Praise then darkness, and creation unfinished

Though this is the first example of a human-to-plant pathogen transfer, the team thinks the same bacterium may live in other domesticated plants, and that other types of bacteria may also have transferred from humans to plants, Campisano said.

"There's something about this place that has allowed them to endure the blight," said Nathan Klaus, a biologist with the Georgia Department of Natural Resources who spotted the trees. "It's either that these trees are able to resist the blight, which is unlikely, or Pine Mountain has something unique that is giving these trees resistance."

Experts say it could be that the chestnuts have less competition from other trees along the dry, rocky ridge. The fungus that causes the blight thrives in a moist environment.

The largest of the half-dozen or so trees is about 40 feet tall and 20 to 30 years old, and is believed to be the southernmost American chestnut discovered so far that is capable of flowering and producing nuts.

Turtles belong to the reptilian grade of physiological organization. They are ectothermic and have relatively low metabolic rates. Being ectotherms, their body temperature remains close to the temperature of their environment, and they are entirely reliant on external sources of heat. Many turtles bask in the sun to raise their body temperature to a point where bodily functions can operate optimally. One species, the leatherback, can maintain a body temperature above that of its environment, but how this is achieved is yet to be determined. Most turtles cannot be active during very hot or very cold periods. Therefore, hibernation in winter and aestivation in summer is common for members of this group.

Turtles breathe with lungs located inside of a rigid ribcage. They therefore must use a different mechanism for breathing than most vertebrates. Muscles in the region of the leg pockets act to inflate the lungs, muscles on the surface of the lungs dorsally and ventrally deflate them. Many turtles augment gas exchange at the lungs with gas exchange in the throat or in the cloaca.

In addition to providing protection for the turtle, the shell of at least some species has an important physiological function. It acts as a "calcium bank". Calcium and other cations are taken from the carapace and plastron to buffer the blood during hibernation when metabolic acids are likely to build up. In other species, it appears that in reproductively active females, calcium is removed from the shell and incorporated into eggshells forming around follicles in the oviducts.