Jw. Nijburg et al., COMPETITION FOR NITRATE AND GLUCOSE BETWEEN PSEUDOMONAS-FLUORESCENS AND BACILLUS-LICHENIFORMIS UNDER CONTINUOUS OR FLUCTUATING ANOXIC CONDITIONS, FEMS microbiology, ecology, 26(4), 1998, pp. 345-356
The dissimilatory nitrate-reducing bacterial community in the rhizosph
ere of aerenchymatous plant species such as Glyceria maxima, consists
of oxidative. denitrifying and fermentative nitrate-ammonifying bacter
ia. To study the respective ecological niches of both types of nitrate
-reducing bacteria, competition for nitrate or glucose between the rep
resentative denitrifier Pseudomonas fluorescens and the representative
fermentative nitrate-ammonifying Bacillus licheniformis under continu
ous or fluctuating anoxic conditions were performed in continuous cult
ure. Competition started by mixing the separate, steady-slate mono-cul
tures of the two species at different ratios. All the experiments were
performed at a dilution rate of 0.05 h(-1). The competition was follo
wed by measuring concentrations of nitrogen, glucose and fatty acids a
nd by determining the cell numbers of P. fluorescens and B. lichenifor
mis. Under continuous anoxic nitrate-limited conditions and under cert
ain fluctuating anoxic conditions (8 h 10% and 16 h 0% air saturation)
, B. licheniformis was able to maintain itself in the chemostat at a l
ow percentage of 4-7%. Under continuous anoxic glucose-limited conditi
ons and under specific fluctuating anoxic (16 h 10% and 8 h 0% air sat
uration) conditions, B. licheniformis washed out. The outcome of the c
ompetition was explained by a higher affinity of P. fluorescens for ni
trate arid glucose compared to B. licheniformis. B. licheniformis was
able to maintain itself in the chemostat under continuous anoxic nitra
te-limited conditions and under certain fluctuating anoxic conditions
(8 h 10% and 16 h 0% air saturation) due to the fer;mentation of the r
emaining glucose. (C) 1998 Federation of European Microbiological Soci
eties. Published by Elsevier Science B.V. All rights reserved.