“Ocean Bacteria Glow to Turn Themselves Into Bait”

Aaaand we’re back! I hope you had a lovely break, and that one of your new year’s resolutions was to read even more science! I’ve been off in the non-virtual world for the past week, but it is time to get back to business. And remember that for more science goodness you can follow Science Picks on Twitter at @SciencePicks, or if you’re Twitter-averse you can see the extra links I tweet on the sidebar to the right. 

Not Exactly Rocket Science has an interesting article on glowing ocean bacteria and why they do what they do, with a bit of an introduction here:

On 25 January 1995, the British merchant vessel SS Lima was sailing through the Indian Ocean when its crew noticed something odd. In the ship’s log, the captain wrote, “A whitish glow was observed on the horizon and, after 15 minutes of steaming, the ship was completely surrounded by a sea of milky-white color.” The eerie glow appeared to “cover the entire sea area, from horizon to horizon . . . and it appeared as though the ship was sailing over a field of snow or gliding over the clouds”. The ship took six hours to sail through it.

These glowing seas have featured in sailor stories for centuries. The crew of the Nautilius encountered the phenomenon in Jules Verne’s Twenty Thousand Leagues Under the Sea. And in 2006,  Steven Miller actually managed to recover satellite images of the very same patch seen by the crew of the SS Lima – it stretched over 15,000 square kilometres, the size of Connecticut or Yorkshire.

The glowing waters are the work of bioluminescent bacteria – microbes that can produce their own light. They are found throughout the oceans, although usually in smaller numbers than the giant bloom responsible for the SS Lima’s sighting. In many cases, they form partnerships with animals like fish and squid, taking up residence inside their hosts and paying their rent by providing light for navigation or defence.

But many glowing bacteria live freely in the open ocean, and they glow nonetheless. Creating light takes energy, and it’s not something that’s done needlessly. So why do the bacteria shine? One of the most common answers – and one that Miller proposed to explain his satellite images – is that the bacteria are screaming “Eat me!” at passing fish. A fish’s guts are full of nutrients, and it can carry bacteria across large distances. The bacteria, by turning themselves into glowing bait, get a lift and a meal.

The article goes on to explain a study that showed this in action: basically, zooplankton – a classification for small organisms that drift around in bodies of water – were given a choice of eating glowing or non-glowing bacteria, and they tended to choose the glowing bacteria. Presumably this is because the bacteria only glow when they’re grouped together, which happens when they find a tasty piece of detritus to hang onto. Glowing bacteria means there’s food around, so they’re a nice target.

As a side effect, organisms that eat glowing bacteria will sometimes end up glowing themselves, making them big targets for fish. A deadly circle of life, all so that some bacteria can hitch a ride. 

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Very Alternative Energy: Bacteria, Sewage and Saltwater

Most of the renewable energy sources that are under consideration involve an obvious source of energy—light, heat, or motion. But this is the second time this year there has been a paper that has focused on a less obvious source: the potential difference between fresh river water and the salty oceans it flows into. But this paper doesn’t simply use the difference to produce some electricity; instead, it adds bacteria to the process and takes out a portable fuel: hydrogen.

Nobel Intent brings us: the poop power plant. When freshwater meets saltwater with a membrane between (through which water cannot pass), ions will pass from the saltwater to the freshwater, creating a potential difference = power. Meanwhile, bacteria can liberate electrons in the process of digesting organic matter. Neither of these alone create much voltage, but when you combine them (not so clear on how this part works), you have enough voltage to release hydrogen from water molecules, which you can later use for power in fuel cells. You also need organic matter for bacteria to digest, so a potential system to use this in is, for example, where sewage empties out.

And there you have it – poop power plants. The future may not be as shiny and clean as we thought…

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