BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: yeast

Hibernating Ribosomes?

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On October 22, 2024

In Student Post

Scientists in the European Molecular Biology Laboratory have discovered a remarkable adaptation to starvation in yeast cells. When a yeast cell yearns for nutrients, its ribosomes begin to coat the cell’s mitochondria. It turns out these ribosomes aren’t producing anything, but rather they are in hibernation. Producing proteins requires a lot of energy, so the conservation of energy through hibernation allows the cell to survive. 

Spoon with active dry yeast for baking bread

Scientists were curious about why the ribosomes specifically cling to the mitochondria.  One explanation is that the mitochondria could provide protection to the ribosomes. There are forms of mitochondria that can protect parts of the cell, so this is a possible outlook. Another potential explanation for the ribosomes activity is starving cells need a way to quickly start producing energy once nutrients are available again. Since mitochondria are the energy producers of the cell, having ribosomes nearby to produce necessary proteins might speed this process. 

The most surprising part of this study was that the ribosomes attached to the mitochondrial outer membrane in a way that is completely different from what is known. Normally, ribosomes interact with the mitochondria via the large subunit, but in the yeast, the ribosomes were interacting with the small subunit. The research team plans to follow up this study by learning more about why this difference occurs. 

This study is critical in understanding the spread of cancer cells. Cancer cells grow so rapidly that their demand for nutrients and oxygen outpaces the supply. This means most cancer cells are constantly starving themselves. Yet, they survive and multiply. If we can understand the foundations of this adaptation, maybe we can find a way to take advantage of the starving cancer cells and make them more susceptible to treatment. 

This connects to AP Bio because the curriculum covers the functions of the mitochondria and ribosomes but this research shows an abnormal aspect of them. Normally, the mitochondria is the site of cell respiration, converting glucose into ATP. The enzymes that  perform reactions in the matrix are embedded in the mitochondrial membrane. The ribosomes can be bound to the mitochondria while manufacturing proteins that are inserted into membranes in the cell. I just fasted for Yom Kippur, so I wonder if any of the ribosomes in my cells hibernated due to the lack of nutrients my body received. What do you think of this new discovery and its potential application?



XRN1: The Virus Hitman

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On October 12, 2016

In Student Post

When I think of the words killer and assassin, my mind drifts to shady men in all black equipped with sniper rifles. However, recent research conducted by the University of Idaho and the University of Colorado Boulder has indicated that I should expand that mental list to include XRN1, a gene in saccharomyces cerevisiae which, according to a recent study, kills viruses within the yeast. Upon stumbling onto this subject, I was intrigued because it was a fairly simple procedure that led to a huge discovery. To grasp the significance of such a discovery, one must understand it on a molecular level. XRN1’s duty in yeasts is to create a protein which breaks down old RNA. The image below shows the generic process of the creation of a new protein through gene regulation.

Wikipedia- Regulation of Gene Expression

Wikipedia- Regulation of Gene Expression

Yeasts also contain viral RNA since practically all yeasts are infected by viruses. When scientists removed XRN1 from the yeasts, the viruses within yeasts replicated much faster, and when they expressed high amounts of XRN1, the virus was completely eradicated. This is because the XRN1 gene was inadvertently breaking down the viral RNA, mistakenly taking it for the yeast’s RNA. Scientists continued the research by using XRN1 from other saccharomyces yeast species. The virus continued replicating rapidly but the XRN1 did continue its job of breaking down the yeast’s RNA. This shows that the XRN1 from each yeast species evolves to attack the specific viruses that occur in its host while still maintaining their basic role as the RNA eaters. Scientists are hopeful about this study’s human health implications. Viruses such as Polio and Hepatitis C work by degrading XRN1 and not allowing it to break down RNA, respectively. Dengue Fever also occurs when XRN1 is unable to perform its function of RNA breakdown. These studies on Dengue Fever and Hepatitis C elaborate on the implications of XRN1 not breaking down RNA. Scientists hope that this discovery could lead to the triumph of XRN1 over these viruses. Could this really be the discovery that leads to the first ever Hepatitis C vaccine? Do you think that XRN1’s success against virus in yeasts guarantees eventual success against viruses in humans?

 

Original Article: http://phys.org/news/2016-10-yeast-gene-rapidly-evolves-viruses.html

 

No Drinking Age for Fruit Flies!

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On February 27, 2012

In Student Post

Photo Credit: digicla

Why can’t I drink alcohol but a mere fruit fly is able to, you ask? Well unless you wish for wasps to lay their eggs inside you I suggest you drop that argument.

A new article explains what is going on. Fruit flies eat a lot of yeast (which as we know from our studies breaks down sugar and in the process produces alcohol). They do this because a certain kind of wasp actually lays its’ eggs inside of a fruit fly, so that when the eggs hatch the baby wasps can eat the living fly and eventually leave the body when they are grown. Beware because things get more disgusting than that…

To prevent such malicious murder, the flies have a trick of their own. They consume so much yeast that they are considered “drunk”. The alcohol smells so bad to the wasps that not only do they choose to not lay their eggs within that particular fly, but any eggs they do lay meet a very violent end.

Here is where things get worse. In a study done by Dr. Schlenke, wasps were allowed to lay eggs in two flies. One fly was perfectly sober, and one was fed food that had 6% alcohol in it. As I’ve said, more wasps layer their eggs in the sober fly, and less in the drunk fly. However, the eggs that did get laid in the drunk fly did not meet an honorable end. Dr. Schlenke found that 65 percent of the eggs inside of the drunk fly not only died, but died because all of their tiny inside organs had shot out through their anus. At this point I wish that I was not writing about this article, but the show must go on.

It was also discovered by Dr. Schlenke that if a fly ate the alcohol ridden yeast before being violated by the wasps, it made no difference. Such a discovery lead scientists to ponder whether the flies realized the deadly wasps inside of them and so chose to eat the yeast then, in order to kill off the parasite. Further experiments with flies showed that the flies do indeed seek out the alcohol as a self medication to kill off the wasps inside of them.

Smart flies right? Can you believe that this is what fruit flies have to put up with? Or that little tiny flies can get drunk off the alcohol produced by yeast? I, for one, will take a drinking age of 21 any day instead of having tiny wasps live inside me. But thats just me, what do you think?

from single cell to multi-cellular

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On February 27, 2012

In Student Post

Have you ever wondered how single cellular organism evolved into multicellular organisms? In a recent New York Times article, some scientists decided to see if they could get single cellular organisms to somehow evolve into multicellular ones. The problem that they thought of was that in multicellular organisms there are many cells which die so that the entire organism can live on. Why single cell organisms would group together with other single cell organisms just to die for the new multicellular organism was puzzling.

They designed an experiment where they had yeast in flasks of broth where they were being shaken for a day and then left alone for the yeast to settle. Then a drop of the settled yeast was taken and transferred to a new flask where the yeast could continue to grow. This process was continued and would allow the yeast which had evolved to be the densest and to settle furthest down to be carried to the next flask. after a few weeks the scientists observed that the yeast was falling faster and was becoming cloudy at the bottom. When looked at under the microscope the scientists found that the yeast had evolved into snowflake shaped clumps of hundreds of yeast cells stuck together. These cells were not just unrelated clumps since when separated individually, cells would recreate these snowflake shaped clumps. This property of clusters of single celled organisms to make a multicellular like organism is not special to yeast. Another organism called choanoflagellates is a single celled organism that also exhibits these traits.

One of the more amazing parts about this was that to reproduce, branches of the snowflake clump would break off after growing too large. When looked at closer they found that a section of the cells near the branch commit suicide to separate the branch to allow it to grow into a new clump. Being able to create multicellular organisms that had cells willing to commit suicide for the rest of the organism in a matter of weeks was amazing and could mean that the history of single celled organisms evolving into multicellular ones might not be as complicated as previously thought. Even though this form of natural selection was done in flasks, the natural environment could have preferred multicellular organisms over single cellular organisms for a number of reasons.

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