Posts Tagged ‘Bacteria’

The red queen, sex and nematode worms

// July 28th, 2011 // 1 Comment » // Recent Research, Sex and Reproduction


Alice and the Red Queen by John Tenniel

In Lewis Carroll’s Through the looking-glass– a whacky book if I ever read one – the laws of physics don’t really apply. Hills can become valleys, straight can become curvy, and forward is really backward.

In one scene, Alice chases after the Red Queen, both running as fast as they can, but when they stop Alice realises they are still right where they started. “Now, here, you see, it takes all the running you can do to keep in the same place” says the Red Queen.

And it might be the same with the evolution of predator and prey, host and parasite. Running doesn’t get you anywhere. So says the Red Queen Hypothesis.

c elegans embryo

C elegans embryo. Image by Monica Gotta

As the host adapts to fight the parasite, the parasite evolves to infect the host. It’s an endless race, and extinction faces the first organism to stop running.

So what’s this got to do with sex? Sex is evolution on turbo. Mixing and matching genes increases genetic diversity, giving a species more opportunities to outlast in the ultimate game of survivor.

Field data supports the Red Queen Hypothesis as describing an adaptive advantage of sex. Models and maths support the idea that coevolving species could select for rare genes and unusual combination randomly created by sex. Direct experimentation of coevolution and nookie is tricky business.

New research, published in Science, grew several populations of nematode worms (C. elegans, roundworms) which are usually asexually, but reproduce sexually 20% of the time.

The populations were differently exposed to bacterial parasites (Serratia marcescens) as shown.

C Elegans Sex Research

C Elegans image by Bob Goldstein, University of Carolina, Chapel Hill, remixed by Science Journal. Creative Commons License

One population was given the parasites and left to their own devices. They and their bacteria could evolve together. These nematode worms increased their rate of sexual reproduction to 80-90% over time, and maintained a high level of sexy-times.

The other nematodes were given frozen stocks of bacteria every generation, so the parasites weren’t evolving as the worms did. At first, sexual reproduction increased in the worms, but then it dropped back down to 20% – the same level as nematodes which hadn’t been exposed to the bacteria at all.Alice meets dodo

Parasites on their own don’t increase sex – coevolution does.

A second experiment supported their conclusion. Nematodes mutated to be unable to reproduce sexually (asexual obligates) became extinct after 20 generations when exposed to the parasites. But mutants that always required sex to reproduce (sexual obligates) never became extinct.

When it comes to coevolution, it’s fall behind and be left behind.

Never stop running.

Morran, L. et al (2011). Running with the Red Queen: Host-Parasite Coevolution Selects for Biparental Sex Science, 333 (6039), 216-218 DOI: 10.1126/science.1206360
Brockhurst, M. (2011). Sex, Death, and the Red Queen Science, 333 (6039), 166-167 DOI: 10.1126/science.1209420

Bacteria solve sudoku

// November 17th, 2010 // 1 Comment » // Just for Fun, Recent Research

Image by UT-Tokyo for iGEM

Nobody loves sudoku like my granddad, unless it’s these Tokyo scientists. They genetically engineered e-coli to let them solve sudoku puzzles.

The puzzle was a 4×4, not quite the 9×9 that we’re used to. An example is shown in the picture. Each number was assigned a colour, so a red colony was the number one, and blue was two. The bacteria had to become the right colour to fit into the sudoku solution.

To solve the puzzle, the bacteria have to know what numbers are around it. For example, the position in the top left has the following data: There is a one in the column, a three in the row and a two in the box. Therefore it needs to be a four.

To become a number four, it needs to receive signals for one, two and three which makes it flip on a switch to say “four.” The switch works only when it receives three different signals.

Signals were transferred between bacteria using phage – viruses that infect bacteria. For example, a number one bacteria would produce a phage which says “Yo, I’m number one.” When that phage infects bacteria around it, they know they are in the presence of a number one. That helps flip the right switch for the bacteria to solve the puzzle.

More details on the project, which was part of the iGEM competition, can be found here.

Hat tip to The Loom.

Microbes, photographic film and a self portrait

// November 4th, 2010 // 1 Comment » // Science Art

Image by Erno-Eric Raitanen

This art is made of film degraded by bacteria.

It’s a self-portrait of the artist Erno-Eric Raitanen. The bacteria was harvested from his own body and cultivated on the gelatin surface of photographic film.

It’s a similar process to growing bacteria on a plate of agar. As the bacteria gnaw away at the gelatin, the film starts to degrade and creates some interesting patterns. He calls them bacteriograms.

I recommend you flick through his online gallery. I like to think I could make some myself one day, except with added science. Maybe add some antibacterials to part of the film and influence the pattern. OR add a mild antibacterial to the whole surface and make a picture of antibiotic-resistant bacteria!

I know I’ve got some scientist readers out there who are into bacteria. What would you make a bacteriogram of? What about virologists, how could you get some viral action happening on film?

World’s sweetest antibiotic? The five ways honey kills bacteria.

// July 13th, 2010 // 5 Comments » // Drugs, How Things Work, Recent Research, Science at Home

HoneyYou’re at the doctors with a suspected infection, but instead of offering penicillin or erythromycin, they prescribe honey. Would you switch toast toppings? Take a honey pill? How about letting the doctor smear medical grade honey over the infected area?

People have been using honey (not mad honey) as medicine since ancient times, but until now we have never fully understood how it works. Research lead by Dr. Paulus Kwakman from the University of Amsterdam and his team have finally identified the key elements which give honey its antibacterial activity.

Bacteria are becoming resistant to drugs faster than we’re developing them. Honey might help because it works when other drugs don’t. Studies show it has good activity in vitro against antibiotic-resistant bacteria. An older study reports successful treatment of a chronic wound infections not responding to normal medicine.

So how does it work? It’s a combination of five factors.

1. Hydrogen peroxide, a kind of bleach. The honey enzyme called glucose oxidase makes hydrogen peroxide when honey is diluted with water. We clean toilets with bleach, and it’s pretty good at killing bacteria.

2. Sugar. Honey has so much sugar there’s hardly any water for bacteria to grow in.

3. Methylglyoxal (MGO), an antibacterial compound found in New Zealand Manuka honey a couple of years ago. It’s also found in medical grade honey which is made in controlled greenhouses, albeit in smaller amounts.

4. Bee defensin 1, a protein found in royal jelly (special food for queen bee larva.) This report is the first time bee defensin 1 has been identified in honey, and it works as an antibiotic.

5. Acid. Diluted honey has a pH of around 3.5, the acidic environment slows down bacterial growth.

These five things work together to provide a broad spectrum activity against bacteria. For example, S. aureus is vulnerable hydrogen peroxide, while B. subtillis is challenged only if MGO and bee defensin 1 are working simultaneously. Honey has the right mix for maximum destruction.

So that’s how bees keep their honey fresh and unspoiled by bacterial growth. Perhaps with this information we’ll create enhanced honey to guard against infection, improving on nature like we did with penicillin. Until then, I know what I’m having on my toast.

A Schooner of Science could be named Australia’s best science blog. If you enjoyed reading, please vote for me.

ResearchBlogging.orgKwakman, P., te Velde, A., de Boer, L., Speijer, D., Vandenbroucke-Grauls, C., & Zaat, S. (2010). How honey kills bacteria The FASEB Journal, 24 (7), 2576-2582 DOI: 10.1096/fj.09-150789

What is the synthetic cell?

// May 22nd, 2010 // 1 Comment » // How Things Work, Recent Research

Two days ago scientists at J. Craig Venter announced the creation of the first self-replicating synthetic cell, a bacteria with DNA made in a lab. How did they do it, and what does it mean for us in the future?

First up, the scientists didn’t make life out of nothing, and they didn’t make a new species. They recreated a bacteria that already existed, and developed the techniques to do it.

The bacteria is Mycoplasma mycoides. It’s a parasite which lives in cows, and some subspecies cause cow lung disease. It has a circular chromosome made of just under 600,000 base pairs, making it a small genome.

The scientists had the genome sequence of M. mycoides and split it into bite-size portions and then synthesised. Synthesising DNA is nothing new, scientists have been able to write DNA code for quite a while, and can write whatever code they want to.

These little chunks were put into yeast, which can be forced to absorb little bits of DNA. Inside the yeast, the chunks can be sewn together. It’s called recombination. The resulting medium chunks were taken out and put into more yeast to be sewn together making large chunks. There were 11 large chunks were put into more yeast, and sewn together into one complete genome.

Along the way and at the end they checked the code was right by doing PCR tests, genetic fingerprinting made famous by CSI.

Result: A synthetic genome, written by a computer and put together in yeast sweatshops.

Now they had to get it into a bacterial cell. At first they tried to put the DNA into bacterial cells of a similar species, M. capricolum. They ran into trouble at first, because the DNA they had was unmethylated (lacking methyl groups) and the bacteria destroys DNA which is unmethylated. It’s a clever defense mechanism, and they got around it by methylating the DNA before putting it in.

Finally success. The synthetic genome was put into an M. capricolum bacteria where it replaced the normal genome. The bacteria were controlled by the new, synthetic chromosome and were able to replicate billions of times.

What does it mean for us in the future? The technology these guys have developed could be used to alter the DNA of bacteria and make them do new things. From medicine to clean water, the benefits could be huge. We already have this ability to some extent, but it opens up some new doors.

Some organisations have raised concerns about the work. Could a new bacteria be unleashed and take over the world? Probably not. It’s hard to predict how new genes will work in cells, and everything is linked together in a way we don’t understand now. Too much tinkering to the genome will probably not be tolerated by the cell. And if it did get outside, it would probably be extinct pretty quickly because it doesn’t have thousands of years of evolution to prepare it for the world.

If it did get out, we could track it back to the company in charge. These guys watermarked their genome by adding some quotes into the DNA/protein code. Now that’s just epically geeky!

ResearchBlogging.orgGibson, D., & et al (2010). Creation of a Bacterial Cell Controlled by a Chemically Synthesized Genome Science DOI: 10.1126/science.1190719

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