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The dissimilatory nitrate-reducing bacterial community in the rhizosphere of aerenchymatous plant species such as Glyceria maxima, consists of oxidative. denitrifying and fermentative nitrate-ammonifying bacteria. To study the respective ecological niches of both types of nitrate-reducing bacteria, competition for nitrate or glucose between the representative denitrifier Pseudomonas fluorescens and the representative fermentative nitrate-ammonifying Bacillus licheniformis under continuous or fluctuating anoxic conditions were performed in continuous culture. Competition started by mixing the separate, steady-slate mono-cultures of the two species at different ratios. All the experiments were performed at a dilution rate of 0.05 h(-1). The competition was followed by measuring concentrations of nitrogen, glucose and fatty acids and by determining the cell numbers of P. fluorescens and B. licheniformis. Under continuous anoxic nitrate-limited conditions and under certain fluctuating anoxic conditions (8 h 10% and 16 h 0% air saturation), B. licheniformis was able to maintain itself in the chemostat at a low percentage of 4-7%. Under continuous anoxic glucose-limited conditions and under specific fluctuating anoxic (16 h 10% and 8 h 0% air saturation) conditions, B. licheniformis washed out. The outcome of the competition was explained by a higher affinity of P. fluorescens for nitrate arid glucose compared to B. licheniformis. B. licheniformis was able to maintain itself in the chemostat under continuous anoxic nitrate-limited conditions and under certain fluctuating anoxic conditions (8 h 10% and 16 h 0% air saturation) due to the fer;mentation of the remaining glucose. [KEYWORDS: competition; nitrate reduction; chemostat; Pseudomonas fluorescens; Bacillus licheniformis Denitrification; oxygen; rhizosphere; transient; culture]
Original languageEnglish
Pages (from-to)345-356
JournalFEMS Microbiology Ecology
Volume26
Issue number4
DOI
StatePublished - 1998

ID: 315309