Abstract:
Nitrosomonas europaea is an autotrophic ammonia-oxidizer that has been found to cometabolize various halogenated hydrocarbons. This ability to cometabolize various compounds (many of which are considered contaminants) has caused N. europaea to be considered a potential bioremediational organism. However, ifN. europaea is to be used for bioremediation purposes, it will be necessary to understand N. europaea's normal state in its natural environment, (thought to be a dormancy stage), and to understand how N. europaea may be activated to cometabolize desired compounds. N. europaea was shown to enter a dormancy phase under stress and starvation conditions. This dormancy phase was exhibited by an extended lag time needed to achieve full growth when inocula taken from cultures 11 and 12 days old. The lag time was found to be related to the loss of the enzyme ammonia monooxygenase, but not to the enzyme hydroxylamine oxidoreductase. Cells could be temporarily prevented from entering dormancy stage and exhibiting long lag times by resuspending in medium containing no growth substrate. This temporary suspension of the aging process could be maintained for up to 5 days.
