Biofungicidal Fumigants from Compost Tea

fAntifungal Effect of Volatile Organic Compounds from Bacillus velezensis CT32 against Verticillium dahliae and Fusarium oxysporum
December 2020
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       Here's a doozy.    A group of scientists in China wanted to look into whether or not microbes in compost tea have the ability to ward off disease-causing fungi by producing volatile, anti-fungal compounds.  
      Volatile Organic Compounds (VOCs) are substances that freely dissipate into the environment.  You have probably heard about low-VOC paints, which are paints that do not release toxic fumes, sparing the brain cells of many hardworking painters.  In this experiment, the scientists were looking for bacteria that were good at producing VOCs in order to stave off the growth of phytopathogenic fungi.
       The researchers first made compost from corn stave (which is the remainder of the corn crop after the cobs and the kernels have been harvested) and cow manure.  They used 1 part manure to 5 parts stave.  This was turned every seven days for five weeks.  Then this compost was used to make an aerated tea.   A sample from the tea was taken, and then diluted and plated onto petri dishes so that individual colonies of bacteria could be isolated.  The individual colonies were then identified using PCR, and assayed for biofungicidal VOC action.  This was done by growing the isolated microbes alongside pathogenic fungi.  The bacteria and fungi were separated so that the only thing they shared was air.  The growth, or lack thereof, of the pathogenic fungi was used to determine if the bacteria was producing an inhibitory VOC.  The scientists then selected  the most effective VOC producing microbe, which turned out to be the one and only, Bacillus velezensis strain CT32.
      Once the researchers had their VOC star-microbe, they looked further at the VOCs being produced.  They found that the bacteria was making 30 unique VOCs, 6 of which had never been seen in bacteria or fungi before.  Then the scientists went even further, separating out each VOC and testing them individually for the inhibitory action against fungi.   Eight of the thirty compounds proved to have anti-fungal properties.   The scientists propose that this microbe, and others like it, could be used as biofumigants in order to help prevent vascular wilt infections from pathogenic fungi.  
      There was a lot of science done in this experiment.  The researchers kept looking further and further and finally were able to make a definitive statement about what is happening with our teas and why they work the magic that they do.  Thank you very much to the researchers in China for furthering our understanding of this amazing microbial world.   

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