Bayblab

Do Not Fear; Solar Power Plants are Almost Here

2008-05-12T00:40:00.004-04:00

I thought this NPR Podcast from back in March was pretty good. Ira talks to a bunch of people from the solar power industry and the message is surprisingly optimistic. Large-scale solar power plants are apparently on the verge of becoming profitable, and utility companies are getting seriously interested. The clincher is that if the ball gets rolling, they claim that a hundred square-mile plant would be enough to provide a sustainable source of energy to the entire US (does this include the aircraft carriers and nuclear submarines?).

Maybe the imminent end of oil doesn't spell Armageddon for civilization after all. Although it's not clear how efficient fertilizer production would be without fossil fuels as a hydrogen source, and we'd still need to come up with a replacement material for the plastic in those Falcon tubes. But, unlike biofuels, solar power may provide a feasible option for a sustainable, but still modern economy.

Who Wants to Solve a Protein Structure?

2008-05-09T15:01:00.005-04:00

The Folding@Home project allows PS3 and computer owners to use spare processor cycles to help solve 3-dimensional protein structures. A new game allows players to use spare brain power to do the same. Foldit taps into human 3-D problem solving skills getting players to fold proteins in a video game interface, giving points based on energy required for a given configuration. The game has been in testing phase using proteins with known structures, but is about to challenge players with unknown structures.

Try it out or read more about the game here.

A Challenge for Science Bloggers

2008-05-08T15:16:00.002-04:00

Skull in the stars has issued a challenge to science bloggers: "Read and research an old, classic scientific paper and write a blog post about it." The suggestion is pre-WWII papers, but I've decided to pick something slightly more recent (pre-Woodstock, instead).

So that's the challenge: Pick a classic, write a post and submit the link in the comments over there so they can all be compiled in one list. Get it all done by the end of May. Have fun!

On Codon Usage

2008-05-07T15:47:00.006-04:00

Each amino acid in a protein sequence is represented by a 3-letter 'word' (codon) in the genetic code. Since there are 4 'letters' (A,C,G,T) there are 64 potential words to represent 20 amino acids, plus stop codons. The code is unambiguous - each codon represents only a single amino acid. It also has redundancies - most amino acids are represented by multiple codons (glycine, for example, can be represented 4 different ways). One might think that the diversity of life on the planet would come with a diverse difference in codon usage. This is not the case. There are differences in codon preference, both within and across species but usage is almost universal. For example, in humans the triplet ATC (20.8 codons/1000 codons) is preferred over the triplet ATA (7.5 codons/1000 codons) and in the yeast S. cerevisiae ATT is preffered to both of those (30.1 codons/1000 codons). However, in each of those cases - and virtually every other species - all three of those triplets code for isoleucine. Codon preference is related to abundance of the respective transfer RNA. (Larry Moran touches upon codon bias and why mutations that change the codon but not the amino acid may not be neutral in an article here)

There is experimental evidence for a universal genetic code:

mRNAs can be correctly translated by the protein synthesizing machinery of very different species. For example, human hemoglobin mRNA is correctly translated by a wheat-germ extract [...] bacteria efficiently express recombinant DNA molecules encoding human proteins such as insulin.
(Stryer, L. Biochemistry 3rd Ed. p 108)

A universal code is the basis of many techniques (and headaches) in the lab. For example, in vitro protein synthesis can involve rabbit reticulocyte lysates (or wheat germ, as above) translating non-rabbit proteins. Non-mouse sequences can be used to introduce genes into mice. E. coli is often used for recombinant protein production. In this latter case, the difference in codon preference between E. coli and other species is a common problem for high level recombinant expression (eg. if a codon is preferred in humans - CCC for proline - but not in E. coli, this limiting tRNA could hinder protein production).

That the genetic code is universal is not entirely true; some inter-species differences are being discovered. There are some species, such as ciliated protozoa have slight variations (in ciliates, TAA and TAG are glutamine rather than stop codons). Mitochondria are another important exception.

Mitochondria carry their own circular DNA which encodes for, among other things, a set of 22 tRNAs. Because it doesn't use the set of nuclear-encoded tRNAs, it isn't restricted to the standard code. In fact, human mitochondrial codon use differs from nuclear codon use in 4 places. For example, in the isoleucine example above, the codon AUA codes for methionine in mitochondria (see table, reproduced from Stryer). This isn't news, but something I failed to appreciate before. A difference in codon usage between species might not be surprising (in fact the consistancy in usage among species is surprising - until you consider the far reaching effects a change in codon use would have: Every protein would be affected). A difference in usage within a single cell is more striking, unless you're familiar with endosymbiotic theory.

Endosymbiotic theory, popularized by Lynn Margulis, describes the origins of eukaryotic organelles: mitochondria and chloroplasts. These organelles were once autonomous organisms that were taken up by other cells in a symbiotic relationship. Both organelles have strong resemblences to the proposed parent prokaryotes, as detailed in the above link. Codon use separate from nuclear DNA can be added to that list.

Read more about the different codon usage sets here.
Codon preference numbers from here.

Platypus Genome Complete

2008-05-07T14:55:00.002-04:00

We've talked before about the platypus and all it's strangeness. The platypus genome has has just been sequenced, revealing some things we already suspected: the platypus shares features with birds, reptiles and mammals. Follow the link for the Nature News story, podcast and video interview with the authors behind the project.

Lethal Injection

2008-05-07T11:28:00.004-04:00

I have had to euthanize mice for experiments before. The animal care people here are very adamant that the animals experience the least amount of discomfort as possible, as they should, it's their job. One acceptable way to euthanize a mouse is an intraperitoneal injection of euthasol, which is a barbituate, a class of CNS inhibitors commonly used as anesthetic.
If this is the most humane way to euthanize that should mean that lethal injections, as practiced by countries that euthanize convicted criminals as part of capital punishment, should be the same. I guess, that is, assuming that the point of lethal injection is to be more humane than previous methods of euthanization. I was surprised to learn that lethal injection is not very simple.
Lethal injection in the United States consists of three sequentially administered drugs. These drugs are sodium thiopental, pancuronium bromide, and potassium chloride given intravenously in that order. This is a similar procedure to what is on wikipedia for physician assisted suicide.
Sodium thiopental, also used as 'truth serum', induces relaxation and release from social inhibitions. It is a short-acting barbituate that at the doses for lethal injection rapidly induces a coma. It inhibits CNS activity by activating GABAa receptors. Alcohol acts on these same receptors, however, barbituates are not used much recreationally anymore, I think, as they have been largely replaced by benzodiazepines. 'benzos' (apparently safer and more fun). Relevant to lethal injection is that sodium thiopental has no analgesic effects ie. not a painkiller.
Then comes the pancuronium bromide. This blocks acetylcholine at neuromuscular junctions, rendering the convicted paralyzed, including breathing muscles. Hopefully that thiopental coma is going well or it would be like drowning.
Then just to ensure death, potassium chloride. Such a simple salt of two ions that are very common in your body is deadly? Really it is because the large bolus IV injection at a high dose messes with the electrochemical gradient needed for proper cardiac muscle function. The heart is stopped.
I wonder how much this combo has to do with ensuring death, and making it less traumatic for the witnesses than it does with being humane. A good way to go might be an overdose of an opiate or something but seeing a convict get all high and say weird things might be too much.

Greatest application of physics and the internet EVAR!

2008-05-06T13:00:00.003-04:00

In the quest for perfect BT (bra technology), the folks at 'shock absorber' have managed to create a mesmerizing website. To check out the bounceometer be sure to have your cup size and an estimation of your level of activity ready, and watch the efficiency of the 'shock absorber'.

Viagra nation

2008-05-05T10:10:00.004-04:00

I watched the newest vidcast of diggnation over the weekend, as I usually do. It is a reasonably good show about the most popular stories covered on digg.com. Alex Albrecht is too cool, mostly because he drinks beer, plays pencil and paper D&D, is on the totallyradshow, and kicks Kevin Roses arse at Call of Duty 4. That is some serious geek street cred.
This past eppisode though, they revealed some ignorance about the mechanism of Viagra. Kevin Rose (seriously check out how badly he is pwned by Albrecht on CoD4) thought that you could take Viagra and have a voluntary errection where you would have to 'be in the mood'. Someone from the audience who identified themselves as a 'life scientist' said that it was not voluntary. Well, Kevin Rose was right and the 'life scientist' was wrong. Strange since I find Kevin Rose usually talks out his ass.
As I understand it viagra mearly inhibits the degradation of cGMP, which directly initiates and maintains an errection. However it is produced in response to nitric oxide. The nitric oxide is produced upon sexual stimulation, therefore even with viagra it should still be a voluntary thing. That's got to be a relief for those who take the drug since you are supposed to take it 4 hours before you think you will need it. That would be a long 4 hours if it was involuntary.

Photo Caption Contest

2008-05-02T15:14:00.003-04:00

I stole this idea from Rob, but he's a bit busy to post it himself.

This photo of the Governator in 'research mode' is just begging for a witty caption, so have at it! After an inderminate amount of time, the funniest one will be chosen arbitrarily and the author showered with praise (sorry, our prize budget doesn't allow for much more than that).(Photo source: Nature News)

Just to get things going, here's my entry: "It's not a too-mah."

1000th post!

2008-05-02T13:50:00.003-04:00

For the occasion I wish to share with you interesting tidbits about penguin sexuality:

Penguins are famous for engaging in animal homosexual behaviour. They even sometimes steal eggs from heterosexual couples and rear the youngs. A famous case at the NY zoo, and reports in zoos from all over the world have confirmed that not only are homosexual couples frequent, but the bonding between the gay partnersis strong . Case in point: a zoo in Germany tried importing Swedish chicks and even they couldn't lure the males away!

Penguins are also known to prostitute themselves for a rock. They will let other penguins exchange sexual favors for nest building material.

Penguins sometimes engage in inter-species sex. Perhaps unwillingly. sometimes sexually frustrated seals molest penguins on the beach. I am not even making that stuff up!

Cancer Carnival #9 is Here!

2008-05-02T09:54:00.003-04:00

The 9th Edition of the Cancer Research Blog Carnival has gone live at Hematopoiesis. Your host, Alexey, has a nice collection of posts, including news from the recent AACR meeting. The next edition is set for June 6 so start penning your submissions. Contact the Bayblab if you're interested in hosting a future edition.

Thanks to Alexey for a great job and, as always, hats off to Ben for designing the logo.

Insurance and the Age of Personal Genetics

2008-04-29T14:29:00.002-04:00

In the age of the personal genome, companies like 23andMe are springing up, offering personal genetic profiling and ancestry tracing. While there are questions about the accuracy of their claims, the interpretation of the results (are we about to see a boom in genetic counsellors?) and other ethical and privacy considerations, the US Senate has made a pro-active move in passing a bill banning genetic discrimination. In short, the bill prohibits employers or insurers to use personal genetic information in decision making. Ars technica takes a closer look at the insurance angle, explaining why the bill is a good idea. From the article:

Worse yet, the very concept [of insurance based on genetics] threatens to undermine another of the greatest potential benefits of the genome: personalized medicine. The goal of personalized medicine is to tailor treatments to a the unique genetic defects that have helped foster a disease, be it diabetes or cancer. But, if insurers can deny coverage based on those same genetic traits, the patient may never see the treatment.

GSK acquires Sirtris Pharmaceuticals

2008-04-29T11:22:00.000-04:00

Pharm giant GlaxoSmithKline acquired Sirtris Pharmaceuticals for the tidy sum of $720 million US last week.

This story is interesting not because of the excitement of corporate deals and stock market fluctuations, but because Sirtris Pharmaceuticals specializes in developing small molecule activators of SirT1. And anything involving SirT1 - my protein of interest - is inherently fascinating.

It's actually more interesting for other reasons. Previously on this blog, I've echoed a sentiment common in the skeptical blogosphere: There's no such thing as alternative medicine. Once a treatment has been shown to work, it becomes part of mainstream medicine. Resveratrol, a polyphenol, is a SirT1 activator. SirT1 (I told you it was interesting) has been shown to be involved in insulin signaling, energy metabolism and lifespan extension in model organisms. Other work has shown resveratrol to have cardioprotective and anti-cancer effects. Resveratrol has long been thought to be a molecule behind the 'drink red wine' wisdom.

This all sounds great. And 'alties' probably feel vindicated: Resveratrol has been on sale in health food and dietary supplement stores for ages. Before many of the studies mentioned above had been done, in fact. But don't go reaching for your wineskin just yet. Studies have also shown that oral resveratrol has poor bioavailability.

That's where Sirtris comes in. They develop compounds that are analogs of resveratrol to improve potency and bioavailability (and patentability), and test those compounds. And Big Pharma (GSK) has taken notice, decided this is viable science, and acquired Sirtris in the hopes of turning these compounds into diabetes, anti-obesity or anti-aging drugs. Like other examples we've discussed this is a case of a natural or alternative medicine becoming mainstream (or, rather, the beginning steps of that process).

The moral of the story isn't that natural products work. In this case it doesn't - all resveratrol supplements will give you is expensive urine. The point is that if the science is there, the medicine will come.

There's still a possibility that these compounds will fail for one reason or another. Perhaps they won't be effective in humans as in rodents. Maybe there will be toxicity issues. If this happens, no doubt that Big Pharma conspiracy theorists will jump up and down saying that GSK made the purchase to squash a promising natural medicine. An almost 1 billion dollar investment seems to be a bit much for such a petty goal. If I was the big, evil corporation, I'd sink that money into the supplement makers and keep it on the shelves. But shrewd companies know that a tested drug has more value than an untested one. The only reason not to get science onside is if you don't think it will support you.

State-of-the-Art Geeky Coffee

2008-04-27T23:23:00.011-04:00

The coffee-maker pictured above is known as a Japanese siphon bar (see the NY Times website to see a slide-show of the thing in action). It is the only one of its kind in the US, imported for a mere $20,000. Eleven dollar globes of the non-espresso coffee product are apparently all the rage on the San Fransisco hipster-blogger-academe coffee-shop scene. The Times recently reported on this new trend in high-end brewed coffee making. The siphon bar is found at the Blue Bottle Coffee Company. Owner James Freeman explains the concept:

“Does coffee brewed from single-origin beans in a siphon or a Clover taste more yummy than, say, Folgers from a percolator? I believe it does. But it would be hubris to suggest that we’re making better coffee than anyone ever has. My feeling is, there are already enough places where you can get a cinnamon latte and a muffin wrapped in plastic. Why would I want to build another one of those?”

Supposedly this thing makes the greatest cup of coffee known to (wo)man. No less than Starbucks has bought the rights to similar technology (the mystical "Clover"). I'll admit, my curiosity has been aroused. But I'm sure as hell not going to pay that kind of cash for a taste (not to mention the plane ticket). So I fired up the YouTube and did a little commercial espionage (see video clip and watch the brewing process in action). Turns out these guys are a bunch of scientist wannabes! I figure it'd be pretty easy to rig one up with a bunsen burner, a couple of flasks, a Buchner funnel and a vacuum line. All easily found within your standard biomedical research lab...except for the Yo-Yo stunt man...

Unscientific Art

2008-04-26T11:31:00.003-04:00

Found on BoingBoing.
"Science painter Cornelia Hesse-Honegger collects and paints mutant bugs in the vicinity of irradiated wastelands like Chernorbyl, around nuclear plants, and nuclear refining sites."
Here is a link to the title page of this work.
Awesome paintings of messed up bugs. Too bad that's pretty much all it is, and claims that the observed mutant phenotype of the insects has something to do with radiation from nuclear power plants is probably just to attract some attention to the great artwork.
I love entomology and genetics so otherwise this would have been really cool with some statistics and some controls.

IA updates

2008-04-24T15:32:00.002-04:00

Once again informationaddiction.com has some updates. Infrequently updated but always good.

Carnival Call for Submissions

2008-04-24T14:12:00.001-04:00

The next edition of the cancer Carnival (#9) is coming up on Friday, May 2nd. Make sure you submit your posts here by May 1st (one week from today). This edition will be hosted by Alexey at Hematopoeisis.

The Joys of Scientific Discovery

2008-04-24T10:40:00.004-04:00

Man this little story was just too funny not to make a Ctrl+C, Ctrl+V blog post:

I hope that e-lab notebooks don't catch on, because they lose a lot of character when 'people are watching'. I remember doing in vivo recordings, sometimes for ~20 hours, in grad school. If the neurons were alive, I was recording. Things were pretty automated, so I would pass the time looking at the oscilloscope during stimulation trials while drinking Busch light. After about 10 beers one night, I finally realized what the neurons were doing and got a C/N/S paper out of it. I remember looking at my notes from that fateful night, scribbled with the drunken uncoordination that is only found on pub toilet walls: "THEY'RE FUCKING OSCILLATING!!!!" I wrote this about 10 times as I went back and looked at the sweeps from previous experiments that I had pasted into my notebook. Then, I perfused the animal, drank 2 more beers, had a smoke in our fume hood, and passed out. I was awoken by our TurboTech at 7 am.

I still have the notebook, complete with beer stains and coffee stains (and probably some drool). That's not something I'd be willing to live-blog, or even transfer onto the web, though. It could only be appreciated as a scratch-and-sniff YouTube video; or in my blurred memories of grad school.

This great anecdote courtesy of TreeFish, commenting in response to a post by PhysioProf on the idea of open digital lab books ("Science 2.0 Open Access Lab Notebooks" Is Completely Absurd) over at DrugMonkey.

Sugar and spice and everything nice...

2008-04-23T15:20:00.000-04:00

...that's what little boys are made of? Nature News is reporting on a paper that suggests that that diet influences the gender of your offspring. In a retrospective study, the authors asked women about their diet in the weeks leading up to pregnancy and analyzed the results. They found that women with a higher caloric intake were more likely to have boys. The researchers think it may have to do with high blood glucose levels. Though a potential mechanism is unclear, they note that many animals give birth to more males when resources are plentiful.

How can chromosome numbers change?

2008-04-21T13:35:00.003-04:00

The question:

How did life evolve from one (I suspect) chromosome to... 64 in horses, or whatever organism you want to pick. How is it possible for a sexually reproducing population of organisms to change chromosome numbers over time?

For the answer read this.

Top 5 McGyver moments in the lab

2008-04-18T15:28:00.006-04:00

Have you ever had one of those McGyver moments in the lab where you inventively use lab supplies or household objects to make an experiment work? These people brought it one step further:

1- Michelle Kline at the University of California had to improvise a material to build microfluidics chambers when her funding dried out. She turned to Shrinky Dinks, and created a low cost alternative!

2- Ellie Wollman and François Jacob had to improvise a way to look at bacterial conjugation and to map the genome simply by measuring the time of transfer. But they needed a way to abruptly stop conjugation, so they use a blender to sever the pili and stop the transfer!

3-Hans Spemman was studying embryology in the 1930's and one of the questions of the time was if every cell has a deterministic fate from the first division on or if they acquire their fate later in embryo development. To divide a cell before it's first division Spemman used a baby hair (since they are sturdy yet very fine) to cleave the cell. In fact just by using this technique and tweezers he was even able to do nuclear transfers and kickstart the study of stem cells. Talk about being ahead of your time.

4-In one the labs I've worked in in the past, we use to cut corners and make our own DNA ladder and our own TAQ polymerase. But Orac takes it further and contemplates how to create your own electrophoresis box. And of course you can make your own DNA columns if you visit the local potery shop, or just reuse your Qiagen columns.

5- Submit your story in the comments, and we'll see if it's McGyver-worthy...

Blogging about Blogging about Blogging

2008-04-18T11:39:00.003-04:00

AC recently lamented:

"This blog was more fun when it was about quirky research papers and fart & dick jokes. All this meta 'blogging about blogging' stuff is intellectual masturbation."

I'm not sure what intellectual masturbation is exactly, but if it's anything like the real thing... Anyhow, nobody likes an unhappy Coward so here are some Bayblab blasts from the past:

The post that started it all - an innocent link to a BBC interview with hacker Gary McKinnon

Our messy bench contest that drew maybe 3 entries (perhaps it's time to start that one again?)

Our first podcast meets rave reviews.

AC and I battle over who can find the weirdest case of supernumerary body parts. (AC wins)

Bayblab almost gets sued

Bayman tries to convince us of left-hand superiority (he's still deluded)

We try to ferment a pumpkin

And finally, The famous animal penis post (this is our all-time most popular post)

For those looking for some new material, here are some quick hits:

Masturbation cuts prostate cancer risk (Does intellectual masturbation count?)

20 years of penis gun-shot wounds

Scientists find, and kill, the oldest living animal

Do elephants ever forget? (unclear, but they do develop vision problems)

Women say that size doesn't matter (Right, like we believe FoxNews)

And now back to your regularly scheduled programming

Arguing From "Authority" Instead of Evidence

2008-04-16T23:54:00.005-04:00

DrugMonkey has written up a great post on the problem of relying on "authority" or credentials in scientific discourse:

"In science, the distinction arises when one wishes to short-circuit the process by which the expert demonstrates her expertise by providing the interpretive narrative and rationale by which she has arrived at her conclusions. Once one moves on to the "just trust me on this" or "well, my professional experience and judgment lets me know that ...." argument, it becomes an appeal to "authority" for authority's sake, as opposed to an appeal to the experienced individual's actual related expertise."

One would think this would be self-evident, especially to bloggers professing to be scientists of great "authority". However it was none other than Greg Laden who kicked off the whole discussion with commentary following Kamel's recent post on anonymous blogging. Laden seemed to be arguing that anonymous blogging is a bad thing because one is unable to assess the credentials of the speaker, and therefore unable to determine the validity of their arguments.

I've said most of what I have to say on this topic in the comments to Kamel's post and over at DrugMonkey's place. Here I'll summarize by saying I tend to think that the validity of an argument has to do with evidence and reasoning, and not how many degrees or prizes the speaker has won. An accurate statistic quoted by an anonymous blogger for example, is no less accurate because the identity of the person citing it is unknown. Likewise, it is no more likely that HIV is not the cause of AIDS just because Kary Mullis won a Nobel prize for the invention of PCR.

But that's just my opinion.

UPDATE - Greg Laden has now posted a clarification of his position on anonymous/pseudononymous blogging at his place. Go there to read his opinion for yourself.

Random Genetic Drift

2008-04-16T15:53:00.002-04:00

The anti-evolution film Expelled: No Intelligence Allowed is being released on Friday and the US National Centre for Science Education site Expelled Exposed has gone live. The site is a point-by-point examination and de-bunking of the claims made in the film. The site hit Digg and is currently working out the high traffic issues, but some of the comments at Digg were interesting.

I am not an evolutionary biologist, but the comments seemed off. Most of the pro-science commenters there equate evolution with Darwinism - that is, speciation by mutation and natural selection. Natural selection is one evolutionary mechanism - indeed, the one people are most familiar with - but it is not the only one. Larry Moran at Sandwalk kicked off a bit of a discussion of this when he asked his readers to define evolution, and many different ideas were kicked around. Larry also has a nice explanation of one of those mechanisms, random genetic drift, in a piece at talkorigins.org. From the article:

"If a population is finite in size (as all populations are) and if a given pair of parents have only a small number of offspring, then even in the absence of all selective forces, the frequency of a gene will not be exactly reproduced in the next generation because of sampling error. If in a population of 1000 individuals the frequency of "a" is 0.5 in one generation, then it may by chance be 0.493 or 0.505 in the next generation because of the chance production of a few more or less progeny of each genotype. In the second generation, there is another sampling error based on the new gene frequency, so the frequency of "a" may go from 0.505 to 0.510 or back to 0.498. This process of random fluctuation continues generation after generation, with no force pushing the frequency back to its initial state because the population has no "genetic memory" of its state many generations ago. Each generation is an independent event. The final result of this random change in allele frequency is that the population eventually drifts to p=1 or p=0. After this point, no further change is possible; the population has become homozygous. A different population, isolated from the first, also undergoes this random genetic drift, but it may become homozygous for allele "A", whereas the first population has become homozygous for allele "a". As time goes on, isolated populations diverge from each other, each losing heterozygosity. The variation originally present within populations now appears as variation between populations." (Suzuki, D.T., Griffiths, A.J.F., Miller, J.H. and Lewontin, R.C. in An Introduction to Genetic Analysis 4th ed. W.H. Freeman 1989 p.704)

(A quote of a quote? How meta.) I think some of the numbers were miscopied from Suzuki et al. so I've changed them here, but it isn't the actual numbers that are important so much as the concept. Read the full article, it's quite informative and covers a variety of examples of genetic drift.

Magnetotactic Bacteria

2008-04-15T15:30:00.003-04:00

Recently heard about this strange class of microbes, magnetotactic bacteria, which produce and contain magnetosomes. These are iron complexed with protein and are arranged intracellularly as a chain. The iron is in the form of magnetite, the same form present in naturally occurring lodestone. Magnetite, as you might have guessed, is magnetic. The magnetosomes in the magnetotactic bacteria facilitates magnetotaxis ie. their movement based upon the magnetic field of their environment. And this, it is thought, is the purpose of these structures in the magnetotactic bacteria. These bacteria are very senstive to the redox potential of their environment and use the magnetic field of the earth in order to find "down" to a less oxygen rich environment. Thus bacteria in the northern hemisphere have their magnetosomes arranged in such a way as to get them to swim to magnetic north, which is slightly down in the northern hemisphere, away from oxygen. The opposite it was thought was true in the southern hemisphere. I ran into a great science article that sheds some doubt as to this purpose of magnetosomes. Apparently this group found "south-seeking" magnetotactic bacteria in the northern hemisphere.
I'm just guessing here but when I first heard about these bacteria I thought that the magnetic field they produced might have been useful for biofilms or to arrange themselves in some bacterial community. But that's a nature paper for someone else.
Magnetosomes are pretty interesting themselves and have some biotechnology applications.
What is actually pretty spooky is that not only do migrating birds and salmon have magentosomes, but so does the human brain.