Throughout the last decade, scientists have shown that bacteria can transfer electrons between one another to produce electric currents. Some of them do so with hair-like extensions called pili, which act as tiny electric wires. Now, we know that some can use iron minerals to transfer electrons instead.
All living things rely on relays of electrons. In our cells, proteins strip electrons from food and pass them along to one another, eventually depositing them onto oxygen. This releases the energy that fuels our existence. In animals and plants, these electron transfer chains are restricted to individual cells. But in bacteria, the chains encompass many cells, even those that belong to different species.
One bacterium can rip electrons away from potential food, and pass them to another, which deposits them onto oxygen or another accepting molecule. The former “eats”, the latter “breathes”, and neither could do so without the other. In this way, many species can cooperate to thrive in conditions that neither can live in alone. And electrons are the currency that seals their alliance.
Two years ago, Danish scientists showed that different species can transfer electrons over centimetres. That’s a massive distance for a tiny microbe, and no one knew how they did it. A group of Japanese researchers have now found a possible answer. They showed that bacteria can use conductive iron minerals like magnetite to shuttle electrons between each another.
Imagine then, a grid of bacteria connected by wires of rock, pulsing with electricity in the deep ocean and working together to survive.
I’ve written about this new discovery for The Scientist, so head over there for more details on the new experiments.
Image by Nixdorf
Your laziest days are positively frenetic compared to the lifestyle of some deep-sea bacteria, buried in the sediments of the Pacific Ocean. These microbes are pushing a slow-going lifestyle to an extreme. They subsist on vanishingly low levels of oxygen, in sediments that have not received any new food sources since the time of the dinosaurs. And yes, they survive.
Not only that, but these microbes could make up 90 per cent of those on the planet. “We’re looking at the most common forms of life on this planet, and we know almost nothing about them,” said Hans Røy, who has been studying them for many years. Now, Røy has finally measured just how slow their metabolism really is.
I’ve written about this discovery for The Scientist, so head over there for the full story.
Image by Shelly Carpenter, NOAA Ocean Explorer
A child from the village of Chamba in rural Malawi has very little in common with one living in the city of Philadelphia in the USA. They eat different food, speak different languages, and enjoy different lifestyles. But they are both united by the fact that they are vessels for teeming hordes of bacteria.
These children, like all of us, are home to trillions of bacteria and other microbes. These passengers outnumber our own cells by ten to one, and their genes outnumber ours by a hundred to one. Collectively, they’re known as the microbiome, and they are as much a part of us as any one of our own organs. They break down our food, safeguard our health, and affect our minds. And they have become intensely fashionable.
Microbiome research is booming, fuelled by the realisation that these microbes might provide a deeper understanding of our bodies, and new ways of diagnosing or treating diseases. But, with some exceptions, most microbiome studies have focused on wealthy populations from Europe, North America and Japan. There’s a risk that the bacteria of people from the developing world will be ignored.
Tanya Yatsunenko has led one of the largest efforts yet to remedy that problem. Working with Rob Knight and Jeffrey Gordon, she amassed an international collection of faecal samples and studied the gut microbes of people three diverse populations: 100 Guahibo people from the Venezuelan Amazon; 115 people from four Malawian villages; and 316 people from three American cities. The recruits ranged from newborn babies to 70-year-old adults.
“The paper represents a heroic effort,” says David Relman, who studies the microbiome at Stanford University. “It’s the most definitive cross-culture and multi-age assessment of the human microbiome to date.”
For almost a decade, Jillian Banfield has been travelling to a place that “pushes the limits of human endurance” – Richmond Mine in Northern California. Its abandoned caverns can reach 48 degrees Celsius and 100 per cent humidity. They are low in oxygen. They contain possibly the most acidic naturally occurring water on Earth, with a pH value of -3.6.
But even in these conditions, there is life. Bacteria grow within the cave, floating in thin films on top of its hot, acidic water. They are the lords of their extreme world, and they provide an unrivalled opportunity to study how wild microbes evolve.
Many insects eventually evolve to resist insecticides. This process typically takes many generations and involves tweaks to the insect’s genes. But there is a quicker route. Japanese scientists have found that a bean bug can become instantly resistant to a common insecticide by swallowing the right bacteria.
The bug forms an alliance with Burkholderia bacteria, and can harbour up to 100 million of these microbes in a special organ in its gut (see arrow above). Some strains of Burkholderia can break down the insecticide fenitrothion, detoxifying it into forms that are harmless to insects. In fields where the chemical is sprayed, these pesticide-breaking bacteria rise in number. And if bugs swallow them, they become immune to the otherwise deadly chemical.
I’ve written about this story for The Scientist, so head over there to read the details of the study.
The caverns of Lechuguilla Cave are some of the strangest on the planet. Its acid-carved passages extend for over 120 miles. They’re filled with a wonderland of straws, balloons, plates, stalactites of rust, and chandeliers of crystal.
Parts of Lechuguilla have been cut off from the surface for four to seven million years, and the life-forms there – mainly bacteria and other microbes – have charted their own evolutionary courses. But Gerry Wright from McMaster University in Canada has found that many of these cave bacteria can resist our antibiotics. They have been living underground for as long as modern humans have existed, but they can fend off our most potent weapons. Drug resistance may be causing problems for us now, but for bacteria, it’s just an ancient solution to an ancient problem.
I regularly write about the microbiome – the trillions of bacteria that share our bodies with us, and the genes that they carry. At the recent International Human Microbiome Congress in Paris, I was immediately struck by two things. First, the field is clearly growing. It’s full of scientists who are doing great work to understand our bacterial associates, and who are glad that the microbes are finally hitting the big time.
But I also felt a familiar twang. When one of the initial speakers described the quest to sequence our microbiome as the “biggest life sciences project of all time”, and when people spoke of new ways to diagnose and treat diseases, I was reminded about the hype that surrounded the Human Genome Project, back when our DNA had not yet been fully sequenced. When people showed communities of microbes that were associated with diseases, with no clear sense as to which caused which, I thought of the endless number of observational studies looking at risk factors for cancer, heart disease, autism, and other conditions.
And it worried me. While I’m fascinated by the microbiome, and was thrilled to be part of the conference, I also wondered if the current optimism would lead to a backlash down the line. There’s precedent for this. The Human Genome Project is currently experiencing just such a backlash, as are large studies that try to find genetic variants that underlie human diseases. The so-called War on Cancer is still being fought several decades later, and patients are getting impatient. And I found many other microbiome scientists who shared my concerns, at the conference and beyond.
This was the basis of a piece that I wrote for Nature News. It looks at the potential for hyping yet another ‘Big Science’ endeavour. But it also considers legitimate reasons why the microbiome may deliver on its promises more quickly than the genome has. In particular, diagnostic tests seem to be a rich area to focus on, with a good chance of providing short-term gains. Check out the full piece for more.
Last year, I wrote about an intriguing study which showed that our hordes of gut bacteria tend to cluster into one of three communities. Each individual has one of these three “enterotypes”. As I wrote at the time, “There seem to be just three preferred ways of building a community of gut bacteria.”
Or are there? I’ve just spent three days at the International Human Microbiome Congress in Paris, where several hundred scientists gathered to discuss the nature of the several trillion bacteria we carry. One of the most intriguing debates, which ran across the first days of the conference, revolved around whether the enterotypes are actually discrete meaningful entities, or just points along a continuum of gut bacteria.
This reflects an age-old debate in science between “lumpers and spliiters” but it matters if, as suggested, the enterotypes could one day be used to stratify patients according to their risk of disease or which treatments they should receive. I wrote about the debate for Nature News. Head over there for more details.
Disclosure: MetaHIT, the conference organisers and the scientists behind the enterotype paper, paid for my travel and accommodation to the conference, so that I could chair the final panel on the future of the microbiome.
A black bean aphid is about to have a rough day. It has been targeted by a parasitic wasp, which lays several eggs inside its body. When the eggs hatch, the wasp grubs will try to eat the aphid from the inside out. If they succeed, the aphid will die, and the young wasps will burst from its corpse to find aphids of their own.
But the aphid isn’t necessarily doomed. There’s a chance that it will resist the attempt to usurp its body. If it does, the wasps will have done it a favour. When the mother wasp implanted its eggs, it also infected the aphid with bacteria that protect against parasitic wasps. It inadvertently vaccinated the aphid against its own kind.
A bout of Salmonella food poisoning isn’t a pretty affair. Your digestive tract churns, you can’t keep your food down, and you feel exhausted. But you aren’t the only one affected. Your gut contains trillions of bacteria, which outnumber your own cells by ten to one. They are your partners in life, and they are also transformed by the presence of the invading Salmonella.
Minority members of this intestinal community start to bloom, greatly increasing in number as the guts around them become inflamed. And these gut bacteria start to trade genes with Salmonella.
These swaps are a regular part of bacterial life. In their version of sex, two cells become united by a physical bridge, through which they shunt rings of DNA called plasmids. These rings can act like mobile weapons packages. Some give otherwise harmless bacteria the ability to cause disease. Others confer resistance to antibiotics. It’s a network of shady arms trading, and in your inflamed bowels, it happens at an unprecedented level.