How do Less-expensive Nitrogen Alternatives Affect Legume Sanctions on Rhizobia?

Mutualistic interactions involving multiple partners require ‘sanctioning’ - the ability to influence the fitness of each partner based on its respective contribution. Sanctions must be sensitive to even small differences if even slightly less-beneficial partners could gain a fitness advantage by diverting resources away from the mutualistic service towards their own reproductive fitness. Here, we test whether legume hosts sanction even mediocre N2-fixing rhizobial strains by influencing either its nodule growth or carbon accumulation (polyhydroxybutryate or PHB) per rhizobia cell. We also test if sanctions depend on the availability of less-expensive nitrogen alternatives, either as nitrate or co-inoculation with a more-efficient isogenic strain. We found that nitrate eliminated differences in nodule size between the mediocre and more-efficient strains, suggesting that host sanctions were compromised. However, nitrate additions also decreased PHB accumulation by the mediocre strain, wh..., Dataset was collected by two undergraduate students, first into a lab notebook, and then added to Microsoft Excel. That data are then accessed for analyses by exporting to .csv and importing into R Studio. We provide the main dataset .csv file and multiple .R files. , , # How do less-expensive nitrogen alternatives affect legume sanctions on rhizobia?

## README file generated on 2020-07-31 by Katherine Muller.

### Info on the experiment:

Growing conditions: KM notebook 7

-Bean plants were grown in 2 magenta units filled with a 1:1 mixture of vermiculite and sand (see p. 70). N-free nutreint solution (Fujikake) was wicked from the bottom with cotton cord. For the first two weeks after germination, 0.5mM of KNO3 was added to the nutrient solution to help early growth before nodulation.

Plants were grown in batches of 8 (four plants per inoculum strain). The first batch, started on Dec. 21st, 2016 (see p. 56-58), had some issues that were (hopefully) resolved during the second batch, which was started on 2017-02-15 (there were a false start on Jan. 30th and Feb. 15th). THe main issue with the first batch that the PHB knockout (SAM 100) did not grow well in the YMB media I used to start inoculum cultures. I used TY for the second and third batch of pl...