Substrate inhibition under stationary growth conditions - nutristat experiments with Ralstonia eutropha JMP 134 during growth on phenol and 2,4-dichlorophenoxyacetate

Delftia acidovoransMC1 Resists High Herbicide Concentrations — a Study of Nutristat Growth on (RS)-2-(2,4-Dichlorophenoxy)propionate and 2,4-Dichlorophenoxyacetate

“…These results are detrimental to the behavior of Ralstonia eutropha JMP134, which showed a drastic decrease in growth under nutristat conditions after just 1 day's exposure to 0.5 mM 2,4-D and was explained by a significant reduction in the net energy gain. 14) It is also worth mentioning that the figures obtained in carbon substrate-limited chemostat cultivation of strain MC1 agreed with this pattern, which is in addition considered indicative of non-inhibited growth at nutristat (Fig. 10).…”

“…Extensive uncoupling caused by, for example, weak organic acids which might dissipate energy 25) are rather unlikely at alkaline pH values as the substrate is almost completely dissociated. Any pronounced impairment did not apparently apply at pH 7 either, a condition at which the extensive inhibition of growth was observed with Alcaligenes eutrophus (Ralstonia eutropha) JMP134 in the presence of 2,4-D. 14) Thus any effects caused by the milieu conditions might easily be compensated for in this case by the regulatory potential of strain MC1. Examination of the individual nucleotides shows that kinetically based effects might contribute to homeostasis rather than drain off the energy pools.…”

“…26) Fig. 11 also illustrate by way of comparison the values obtained with strain JMP134, 14) which were shown to be qualitatively distinct with respect to carbon substrate-limited and nutristat growth. Cellular responses being raised by external factors is a matter of fact.…”

“…Details of equipment and kinetic pattern in nutristat technique are given elsewhere. 14) The pattern in Fig. 2 shows qs-values of 2,4-D higher than those calculated for the individual enantiomers of 2,4-DP.…”

“…12,13) But it may also result from the fact that the efficiency of productive degradation is reduced or even repressed by too high a level of the toxicant. This was shown to be the case with Alcaligenes eutrophus (Ralstonia eutropha) JMP134 during longterm exposure to 2,4-D. 14) When we studied herbicide degradation in polluted building rubble with herbicide concentrations of up to 5 mM and pH values > 11 in the aqueous eluates, i.e. under one of the unfavorable milieu conditions mentioned above, degradative activity could not be stimulated under in situ conditions, meaning that any process of productive degradation did not run with the autochthonous microbes to a significant extent.…”