Tag Archives: biology

Video showing malaria breaking into cell

Malaria caught on camera breaking and entering cell [the broken link has been removed]

The Plasmodium parasite responsible for malaria is transmitted by the bite of infected mosquitoes, and is thought to kill almost 1 million people worldwide each year.

Jake Baum at the Walter and Eliza Hall Institute of Medical Research in Melbourne, Australia, and colleagues used transmission electron microscopy and 3D immuno-fluorescence microscopy to record a series of still images during the 30-second-long invasion, and combined them into a movie.

Naturally Curious Children

I write this blog because when I was a kid I was curious and had parents who gave me enough interesting answers and interesting resources to build on that curiosity. And I am still curious today. I love learning. And I love to hear about kids learning.

The Big Girl has worked out evolution

She was ecstatic when we ended up with a rooster in our ‘sexed’ chickens even though Mummy and Daddy weren’t too impressed, because she wants more little fluffy chicks. I think that counts as evidence she knows you need boys and girls to get babies.
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“What would happen if there were no boys?” This is the question she came out with the other day.

“Well, there would be no babies.” I didn’t quite get the problem seeing we were feeding the rather prolific guinea pigs at the time and we’ve been talking about separating them.
“But what if there were no boys at all? So no-one could have babies?”
“Eventually, they would all die.”
“But there wouldn’t be any left!”
“No, they would die out.”
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“How did humans start?”… a puzzled little crease in her forehead. “Because if there weren’t any around with the dinosaurs they must have started sometime. How could there be no humans and then they’re there? What was the Mummy?”
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“Well, they weren’t sudden. You know how you are a little bit different to Mummy and Daddy? That’s how it happened. The babies were just a little bit different to their parents and over a really, really long time they became people.”
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“But if there was only one it would die out.”
Well that came out of nowhere, did I miss half of this conversation?
“You know, the first person. It needs to have both a boy and a girl to have more people babies. So if there was only one it would die out.”
“Oh, from yesterday. Yes, you’re right. But people live in groups, so they’re all changing a tiny little bit at the same time.”

It is great to see developing minds at work. Exploring their natural curiosity. And taking in new information puzzling it out over time and then coming back to the ideas. This kind of curiosity is what drives learning and success.

Changing Life as We Know It

Update: Independent researchers find no evidence for arsenic life in Mono Lake

NASA has made a discovery that changes our understanding of the very makeup of life itself on earth. I think my favorite scientific discipline name is astrobiology. NASA pursues a great deal of this research not just out in space but also looking at earth based life. Their astrobiology research has changed the fundamental knowledge about what comprises all known life on Earth.

Felisa Wolfe-Simon processing mud from Mono Lake to inoculate media to grow microbes on arsenic.

Carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur are the six basic building blocks of all known forms of life on Earth. Phosphorus is part of the chemical backbone of DNA and RNA, the structures that carry genetic instructions for life, and is considered an essential element for all living cells.

Phosphorus is a central component of the energy-carrying molecule in all cells (adenosine triphosphate) and also the phospholipids that form all cell membranes. Arsenic, which is chemically similar to phosphorus, is poisonous for most life on Earth. Arsenic disrupts metabolic pathways because chemically it behaves similarly to phosphate.

Researchers conducting tests in the harsh, but beautiful (see photo), environment of Mono Lake in California have discovered the first known microorganism on Earth able to thrive and reproduce using the toxic chemical arsenic. The microorganism substitutes arsenic for phosphorus in its cell components.

“The definition of life has just expanded,” said Ed Weiler, NASA’s associate administrator for the Science Mission Directorate. “As we pursue our efforts to seek signs of life in the solar system, we have to think more broadly, more diversely and consider life as we do not know it.” This finding of an alternative biochemistry makeup will alter biology textbooks and expand the scope of the search for life beyond Earth.

In science such huge breakthroughs are not just excepted without debate, however, which is wise.

Thriving on Arsenic:

In other words, every experiment Wolfe-Simon performed pointed to the same conclusion: GFAJ-1 can substitute arsenic for phosphorus in its DNA. “I really have no idea what another explanation would be,” Wolfe-Simon says.

But Steven Benner, a distinguished fellow at the Foundation for Applied Molecular Evolution in Gainesville, FL, remains skeptical. If you “replace all the phosphates by arsenates,” in the backbone of DNA, he says, “every bond in that chain is going to hydrolyze [react with water and fall apart] with a half-life on the order of minutes, say 10 minutes.” So “if there is an arsenate equivalent of DNA in that bug, it has to be seriously stabilized” by some as-yet-unknown mechanism.

It is sure a great story if it is true though. Other scientists will examine more data and confirm or disprove the claims.

“We know that some microbes can breathe arsenic, but what we’ve found is a microbe doing something new — building parts of itself out of arsenic,” said Felisa Wolfe-Simon, a NASA Astrobiology Research Fellow in residence at the U.S. Geological Survey in Menlo Park, Calif., and the research team’s lead scientist. “If something here on Earth can do something so unexpected, what else can life do that we haven’t seen yet?”
Continue reading →

Monarch Migration Research

Monarch Butterfly

Monarch butterflies – renowned for their lengthy annual migration to and from Mexico – complete an even more spectacular journey home than previously thought.

New research from the University of Guelph reveals that some North American monarchs born in the Midwest and Great Lakes fly directly east over the Appalachians and settle along the eastern seaboard. Previously, scientists believed the majority of monarchs migrated north directly from the Gulf Coast.

Unfortunately the press release doesn’t provide a link to the study – maybe it is not open science. Often organization focused on closed science don’t do well providing web links (though even open science organizations fall down on this more than they should).

“It solves the long-standing mystery of why monarchs always show up later on the east coast compared to the interior,” he said. “Importantly, it means that the viability of east coast populations is highly dependent upon productivity on the other side of the mountains.”

Monarchs travel thousands of kilometres each year from wintering sites in central Mexico back to North America’s eastern coast, a journey that requires multiple generations (in the same year) produced at various breeding regions.

Biologists had suspected that monarchs fly back from Mexico west-to-east over the Appalachians, but no evidence existed to support the theory. “Ours is the first proof of longitudinal migration,” Miller said.

For the study, the researchers collected 90 monarch samples from 17 sites between Maine and Virginia in June and July of 2009. They also collected 180 samples of milkweed (the only plant monarch larvae can eat) from 36 sites along the eastern coast between May and July of that year.

They then used hydrogen and carbon isotope measurements to determine when and where the monarchs were born. Isotope values in milkweed vary longitudinally and can be measured in monarch wings, Miller said. The researchers discovered that 88 per cent of the monarchs sampled originated in the Midwest and Great Lakes regions.

“This means that the recolonization of the east coast is by second-generation monarchs that hatched around the Great Lakes and then migrated eastward over the Appalachians,” Miller said. “We must target the Great Lakes region to conserve the east coast monarch populations.”

Full press release

All present-day Life on Earth Has A Single Ancestor

All present-day life arose from a single ancestor

All life on Earth shares a single common ancestor, a new statistical analysis confirms.
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Because microorganisms of different species often swap genes, some scientists have proposed that multiple primordial life forms could have tossed their genetic material into life’s mix, creating a web, rather than a tree of life.
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A universal common ancestor is at least 10^2,860 times more probable than having multiple ancestors, Theobald calculates.
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For his analysis, Theobald selected 23 proteins that are found across the taxonomic spectrum but have structures that differ from one species to another. He looked at those proteins in 12 species – four each from the bacterial, archaeal and eukaryotic domains of life.

Then he performed computer simulations to evaluate how likely various evolutionary scenarios were to produce the observed array of proteins. Theobald found that scenarios featuring a universal common ancestor won hands down against even the best-performing multi-ancestor models.

Very interesting. Surprising too. As the article points out this doesn’t mean all life ever on Earth evolved from the single ancestor – life that has gone extinct could be from outside this single “tree.”

Engineered Circuits That can Count Cellular Events

Engineered circuits can count cellular events by Anne Trafton

MIT and Boston University engineers have designed cells that can count and “remember” cellular events, using simple circuits in which a series of genes are activated in a specific order.
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The first counter, dubbed the RTC (Riboregulated Transcriptional Cascade) Counter, consists of a series of genes, each of which produces a protein that activates the next gene in the sequence.

With the first stimulus — for example, an influx of sugar into the cell — the cell produces the first protein in the sequence, an RNA polymerase (an enzyme that controls transcription of another gene). During the second influx, the first RNA polymerase initiates production of the second protein, a different RNA polymerase.

The number of steps in the sequence is, in theory, limited only by the number of distinct bacterial RNA polymerases. “Our goal is to use a library of these genes to create larger and larger cascades,” said Lu.

The counter’s timescale is minutes or hours, making it suitable for keeping track of cell divisions. Such a counter would be potentially useful in studies of aging.

The RTC Counter can be “reset” to start counting the same series over again, but it has no way to “remember” what it has counted. The team’s second counter, called the DIC (DNA Invertase Cascade) Counter, can encode digital memory, storing a series of “bits” of information.

The process relies on an enzyme known as invertase, which chops out a specific section of double-stranded DNA, flips it over and re-inserts it, altering the sequence in a predictable way.

The DIC Counter consists of a series of DNA sequences. Each sequence includes a gene for a different invertase enzyme. When the first activation occurs, the first invertase gene is transcribed and assembled. It then binds the DNA and flips it over, ending its own transcription and setting up the gene for the second invertase to be transcribed next.

When the second stimulus is received, the cycle repeats: The second invertase is produced, then flips the DNA, setting up the third invertase gene for transcription. The output of the system can be determined when an output gene, such as the gene for green fluorescent protein, is inserted into the cascade and is produced after a certain number of inputs or by sequencing the cell’s DNA.

This circuit could in theory go up to 100 steps (the number of different invertases that have been identified). Because it tracks a specific sequence of stimuli, such a counter could be useful for studying the unfolding of events that occur during embryonic development, said Lu.

Other potential applications include programming cells to act as environmental sensors for pollutants such as arsenic. Engineers would also be able to specify the length of time an input needs to be present to be counted, and the length of time that can fall between two inputs so they are counted as two events instead of one.

Dennis Bray Podcast on Microbes As Computers

Carl Zimmer interviews Dennis Bray in an interesting podcast:

Dennis Bray is an active professor emeritus in both the Department of Physiology and Department of Neuroscience at the University of Cambridge. He studies the behavior of microbes–how they “decide” where to swim, when to divide, and how best to manage the millions of chemical reactions taking place inside their membranes. For Bray, microbes are tiny, living computers, with genes and proteins serving the roles of microprocessors.

2009 Nobel Prize in Physiology or Medicine

This year’s Nobel Prize in Physiology or Medicine is awarded to three scientists who have solved a major problem in biology: how the chromosomes can be copied in a complete way during cell divisions and how they are protected against degradation. The Nobel Laureates have shown that the solution is to be found in the ends of the chromosomes – the telomeres – and in an enzyme that forms them – telomerase.

The long, thread-like DNA molecules that carry our genes are packed into chromosomes, the telomeres being the caps on their ends. Elizabeth Blackburn and Jack Szostak discovered that a unique DNA sequence in the telomeres protects the chromosomes from degradation. Carol Greider and Elizabeth Blackburn identified telomerase, the enzyme that makes telomere DNA. These discoveries explained how the ends of the chromosomes are protected by the telomeres and that they are built by telomerase.

If the telomeres are shortened, cells age. Conversely, if telomerase activity is high, telomere length is maintained, and cellular senescence is delayed. This is the case in cancer cells, which can be considered to have eternal life. Certain inherited diseases, in contrast, are characterized by a defective telomerase, resulting in damaged cells. The award of the Nobel Prize recognizes the discovery of a fundamental mechanism in the cell, a discovery that has stimulated the development of new therapeutic strategies.

Scientists began to investigate what roles the telomere might play in the cell. Szostak’s group identified yeast cells with mutations that led to a gradual shortening of the telomeres. Such cells grew poorly and eventually stopped dividing. Blackburn and her co-workers made mutations in the RNA of the telomerase and observed similar effects in Tetrahymena. In both cases, this led to premature cellular ageing – senescence. In contrast, functional telomeres instead prevent chromosomal damage and delay cellular senescence. Later on, Greider’s group showed that the senescence of human cells is also delayed by telomerase. Research in this area has been intense and it is now known that the DNA sequence in the telomere attracts proteins that form a protective cap around the fragile ends of the DNA strands.

Many scientists speculated that telomere shortening could be the reason for ageing, not only in the individual cells but also in the organism as a whole. But the ageing process has turned out to be complex and it is now thought to depend on several different factors, the telomere being one of them. Research in this area remains intense.

The 3 awardees are citizens of the USA; two were born elsewhere.
Read more about their research at the Nobel Prize web site.

Molecular biologist Elizabeth Blackburn–one of Time magazine’s 100 “Most Influential People in the World” in 2007–made headlines in 2004 when she was dismissed from the President’s Council on Bioethics after objecting to the council’s call for a moratorium on stem cell research and protesting the suppression of relevant scientific evidence in its final report.

Webcast of Dr. Elizabeth Blackburn speaking at Google:
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Norman E. Borlaug 1914-2009

The Father Of the Green Revolution

Norman E. Borlaug, 95, an American plant pathologist who won the Nobel Peace Prize in 1970 for starting the “Green Revolution” that dramatically increased food production in developing nations and saved countless people from starvation, died Saturday at his home in Dallas.

“More than any other single person of this age, he has helped provide bread for a hungry world,” the Nobel committee said in honoring him. “Dr. Borlaug has introduced a dynamic factor into our assessment of the future and its potential.”
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In his lecture accepting the Nobel Prize, he said an adequate supply of food is “the first component of social justice. . . . Otherwise there will be no peace.”
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In 1977, Dr. Borlaug received the Medal of Freedom, the highest civilian honor of the U.S. government.

Billions Served: Norman Borlaug interviewed by Ronald Bailey

As a matter of fact, Mother Nature has crossed species barriers, and sometimes nature crosses barriers between genera–that is, between unrelated groups of species. Take the case of wheat. It is the result of a natural cross made by Mother Nature long before there was scientific man. Today’s modern red wheat variety is made up of three groups of seven chromosomes, and each of those three groups of seven chromosomes came from a different wild grass. First, Mother Nature crossed two of the grasses, and this cross became the durum wheats, which were the commercial grains of the first civilizations spanning from Sumeria until well into the Roman period. Then Mother Nature crossed that 14-chromosome durum wheat with another wild wheat grass to create what was essentially modern wheat at the time of the Roman Empire.

Durum wheat was OK for making flat Arab bread, but it didn’t have elastic gluten. The thing that makes modern wheat different from all of the other cereals is that it has two proteins that give it the doughy quality when it’s mixed with water. Durum wheats don’t have gluten, and that’s why we use them to make spaghetti today. The second cross of durum wheat with the other wild wheat produced a wheat whose dough could be fermented with yeast to produce a big loaf. So modern bread wheat is the result of crossing three species barriers, a kind of natural genetic engineering.
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I see no difference between the varieties carrying a BT gene or a herbicide resistance gene, or other genes that will come to be incorporated, and the varieties created by conventional plant breeding. I think the activists have blown the health risks of biotech all out of proportion.
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the data that’s put out by the World Health Organization and [the U.N.’s Food and Agriculture Organization], there are probably 800 million people who are undernourished in the world. So there’s still a lot of work to do.

I am a bit more cautious about supporting genetic engineering in our food supply but I agree with him that we need to remain focused on the lives of hundreds of millions of hungry people (which is far too often ignored). I am worried about the risks to the environment and human health. I am also worried about the concentration of food plants in a greatly reduced genetic varieties that are more productive in general but increase the risks of massive food failures (due to limited genetic varieties).

Tiny Machine Commands a Swarm of Bacteria

Researchers in Canada have created a solar-powered micro-machine that is no bigger than the period at the end of this sentence. The tiny machine can carry out basic sensing tasks and can indirectly control the movement of a swarm of bacteria in the same Petri dish.

Sylvain Martel, Director of the NanoRobotics Laboratory at the Ã‰cole Polytechnique de MontrÃ©al, previously showed a way to control bacteria attached to microbeads using an MRI machine. His new micro-machine, which measure 300×300 microns and carry tiny solar panels, will be presented this week at ICRA ’09 in Japan.

On such a small device there is little room for batteries, sensors or transmitters. So the solar cell on top delivers power, sending an electric current to both a sensor and a communication circuit. The communication component sends tiny electromagnetic pulses that are detected by an external computer.

The sensor meanwhile detects surrounding pH levels–the higher the pH concentration, the faster the electromagnetic pulses emitted by the micro-machine. The external computer uses these signals to direct a swarm of about 3,000 magnetically-sensitive bacteria, which push the micro-machine around as it pulses. The bacteria push the micro-machine closer to the higher pH concentrations and change its direction if it pulses too slowly. This is more practical than trying to attach the bacteria onto the micro-machines, says Martel, since the bacteria only have a lifespan of a few hours. “It’s like having a propulsion engine on demand,” he says…