ISSN:
1574-6968
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Biologie
Notizen:
Abstract The competitive advantages provided by a capacity for aerobic denitrification have been tested by comparing Thiosphaera pantotropha (which denitrifies aerobically and anaerobically), with a strain of Paracoccus denitrificans (which only denitrifies under anaerobic conditions) in acetate-limited chemostats. A comparison of μ-Cs curves based on Ks and μmax measurements indicated that Pa. denitrificans could be expected to dominate mixtures of the two species at high growth rates when the dissolved oxygen was above 80% of air saturation and NH3 was the sole source of nitrogen. The comparison also suggested t that at lower growth rates, lower dissolved oxygen tensions, and/or in the presence of nitrate, Tsa. pantotropha should have the competitive advantage. Chemostat experiments with mixtures of the two species showed that Tsa. pantotropha did, indeed, dominate the population when expected. However, when Pa. denitrificans was expected to dominate, only a small increase in the Pa. denitrificans numbers was possible before Tsa. pantotropha formed a biofilm on the walls of the chemostat instead of washing out, and was again able to out-compete Pa. denitrificans for acetate. Experiments with axenic chemostat cultures subjected to aerobic/anaerobic switches showed that Tsa. pantotropha, with its constitutive denitrifying system, was able to adjust smoothly to the changing environmental conditions and thus continued to grow. Pa. denitrificans does not have constitutive denitrifying enzymes, and could consequently not adjust its metabolism to the lack of oxygen rapidly enough. It therefore washed out at a rate equivalent to the dilution rate.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1574-6968.1992.tb04813.x
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