HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Google Scholar Articles by Dötsch, A. Articles by Kreft, J.-U. PubMed PubMed Citation Articles by Dötsch, A. Articles by Kreft, J.-U. Agricola Articles by Dötsch, A. Articles by Kreft, J.-U.

A mathematical model for growth and osmoregulation in halophilic bacteria

Andreas Dötsch^1,2,

¹ Theoretical Biology, University of Bonn, Kirschallee 1, 53115 Bonn, Germany
² Institute for Microbiology and Biotechnology, University of Bonn, Meckenheimer Allee 168, 53115 Bonn, Germany
³ Centre for Systems Biology, School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK

Correspondence
Andreas Dötsch
Andreas.Doetsch{at}helmholtz-hzi.de

Many molecular details of the ecophysiology of halophilic bacteria that use compatible solutes to maintain osmotic equilibrium have been examined. We ask whether the details are consistent and complete enough to predict growth and osmoregulation in these bacteria by integrating this information in a mathematical model. Parameterized for the halophilic organism Halomonas elongata, the model predicts the substrate and salt dependence of growth, the uptake of potassium and ectoine and the synthesis of ectoine. It is shown that salt (NaCl) dependence of growth can be modelled by substrate inhibition kinetics. Osmoregulation is known to involve accumulation of both ectoine and potassium glutamate in H. elongata. Using published and newly determined parameters, osmoregulatory models using either direct turgor or two-step (turgor and potassium) signalling are compared. The results are consistent with a role for potassium as a second messenger for hyperosmotic stress. Simulations of osmotic upshifts show a transient overregulation of the intracellular solute levels, as has been previously observed in experiments. A possible adaptive value of this overregulation as ‘pre-emptive’ behaviour in an environment with frequent dry periods leading to steadily increasing osmolarity is proposed. As a result of growth parameter estimation, a maximum P : O value of 2 for H. elongata can be inferred. In conclusion, the model developed here reproduces essential aspects of growth and osmoregulation in halophilic bacteria with a minimal set of assumptions.