UNC-TV Science Week In Review: August 1, 2013
Prince, Dragon or Both?
The universe rarely behaves like a fairy tale. Science shows us that forces and molecules and organisms cannot be divided into good princes and evil dragons. More often than not, the princes secretly breathe fire while the dragons unwittingly save the day.
Take oxygen for example. Oxygen allows us to digest our food and burn the fuels that give us heat and the ability to travel the world. Old element number 8 looks pretty princely, right?
Oxygen, however, was one of the meanest dragons in Earth’s history. It tears up DNA so when it appeared 2.4 billion years ago, it wiped out all the organisms that weren’t lucky enough to be able to metabolize it. Prince indeed.
In the natural world, even our greatest allies can be enemies and vice versa, as North Carolina researchers discovered this week.
This Little Piggy Spreads Antibiotic Resistant Bacteria
Personally, I tend to put Carolina barbecue and Buffalo wings in the good column, and North Carolina farms provide much of the swine and poultry used to make them. But scientists from UNC Chapel Hill and Johns Hopkins University say something else is coming from those farms, bacteria resistant to antibiotics.
The researchers investigated whether the bacteria at factory farms, which commonly use antibiotics to help their livestock grow, were different from the bacteria at farms where no antibiotics were used. They also tried to determine whether these bacteria made their way into the farm workers.
The particular bacteria in the spotlight were strains of Staphylococcus aureus resistant to methicillin (MRSA) and multiple drugs (MDRSA). The researchers took nasal swabs from 204 North Carolina farm workers on both antibiotic and antibiotic-free farms.
MRSA appeared in on both types of farms, but MDRSA was more prevalent at the farms using antibiotics, suggesting that the antibiotics contributed to more resistant strains. The study does not show, however, that these bacteria wind up in the pork and chicken that ends up in the supermarket. The researchers wrote that future studies would test both the workers and the animals.
Taxing Sugary Drinks Not a Silver Bullet
Studies show that the United States spends $147 billion on medical bills related to obesity every year. Experts point to sugar sweetened beverages such as sodas, juices and sports drinks as major contributors to obesity. A possible measure to curb consumption of sugar sweetened beverages is to tax them, just like cigarettes.
A study from RTI International, however, shows that taxing these sugary drinks may not have all the desired effects. With data a one-year survey of more than 27,000 households the researchers examined buying habits and calorie consumption after a tax had been levied on sugar sweetened beverages.
They found that people bought fewer sugary drinks and consumed fewer calories on average. However, those effects were somewhat dampened as people bought more snacks and candy as a substitute.
Also, when the researchers compared high and low-income households, the low-income households spent just as much if not more on the tax as high-income households, thus putting a greater burden on low-income families.
The study appeared in the Journal of Agricultural Economics.
Strep Throat Bacteria Lend Genetic Engineers a Hand
Think of DNA as a 3 billion letter long set of instructions written out in a gigantic Word document. Genetic engineers make changes to this document; writing, cutting, copying and pasting their way to everything from gene therapies to bigger pumpkins. The process is painstakingly difficult, but with a little help from strep throat bacteria, Duke researchers made it a little easier.
Streptococcus pyogenes, like other bacteria, has an immune system written into its DNA. This system, called CRISPR* is a set of instructions S. pyogenes uses to fight invaders. Written out, it would read “cut – cut – cut.” When a virus injects DNA into S. pyogenes, it grabs a piece and pastes it into CRISPR’s instructions, so it reads “cut – viral DNA – cut.” Following the new CRISPR code, S. pyogenes makes enzymes to carry out those instructions: find that specific viral DNA and cut it.
The researchers at Duke used a mutant enzyme with slightly different instructions. The mutant (dCas9) has instructions to “bold” instead of “cut.” The scientists injected eight human genes into S. pyogenes and harvested the dCas9. Instead of cutting, the dCas9 recognized and turned on the eight genes the scientists wanted.
As complicated as this process sounds, it is much simpler than technology currently available to turn on specific genes, and the research, published in the journal Nature Methods, has the potential to greatly expand the applications of gene therapy as scientists perfect it in the future.
*CRISPR, by the way, stands for Clustered Regularly Interspaced Short Palindromic Repeats. Try saying that 5 times fast!
Wait . . . No Fair!
Menopause is something that every women and (unfairly) no man goes through. Now researchers from Duke and UNC-Charlotte have revealed an even greater version of this evolutionary injustice. Women are not just the only humans, but also the only primates to go through menopause.
The researchers followed 700 wild primates of 7 different species. They all showed signs of reproductive decline in old age, but they usually died before they were completely infertile.
This might seem obvious. Baboons and chimps don’t have doctors and hospitals to keep them alive past their child-rearing years. However, the researchers also studied a hunter-gatherer tribe called the !Kung, who do not use modern medicine. !Kung women lived well beyond their reproductive years, showing that humans, unlike the apes, monkeys and lemurs that make up our taxonomic order, naturally go through menopause.
The next question is why humans evolved to live for longer than they can reproduce? And while human women have no primates to share the experience with, there are always killer whales, who live to 70 but stop reproducing in their 30’s.
- Daniel Lane
Daniel Lane covers science, medicine and the environment as a reporter/writer. He is currently pursuing a master's degree in medical and science journalism at UNC - Chapel Hill.