Let your life lightly dance on the edges of time like dew on the tip of a leaf.

- Rabindranath Tagore

INTP - The Thinkers

The logical and analytical type. They are especially attuned to difficult creative and intellectual challenges and always look for something more complex to dig into. They are great at finding subtle connections between things and imagine far-reaching implications.

They enjoy working with complex things using a lot of concepts and imaginative models of reality. Since they are not very good at seeing and understanding the needs of other people, they might come across as arrogant, impatient and insensitive to people that need some time to understand what they are talking about.

Only one out of ten cells in our body is human

In a certain sense, every man is an island; this interesting finding comes from Jeffrey Gordon’s lab in Washington University. To understand why that is so, we need to understand something about the make up of our bodies. Adult human bodies are comprised of 10¹³ cells. These cells are broadly divided into different types that compose the tissues and organs that make us function the way we do. However, those are not all the cells that are in the human body. In addition to our own cells, we have 10¹⁴ bacterial cells that reside in and on us. Think about it: only one out of ten cells in our bodies contain the DNA inherited from our parents. The other nine cells are not human.

Most of the bacterial cells in our body are located in our gut, about 1.5 kg of bacteria. All along our gastrointestinal tract really, from our mouth to our anus. The others are on our skin, our respiratory system (lungs, trachea, nose) and ears. These bacteria too, are roughly divided into different types that perform different functions, some of them actually beneficial to us. Skin bacteria, mostly benign, actually prevent the colonization of our skin by disease causing bacteria. Our mouth is a slightly different story: the bacteria sitting on our teeth form plaque, a rough surface which accelerated the colonization by by other bacteria that metabolise sugar into acid. This acid eats through the tooth enamel and causes dental caries. That is why we wage a constant battle with toothbrush and toothpaste against bacteria. Other interesting stories are associated with our respiratory tract, our ears, and the upper GI tract.

But today we will talk about our gut, the bacteria that live there and some surprising findings on how they affect, and are affected by, our body weight. Oh yes, and why every man is an island.

“It’s not your fault, it’s your gut microflora”

Two years ago, Gordon’s group published two papers that made quite a splash both in the scientific world and in the popular media. They have shown that there is a difference in the bacterial taxonomic composition between obese and non-obese humans. They have shown that obese mice and people harbour in their guts a dominant population from the bacterial division Firmicutes. At the same time, lean people (or even those on a weight-loss diet) and lean mice, have less bacteria from the Firmicutes division and more from the Bacteroidetes division. To try and understand why that is, they performed a comparative metagenomic functional analysis of mouse gut bacteria. They compared a sample of DNA sequences extracted from the population of bacteria in the guts on lean mice, to DNA sequences from bacteria in obese mice. They found that in obese mice the gut bacterial population contained more enzymes that broke up complex carbohydrates, like starch. Other experiments showed that indeed, the population of bacteria in obese mice break up complex sugars more efficiently; that is, the bacterial populations of obese mice provide their hosts with smaller sugar molecules that are readily absorbed through the gut, creating a vicious feed-forward cycle: if you are a fat mouse, you will get more calories from the same piece of chow than if you are a lean mouse. Their conclusion was that the human gut bacterial population is intimately connected with what we eat. High poly-carbohydrate foods eventually enrich their consumers’ guts with carbohydrate loving bacteria; and those, in turn, “reward” their hosts with the back-handed compliment of making more simple and easily absorbable carbohydrates available to them, making them fatter.

So here is another another way in which bacteria affect our well-being: our gut flora controls our caloric intake. Consider a slice of whole wheat bread, about 100 calories.* This means that the actual caloric intake from a slice of bread will differ between individuals. Unfortunately, it is the fatter person who will, quite probably, receive more calories from eating the same slice of bread, because his gut bacteria will deliver more available calories to him.

This is not the first time such an observation was made. In 2004 the Gordon lab published a paper in PNAS, where they showed that Bateroidetes theta suppresses the formation of FIAF: Fasting-induced Adipocyte Factor. FIAF normally prevents the creation of fat, but high level of B. theta, associated with stress in humans, induce both a higher intake of carbohydrates, and the formation of fat from that intake. Here is a case of bacteria exerting a hormonal influence on our bodies affecting our energy balance and our weight.

So we have an incredibly intimate association with the bacteria in our bodies, at times as strong as that we have with our own.. actually, it’s getting hard to distinguish where we end and where our microflora begins. Well, not really: a eukaryotic cell with the DNA we got from mom and dad in a double package of 23 chromosomes is probably more ours than a prokaryotic cell with a single or double chromosome. The point is that the bacterial population is as important to our well being as some of our “human-cell” tissues.

But do all obese people have the same microflora? How much of our own genetic makeup influences our bacterial gut population and thus our body weight? And what about the headline “Every Man an Island”, what does that have to do with anything? Well, I’m pretty much getting to the end of this post, so please be patient, part 2 is coming up with some more interesting insights; and an explanation of the headline.

Bdelloids Survive 100 million years without Sex

Life without sex is conjectured to lead to extinction because of the way DNA naturally accumulates mutations so asexual species, lacking such a means of DNA repair, are thought to accrue harmful mutations over time that can help bring an end to a species. However, asexual bdelloids have proven quite prolific diversifying into at least 400 species.

To see how bdelloids might have prospered without sex and its DNA repair mechanisms, scientists zapped them with gamma rays to shatter their DNA into many pieces but even at five times the levels of radiation that all other animals are known to endure, bdelloids were able to continue reproducing.

Scientists believe that at some point the entire genome of the first bdelloid got duplicated giving it four copies of each chromosome and thus of each gene. The bdelloids kept most of its extra genes over time, and "we believe they have kept most of their duplicate genes because they are serving as templates for DNA repair," says evolutionary biologist David Mark Welch.

A better understanding of how bdelloids live without sex could shed light on how sex evolved in the first place.

Photo: Photo: "Scanning electron micrographs showing morphological variation of bdelloid rotifers and their jaws" by Diego Fontaneto Creative Commons All PLoS content published under CC-BY license

Darwinian Evolution on a Chip

Laboratory evolution is greatly accelerated compared with natural evolution, but it usually requires substantial manipulation by the experimenter. Researchers Brian M. Paegel and Gerald F. Joyce have developed a system that relies on computer control and microfluidic chip technology to automate the directed evolution of functional molecules in much the same way that one would execute a computer program using a population of billions of RNA enzymes with RNA-joining activity, which were challenged to react in the presence of progressively lower concentrations of substrate.

The steps were repeated automatically for 500 iterations of 10-fold exponential growth followed by 10-fold dilution. The researchers observed evolution in real time as the population adapted to the imposed selection constraints and achieved progressively faster growth rates over time.

The original research paper is available on PLOS Biology, the open-access, peer-reviewed journal.

Smart Brake Lights Could Save Lives

You are driving in heavy traffic on a rainy evening when the brake lights on the car in front of you come on. Is the car just slowing down or is it going to stop abruptly? “The problem is that brake lights are yes and no – on and off,” says Mechanical Engineer John Hennage. “The driver behind does not know the speed at which the car in front is slowing or stopping. It’s not enough information for the following driver.”

The solution is an intelligent brake light system that communicates slowing and urgent stopping – rather than simply that the brake pedal is being touched. Hennage and other engineers at Virginia Tech’s College of Engineering have developed a gravity or deceleration sensor control so that under normal braking – to slow or to stop slowly – the tail lights work in the normal fashion, when stopping speed crosses a threshold to urgent, red lights flash on either side of the amber lights, and if deceleration is rapid, all of the lights flash red.

The team now has a working prototype and is looking for a manufacturer to take the specifications and produce the circuit in mass quantities.

Did Universe Run Backwards before the Big Bang?

Until recently, asking physicists what happened before the Big Bang was considered a question that didn’t make sense from a scientific view but a new theory called Loop Quantum Gravity (LQG) has emerged suggesting the possibility of a “quantum bounce,” where our universe stems from the collapse of a previous universe. However no observations of our current universe could lead to any understanding of the state of the pre-bounce universe, as nothing was preserved across the bounce - a form of “cosmic amnesia.”

Now two scientists have modified the theory showing that relative fluctuations of volume and momentum in the pre-bounce universe are conserved across the bounce. “This means that the twin universe will have the same laws of physics and, in particular, the same notion of time as in ours,” says Parampreet Singh from the Perimeter Institute for Theoretical Physics in Ontario. “In our analogy, it will look identical to its twin when seen from afar; one could not distinguish them.”

Does this mean there was another you that existed at some point, someone who has already lived your life? “If one were able to look at certain microscopic properties with a very strong microscope – a very high-energy experiment probing the Planck scale – one might see differences in some quantities, just as one might see that twins have different fingerprints or one has a mole and the other does not, or a different DNA,” Singh added.