Presentation Title

Testing Competition and Relationships in Rhizobia-Legume Mutualisms

Start Date

November 2016

End Date

November 2016

Location

HUB 302-#159

Type of Presentation

Poster

Abstract

Rhizobia bacteria in soil provide leguminous plants useable nitrogen through their capability to fix atmospheric nitrogen (N2) into ammonia (NH3). This mutualism is reciprocally beneficial as rhizobia fixing nitrogen in nodules, specific root structures, get carbohydrates from the plants. This process of fixing nitrogen, however, is energetically costly to the rhizobia as it uses resources that could be used towards growth and reproduction. Therefore, it is reasonable to assume that natural selection favors rhizobia that live in nodules but fix less nitrogen otherwise known as ‘cheaters’. In order to maintain this mutualistic relationship, plants must favor the rhizobia that fix the most nitrogen and/or use sanctions in order to penalize the ‘cheaters’. I am looking more into this relationship and the interactions of different rhizobia. Five bacterial strains were isolated from soil-trapping experiments and the nodules of Lupinus sp. and Pisum sativum. 16S rDNA analysis shows that four of the strains are Rhizobium leguminosarum and the other is R. rhizogenes. Initial testing reveals that the co-inoculation with nodulating and non-nodulating bacteria causes the plant to be more stressed than inoculation with a nodulating bacterium alone. Antibiotic resistance profiles for isolates were determined in preparation to introduce green fluorescent protein (GFP) and mCherry into the bacteria. These fluorescent markers will be used for the identification of each bacterium in co-inoculated Pisum sativum nodules to aid in finding occupancy patterns.

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Testing Competition and Relationships in Rhizobia-Legume Mutualisms

HUB 302-#159

Rhizobia bacteria in soil provide leguminous plants useable nitrogen through their capability to fix atmospheric nitrogen (N2) into ammonia (NH3). This mutualism is reciprocally beneficial as rhizobia fixing nitrogen in nodules, specific root structures, get carbohydrates from the plants. This process of fixing nitrogen, however, is energetically costly to the rhizobia as it uses resources that could be used towards growth and reproduction. Therefore, it is reasonable to assume that natural selection favors rhizobia that live in nodules but fix less nitrogen otherwise known as ‘cheaters’. In order to maintain this mutualistic relationship, plants must favor the rhizobia that fix the most nitrogen and/or use sanctions in order to penalize the ‘cheaters’. I am looking more into this relationship and the interactions of different rhizobia. Five bacterial strains were isolated from soil-trapping experiments and the nodules of Lupinus sp. and Pisum sativum. 16S rDNA analysis shows that four of the strains are Rhizobium leguminosarum and the other is R. rhizogenes. Initial testing reveals that the co-inoculation with nodulating and non-nodulating bacteria causes the plant to be more stressed than inoculation with a nodulating bacterium alone. Antibiotic resistance profiles for isolates were determined in preparation to introduce green fluorescent protein (GFP) and mCherry into the bacteria. These fluorescent markers will be used for the identification of each bacterium in co-inoculated Pisum sativum nodules to aid in finding occupancy patterns.