Post Tagged with: "E. Coli"

Long-term Experiments

I recently read this Nature article, where is described what is probably one of the longest experiments ever to be conducted. A population of E. coli was kept for 20 years (!) in a nutrient solution (low on glucose), and samples were taken and deep-frozen after 2000, 5000, 10000, 15000, 20000 and 40000 generations. The authors sequenced the genome of the sample bacteria to investigate the rate of mutations.

Up to generation 20K, the number of mutations grew steadily to a total of 45. The adaptation to the environment, however, only increased strongly in the beginning. It was concluded that the most beneficial mutations were the first to occur. After generation 20K, a change in the mutT gene caused a rapid increase in the mutation rate to result in 653 mutation at generation 40K, but with a neutral signature, i.e. no further adaptation.

What I find most fascinating about this extreme long-term experiment is the confidence of the researchers that it would be possible to analyze the genes at a later point; this was not at all self-evident in the late ’80s! In addition, some work had to be done each day, for twenty years. What if the power had failed for a week or so? Of course, this unique opportunity to watch evolution as it happens is very intriguing.

An experiment that took even longer was awarded this year’s Ig Nobel Prize in medicine: Donald L. Unger of Thousand Oaks, CA, cracked the knuckles of his left hand, but not his right hand, every day for 50 years to see if knuckle-cracking leads to arthritis. After this time, both hands were fine, so he concluded: “While a larger group would be necessary to confirm this result, this preliminary investigation suggests a lack of correlation between knuckle cracking and the development of arthritis of the fingers.” Apparently, the experiment must be repeated.

By October 23, 2009 2 comments Uncategorized

Irradiation to enhance food safety

Does anyone remember the E. Coli breakout back in 2006? I do. There has never been a quicker way to convince a 19-year-old to eat vegetables until you take lettuce out of their sandwiches for a couple of months.

According to the LA Times report[1], these greens are washed in potent chlorine bath, often up to three times, before they are bagged and shipped to the retailer. This standard procedure has a reported 90% effectiveness in killing the microorganisms that may cause harmful effects to the human body.

I don’t know about you, but I would rather not take that 10% chance to get sick. In the single breakout of E. Coli due to cross contamination with the cattle back in 2006, 200 people became ill and three lost their lives. That’s the 10% chance that nobody should have to take.

This past month at the ACS National Meeting in New Orleans, researchers from the USDA presented their findings and results of radiation treatment of fresh produces. Irradiation of high energy beams of photons or electrons, said the scientist, can disrupt the DNA of these pathogens. While the chlorine rinse offers a 90% effectiveness in killing bacterias on the surface of the leaves, it is not able to penetrate beneath the surface. Irradiation method has a reported >99.9% effectiveness in wiping out pathogens such as E. coli, salmonella and listeria, and the high energy beams allows penetrating power that works inside and outside the leaves.

Some members of the scientific community are calling irradiation one of the “few intervention steps that indeed can penetrate the leaf surface and kill microorganisms.”

Irradiation for enhancement of food safety is permitted for some hamburger meat, poultry and spices, but not for fruits and vegetables. However, there has not been any health problems associated with eating irradiated food. So why is FDA steering away from adopting an improved method that could potentially save lives?

Consumer experts and food safety researchers offer some of their speculations:

1. Irradiation may damage the apparence of the product, which may not be as appealing to the customers
2. Nobody would buy lettuce from a bag with a radiation sticker
3. The treatment could shorten shelf lives of the products
4. Technically, irradiated produces cannot be certified organic

Though reasonable, it is hard to believe that the above mentioned points would stop either FDA or independent research institutes from further investigating in a method that could possibly be so much more potent in eradicating pathogens than the existing practice. Perhaps these novel ideas would not suffer as much if we could deliver more transparent and correct ideas regarding the applications of radiation.

Using innovative ideas to improve the quality of our everyday lives, isn’t that what science is all about?


[1] USDA scientists say irradiation could be key to food safety

P.S. True to scientific spirit and for the benefit of the minorities out there, I will summarize and translate my discussion in lolcat. I can has radeashuns: on ur vegitablez, keelin ur baktiriaz.

Edit: Originally mentioned by Bethany Halford and Lisa Jarvis in Chemistry Newsbytes.

By April 22, 2008 9 comments nuclear chemistry, science news