Tag Archives: Biology

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Why the Tropics are an evolutionary hotbed

fossilantTropical climates are famously rich in biodiversity, perhaps because old lineages persist well in those regions instead of being simply replaced by new ones, or perhaps because the tropical environment promotes fast speciation. A new study of the ant family tree suggests that both these explanations may be right.

For the study, published this week in Evolution, the researchers traced the locations and rates of ant speciation since they emerged 139 million–158 million years ago1. The results suggest that a region known as the neotropics — which includes South America, Central America and part of North America — is both the source of the first ants and the liveliest incubator of their diversity.

Read the rest of this news story at Nature News [html] [pdf]

Predictable evolution trumps randomness of mutations

Although mutations, the driver of evolution, occur at random, a study of the bacterium Escherichia coli reveals that nature often finds the same solution to the same problem again and again.

Over time, random mutations enable organisms to adapt and diversify, often when geographically separated groups of the same species grow better suited to their local environment and less like members of the other group.

But that’s not the only way that genetic diversity can arise. Researchers have reported cases of cichlid fish, palm trees and finches adapting to different ecological niches and splitting into different species despite living in the same place1–3. In 2008, evolutionary biologist Michael Doebeli of the University of British Columbia (UBC) in Vancouver and colleagues reported that E. coli bacteria can also diversify while sharing a test tube4.

In that study, they fed easy-to-digest glucose and a harder-to-stomach acetate to homogeneous populations of the bacteria, and let the bacteria chomp away. E. coli can switch between the two foods, but the team found that in each test tube two groups emerged, specialized in consuming either glucose or acetate. What they did not know was which genetic path each group took to achieve its specialisation.

Read the rest of this news story at Nature News [html] [pdf]

Scientific American also picked up the story [html]

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Point-of-care tests poised to alter course of HIV treatment

Testing for HIV does not simply end with the diagnosis that the virus is present in a patient; caregivers also need to track the disease’s progress to adjust ongoing treatment. Yet tests for monitoring HIV infection require sophisticated instruments, well-trained clinicians and expensive lab ware. All those are in short supply on HIV’s front line in places such as rural sub-Saharan Africa. “It’s a problem not just of cost,” explains hematologist Helen Lee of the University of Cambridge in the UK. “It’s a problem of having access.” In the last year, stripped-down standalone tests have appeared on the market, offering rural patients a cheaper, faster count of their CD4 immune cells. And in the coming months, a class of tests that measure viral load should enter routine point-of-care use, too, offering caregivers a choice of simple tools for measuring HIV infections.

Read the rest of this news story at Nature Medicine [html] or see it as it appeared in print [pdf].

Dynamic duo helps to heal irradiated mice

An antibiotic and a protein can work together to fight radiation-induced infections better than either can manage alone. Doctors already use antibiotics to treat radiation sickness. But the addition of a protein from the immune system — bactericidal/permeability-increasing protein (BPI), which acts against poisons called endotoxins — improves the survival rate of irradiated mice, according to a study published today in Science Translational Medicine.

The combination of BPI with the antibiotic fluoroquinolone helped mice that were treated up to a day after exposure to radiation. This is important, because most existing treatments for radiation sickness — including those stockpiled by the US government, such as potassium iodide and the protein granulocyte colony-stimulating factor — must be taken before or within hours of exposure, which is not always possible. In the event of a nuclear crisis that exposes hundreds or thousands of people to radiation, the ensuing chaos could delay treatment.

“The most important thing about the BPI and fluoroquinolone combination is that it is effective at 24 hours after exposure,” says Eva Guinan, a haematologist at Harvard Medical School in Boston, Massachusetts, who led the study.

Read the rest of this news story at Nature News or here: [pdf]