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SCIENCE UPDATE
Ancient organism challenges cell evolution
Scientists have found an organelle, an enclosed free-floating specialized structure, inside a primitive cell for the first time. Prokaryotic cells are relatively simple cells, without nuclei, such as bacteria.
It is believed they evolved first then absorbed other prokaryotes and became eukaryotes, complex cells that have nuclei and structures like the energy-producing mitochondria.
Finding a self-contained organelle inside a prokaryote is a puzzle as it suggests that the evolution of cells, the basic building block of organisms, may have to be reconsidered.
The organelle in question may also have a role in human diseases, such as malaria and African sleeping sickness. Biologists recognize two types of cell in nature that are fundamentally different because of their size and internal construction.
Prokaryotes are relatively small cells that contain regions inside them where genes congregate but no membrane separates them from the rest of the cell. They lack so-called organelles, such as chloroplasts and mitochondria. More complicated are the Eukaryotes, the cells that comprise all other living things. They have their genetic material enclosed in a membrane and have other enclosed structures (organelles) within them as well.
Prof Roberto Docampo of the University of Illinois, US, has been studying the unicellular organism Agrobacterium tumefaciens. It is responsible for gall disease in many plants. It is also a geneticist’s favourite as its method of DNA transfer can be utilized by them.
The organelle he found inside the bacteria is practically identical to an organelle he found inside unicellular eukaryotes. This particular organelle helps the bacteria regulate its acidic content.
According to him it is significant that the same organelle is found in the more complicated eukaryotes implying that it may have a common evolutionary origin for both types of cell.
Finally, the organelle is known to be present in a number of pathogenic organisms, including those that cause malaria, toxoplasmosis, African sleeping sickness and Chagas disease among others.
This may provide scientists with a technique to tackle these diseases. Because the organelle is not present in animal cells it may be a useful target for chemotherapy for those diseases.
New view shows galaxies’ secrets
A new wide-angle view of the universe looks back to a mere billion years after the Big Bang, revealing secrets about the lives of galaxies and the black holes at their hearts, scientists have reported.
The new view is contained in one extraordinary image, compiled by astronomers using a super-high-resolution camera aboard NASA’s Hubble Space Telescope, along with a catalogue of objects giving off strong X-rays from space, detected by the Chandra X-Ray Observatory, another NASA-affiliated instrument.
The image shows a section of sky about one-tenth the size of the full Moon viewed from Earth. Though this may seem narrow, it is about 30 times wider than the last deep look into the universe, the Hubble Deep Field observation released in 1996.
That earlier vision was described as a keyhole view; this one might reasonably be called a picture window. Both images sought to peer far enough away from Earth to see back in time to when the light from some of the oldest galaxies headed toward our spot in the cosmos. They also captured cosmic objects from later periods.
As in that earlier path-breaking picture, the galaxies in the new image look like smudged jewels on black velvet, with distinct shapes and colours, their whirling arms and oval forms apparent.
But the new image, known as GOODS for Great Observatories Origins Deep Survey, managed to look back further, more than 12 billion years to when the universe was a billion years old. Astronomers put the age of the universe at 13.7 billion years.
It was also revealed that the GOODS image is sharp enough at great distances to allow astronomers to try to match up hundreds of X-ray sources, thought to indicate black holes, with the galaxies they inhabit.
Dark matter is mostly cold
A new study shows that about 80 per cent of dark matter is the cold variety. Nobody knows what dark matter is. But astronomers know it exists because without it, galaxies could not look like they do, stars simply wouldn’t be held into the orbital formations that are seen. Theorists imagine dark matter being subatomic particles of some sort that interact with each other and “normal” matter only through gravity.
Cold dark matter is presumed to exist based on a theory holding that that dark matter particles in the early universe were moving slowly when galaxies and galaxy clusters began to form.
In the new study, astronomers used NASA’s Chandra X-ray Observatory to make the most detailed probe yet of the distribution of dark matter in a massive cluster of galaxies.
This discovery agrees with predictions of cold dark matter models and is contrary to other models that predict a leveling off of the amount of dark matter in the centre of the cluster.
The observations showed the distribution of X-rays from the hot gas, which is held in the cluster primarily by the gravity of the dark matter, Lewis and colleagues explained, so the distribution of the hot gas reveals the distribution of dark matter. — Dawn ScienceDotcom Report
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