University of California, Berkeley researchers have now found another unusual creature lurking in the lake's briny shallows—one that could tell scientists about the origin of animals more than 650 million years ago.

The organism is a choanoflagellate, a microscopic, single-celled form of life that can divide and develop into multicellular colonies in a way that's similar to how animal embryos form. It's not a type of animal, however, but a member of a sister group to all animals. And as animals' closest living relative, the choanoflagellate is a crucial model for the leap from one-celled to multicellular life.

Surprisingly, it harbors its own microbiome, making it the first choanoflagellate known to establish a stable physical relationship with bacteria, instead of solely eating them. As such, it's one of the simplest organisms known to have a microbiome.

"Very little is known about choanoflagellates, and there are interesting biological phenomena that we can only gain insight into if we understand their ecology," said Nicole King, a UC Berkeley professor of molecular and cell biology and a Howard Hughes Medical Institute (HHMI) investigator who studies choanoflagellates as a model for what early life was like in ancient oceans.