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Vermicompost vs vermitea - In-depth look at microbial communities

Updated: Apr 25

Hi everyone - I hope your New Year if off to a great start! One of my resolutions is to put out some more blog posts of ideas I've been chewing on for awhile.

Now that I am getting some of the individual reports out to people, I have a more granular look at the samples. We are going to look at data from one producer in the study who submitted both vermicompost and vermitea made from the same vermicompost submitted.

It's important to note that this vermitea was made with the addition of humic acid, kelp meal, and fish hydrolysate. This is a pretty standard vermitea recipe, but it's important to not confuse it with vermi- "extract" which is vermicompost bubbled inw ater without any additives. Stay tuned for a look at extract microbial communities in the near future.

Ok on to the data! Below are two "krona" graphs of all the organisms found in the vermicompost and the tea. Each "ring" represents a taxonomic level, so the closer to the center the higher or more broad the classification. The closer to the outside, the more specific the identification. These plots are usually interactive in a web browser but unfortunately they are a too complex for this site to handle. However, you can download this zipped file below if you would like a closer look or play around with the plots.

Type_krona -
Download ZIP • 59KB

Vermicompost Microbial Community

In the below vermicompost graph, I've highlighted a lot of the organisms we've talked about previously in the core microbiome that have been identified as potential plant growth promoting organisms. As you can tell, the majority of organisms found in vermicompost are potentially plant growth promoting. I am still working on identifying them all so there is likely even more.

So what do we get when we take our vermicompost, bubble it in water, add humic acids, kelp meal, and fish hydrolysate? We get a drastically different community. I don't think this unexpected or a bad because we've gone from a semi-oxic soil environment to a highly oxygenated aquatic environment loaded with nutrients. This new environment is going to select for differ organisms based on how well adapted they are for the new conditions.

Vermitea Microbial Community

Again, I've highlighted organisms found in vermitea that are potentially plant growth promoting.

One of the biggest differences going from vermicompost to tea is the explosion of Gammaproteobacteria (red) which account for 60% of all the organisms. Potentially plant growth promoting Gammaproteobacteria including Psudeomonas, Acinetobacter,and Massilia become 20x- 120x more abundant in vermitea (0.8%, 0.06% and 0.06% to 17%, 8% and 6%, respectively). What's also really interesting, but maybe not unexpected, is that every organism found in vermitea sample is also found in vermicompost. This suggests that the vermicompost seed community, especially the low abundance organisms could affect the outcome of the final vermitea community.

With the increase of these beneficial organisms in vermitea we see a disappearance or drastic reduction is some of the beneficial organisms in the original vermicompost. For example Rhizobiales goes from 8% in vermicompost to 2% and Microscillaceae from goes from 10% to 0.4%. I think this data makes the case that vermitea and vermicompost provide very different types of beneficial organisms to plants and using them in conjunction would provide the greatest biological diversity.

It's not all good news though...

What I find troubling in this vermitea sample is the growth of Enterobacetriaceae or "enteric bacteria." Several members of this group live in the intestines of animals and include pathogenic bacteria such as Citrobacter, Salmonella, Escherichia coli, Klebsiella, and Shigella. Below is a zoom in of this group from the vermitea samples.

First, I want to be clear that this does not mean that this tea has pathogenic bacteria. Because we cannot identify down to the species or even strain level it's possible to know. That being said, I would definitely not recommend anyone drink this brew. The presence of Salmonella, Klebsiella, Enterobacteriaceae, and Citrobacter is concerning. I would describe these organisms as potential pathogens or pathogen indicator organisms. Because of the limited number of vermitea samples I've sequenced I am unsure of these organisms are found in most teas or is these samples are outliers in this regard.

That's it for now, if you have any questions please ask! Coming up there will be posts on bacteria to fungal ratios, endophytes, and submitting samples for sequencing through my company Aggrego Data. I am currently accepting samples for sequencing so please reach out if you are interested.

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