Plants have a commensal relationship with bacteria, much in the same way that humans also have a beneficial symbiotic microbiome. This affords the plants a level of protection against pathogens like other bacteria, viruses, and fungi. A new study has found that this microbiome starts when the plant is a seed, ensuring that the young plant is protected right from the earliest stages. The research was led by Shaun Lee from the University of Notre Dame, and the results were presented at the 5th Association Society for Microbiology Conference on Beneficial Microbes.
“This was a genuine curiosity that my colleague and I had about whether commensal bacteria could be found in various plant sources, including seed supplies,” Lee said in a press release. “The fact that we could isolate and grow a bacterium that was packaged inside a seed was quite surprising.”
To test whether or not this microbiome exists from the seed's inception, the team sterilized the outer portion of the mung bean seed to protect against any cross contamination. The middle of the seed was extracted and cultured in agar. After incubation, the researchers found a strain of Gram-positive bacteria called Bacillus pumilus. This bacterium is found throughout the plant, though there are no deleterious consequences to the plant itself.
Genetic analysis has revealed that B. pumilus has antimicrobial properties from three clusters of genes. This allows each bacterium to ward off natural predators. The resistance against these pathogens from the bacterium is then transferred along to the plant. It's a win-win situation, as the bacteria is given a host and the plant is given a level of protection with neither party having to sacrifice anything for this relationship to continue.
Not only does this allow scientists to have a deeper understanding of the symbiotic relationship between microbes and plants within the microbiome, but it could also be used to create safer food that would protect against illness caused by certain strains of E. coli and similar microbes. Additionally, the winning 2014 Google Science Fair project involved a team of girls who used the microbiome of cereal crops in order to accelerate germination and produce more food crops. The possibilities to manipulate the plant microbiome could have profound implications.
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