Chemolithotrophic oxidation of ammonia to nitrate via nitrite (autotrophic nitrification) is a key link in the cycling of nitrogen in the biosphere.  It is facilitated by diverse communities of microorganisms including the autotrophic ammonia oxidising bacteria (AOB).  A good understanding of niche differentiation among members of such communities will aid in the prediction of how a community structure and function may respond to environmental change. The work presented here aims to extend the available ecophysiological data on soil AOB with an emphasis on comparative observations between organisms under the same conditions.  Under a set of standardised conditions, several potentially ecologically relevant traits were quantified and comparisons were made between organisms in the context of their phylogenetic relationships.  <i>Nitrosomonas europaea </i>ATCC 19718, <i>Nitrosomonas europaea </i>ATCC 25978, <i>Nitrosospira </i>‘Apple Valley’, <i>Nitrosospira briensis </i>C-128, <i>Nitrosospira multiformis </i>ATCC 25196, <i>Nitrosospira tenuis </i>NV-12, and <i>Nitrosospira </i>40KI in pure culture were examined. Specific growth rates in batch culture, maximum velocities, Michaelis constants and specific oxidation velocities of ammonia oxidation, AMO transcript decay half-life and transcriptional and metabolic response to re-supply of ammonia following energy starvation were quantified.  Significant phenotypic diversity was observed and hypotheses were tested with respect to trade-offs in niche adaptation and the influence of phylogeny.  It is hoped these new data will aid in the formation and testing of further ecological and evolutionary hypotheses and will contribute to the long term goal of developing predictive models for biogeochemical cycling.

Thesis (Ph.D) -- University of the Western Cape, 2008. / Includes bibliographic references (leaves 187-206).

Thesis (Ph. D.) -- Lincoln University, 2009. / Also available via the World Wide Web.

Title from first page of PDF document. Includes bibliographical references (p. 22-27).