Do They Taste Light?

My previous post was about the fact that C.elegans were sensitive to UV light. What made this more interesting was the protein that was discovered as responsible for this special character.

Conventional studies in these nematodes by Stacey L. Edwards, Kenneth G. Miller, and colleagues allowed them to identify a protein as being behind this interesting property. They called it, lite-1. Curiously, this protein was very similar to those that were known to be involved in tasting. Further investigations established that lite-1 did act as receptor for UV light.

This protein may soon find its way to the tool box of the modern molecular biologists. Perhaps, this protein also shows that there may be other proteins in higher organisms that are waiting to reveal their secrets!

Things are not what they seem to be... especially in the world of biology!

Seeing Light Without Eyes

Many of the ground breaking discoveries in molecular developmental biology were made with the help of simple organisms that can be grown in laboratories with ease. Caenorhabditis elegans is one among them. Measuring about a millimeter in length, these organisms had been a good friend for molecular biologists and neuroscientists for decades. One reason why a common man may find this kind of round worm interesting is that they managed to survive the historic Columbia space Shuttle disaster. (Find more information here.)

These survivors are continuing to surprise their masters and challenging the claim that their physiology is well-studied. Not many would have expected these underground creatures to show any interest in light. Shawn Xu, a neurobiologist from University of Michigan proved just that. Upon observing that these creatures shy away from bright light while he viewed them under the microscope, he set out to explain how these eye-less worms see light.

Further investigations by Xu and his team revealed that four pairs of sensory neurons of C.elegans were responsible for its sensitivity to light. And, these neurons made them reverse their course as soon as the light is switched on.



(Find a more detailed article in ScienceNOW)

It was also found that these worms were more sensitive to the harmful UV-A radiations. This gives a clue to why evolution had gifted these simple organisms with this ability. Without these four neurons and hence the perception of light, the organisms may wander out into the light and get exposed to the harmful radiations. Such behavioral responses to light in such simpler organisms is more crucial to an evolutionary biologist, trying to understand the how higher vertebrates evolved sight.

DNA Crystallization in vivo

Bacteria are some of the marvelous creations of nature. They are known for their adaptability. The humble Escherichia coli that we find in almost all the microbiology and molecular biology labs continues to surprise us with its ingenius ways of handling problems.

Under extreme stress, bacterial cells are known to take many steps to protect themselves. Abraham Minsky of the Weizmann Institute of Science in Rehovot, Israel identified an interesting defense mechanism of E.coli thats slightly different. These unicellular organisms crystallize their own DNA.
This 'novel' defence strategy was found to be the responsibility of a protein called Dps. It resembles ferritin, an iron-storage protein found in humans.

Dps is produced when the cell experiences nutritive or oxidative stress. It binds to DNA (apparently without any specificity) and promotes its crystallisation. Earlier investigations revealed another important function of the Dps protein. It sequesters iron and other metal ions that may help in the generation of free-radicals.

DNA - Dps crystals

Minsky and his collegues genetically engineered a few bacterial cells to over-produce this protein. These cells formed DNA crystals more easily and starvation was sufficient to cause crystallization of DNA. This process was also found to be reversible. "Once nutrients are supplied, [the crystals] disappear within a very short timescale, and the bacteria are viable and growing," says Minsky.

Whats remains to be explained is, how the bacterial DNA integrates itself into a crystal!

Stretching DNA on a chip

DNA carries all information a living organism requires for survival. Reading this information can be made much easier if you can get these 2nm wide polymer strand stretched and untangled. Researchers at Purdue University have done just that.



They have precisely placed strands of DNA on a silicon chip and then stretched out the strands so that their encoded information might be read more clearly. This may prove extremely critical in future electronic devices and computers.

Find more information here.

What made HIV infect Man?

About 4 million years ago, humans had split from apes. At this time, Chimpanzees had to go through some tough times. They were infected with a virus. Scientists discovered this when they found traces of this virus in the DNA of Chimps. This meant that this virus, called PtERV1, infected the Chimp population. Interestingly, the traces of the virus were not found in human genome.

Emerman and his team had an explanation. The humans immune to PtERV1 while Chimps had tough time fighting it. The team of researchers identified TRIM5 as the factor that helped humans protect us from the virus. Removing this protein from the cells made them vulnerable to PtVER1, which were reconstructed from Chimpanzees DNA.

Curiously, these cells were found to be less susceptible to HIV. It seems that in the process of developing resistance to one virus, the immune system of our ancestors had us vulnerable to another deadly virus, the HIV.