Refining the Process

The last few weeks have been a whirlwind of ups and downs. Our first idea, as I mentioned in the last post, was to take a soil sample, preform a PCR analysis to identify different types of bacteria present, and then test for their antagonistic activity against harmful pathogens. But as we started researching, we quickly hit some major roadblocks—PCR is expensive, and even if we did it, we wouldn’t actually have any bacteria to work with afterward. That meant we wouldn’t be able to do anything with the data. This idea was pretty much impossible from the start.

Our next idea was to run soil tests to check for key markers that beneficial bacteria could help fix. One of our main focuses was nitrogen-fixing bacteria, which convert elemental nitrogen from the air into a form plants can use. Instead of using PCR to count the bacteria, we figured we could just measure the nitrogen levels in the soil, which would give us a good estimate of how much nitrogen-fixing bacteria was present. The plan was to create a bacteria-rich medium full of Rhizobia bacteria to replenish the soil’s microbial balance.

Before going too far with this idea, I asked my biology teacher for advice. He quickly pointed out a major flaw—large-scale farms already use this method, and on top of that, many plants don’t even have the right receptors for Rhizobia. I looked it up, and he was right. Rhizobia need to form a symbiotic relationship with plant roots, but a lot of the crops we wanted to test don’t even have the ability to host these bacteria. At this point, we were feeling pretty discouraged and almost quit.

Determined to find another way, I kept researching and came across something important—there are actually two types of Plant Growth-Promoting Bacteria (PGPB):

• Symbiotic bacteria, like Rhizobia, which require specific plant receptors.
• Non-symbiotic/free living bacteria, which are much more versatile and can work with a wide range of plants.

That’s when I found Bacillus Subtilis, a non-symbiotic bacteria that has been shown to significantly boost plant biomass production. Excited by this new lead, I emailed a few professors about the idea: we’d culture a Bacillus Subtilis broth medium and spray it over plants to improve their growth.

But once again, I hit another roadblock. Dr. Bruns, a soil microbiology professor at Penn State, responded with a key issue: even if we drenched the soil with Bacillus Subtilis, the PPM (parts per million) would only reach about 1 billion, while the native bacteria in the soil are already at 100 billion PPM or higher. This meant that our introduced bacteria would be outcompeted almost immediately, making the whole process ineffective.

At this point, I was running out of ideas, but then I remembered something one of my professors in India had told me—there’s another way to introduce microbes to plants: seed coating. Instead of applying the bacteria to the soil, this method involves soaking seeds in a Bacillus Subtilis broth before planting. I looked up some research papers, and they actually confirmed that seed coating solves the PPM problem.

I quickly shared my findings with Dr. Bruns, and this time, she said it was definitely worth testing. Finally, after two weeks of constant roadblocks, we have a solid, expert-approved plan. Now, we can finally move forward with finding the best strains of Bacillus Subtilis and setting up our small-scale lab experiment. Make sure to follow if you are interested in following me on this journey of ending food-insecurity.