Charitable bacteria

E. coliImage credit

A bacterium’s fight against antibiotics seemed to pit each individual prokaryote against the world. If the bacterium had the gene(s) to neutralize the antibiotic, it survived. If it didn’t have those genes, bye-bye bacterium. Whether this bacterium’s neighbor was susceptible or not wasn’t thought to matter.

Research published in today’s Nature shows that antibiotic resistance isn’t so singular. The team led by James Collins found that a single colony of E. coli contains bacteria with differing levels of antibiotic resistance. What’s more, those bacteria that had the stronger resistance seemed to protect the rest of their less resistant colony members from the effects of the antibiotics, even though it came at a cost of fitness to the super-resistant bacteria.

A pure colony of bacteria is essentially a group of clones. In theory, a colony of bacteria is descended from a single bacterium. Because bacteria reproduce by dividing into two identical cells, the colony consists of millions of genetically identical individuals. Mutations can and do occur, and so even bacteria within the same colony can vary slightly. However, two bacteria from Colony A likely have more in common genetically than two bacteria in Colony B. Thus, a “colony” of bacteria could also be conceived of as the equivalent of a family unit.

Collins’ group grew E. coli in a large container called a bioreactor, which allows the researchers to precisely control the bacteria’s environment (and Collins says looks like “a component of a moonshine factory out in the backwoods.” )  They first added the minimum amount of the antibiotic norfloxacin that would inhibit bacterial growth. The researchers took a sample of bacteria every 24 hours, spread the liquid on a petri dish, grew up the bacteria and measured the antibacterial resistance of 12 randomly selected colonies.

Molecular structure of indole

Most of the bacterial colonies had lower antibacterial resistance than the entire system grown in the bioreactor. A few colonies, however, had a much higher bacterial resistance than average. These highly resistant bacteria had high levels of the enzyme tryptophanase, which E. coli uses to synthesize indole. A signaling molecule produced during times of high stress, indole can trigger a bacterium to turn on tiny pumps that remove the norfloxacin from within the cell. Indole can also prevent bacteria from being harmed by the high levels of free radicals created during antibiotic treatment.

The highly resistant bacteria synthesized extra indole not for their own benefit, but for the benefit of other colony members.  Collins hypothesizes that this is a type of “kin selection,” where an organism acts to protect those who share the same genes, even at high cost to the organism. Because the E. coli in the bioreactor were grown from a single colony, their descendents are essentially one big happy family.

Because so many bacterial species produce indole, Collins thinks that targeting indole signaling might be a new path to create new antibiotics.


“Big, bad-ass birds” used their beaks like hatchets

Phorusrhacids weren’t your mama’s parakeet. Known as “terror birds,” a recent biomechanical analysis of a fossilized Andalgalornis steulleti skull shows that it used its oversized, hawk-like, hooked beak as a hatchet to kill its prey.

These gigantic, flightless birds roamed South America during the Cenozoic (62-2 million years ago) before ultimately going extinct. The birds had large skulls and massive beaks, standing between 1-3 meters in height. Andalgalornis was a mid-sized terror bird, about 1.5 meters tall and weighing about 45 kg. Although paleontologists knew terror birds were carnivorous, no one knew exactly how they killed their prey.

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Mirror, Mirror

ResearchBlogging.orgAn interesting paper was published in the online advanced issue of PNAS.  Titled, “Molecular Asymmetry in Extraterrestrial Chemistry,” the researchers looked at the ratios of chemical isomers found on a “pristine meteorite.”  Because the isomeric ratios of biomolecules on earth (especially amino acids and sugars) are very specific, finding different ratios could help us learn a) how life might have started and evolved and b) what life might look like on other planets.
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Ultra-detailed study of human genetic variation released

ResearchBlogging.orgThat modern Homo sapiens emerged out of Africa at some point in time has quite a bit of evidence.  But what has remained uncertain was who these adventurous people were.  What area of Africa were they from?  How many of them were there?  And how did they spread out to populate the globe?

Researchers at the University of Michigan and at the National Institute on Aging conducted a detailed study of genetic variation in human populations, which can pinpoint a person’s genetic heritage to a specific population in a geographic region.  Results at this level of specificity mean that this information is 100 times more detailed than previous studies. Continue reading

New Insights on Apicomplexa Biology

Although viruses and bacteria currently get the lion’s share of research money and media attention, parasitic diseases kill millions of people each year.  Why are they overlooked so frequently?  They largely don’t affect Americans.  It’s the sad, but true, world of science and journalism and research funding.

However, in the most recent edition of PLoS Pathogens, researchers from the University of Georgia and the University of Montana (among others) released a ground-breaking study on Apicomplexa biology.  Hadn’t heard of Apicomplexa?  Neither had I.  But they are a phylum that consists of many of the parasites that have plauged humans for millennia, such as Toxoplasma gondii, Cryptosporidia, and Plasmodium sp., the latter of which cause malaria in hundreds of millions of people each year.  Continue reading

Where I’ve Been

This is one of those days when I realize I need to set a resolution to blog every single day, dammit, lest two months pass and I say “Ummm…ooops!”

My redeeming point is that I have been busy. 
My non-redeeming point is that I haven’t been that busy.

I am starting work on my thesis, a little 40 page ditty on the factors that are causing the epidemic spread of the Chikungunya virus, which means I am going to be having to give up my little pet stories for class on random science topics until May.  Which made me think of this blog (again), and how it would be a perfect home for all of my random drivel.

So I’m back, and looking forward to writing with much greater consistency and quality than before.  Not that three posts, one of which was a cartoon, is much to talk about.  Still, a girl can dream.

Kitchen Science (or why you should quit smoking)

A group of Japanese scientists did this little home experiement that they captured on video

A dramatic view of why smoking gives you cancer.

Still Smoking? Watch This !! – video powered by Metacafe

When I was a student at the School of Public Health at the University of Michigan, there were always a few students in every class who continued to smoke. I understand addiction in my own little way, but still. When the first example in your epidemiology class is working on the stats of lung cancer and smoking, it made me wonder if they should flunk that class. Just, you know, on the spot.

The link comes by way of Scientist, Interrupted (Living the Scientific Life).