ISSN:
1572-9729
Keywords:
oxygen tension
;
2,5-dichlorobenzoic acid
;
mixed substrates
;
continuous culture
;
adaptation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Energy, Environment Protection, Nuclear Power Engineering
,
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract From long-term chemostat experiments, variants ofPseudomonas aeruginosa JB2 were obtained which exhibited altered properties with respect to the metabolism of 2,5-dichlorobenzoic acid (2,5-DBA). Thus, unlike the original strain JB2-WT, strain JB2-var1 is able to grow in continuous culture on 2,5-DBA as the sole limiting carbon and energy source. Yet, at a dilution rate of 0.07 h−1 and a dissolved oxygen concentration of ≤ 12 µM, even with this strain no steady states with 2,5-DBA alone could be established in continuous cultures. Yet another strain was obtained after prolonged continuous growth of JB2-var1 in the chemostat. It has improved 2,5-DBA degrading capabilities which become apparent only during growth in continuous culture: a lower apparent K m for 2,5-DBA and lowered steady-state residual concentrations of 2,5 DBA. Although with this strain steady states were obtained at oxygen concentrations as low as 11 µM, at further lowered concentrations this was no longer possible. In C-limited continuous cultures of JB2-var1 or JB2-var2, addition of benzoic acid (BA) to the feed reduced the amounts of 2,5-DBA degraded, which was most apparent at low oxygen concentrations (〈 30 µM). At higher dissolved oxygen concentrations the addition of BA resulted in increasing cell-densities but did not affect the residual steady state concentration of 2,5-DBA. Indeed, whole cell suspensions from chemostat cultures grown on BA plus 2,5-DBA did show a lower apparent affinity for 2,5-DBA than those from cultures grown on 2,5-DBA alone. These results indicate that in environments with low oxygen concentrations and alternative, more easily degradable, substrates the degradation rates of chloroaromatic compounds by aerobic organisms may be negatively affected.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00702297
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