Investigating the basis of competitive nodulation & N-fixation in Rhizobium leguminosarum
Lead Research Organisation:
University of Oxford
Department Name: Interdisciplinary Bioscience DTP
Abstract
Some soil-dwelling bacteria in the genus Rhizobium can form symbioses with plants of the Legume family, which includes several important crop plants such as peas and beans. Inoculation of leguminous crops with rhizobia can significantly increase yields for farmers while reducing inorganic fertiliser usage, and many commercial inoculants have been developed. The e ectiveness of a strain for use in a commercial inoculant is partly dependent upon the ability of the strain to compete with a soil's native rhizobia to successfully initiate symbioses with the crop plants. High-throughput transposon insertion sequencing (INSeq) techniques are being used to identify and investigate genes contributing to competitiveness. It is hoped that the data can be used to develop competitive and e ective Rhizobium strains for use in commercial inoculants.
BBSRC Priority Areas Addressed
Agriculture and Food Security
Sustainably Enhancing Agricultural Production
Reducing Waste in the Food Chain
Synthetic Biology
AfS, ENWW
BBSRC Priority Areas Addressed
Agriculture and Food Security
Sustainably Enhancing Agricultural Production
Reducing Waste in the Food Chain
Synthetic Biology
AfS, ENWW
People |
ORCID iD |
| Philip Poole (Primary Supervisor) |
Publications
Wheatley RM
(2020)
Lifestyle adaptations of Rhizobium from rhizosphere to symbiosis.
in Proceedings of the National Academy of Sciences of the United States of America
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| BB/M011224/1 | 01/10/2015 | 31/03/2024 | |||
| 1948170 | Studentship | BB/M011224/1 | 01/10/2017 | 30/09/2021 |
| Description | Some soil-dwelling bacteria in the genus Rhizobium can form symbioses with leguminous plants, including important crop species such as peas and beans. During symbiosis, rhizobial bacteroids inhabiting root nodules fix atmospheric dinitrogen into ammonium, which is exchanged with the host plant for fixed carbon from photosynthesis. Inoculation of leguminous crops with highly effective rhizobia can significantly increase crop yields and reduce inorganic fertiliser usage. However, potential yield benefits are reduced or lost if inoculant strains are unable to compete with indigenous rhizobia. High-throughput transposon insertion sequencing (INSeq) techniques were used to assess genes for importance in different stages of symbiosis, including poorly understood genetic factors influencing competitive nodulation ability and development of nitrogen-fixing nodules. INSeq classifications were used as starting points for experimental investigation of mutations found to affect abundance of rhizobia in nodules, including mutations which have both positive and negative effects on fitness. Previous results have revealed that timing of infective and developmental events is likely crucial to nodulation ability, hence a novel mutant screening strategy, aiming to identify mutants delayed in these events, was developed using Lux- and GFP-based biosensors then tested in a combined growth and non-invasive imaging system. Rhizobial mutant strains were generated for 47 genes of interest using established and novel mutagenesis systems. Phenotypes were found for 17 of 35 mutants examined, including seven mutants with significantly impaired competitive nodulation ability, two mutants (mutants in RL0339 & RL3565) with enhanced competitive nodulation ability and one mutant (RL3624 mutant) showing enhanced growth promotion under nitrogen-limited conditions. The results in this thesis provided the basis for further investigation of nodulation kinetics and characterisation of genes which may be utilised for future development of more effective inoculant strains. |
| Exploitation Route | 12 mutant strains were made but not investigated due to time constraints, so this research could be picked up by another researcher in the future. An improved system for mutagenesis of Rhizobium was developed and tested, this can be used by future researchers to make marker-replacement mutants. A screening strategy was developed to investigate the kinetics of nodulation, which could be continued. The mutants which were identified as having increased competitive ability or increased plant growth promotion could be further investigated in future work aiming to uncover the mechanism for the observed phenotypes. |
| Sectors | Agriculture, Food and Drink,Environment,Manufacturing, including Industrial Biotechology |
| Description | Society Conference Grant 2020 |
| Amount | £240 (GBP) |
| Funding ID | GA001906 |
| Organisation | Microbiology Society |
| Sector | Learned Society |
| Country | United Kingdom |
| Start | 02/2020 |
| End | 02/2020 |
| Description | 21st Congress on Nitrogen Fixation - 10th-15th Oct 2019, Wuhan, China - Philip Poole |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Phil gave a talk at this international conference. He had many questions on his work and spent time exchanging ideas with colleagues in this research area. |
| Year(s) Of Engagement Activity | 2019 |
| URL | http://2019icnf.csp.escience.cn/dct/page/65580 |
| Description | Bacterial World Exhibit, Oxford Museum of Natural History |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Public/other audiences |
| Results and Impact | An exhibit on Rhizobium legume symbiosis was set up and run as part of the Natural History Museum's "Bacterial World" event. Members of the public, including families and children, were informed about the importance of rhizobia and got to see stained nodules on pea root systems. |
| Year(s) Of Engagement Activity | 2019 |
| URL | http://www.oum.ox.ac.uk/bacterialworld/ |