Isolation of Nitrogen-fixing Bacteria from Corn and Wheat Soils in Minnesota
Azospirillum is a genus of microaerophilic nitrogen-fixing bacteria well-known in South America for its uses as plant inoculum, where it aids plant growth via various mechanisms, such as the increased production of phytohormones. Preliminary metagenomic sequencing by the Ishii lab has revealed that Minnesota soils also include Azospirillum; this project aimed to isolate and culture Azospirillum using techniques detailed in Cáceres (1982), which utilize the nitrogen-free media NFb and Rojo Congo (RC) media. Though the first batch of samples yielded no Azospirillum, other results are pending. However, nifH PCR surprisingly indicated a lack of nitrogen-fixing bacteria among the entire first two batches of samples. This may be due to inappropriate primers, otherwise it could indicate the isolation of non-nitrogen-fixers able to grow on trace nitrogen in the agar of the RC media. The final batch of samples yielded nifH-positive samples. This study, though unsuccessful in its original goal, brought forth new candidate bacteria for consideration due to their ability to nitrogen-fix, and helped characterize what culturable species exist in Minnesota soils. It also called into question the effectiveness of using NFb and RC to culture Minnesota-native strains of Azospirillum.