The finding points to a life form that requires few genes to function

Researchers have discovered two new and unusual species of bacteria in deep-sea coral in the Gulf of Mexico. The discovery, announced in the journal Nature Communications, points to a type of life that requires surprisingly few genes to function.

Marine biologists found the bacteria in the tissue of two soft coral species that live in complete darkness in the Gulf of Mexico. The microbes are mollicutes, extremely small parasitic organisms that exist symbiotically with their hosts. They have no cell walls and, in this case, have extremely tiny genomes.

The new bacteria, Oceanoplasma callogorgiae and Thalassoplasma callogorgiae, have only 359 and 385 protein-encoding genes, respectively, the researchers wrote. The average bacterium has about 3,000 such genes, while humans have over 20,000.

The bacteria likely live in the corals' mesoglea, a jellylike substance that plays a part in corals' immune systems. Unlike most other living organisms, they don't rely on energy from carbohydrates to survive. Instead, they get their energy from an amino acid within their coral hosts.

"The breakdown of this amino acid provides only tiny amounts of energy," Samuel Vohsen, a postdoctoral research fellow at Lehigh University and the paper's first author, said in a news release. "It is astonishing that the bacteria can survive on so little," he added.

It's unclear whether the new bacteria harm or benefit their hosts, the researchers wrote. But their having "severely reduced" genomes shows just how few genes are needed for cellular life, they noted.

They have proposed a new family name, Oceanoplasmataceae, to describe the strange new bacteria.