‘Netting’ bacteria with DNA: strategies of a social amoeba

Life has survived for more than three billion years because it is robust, and almost no mutations can easily outwit the defense mechanisms built up through eons of exposure to potential pathogens.
–Lawrence M. Krauss

Every second, every minute of your life, your body is under attack. This may be strange to think about, but millions of bacteria, as well as myriad other parasites, are attempting at this very moment to invade the sanctum of your body. Do not be offended, these creatures do not do this out of any sense of malice. They are simply driven by the two greatest necessities of life – survival and reproduction.

Dictyostelium Aggregation
Dictyostelium discoideum

Ever since the first cells arose in the hot, steamy, soup that was our earth’s oceans billions of years ago, organisms have competed fiercely for the same limited resources. Some cells devised ways to halt the growth of or outright kill other cells, while others entered complex beneficial (mutualistic) or harmful (parasitic) interactions with each other. With time, two kinds of life forms emerged – parasites, who attack other organisms to their own benefit and the other’s loss, and hosts, who suffer from the parasites’ attack. A much larger class is that of pathogens – any organism that can directly cause disease in a host is called a pathogen. Host defense mechanisms have, therefore, evolved over eons to outsmart parasites and pathogens. Plants have specialized signaling systems to fight invading bacteria, and multicellular animals like human beings have an immune system with several tiers of defense to combat infection. Yet, at the same time, the parasites have been evolving too, devising sneakier and subtler ways of evading the host’s defense pathways to gain entry and live undetected. Life can, in fact, be described as a continuous arms race between hosts and their parasites, where neither gains the upper hand on the other, even after centuries of creating sophisticated arsenals for the purpose.

This continuous struggle has given rise to some truly ingenious forms of biological innovation. A recent study from Xuezhi Zhang and colleagues, working in a collaboration between the University of Geneva, Switzerland, and Baylor College of Medicine, USA, sheds light on a remarkable and evolutionarily ancient line of defense employed by a class of social amoeba. Simply put, the defense consists of casting a net formed of DNA molecules over bacteria and killing them slowly with poisons embedded in the net.

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The Oldest Stars in our Galaxy

UniverseThe Universe sprang into being about 13.8 billion years ago, expanding exponentially from a point of infinite density and infinite temperature. Such a point is called a singularity, and this event is popularly known as the ‘Big Bang’. Before this point, time and space did not exist, so the word ‘before’ itself ceases to hold meaning. Within the space of a second, the first elementary particles were formed, and the universe shifted from a state of pure energy to one containing matter as well as energy. Within 20 minutes, the universe had cooled down enough to allow protons and neutrons to combine through nuclear fusion, and the nuclei of the first atoms graced the universe. These were the nuclei of hydrogen (simply a proton), helium, and a tiny bit of lithium. The first true atoms, with positively charged nuclei surrounded by negatively charged electrons, would not arise till about 300,000 years later.

The first stars were created about 100 – 200 million years after the big bang, when areas of large matter densities began to cool and undergo gravitational collapse. These first stars were composed primarily of hydrogen and helium, the first elements in the universe, with perhaps a trace of lithium. These stars were probably massive, many hundreds of times the mass of our sun, significantly hotter, and relatively-short lived. Higher molecular weight elements (rather confusingly called ‘metals’ by astronomers) were formed within these stars as a result of thermonuclear reactions, and when these stars exploded as supernovae, these metals were flung far and wide, finding their way into clouds from which the next generation of stars took birth. As a result, newer stars (our own sun being one of these) are much more metal-rich than those formed during the dawn of the universe.

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Freud, Cocaine and the Dopamine Hypothesis of Addiction

Sigmund Freud LIFE
Sigmund Freud
Sigmund Freud, the venerable father of psychoanalysis, had a lesser known distinction up his sleeve. He produced one of the first comprehensive scientific analyses of the drug Cocaine, published in 1884 under the title ‘Über Coca’. In this remarkable manuscript, amidst sections such as a detailed description of the cocaine plant (Erythroxylon coca, for the curious), Freud inserted his meticulous observations on the effects of cocaine on the human body. As he was quite free in admitting, he based his remarks on the “some dozen times” he consumed the ‘coca’ himself, ostensibly for research purposes. Once the effects wore off, Freud reported no lasting side effects, and was quite positive in denying any craving or addiction like symptoms.

It seems to me noteworthy – and I discovered this in myself and in other observers who were capable of judging such things – that a first dose or even repeated doses of coca produce no compulsive desire to use the stimulant further; on the contrary, one feels a certain unmotivated aversion to the substance.

– Sigmund Freud, Über Coca

Till the end of his days, Freud remained convinced about the beneficial nature of cocaine, and strongly advocated its use for medicinal purposes. In an idea that was surprisingly ahead of his time, though ultimately misguided, he even suggested that cocaine be used as a substitution therapy for de-addicting patients from morphine or alcohol.

Freud isn’t alone among illustrious personalities in having dabbled with cocaine, heroin, morphine or any of the other well-known drugs of abuse. Recreational drug use has always been common, particularly among certain social, occupational or age groups, drug prohibition laws notwithstanding. And a really curious fact that is rarely talked about in scientific literature is that many of these users somehow escape without any negative consequences, and never develop the compulsive addiction that makes these drugs so deadly to the population at large.

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The Secret Lives of Bees

If you have ever felt a yearning for a perfect picture of domestic bliss, take one look inside a simple beehive. The life of the social bee is a life of contentment and diligence, of strict order and unfailing discipline, of stratified classes and organized division of labor, and above all, of a collective mind which puts the survival of the colony above the survival of the individual. Bees are close relatives of wasps and ants, and are found on every continent except Antarctica. They also tend to exhibit some of most sophisticated behaviors in the animal world. In many species of social bees (honeybees being the best known example), hives consist of a reproductive queen, male drones whose only function is to mate with the queen, and several sterile, female worker bees. This week’s Current Biology carries a bunch of interesting studies concerning bees, which bring to light the layers of complexity that underlie the routine behaviors of these remarkable creatures. We are going to take a brief look at each of these studies.

Tricking a bee with a cup of coffee

honey bee photo
Photo by eleZeta

Honeybees feed on nectar, a sweet tasting, sugar-rich substance produced by several species of flowering plants. Nectar carried back to the nests is used to prepare honey, which is stored as food for the young ones, and as surplus rations for the winter. The plants are benefitted by this, as pollen sticking to hairy bristles on the honeybee’s body helps cross-pollinate flowers. The nectar serves as incentive to get the bees to help in this process. So far this seems like a win-win situation for the plant and the bee (a relationship known as ‘mutualism’ in ecology), but nothing in biology is that simple. In light of recent evidence, it now appears that the plants are not as keen as the bees on providing an honest deal, and can trick the bees in a rather ingenious way.

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Underwater adhesives, Disappearing frogs and Electric Eels

Hello Folks! As promised, here is part II of our roundup of the most interesting breakthroughs in the world of science in the last couple of weeks. If you missed Part I, you can read it here. You will learn about mysterious brain cells of male roundworms, methods for remote-controlling cancer-fighting immune cells, the latest findings concerning Pluto by the New Horizons spacecraft, and much more.

And now, for the rest.

A glue inspired by nature

<a href="https://pixabay.com/users/Mhy/">Mhy</a> / Pixabay

Making glues that work underwater has long been a challenge for chemical engineers. Since a long time, researchers have been trying to exploit their knowledge of marine mussels to overcome this problem. Mussels stick to rocks in shallow waters using thread-like processes and can withstand battering by heavy waves without losing their grip. They do this by using a family of proteins, called mussel foot proteins (mfps) which they secrete near their points of contact with the rocks. A lot of interest, therefore, lies in uncovering the special properties of mfps that allow them to adhere underwater. Chemically, the main suspects are modified amino acids called catechols, the presence of large numbers of positive and negative charges in the same protein, and non-polar, hydrophobic elements interspersed throughout. Researchers at University of California, Santa Barbara, decided to strip away all the extraneous stuff and design a single small molecule that would incorporate all these components. This they achieved by chemically modifying a zwitterionic (having both positive and negative charges) detergent molecule to include the important catechol group alongside a few other small modifications. When this new material was tested for its stickiness, is was found to be highly adhesive, much stronger than the mfp proteins themselves, and could easily stick underwater forming a thin, uniform layer. According to the scientists, this might have important applications in the field of nanofabrication.

Read moreUnderwater adhesives, Disappearing frogs and Electric Eels

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PublicDomainImages / Pixabay

Nobel Prize, Ancient humans and the Autism debate

Hi everyone! I meant to post this last Sunday, but as you can see, I’ve been running a little behind schedule. Nevertheless, it’s time for a short review of what has been happening in the world of science, and last week has been an interesting week as far as that goes. Let’s start with the big news.

Announcement of the 2015 Nobel Prizes

Earlier last week, the Nobel Assembly at Karolinska Institutet, and the Royal Swedish Academy of Sciences announced the names of the recipients of the 2015 Nobel Prizes in Physiology and Medicine, Physics and Chemistry. Here’re the announcements from the official website

Tu Youyou 1951
Tu Youyou in 1951

The Nobel Prize in Physiology or Medicine 2015 was divided, one half jointly to William C. Campbell and Satoshi Ōmura “for their discoveries concerning a novel therapy against infections caused by roundworm parasites” and the other half to Youyou Tu “for her discoveries concerning a novel therapy against Malaria“.

The Nobel Prize in Physics 2015 was awarded jointly to Takaaki Kajita and Arthur B. McDonald “for the discovery of neutrino oscillations, which shows that neutrinos have mass

The Nobel Prize in Chemistry 2015 was awarded jointly to Tomas Lindahl, Paul Modrich and Aziz Sancar “for mechanistic studies of DNA repair“.

We’ll be exploring each of these awards in more detail in the coming week, along with a brief look at the life and career of each of the eight awardees.

Hands and Feet of ancient humans

homo naledi photo
Photo by GovernmentZA

In late 2013, a pair of explorers entering a cave in the Rising Star system in South Africa stumbled upon a narrow chamber filled with what looked like human bones. It soon became clear that the bones belonged to a human species that no one had ever seen before. Over several weeks of excavation and digging, more than 1500 bone fragments were found, belonging to at least 15 different individuals. The new species was named Homo naledi (a nod to the cave of origin, ‘naledi’ means ‘star’ in the Sotho language). Homo naledi had features both primitive and modern – diminutive in size, small- brained, but with a bone structure eerily similar to modern humans. This week, researchers published their analysis of the hand of Homo naledi, as assessed from bone fragments found in the Rising Star cave.

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francok35 / Pixabay

New planets, 1000 genomes and tricky parasites

Hi everyone! It has been an exciting week in science, and since it is Sunday evening, I thought I’d give you a brief overview of what has been happening in the scientific world this week.

Discovery of a new Jupiter-like planet

PeteLinforth / Pixabay
Jupiter, whom the new planet closely resembles

Scientists have discovered a new exoplanet that closely resembles our solar system’s Jupiter, using the Gemini Planet Imager. The Gemini Planet imager, a high-contrast imaging instrument, went live in 2013 and allows direct imaging of distant planets (as opposed to using indirect observations, like small wobbles in star orbits, to deduce their existence). The new planet, named 51 ERI B is located around a star called 51 Eridani, located a little less than 100 lightyears away from earth. This discovery is particularly interesting because 51 Eridani is a really young star, only about 20 million years old (the sun and the solar system are estimated to be around 4.5 billion years old, by comparison), and studying it can give us vital clues about the origin of Jupiter and other gas giants. The new planet is about twice the size of Jupiter, has a surface temperature of 600 – 750 Kelvin, and has large amounts of methane and water vapor.

Completion of the 1000 Genomes Project

<a href="https://pixabay.com/users/PublicDomainPictures/">PublicDomainPictures</a> / PixabayThis week also marks the completion of the 1000 genomes project. This project, started in January, 2008, mapped the genomes of 2504 participants, spread over 26 populations, and coming from a multitude of ethnicities. Five of the six inhabited continents were represented (Australia being the exception). The project aimed to identify all variations that occurred at a frequency of least 1% in the population (i.e. existed in at least 1 out of 100 individuals). The project identified over 88 million DNA sequence variants, and have published their results in the current issue of Nature. The data they collected is freely available on their website. On a similar note, the UK10K project, which plans to sequence the genomes of 10000 individuals in the UK from diseased as well as healthy backgrounds to identify potential disease-causing or biomedically relevant variants, also published their results in the same issue.

How the HIV proteins outsmart their host

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‘Sonogenetics’ – Using sound waves to activate brain cells

Scientists at the Salk Institute, USA have discovered a way to control brain cells using ultrasonic sound waves. Their method, which they call ‘sonogenetics’, has been applied to the tiny worm Caenorhabditis elegans, and can pave the way for advanced research into brain function by letting researchers target individual neurons in the brain.

<a href="https://pixabay.com/users/geralt/">geralt</a> / Pixabay

This is a welcome addition to the burgeoning field of neuroscience research that uses various strategies to specifically target single neurons or neuronal subpopulations in the brain. A whole field of evidence has confirmed that neurons in the brain are surprisingly heterogenous, and even neurons situated next to each other can be performing quite different functions. Teasing out the functions of whole circuits requires specialized techniques for perturbing the activities of small groups of neurons. Being able to activate and inactivate neurons in a controlled manner is of critical importance not only for understanding how the brain works, but also for figuring out what goes wrong in case of neurological diseases like Alzheimer’s disease or bipolar disorder.

Read more‘Sonogenetics’ – Using sound waves to activate brain cells

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A stink bug is the first animal known to actively control egg color

spined soldier bug photo
Podisus maculiventris, the spined soldier bug (Photo by Sam Fraser-Smith)

The spined soldier bug, despite having a really cool name, is rather unimpressive in appearance. About the size of a fingernail and a muddy, mottled brown in color, this little bug does not look like it might be hiding any deep secrets. Also called the stink bug, it is often introduced in agricultural fields as a biological pest-control system, since it feeds on the larva of various moths and beetles that destroy crops. About a month ago, researchers over at the University of Montreal, Canada, discovered and published a remarkable fact – the female spined soldier bug is the first animal ever shown to actively control the color of the eggs that it lays.

Read moreA stink bug is the first animal known to actively control egg color

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