The experiment demonstrates natural selection at work. And because samples are frozen and available for later study, when something new emerges, scientists can go back to earlier generations to look for the steps that happened along the way.

Last month, Zachary Blount, Lenski and colleagues published a paper in Nature detailing a new evolution in E. coli—the ability to eat citrate.

Shannon Bennett, associate curator of the Academy’s Microbiology department, explains why this is so unusual.

E. coli doesn’t normally eat citrate unless it is desperate (there’s no glucose, no oxygen). But these E. coli did evolve the ability to eat citrate, in fact thrive on it, in the presence of both oxygen and glucose.

They were able to evolve to do this when certain individuals made mistakes and copied their citrate gene (which usually is turned on only under oxygen-poor conditions) to a different spot in the genome near a switch point that turns on in the presence of oxygen.

Blount was able to trace this new trait through generations and uncover a three-step process in which the bacteria developed this new ability.

The first stage was potentiation, when the E. coli accumulated at least two mutations that set the stage for later events (see Shannon’s explanation above). The second step, actualization, is when the bacteria first began eating citrate, but only just barely nibbling at it. The final stage, refinement, involved mutations that greatly improved the initially weak function. This allowed the citrate eaters to wolf down their new food source and to become dominant in the population.

“We were particularly excited about the actualization stage,” Blount says. “The actual mutation involved is quite complex. It re-arranged part of the bacteria’s DNA, making a new regulatory module that had not existed before. This new module causes the production of a protein that allows the bacteria to bring citrate into the cell when oxygen is present. That is a new trick for E. coli.

“It wasn’t a typical mutation at all, where just one base-pair, one letter, in the genome is changed,” he continues. “Instead, part of the genome was copied so that two chunks of DNA were stitched together in a new way. One chunk encoded a protein to get citrate into the cell, and the other chunk caused that protein to be expressed.”

Shannon explains why this study is so exciting:

This study is cool because it shows many of the important mechanisms in evolution, namely gene duplication and gene regulation (turning genes on and off at different times). It all went on in a series of test tubes, so it’s “artificial” evolution, but what’s nice about that is, they were able to freeze samples down at early time points through to the present, to trace the path of evolution, and that they used a model organism, Escherichia coli, that evolves very quickly (not as quick as viruses, but much faster that vertebrates). My work takes advantage of the same historical sampling and evolutionary speed, only I’ve focused on “natural” experiments in the viruses I work on.

Much exciting news came out of the conference, read on…

First up: Bacteria that make you smarter and calmer

On Monday, researchers announced that exposure to specific bacteria in the outside environment could increase learning behavior.

The bacteria are Mycobacterium vaccae, a natural soil bacterium that “people likely ingest or breath in when they spend time in nature,” says Dorothy Matthews, PhD of The Sage Colleges in Troy, New York, one of researchers on the project.

The researchers fed mice the live bacteria and assessed their ability to navigate a maze compared to control mice that were not fed the bacteria. “We found that mice that were fed live M. vaccae navigated the maze twice as fast and with less demonstrated anxiety behaviors as control mice,” says Matthews.

She continues, “It is interesting to speculate that creating learning environments in schools that include time in the outdoors where M. vaccae is present may decrease anxiety and improve the ability to learn new tasks.”

Next: Honey Bee Colony Collapse Disorder

Yesterday the news was not so good. Scientists from the US Department of Agriculture presented a study blaming a fungus and a family of viruses for the worldwide honeybee disappearance also known as Colony Collapse Disorder (CCD).

According to the BBC,

David Mendes, the president of the American Beekeeping Federation, says that biological pathogens are certainly involved – but that there might be something that affects the bees’ immune system in the first place that then allows these pathogens to infect them more easily.

Whichever came first, scientists are hoping that at least knowing the cause, they can start to help the much-needed bees. Good nutrition seems to help stop the fungus and some beekeepers are looking toward queen bees that are resistant to that family of viruses.

Au Currant Microbes: Bacteria Cleaning-up the Oil Spill

New Scientist described today that at the conference:

Jay Grimes of the University of Southern Mississippi in Hattiesburg reported that over the past few years, researchers have found that dozens of different kinds of marine bacteria have a healthy appetite for oil.

He said that water samples from the Gulf of Mexico are showing signs that marine bacteria are already pitching in to help with clean-up efforts, and that populations of these bacteria in this area are likely to boom as they feast on the oil from the Deepwater Horizon disaster.

The bacteria better be careful, however, because the dispersants added to breakdown the oil maybe harmful to the microbes. A team of scientists funded by NSF is headed to the Gulf to find out:

The team seeks to understand how the dispersants added to the spill will interact with natural compounds produced by microbes, and how this will impact the ability of different microbes to break down the oil.

For Bonus Points: Bacteria that causes rain and snow.

And finally, The New York Times published a great story earlier this week about bacteria that may be involved with precipitation in the atmosphere—essentially, rain and snow. It’s been studied for over 30 years, but new tools and technology are providing clearer pictures, making it an exciting field of microbiology research.