title: Effects of long-term treatment with acetylene on nitrogen-fixing microorganisms.
abstract: Long periods of experimental incubation with acetylene led to a multifold enhancement of acetylene-reducing activity in Anabaena cylindrica, Anabaenopsis circularis, Rhodospirillum rubrum, and Azotobacter vinelandii. Rates of acetylene reduction showed a gradual increase and reached a peak after 2 to 6 h of continuous incubation under acetylene. Thereafter, enzyme activity rapidly declined. A similar enhancement of ethylene production was observed when pretreatment with acetylene was interrupted periodically by a brief exposure to ambient (or oxygen-free) atmosphere without acetylene although the decline of acetylene-reducing activity was less rapid. Pretreatment with acetylene depressed photosynthetic 14CO2 fixation and 15N2 incorporation in Anabaena cylindrica. It is concluded that assessments based on long-term experimental incubation with acetylene may grossly overestimate the actual quantities of fixed nitrogen in the field.
mesh_terms: D000114:Acetylene / Q000378:metabolism* / Q000494:pharmacology; D001395:Azotobacter / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D000458:Cyanobacteria / Q000378:metabolism*; D005030:Ethylenes / Q000378:metabolism; D009586:Nitrogen Fixation; D010084:Oxidation-Reduction; D010313:Partial Pressure; D010788:Photosynthesis; D012247:Rhodospirillum rubrum / Q000378:metabolism*; D012995:Solubility; D013997:Time Factors
chemical_list: D005030:Ethylenes; D002245:Carbon Dioxide; D000114:Acetylene