Unusual bacteria discovered in deep ocean trench

Researchers from Japan discovered microscopic bacteria thrive in the canyon called Challenger Deep, which is the lowest point on Earth's surface and the deepest part of the Mariana Trench, the team reports in the journal Proceedings of the National Academy of Sciences. In particular, they found an unusual community of bacteria there called heterotrophs, or microbes that cannot produce their own food and must eat what they find in the water.

The heterotrophs in the Challenger Deep likely derive food from sinking particles, such as dissolved fecal pellets or dust, or possibly from geologic processes such as earthquake-triggered landslides, which could send organic-rich sediments tumbling into the canyon's depths.

The research found that ocean's microbial diversity varied with depth. Genetic-fingerprinting techniques identified different microbes based on certain genes, and also indicated the relative abundance of different species.

The ocean's invisible life was found at all depths, but microbes were most abundant near the surface and on the ocean floor, where they can find the most food. The ocean was stratified into layers, with a warm, salty layer on top and a colder, less salty layer starting about 1,300 feet (400 m) below the surface. The deepest water was about 1 degree Celsius (34 degrees Fahrenheit).

Plantlike phytoplankton crowded the surface waters. (Light only penetrates into the upper 328 feet, or 100 m, of the ocean.) Chemolithotrophs, or microbes that survive by converting compounds such as sulfur and ammonia into food, were abundant in the nutrient-poor abyssal zone but declined below a depth of 19,685 feet (6,000 m), to be replaced by heterotrophs, the study found. The abyssal zone ranges from 6,560 feet to 16,400 feet (2,000 m to 5,000 m).

For further details see Microbe World.

Posted by Tim Sandle