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Applied and Environmental Microbiology, March 2002, p. 1064-1070, Vol. 68, No. 3
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.3.1064-1070.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Morphological Changes of Rhizobia in Peat Cultures

Lu Feng, Rodney J. Roughley, and Les Copeland*

Department of Agricultural Chemistry and Soil Science, University of Sydney, Sydney, New South Wales 2006, Australia

Received 31 August 2001/ Accepted 13 December 2001

Morphological changes that take place in peat cultures of several species of rhizobia were examined. These changes seemed to be associated with enhanced survival of cells in peat and after inoculation onto plastic beads, which were used as a model system for seeds. Cell wall changes, in which the periplasmic space appeared to be occluded with electron-dense material, were observed in Rhizobium sp. strain SU343 and Bradyrhizobium lupini WU425 cells after 7 and 14 days in peat, respectively. Nutrient limitation and low O2 concentration in peat are suggested to be factors involved in the induction of the morphological changes. Polyhydroxybutyrate reserves, which were present in broth-cultured cells of both species of rhizobia, were mobilized after transfer into peat but did not appear to influence survival after inoculation onto beads. Enhanced expression of an iron-manganese superoxide dismutase was also observed after the cells were transferred into peat. We conclude that cell wall thickening in rhizobia after transfer from broth cultures into peat is an adaptive response for long-term survival under nutrient-limited conditions in peat. Cells with thickened walls may also be more resistant to other types of stress, such as that encountered on a seed surface.

* Corresponding author. Mailing address: Faculty of Agriculture, A05, University of Sydney, Sydney NSW, Australia, 2006. Phone: 61 2 9351 2935. Fax: 61 2 9351 2945. E-mail: l.copeland{at}acss.usyd.edu.au.

Applied and Environmental Microbiology, March 2002, p. 1064-1070, Vol. 68, No. 3
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.3.1064-1070.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Vriezen, J. A. C., de Bruijn, F. J., Nusslein, K. (2007). Responses of Rhizobia to Desiccation in Relation to Osmotic Stress, Oxygen, and Temperature. Appl. Environ. Microbiol. 73: 3451-3459 [Full Text]  


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