with the latter substrates were the same and were 50% higher than with lactate. This showed that more ATP was formed when acetyl coenzyme A entered the tricarboxylic acid cycle than when it was converted via acetyl phosphate to acetate. Also, growth with formate as substrate indicated that the reduction of trimethylamine oxide to trimethylamine was coupled with energy conservation by a respiratory mechanism.     

The spark discharge synthesis of amino acids from various hydrocarbons

The spark discharge synthesis of amino acids using an atmosphere of CH₄ + N₂ + H₂O + NH₃ has been investigated with variable pNH₃. The amino acids produced using higher hydrocarbons (ethane, ethylene, acetylene, propane, butane, and isobutane) instead of CH₄ were also investigated. There was considerable range in the absolute yields of amino acids, but the yields relative to glycine (or -amino-n-butyric acid) were more uniform. The relative yields of the C₃ to C₆ aliphatic -amino acids are nearly the same (with a few exceptions) with all the hydrocarbons. The glycine yields are more variable. The precursors to the C₃-C₆ aliphatic amino acids seem to be produced in the same process, which is separate from the synthesis of glycine precursors. It may be possible to use these relative yields as a signature for a spark discharge synthesis provided corrections can be made for subsequent decomposition events (e.g. in the Murchison meteorite).     

Plant size,geitonogamy and seed set in Ipomopsis aggregata

Summary We used powdered fluorescent dyes to estimate receipt of self vs. outcross pollen in the self-incompatible species Ipomopsis aggregata (Polemoniaceae). Flowers on small and large plants received equal amounts of outcross pollen, whereas flowers on large plants received more self pollen, so the proportion of self pollen delivered through geitonogamy increased with plant size. In natural populations emasculation of all flowers on a plant raised average seed set per flower from 5.19 to 6.99 and also raised fruit set, though not significantly. From these results one expects a negative correlation between plant size and seeds per flower. The opposite trend was observed in a sample of plants in the field, suggesting that deleterious effects of geitonogamy on female fecundity in large plants can be overruled by other factors such as size-related fruit or seed abortion. Results are discussed in relation to the evolution of gynodioecy.     

Recombinant cytochrome c peroxidase folds properly without conformational "annealing".

Recombinant cytochrome c peroxidase isolated from Escherichia coli has recently been reported to exhibit an abnormal electronic absorption spectrum that is converted to the normal spectrum after conformational "annealing" of the recombinant enzyme by passage over a cytochrome c affinity column. The current report provides evidence that the abnormal spectrum observed in some preparations of recombinant cytochrome c peroxidase arises from the presence of contaminant, damaged forms cytochrome c peroxidase with altered spectra. Removal of these contaminant forms produces a major cytochrome c peroxidase fraction with a normal spectrum. We conclude that elution of recombinant cytochrome c peroxidase over a cytochrome c affinity column does not produce normal enzyme through conformational "annealing" but that it produces purified enzyme through removal of contaminants.     

Isolation and analysis of cell wall material from beeswing wheat bran (Triticum aestivum)

Cell wall material (CWM) isolated from beeswing wheat bran contains 66% carbohydrate, 12% Klason lignin, 6% protein and 4% ash. The relative proportions of sugars in the CWM are arabinose 34%, xylose 26%, galactose 2%, glucose 32% and uronic acid 6%. The uronic acid was shown to consist of glucuronic acid and its 4-O-Me analogue in the ratio 1.8:1. Partial acid hydrolysis of the CWM yielded neutral sugars and a uronic acid fraction. The latter was shown to contain Glc p A-(1→2)-Xyl p and Glc p A-(1→2)-O-Xyl p-(1→4)-Xyl p and their 4-O-Me substituted uronic acid analogues. Methylation analysis of the whole CWM and partially degraded methylated CWM revealed the nature of the constituent glycosidic linkages. From the combined evidence we infer that the major structural features of the non-cellulosic polysaccharides are a linear chain of xylopyranose units joined by (1→4)-linkages, and arabinofuranose, xylose, galactose (and uronic acid) end groups, which in at least some of the polysaccharides, are attached directly by (1→2)- and/or (1→3)-linkages to the xylan chain. The CWM has been fractionated by successive extractions with water at 80°, 0.2 M (NH₄)₂C₂O₄ at 80°, Na chlorite/HOAc at 70°, 0.2 M (NH₄)₂C₂O₄ at 80°, 1 M and 4 M KOH, and the neutral sugar composition of the fractions determined. It is concluded from these and other experiments that the CWM contains two main types of polysaccharides, the arabinoxylans and cellulosic polymers, and that phenolic ester linkages play a role in holding them together.     

Regulation of amino acid transport in growing cells of Streptomyces hydrogenans

The uptake of various amino acids into Streptomyces hydrogenans grown in chemostatically and turbidostatically controlled steady state cultures has been investigated. A close correlation between transport capacity and the growth rates of the cells was found. As shown by kinetic analysis, the increased transport is due to elevated maximum uptake rates, the apparent Michaelis constants remaining unchanged. Analysis of the unidirectional fluxes of cycloleucine revealed that not only the influx is raised as the growth rate is increased but also the efflux. Hence, the conclusion is drawn that the growth-rate dependent modulation of transport capacity is, at least, partially due to the variation of the concentration of active transport components. Since the cells were grown in the absence of external amino acids the results suggest that amino acid transport into S. hydrogenans is under the control of endogenous effectors.List of Abbreviations AIB 2-aminoisobutyric acid - Cycloleucine 1-aminocyclopentane-1-carboxylic acid