Alternative function of the electron transport system in Azotobacter vinelandii: removal of excess reductant by the cytochrome d pathway

Article Abstract:

There is a mismatch between the effects of two respiratory mechanisms in the nitrogen-fixing bacterium Azotobacter vinelandii: electron transport system and glycolysis. More cytochrome d is synthesized to raise the oxygen uptake rate with increasing oxygen partial pressure. This ensures protection of nitrogenase from molecular oxygen. But the rate of glycolysis also goes high with exposure to excess of glucose. Except for the reinforced electron transport system under higher oxygen partial pressure, there is no system capable of converting the harmful extra glycolytic products.

Physiological aspects, Oxygen, Oxygen transport, Electron transport, Microbial respiration, Cytochromes, Nitrogen-fixing microorganisms, Glycolysis

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Selection and characterization of aspartokinase feedback-insensitive mutants of Azotobacter vinelandii

Article Abstract:

Mutants of Azotobacter vinelandii that are insensitive to threonine feedback inhibition were isolated and found to have either a threonine transport deficiency or a feedback- insensitive aspartokinase. Mutants were selected based on their resistance to L-threonine, beta- hydroxynorvaline, or S-(2-aminoethyl)-L-cysteine. Both lysine and threonine may exert feedback inhibition in A. vinelandii, and the aspartokinase activity of one strain of A. vinelandii may be more sensitive to lysine.

Biological transport, Aspartate kinase

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Effects of calcium on sugar transport in Azotobacter vinelandii

Article Abstract:

The utilization of a capsulated organism as an alternative procedure for the study of sugar uptake on Azotobacter vinelandii is discussed. Rapid oscillatory vibrations were used to aerate the transport experiments which were performed in a 24-well plate. The effect of cations on the sugar uptake was also tested by the method. The utility of the procedure asan alternative to the conventional filtration method was demonstrated.

Analysis, Microbial metabolism, Sugar, Calcium, Calcium (Chemical element)

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