Transcription Dynamics of CBB-Pathway Genes in Acidithiobacillus thiooxidans Growing under Different CO2 Levels

Acidithiobacillus thiooxidans is one of the most stable components in the consortium of microorganisms inhabiting the copper bioleaching heap of Minera Escondida Limitada. CalvinBenson-Bassham (CBB) is the CO2 fixation pathway most used by aerobic bacteria, and is the exclusive pathway used by A. thiooxidans. In this work, the population dynamics and the transcriptomic dynamics of five key genes involved in the A. thiooxidans CBB pathway were studied in bioleaching column and pure culture tests at different concentrations of CO2 availability. Association between CO2 level, population dynamics and relative expression of CBB-genes was discovered. Differences between CBB pathways from closely related species were reported. The transcription profile modelling could provide useful knowledge for improving industrial bioleaching operations.

Hydrogen metabolism in the hyperthermophilic bacterium Aquifex aeolicus

Aquifex aeolicus is a microaerophilic, hydrogen-oxidizing, hyperthermophilic bacterium containing three [NiFe] hydrogenases. Two of these three enzymes (one membrane-bound and one soluble) have been purified and characterized. The Aquifex hydrogenases are thermostable and tolerant to oxygen. A cellular function for the three hydrogenases has been proposed. The two membrane-bound periplasmic hydrogenases may function in energy conservation, whereas the soluble cytoplasmic hydrogenase is probably involved in the CO2 fixation pathway.

Studies on the Ribose-5-Phosphatase of Sugarcane

A study has been made of ribose-5-phosphatase in sugarcane. The enzyme catalyzes the hydrolysis of ribose-5-phosphate to yield free ribose and phosphoric acid. The enzyme was extracted from fresh leaf tissues of 7-month old sugarcane grown in sand culture. Fractionation of cane extracts with ammonium sulfate showed that most of the enzyme was precipitated between 35 to 60 percent saturation. The richest source was spindle tissue. Leaves + 1 and + 2 were employed for studying the enzyme's properties. Dialysis up to 72 hours against several changes of distilled water had no appreciable effect on the phosphatase activity. Optimum pH was 5.5 and the Km was 2.5 X 10-3 moles of ribose-5-phosphate per liter. Good resolution of the enzyme and other protein constituents was obtained by gel filtration on Sephadex G-200. Molybdenum and tungsten inhibited at low concentrations. Molybdenum at 0.1 µmole and tungsten at 1 µmole per ml. severely inhibited the enzyme's action. Inhibition was reversed at higher concentrations. Molybdenum action was specific. Inhibition was lost during prolonged dialysis. It is proposed that ribose-5-phosphatase is a distinctly different enzyme than the other acid phosphatases previously reported for sugarcane. It appears to be functional in the CO2 fixation pathway elucidated by Calvin.