You would think that after 120 years, laboratory science would know everything there is to know about how to reliably “grow” bacteria in a petri dish. And yet, it has been a mystery for decades on why the number of live bacteria grown on plates in the lab aren’t as high as counts from the original sample. This is known as the “great plate anomaly” and has been a source of slow progress in laboratory research around the world for decades. And yet, the solution many turn out to be extremely simple – and to illustrate a good point about “digging for the obvious.”
The key to growing micro-organism cultures in the lab is a gel mixture derived from algae. Everyone who ever went to chemistry class is familiar with its trade name: Agar. This material nourishes the cells which are transferred to it. Or at least that’s what we thought. The issue has been that despite this being the industry standard, only 10% of the cells which transferred from the original source actually flourished in the Agar material.
This is a situation where people working in the system continue to live with a problem because no one can find the time to work on the system. When a microbiologist in Japan at the University of Hokkaido finally decided to stop and look at this, he learned something very obvious. The standard recipe for Agar plates require mixing the material with a phosphate solution before sterilizing them with intense heat – to get them ready for the bacteria to be grown. But after literally a hundred years, Yoichi Kamagata and his team realized that this sequence creates the sterilant Hydrogen Peroxide as a by-product in the Agar – which in turn destroys most of the bacterial cells “seeded” in the Agar material. Sterilize the Agar and the phosphate solution separately? Poof. A roughly 10X increase in cell survival rates.
The moral of the story: Sometimes it’s actually worthwhile to review the basic understanding rather than just accepting it as the only way because it’s been done that way for so long.
Source: Adapted from Y. Kamagata et al./Applied Environmental Microbiology/2014 Dec; 80(24): 7659-7666/American Society for Microbiology, via Discovery.