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

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.

Frogs are (slowly) going extinct

Measuring current extinction rates is a tricky process. Most accepted methods have a high degree of error associated with them, and give huge ranges that are difficult to make sense out of. John Alroy, an ecologist and evolutionary biologist working in Australia, devised a statistical method to measure extinction rates that is highly conservative, i.e. it gives the bare minimum number of species that have gone extinct over a period of time. To get this rate, he used data from several museum databases and publications from field surveys that report sightings of a particular species. The results, if they represent the lowest probability of extinction, are somewhat alarming. It appears that frog extinctions were almost negligible before 1970, but has been accelerating steadily since then, being particularly high in the 1980s and early 1990s.The extinctions are highly geographically localized, with tropical areas, particularly Brazil, New Guinea and Madagascar being amongst the hardest hit. Based on data from a wide variety of geographical regions, Alroy states that at least 3.1% of frog species have already disappeared, and a further 6.9% are going to go extinct by the end of the century, assuming that there isn’t any worsening of environmental conditions.

Electric eels use high voltage pulses to track their prey

Generations of scientists have been fascinated by the electric eel. It’s the very stuff of our nightmares – a slippery, flat faced, snake-like underwater demon that sends electric shocks (often greater than 600 V) through the water that are strong enough to knock a grown horse off its feet. In addition to delivering electric shocks, electric eels also use electricity to sense their prey. In this, they are similar to many other fish that are weakly electrical, and use broadly the same mechanism – basically, generating a low voltage electric field (less than 10 V) in the surrounding waters, and detecting distortions in this field made by moving prey. The other, high voltage electric pulse that the electric eel produces was believed only to be used for incapacitating the prey. However, Kenneth Catania, at Vanderbilt University, USA, discovered that the high voltage, high frequency pulse is used by the electric fish not just for striking the prey, but also for tracking fast-moving prey. Using an ingenious set of experiments involving carbon conductors and plastic rods disguised as fish, he proved that the eels can effectively track prey in the absence of any visual cues using this high voltage output. The mechanism is broadly similar to that of echolocation in bats, where a similar high frequency pulse is emitted by the bats used to track moving prey.

Molecular Oxygen found on Rosetta’s Comet

The comet 67P/Churyumov–Gerasimenko, in addition to having an unpronounceable name, boasts a number of other distinctions. It is the first comet to be orbited by a spacecraft and the first comet ever to be landed on by a space probe. Rosetta is the name of the space probe built by the European Space Agency, which was sent out to meet the comet when it began its orbital approach towards the sun. It reached the comet on 6th August 2014, and achieved a landing on its surface on 12 November, 2015 (using a lander module called ‘Philae’). Since then, it has been sending back a data which charts the comet’s composition and features in excruciating detail. However, the most astonishing discovery so far was released this week, when Rosetta reported the presence of significant levels of molecular oxygen on the comet. Oxygen is the fourth-most common element in the universe, but it is rarely present in molecular form (O₂) due to its highly reactive nature. The only reason earth’s atmosphere has so much of molecular oxygen is because of the billions of photosynthetic bacteria and plants that are continuously generating it. Molecular oxygen, alongside methane, is therefore believed to one of the biggest indicators of life on a planet, and search of extraterrestrial life has been focused on looking for signatures of both these gases on exoplanets. Strangely, Rosetta’s comet has both molecular oxygen and methane, but quite clearly lacks any signs of life. This complicates the search for extraterrestrial life somewhat, as the presence of O₂ and methane can no longer be considered a purely biological signature. The oxygen detected is highly abundant (about 1 – 10 % when normalized to H₂O), and its amount of its outgassing does not appear to be decreasing with time, suggesting that the oxygen is coming from the very core of the comet. This is significant, since this means that the oxygen was present there when the comet formed, many billions of years ago, when the solar system was born. None of the present theories of how the solar system formed can explain this observation, since the conditions predicted by such theories would make it impossible for oxygen to remain in its molecular state. Right now, the general consensus opinion to explain the presence of oxygen on 67P by astronomers worldwide appears to be – ‘We don’t know’.

Exchange of electrons across kingdoms

Methane is a greenhouse gas, large amounts of which is released into the atmosphere each year by a number of natural and man-made processes. One crucial node of control for how much methane is released from the ocean floor is the action of tiny, methane-eating microbes of the domain archae. Archae are prokaryotes like Bacteria (i.e. they lack a true nucleus and membrane-bound organelles), but form a completely different domain of life, chemically almost as different from bacteria as bacteria are from us (Eukarya). These methanotrophic archae oxidize methane by using sulfate according to the reaction – CH₄(aq) + SO₄^2- à HS^– + HCO₃^– + H₂O . Interestingly, on the ocean floor, these archae are found in direct physical association with a group of true bacteria that belong to the sulfate reducing family. Researchers at Max Planck Institute for Marine Biology, Germany, found that the association between the two species was important for the efficiency of methane oxidation by the archae. They also observed small, nanowire-like structures produced by the archae and ‘pili’ like structures produced by the bacteria that connect the two organisms. It was also found that the bacteria started producing cytochrome C, a major electron carrier, whenever the two species were grown together. Together, these observations strongly indicate direct exchange of electrons between the two species to facilitate the methane oxidation process.

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That’s all for today! Have a great weekend and see you next week.