About a month ago I stumbled upon an unknown culture growing on a sucrose plate I had made in the -4 degree fridge. The Doerr lab immediately became invigorated with determining what this "goo" was and why did it grow on my plate. The most common contaminants of any nutrient-rich media are molds. But this didn't look like a mold. It appeared smooth with no filaments protruding and no fuzzy spores sticking out. It looked like a gumdrop that grew overnight!
To determine its structural consistency, I decided to poke it. With camera in hand, biosafety goggles on, I took a pipette tip and pierced the goo. It was so slimy, similar to a booger. Like any good scientist, the next plausible step was to look at it under the microscope. To my surprise, it was a bacteria! It was rod-shaped and resembled E. coli (on a phase microscope). To know which species of bacteria it was, I sent to for 16S sequencing.
16S rRNA gene sequencing is commonly used for identification, classification and quantitation of microbes within complex biological mixtures such as environmental samples. This code is in a specific protein that all DNA-based life forms contain, and thus it can be used to determine the identity of an unknown organism.
After a few days of waiting, the results were in. The unknown "goo" happened to be Pseudomonas reactans! This group of bacteria contains 191 scientifically described species, however, not much is known about this one.
All Pseudomonas produce sugary molecules that surround and incase biofilms. Biofilms are these sticky little communities of microbes that live and thrive together as if one organism. Biofilms can for on nearly any surface and are resistant to many of the commonly used disinfectants. The bacteria around the outside act as a barrier, saving the ones on the inside, that can then multiply and become a biofilm again. These traits make biofilms a huge health problem, allotting to over 2 million associated cases a year.
P. aeurginosa is the most commonly studies Pseudomonas species and is used as a model system to research biofilms! All of these facts are fitting for my mystery "goo".
What once was a complete enigma, has now been made clear. I got to experience what it is like to find an unknown organism and through science, determine not only what species it is, but also why it looked the way to did. The Ph.D. is all about discovery!
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