Windswept Mars, antioxidant-loving cancers, and electric bacteria – Sciencish News for 9/11/2015 (part 1)

Well, it’s been a big week out there in the world of science, and I’m behind! So, we’re going with two posts today. First up, we’ve got big news from the Red Planet, stressed out cancers kept in the balance, and (more) electric bacteria.

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Mars blown dry, but glowing

NASA held a press conference on Friday, the lead up to which was full of speculation. Was life finally found? What about Matt Damon? The news when it was finally announced was a little less spectacular, but had plenty of highlights to get excited about.

It has long been thought that the arid, frigid, planet was once warm and wet back in its ancient history, with flowing streams. For liquid water to flow on Mars would seem to require a much thicker atmosphere with plenty of carbon dioxide. So, where did Mars’ atmosphere, and its water, go? New data from NASA’s orbital Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft suggests that solar winds are responsible. Solar winds are streams of particles, mainly protons and electrons, which pour out of the Sun’s atmosphere at an incredible rate of 400 km/s. When the wind encounters Mars’ atmosphere it generates an electrical field. This whips electrically charged gas molecules into a frenzy, accelerating them so fast they are ripped out of the atmosphere and shot into space (see video below). Solar winds are normally deflected by a planet’s magnetic field, but Mars’ magnetic field is extremely weak, and concentrated only around its South pole, leaving it almost entirely exposed. Understanding this process of solar stripping (or “sputtering”, as it’s delightfully called) is important if we ever try and plan to colonise Mars and give it an “Earth-like” atmosphere. The loss of atmosphere is still going on, and recent solar storms have in fact accelerated the process.

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So Mars’ weakling magnetic field has left it utterly exposed to the elements, but there is an upside to this windy bombardment: it makes the nights spectacular. Back on Christmas Day, 2015, MAVEN saw a bright auroral glow similar to the Northern and Southern Lights here on Earth. Auroras are the result of the charged particles of the solar wind smashing into particles of the atmosphere of a planet. On Earth these particles are deflected by the magnetic field, meaning auroras only appear at the poles. But MAVEN’s newest observations show that, thanks to Mars’ weaker magnetic field, its auroras span almost the entire northern hemisphere, lighting up a massive part of the night sky in greens, reds, and blues. The solar wind particles can almost penetrate much further into the atmosphere, so that an aurora would appear much closer overhead – almost twice as close as on Earth.
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mavenaurora

Credit: NASA/GSFC


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Volatile chemicals keep cancer under pressure

Reactive oxygen species (ROS) are highly volatile molecules that occur naturally during energy production in all cells. Their reactivity means they can inflict significant damage to cell components and even damage DNA, causing mutations that can lead to cancer. Cells therefore produce antioxidants that quench this “oxidative stress”, protecting against ROS’ harmful effects.

As early stage tumours lose control of energy production they typically have fairly high levels of ROS. These in turn causes more DNA mutations, some of which can help the tumour develop and start to grow out of control. But too much ROS activity stresses the young cancer – just as it would a healthy cell. Now, a new study has demonstrated that oxidative stress can even stop full-blown malignant tumours from reaching their final stage, unless they adapt. Once a cancer develops into a malignant tumour, individual tumour cells may invade the blood stream and spread to tissues all over the body, by a process called “metastasis” (see image below). But this is extremely inefficient, and most tumour cells that enter circulation die. However, researchers at the University of Texas, USA, found that tumour cells can increase their odds of survival by ramping-up production of antioxidants, which quench ROS. This suggests that the ability to deal with ROS and oxidative stress is a major factor limiting metastasis of tumour. Excitingly, they found that treating mice with drugs that inhibited production of antioxidants prevented the spread of tumours, opening up potentially powerful means of controlling tumours in patients by inhibiting their ability to quench oxidative stress. It also gives the lie to claims made by some health food evangelists that antioxidant dietary supplements and “super foods” can boost health and prevent disease. Indeed, this new data is in line with previous findings that antioxidant supplements can in fact boost cancer growth!
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Credit: Nature

Credit: Nature

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Find the paper here

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Bacteria spread the good word – electronically!

Following on from last week’s talk of electrical creatures, another story came up this week regarding the amazingly versatile uses that bacteria can put electricity to. Many species of bacteria grow in tight-knit communities called “biofilms”. Belonging to a biofilm can have many advantages for vulnerable single-celled organisms like bacteria, including increased resistance to antibiotics and environmental stresses like drying and heat. Biofilms can therefore cause stubborn infections, and be a serious problem in hospitals where they might coat surfaces or surgical instruments. However, bacteria are normally solitary single-celled souls, meaning that if they want to belong to a community they have to learn how to get along and communicate with their neighbours. In multicellular organisms like animals and plants, cell-cell communication is often achieved by the flow of charged atoms, called “ions”, into and out of cells via specialised ion channels. Bacteria are known to possess ion channels, but a role for them in signalling has never been demonstrated.

Bacillus subtilis lives in biofilms that go through periodic cycles or growth where the colony starts to expand very rapidly, before slowing to a halt. The reasons for this were unclear, but researchers from the University of California, USA, proposed that cycles of starvation played a role. They hypothesised that when B. subtilis biofilms grew too fast, bacteria stuck in the centre of the colony start to run out of nutrients as bacteria on the periphery eat them up, especially the essential amino acid glutamate. Glutamate starvation means interior bacteria can’t produce ammonium, another nutrient that all bacteria in the biofilm rely on, meaning that growth of bacteria at the periphery also halts. Growth then can’t re-start until interior cells can access glutamate. Investigating how bacteria in biofilms might communicate these changing nutrient requirements across the colony, researchers observed fluctuating waves of potassium ions spreading out from the centre of biofilms (see image below). These appeared to be due to central bacteria releasing potassium from their cell into the biofilm environment. Neighbouring bacteria responded to this rise in environmental potassium in turn, by triggering release of their own potassium stores. Potassium ions have a positive electrical charge, and the membrane that encases all bacterial cells maintains a tight control on the balance of positive and negative charge between the interior of the cell and the exterior (what’s known as the “electrical potential”). These waves of potassium release therefore reduce the electrical potential across the bacterial cell membrane as they move through the biofilm. Since uptake of glutamate and ammonium relies on the cell electrical potential, this would prevent bacteria at the periphery from hogging it all, allowing those at the biofilm centre to catch up. The researchers confirmed their findings by showing that experimentally starving bacteria of glutamate induced these potassium waves, while gorging on glutamate dampened them. This is a fascinating example of how single-celled organisms can act as a multicellular whole, with individuals at the biofilm periphery cooperating with this electrical signalling and even sacrificing their own growth for the good of the biofilm.
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Credit:

Credit: Prindle et al. (2015) , Nature

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Find the paper here

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That’s is for part 1 of the news – but check back shortly for stealth drugs, dinosaurs, and high hopes for Canadian science…

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– J