Photographing black holes, discovering new antibiotics and the impact of air pollution

Chemistry – Mark Lorch

Biological chemicals have long been a source of medicines. Examples range from penicillin derived from mould, aspirin from willow and digoxin from foxgloves. Now, in the hunt for chemicals to inspire new pharmaceuticals, researchers are scouring some of the most extreme environments on the planet.

Every corner of our planet is teeming with microbes, even environments that you might expect to be completely desolate. Extremophilic organisms, as these hardy life forms are known, crop up in volcanic springs as caustic as battery acid, and salty lakes with almost ten times the salinity of the seas. To cope with these harsh conditions, extremophiles have evolved unusual biochemistry, and may be an excellent source of novel biologically active chemicals.

A team from the Universities of Utah and California isolated bacteria in the sediments of the Great Salt Lake in Utah that produce some unusual antibiotics. These molecules are peptides made from amino acids that are the mirror image of amino acids commonly found throughout the rest of the biosphere. Amino acids are the building blocks of proteins, some antibiotics and hormones. Most of nature uses just 20 amino acids – almost universally one particular stereoisomer. To explain this; consider your right and left hands. They are constructed in much the same way, from the same bones. But they are stereoisomers (non-superimposable mirror images), hence you can’t put your right hand in your left glove. Something similar occurs with amino acids: there are right-handed versions and left-handed versions, but for some reason nature has decided to use predominantly left-handed amino acids, except for some rare cases.

One of those cases has cropped up in Utah Salt Lake, where bacteria have made antibiotics using right-handed amino acids. This is particularly interesting because right-handed peptides don’t fit well into cellular machinery built from left-handed amino acids (just as your left hand doesn’t fit in your right glove), so cells have trouble degrading them. As a result, these peptides may linger in the body for longer, and thus be more effective antibiotics.

Mark Lorch is a chemist at the University of Hull

Physics – Ceri Brenner

Black holes are the most extreme objects in the Universe. They are truly mysterious – a theoretical suggestion kickstarted by Einstein but never seen. Their mass is so great that the gravitational force they exert can warp space-time and bend light. Each black hole has a point of no return – the event horizon – beyond which nothing can escape, and where the known physical laws of energy and time are assumed to collapse. Even light, the massless flow of electromagnetic waves travelling at the Universe’s speed limit, is trapped.

Physicists have predicted the effects a black hole has on its surroundings, and concluded that a billions of degrees celsius structure of super-high-speed particles would be swirling around the edges of the event horizon as they’re pulled in. Fast-moving particles going round in circles give off radiation. Bingo! We have a black hole tracking system. If only we could build a lens big enough to look right at a black hole.

It took more than 200 scientists to meet this spectacular photography challenge. The Event Horizon Telescope (EHT) project set out to capture an image of the supermassive black hole at the centre of the M87 galaxy, some 55 million light years away. A collection of eight radio telescopes were constructed at specific high-altitude points around the world, and aligned towards M87, to create an Earth-sized virtual telescope. Once they had made their measurements the data was shipped in stacks of hard-drives to specialised supercomputers, where an advanced code synchronised and combined the images, taking into account viewing angles and time of arrival of the radiowaves onto the detectors. The final image was unveiled to the world on 10 April 2019 and published in a special issue of Astrophysical Journal Letters. The first-ever image of a black hole. “This long-sought image provides the strongest evidence to date for the existence of supermassive black holes and opens a new window onto the study of black holes, their event horizons, and gravity,” says the EHT team. Seeing is believing.

Ceri Brenner is a physicist who works for the Science and Technology Facilities Council

Biology – Lydia Leon

Nearly nine million global deaths could be caused by air pollution each year – double previous estimates and more than those caused by smoking, according to research published in the European Heart Journal. Of these, around 659,000 occur in the EU, twice the number acknowledged by the European Environment Agency. Poor air quality may reduce life expectancy on the continent by over two years.

The scientists used the same data on air pollution, global mortality and population characteristics as in a previous study. But they incorporated new data from 41 separate studies on the relationship between air pollution and disease outcomes across 16 countries. The authors point out that a significant amount of uncertainty still exists around their estimates, with the true number of global deaths from air pollution potentially being up to 50 per cent higher or lower.

Although one might associate exposure to dirty air with lung damage, the majority (40-80 per cent) of these early deaths are from cardiovascular diseases, with respiratory diseases being the second biggest killer. Particles in dirty air can damage blood vessels, eventually leading to events such as strokes and heart failure. The study mainly used data on pollution caused by particles in the air that are smaller than 2.5 micrometres in diameter (PM2.5), which pose the highest risk to health. PM2.5 particulates come from a number of sources such as industry, agriculture and wind-blown dust, but by far the biggest contribution is the burning of fossil fuels.

World Health Organisation guidelines stipulate that annual exposure to PM2.5 should not exceed 10µg per m3, although there is evidence that exposure as low as 5µg per m3 can be harmful. Whilst countries such as the US and Canada have guidelines in line with the WHO, European legislation lags well behind with a limit of 25µg per m3, with some countries consistently exceeding this limit. These regulations are critical in mitigating the health impacts of air pollution that, unlike avoidable behaviours such as smoking, can only be altered by government intervention – not individual behaviour.

Lydia Leon has a PhD in women’s health from University College London