Sunday, February 24, 2013

Where have all the geniuses gone?

Nernst, Einstein, Planck, Millikan and Laue in 1931. From Wikimedia commons.

Is scientific genius gone for good? No more Darwin or Einstein on the horizon? That’s the intriguing and slightly provocative question recently raised by UC Davis psychologist Dean Keith Simonton in the comment section of the journal Nature. Simonton has extensively written on the topic of science creativity in books and articles, and here’s how he sums up the problematic:

“Geniuses have played a decisive part in science in two main ways. First, they have founded new scientific disciplines […]. Second, geniuses have revolutionized established disciplines. […] Yet, in my view, neither discipline creation nor revolution is available to contemporary scientists.”

Sunday, February 17, 2013

Coliforms and operational definitions

Recently, I was talking about coliforms with my colleagues from the lab. ‘Coliforms’ is the name given to a group of bacteria that usually serve as indicators of fecal contamination in water and food samples, because most coliforms come from the intestinal flora of animals. For this reason, water and food that contain too high levels of coliforms are deemed unfit for human consumption (the US EPA recommends a limit of 10 or less per liter in drinking water). The most famous coliform, Escherichia coli, is a commensal in our intestine, although some pathogenic strains exist as well (for instance O157:H7, involved in deadly outbreaks in the US and Europe). Coliforms behave similarly as fecal pathogenic bacteria, notably regarding their survival in water. We can thus assume that a sample devoid of coliforms will also be free of fecal pathogens. Commercially-available tests for coliforms, such as the culture medium CHROMagar ECC, also permits us to differentiate between total coliforms and fecal coliforms (mostly E. coli), simply based on the coloration of the bacterial colonies on agar plates.

Tuesday, February 05, 2013

Bacteria in a wastewater treatment plant

Bacteria in activated sludge from a wastewater treatment plant

It is a remarkable fact that we fully depend on microbes to treat or sewage water. In every wastewater treatment plant, from the simplest to the most modern ones, the essential activity is biological and is mainly carried out by bacteria. In modern plants, sewage water is directed to large aerated tanks in which the pollution is consumed by a mixture of microbes and organic matter known as  activated sludge.

The video below shows how an aerated tank looks like. You don’t want to take a swim in there… 

For a microbiologist, a wastewater treatment plant is a delight: I’ve never seen another environment with as much diversity in the size and shapes of cells. It is a true microbial jungle containing countless bacteria and many protozoans that feed on them.