Unwanted guests

Microbial contaminants (three species) on a plate

Microbiologists use Petri dishes, filled with a variety of agar media, to grow microbes. Even a small lab can produce hundreds of plates every week… And it is quite common to store in the fridge those of these plates that are not directly inoculated for a future use. Thus, when you open a microbiologist's fridge, you may find columns of Petri plates labeled with the medium and antibiotics they contain, waiting to be covered with a suspension of microbes.

Sometimes, when you store them for long periods, you can have the disagreeable surprise to find unwanted guests on your plates, that is, contaminant microbes!

Back from ASM General Meeting

I'm just back from the 112^th general meeting of the American Society for Microbiology, which took place from June 16 to 19 in San Francisco. The general meeting is huge: thousands of microbiologists from all over the US and abroad, representing all fields of microbiology; hundreds of talks and more than 3,000 posters presented; about 200 biotech companies showing their products. 

That is something to see! It's great to feel part of this large community of microbiologists. We are one big family, even though we work on topics as varied as human health, environmental ecosystems, agriculture, food safety, biotechnology, etc.

The endosymbiotic theory of Lynn Margulis

Published by Basic Books

Lynn Margulis passed away last November, sadly. She was renowned for the endosymbiotic theory of evolution, which is now part of biology textbooks. She had a wonderful insight: the mitochondria and chloroplasts that are found in eukaryotic cells were, in distant past, free-living bacteria. Thanks to at least two distinct endosymbiosis events, they were incorporated—and not digested—in the eukaryotic ancestor. They became responsible of key functions within the new association, namely respiration and photosynthesis. These symbionts persisted until at some point they were indistinguishable from their host, and all merged to become one new organism, a eukaryotic cell. 

Recently I found a copy of her book Symbiotic Planet (1998) in my usual second-hand bookshop in Davis. It is a short book in which Margulis deals with the scientific idea that has occupied her during most of her career: the serial endosymbiosis theory (or SET). The author sums up the book as follows (p.33):

In short, I believe that most evolutionary novelty arose, and still arises, directly from symbiosis.