These are some clearing zones formed by soil isolates in a lawn of a safe ESKAPE bacterial species. This is what it is all about when it comes to the Small World Initiative. The next steps are to amplify and sequence the 16s rRNA gene from isolates that produce antimicrobials and then do chemical extractions to isolate the antibiotic compound(s).
I found this Winogradsky column setup for a microbiology class at UConn. Windogradsky columns are setup with sediment from a pond, and are left to sit for several months allowing gradients and different layers of microorganisms to form similar to those in the natural environment. This is certainly the most living Winogradsky column I have ever seen. I am surprised there aren’t fish swimming around at the top.