Research student profile: Andrea Casteriano

Project title

The physiological mechanisms of desiccation tolerance in rhizobia.

Project overview

My project aims to improve the survival of rhizobia during delivery to soil particularly when applied to the seed coat. One of the major factors affecting survival is desiccation and this research is focused on exploring the physiological mechanisms for desiccation tolerance in rhizobia. A clearer understanding of these mechanisms will undoubtedly contribute knowledge that the inoculant industry may exploit to enhance the survival of rhizobia during delivery to the legume rhizosphere.

Research has shown that rhizobia survive poorly after inoculation of seed. Previously, findings have demonstrated the toxicity of seed exudates coupled with desiccation stress greatly decreases the number of viable cells delivered to the rhizosphere and this limits nodulation, nitrogen fixation and subsequent yield of legumes.

There is evidence that rhizobia can be exposed to certain conditions during growth that improves their survival when exposed to desiccation stress. Improved survival has been linked to the intracellular accumulation of compatible solutes, particularly trehalose.

To tackle this project my research involves looking at the effect of different pre-conditioning treatments, rate of drying and re-hydration on the rate of survival, intracellular trehalose accumulation and effects of pre-conditioning on the cell membrane. The research will also consider the role of trehalose in desiccation tolerance.

To do this my work involves designing pre-conditioning treatments that osmotically challenge cells during growth and exploring the effects that lead to improved survival. These will be compared to commercially available formulations that have shown to enhance cell survival such as peat.

The role of trehalose in desiccation tolerance will be examined by looking at the formation of biological glasses through the use of differential scanning calorimetry. Fourier Transform Infrared spectroscopy will be used to elucidate the site of trehalose action by focusing on particular bonds of interest. Flow cytometry coupled with electron microscopy will provide an insight on the effects of pre-conditioning and drying on the cell membrane.

From this I hope to demonstrate that desiccation tolerance can be greatly improved by enhancing the inherent tolerance mechanisms in rhizobia. Findings from this work will enable industry to improve the efficacy of more ready to use inoculants products.

Background

I was born in Uruguay and have resided in Sydney since 1987. I graduated from the University of Sydney in 1997 with a Bachelor of Science (Hons). I have a scholarship funded by the Grains Research and Development Corporation.

Publications

  • Deaker, R., Casteriano, A., and Mijajlovic, G. (2008) Estimating the most-probable number of bacteria in multi-strain biofertiliser inoculants using a multiple-tube fermentation test. In Efficient nutrient use in rice production in Vietnam achieved using inoculant biofertilisers. Proceedings of a project (SMCN/2002/073) workshop held in Hanoi, Vietnam 12-13 October 2007. Kennedy, I. R., Choudhury, A.T.M.A., Kecskés, M. and Rose, M. (Eds) ACIAR Proceedings No. 130, 108-116.
  • Kecskés, M., Choudhury, A.T.M.A., Casteriano, A. V. Deaker, R., Roughley, R. J., Lewin, L., Ford, R., and Kennedy, I. R. (2008) Effects of bacterial inoculant biofertilisers on growth, yield and nutrition of rice. In Efficient nutrient use in rice production in Vietnam achieved using inoculant biofertilisers. Proceedings of a project (SMCN/2002/073) workshop held in Hanoi, Vietnam 12-13 October 2007. Kennedy, I. R., Choudhury, A.T.M.A., Kecskés, M. and Rose, M. (Eds) ACIAR Proceedings No. 130, 108-116.

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