NEWS - Researchers from the University of California at Berkeley, the Marine Biological Association of the United Kingdom in Plymouth, and CSIC-Universitat Pompeu Fabra in Barcelona report a tiny new species that forms large colonies, Barroeca monosierra, in a very inhospitable lake.
The strange creature is unusual for other microbes, but it could provide clues to the origins of complex life. B. monosierra belongs to a group of microbes known as choanoflagellates, single-celled organisms that group together to form colonies and act like multicellular life forms.
The new species lives in very salty environments and forms colonies of nearly 100 cells. The center of the colony contains a community of smaller living bacteria, making B. monosierra one of the simplest organisms to have its own microbiome.
Choanoflagellates are a class formally described by William Saville-Kent (1845-1908) in 1880 in A manual of Infusoria, London, vol. 1, p. 324. This class is considered the closest living relative of “non-animal animals.” Colony-forming behavior may bridge the evolutionary gap between single-celled and multicellular organisms.
California’s Mono Lake is nearly three times saltier than the Pacific Ocean and contains chlorides, carbonates and sulfates that have built up over 80,000 years. There’s little life here, mostly alkali flies, brine shrimp and a few species of worms. Researchers carefully examined water samples and found an unknown inhabitant.
“The lake was teeming with choanoflagellates and the largest colonies we’ve ever seen. The colonies are shaped like blastulas, hollow balls of cells that form early in animal development,” said Nicole King of the University of California, Berkeley.
These single-celled organisms resemble sperm cells with flagella to propel themselves. When they form colonies, individuals point their flagella outward to help the entire group spin and roll as a unit. In other choano colonies, the heads of each cell meet in the middle. But B. monosierra has a hollow center with cells connected by an extracellular matrix of proteins and carbohydrates.
The team stained DNA to see the choano cells’ doughnut-shaped chromosomes as expected and a cloud of DNA in the center that should be empty. RNA probes revealed the presence of bacteria in the center, while experiments with fluorescent amino acids showed they were alive.
Phylogenetic analysis showed that only a few types of bacteria were found in Mono Lake within these colonies. The team also cultured the choano colonies with latex microspheres. The bacteria didn’t just float passively and get trapped; they actively entered or were allowed to enter, for their own benefit, the choano’s, or both.
“No one has ever described choanoflagellate with a stable physical interaction with bacteria. We’ve seen choanos reacting to small bacterial molecules floating in the water, or choanos eating bacteria, but there’s never been a case of a potential symbiosis. Or in this case, a microbiome,” King said.
Original research
Hake KH, West PT, McDonald K, Laundon D, Reyes-Rivera J, Garcia De Las Bayonas A, Feng C, Burkhardt P, Richter DJ, Banfield JF, King N. 0. (2024). A large colonial choanoflagellate from Mono Lake harbors live bacteria. mBio 0:e01623-24, DOI:10.1128/mbio.01623-24
The strange creature is unusual for other microbes, but it could provide clues to the origins of complex life. B. monosierra belongs to a group of microbes known as choanoflagellates, single-celled organisms that group together to form colonies and act like multicellular life forms.
The new species lives in very salty environments and forms colonies of nearly 100 cells. The center of the colony contains a community of smaller living bacteria, making B. monosierra one of the simplest organisms to have its own microbiome.
Choanoflagellates are a class formally described by William Saville-Kent (1845-1908) in 1880 in A manual of Infusoria, London, vol. 1, p. 324. This class is considered the closest living relative of “non-animal animals.” Colony-forming behavior may bridge the evolutionary gap between single-celled and multicellular organisms.
California’s Mono Lake is nearly three times saltier than the Pacific Ocean and contains chlorides, carbonates and sulfates that have built up over 80,000 years. There’s little life here, mostly alkali flies, brine shrimp and a few species of worms. Researchers carefully examined water samples and found an unknown inhabitant.
“The lake was teeming with choanoflagellates and the largest colonies we’ve ever seen. The colonies are shaped like blastulas, hollow balls of cells that form early in animal development,” said Nicole King of the University of California, Berkeley.
These single-celled organisms resemble sperm cells with flagella to propel themselves. When they form colonies, individuals point their flagella outward to help the entire group spin and roll as a unit. In other choano colonies, the heads of each cell meet in the middle. But B. monosierra has a hollow center with cells connected by an extracellular matrix of proteins and carbohydrates.
The team stained DNA to see the choano cells’ doughnut-shaped chromosomes as expected and a cloud of DNA in the center that should be empty. RNA probes revealed the presence of bacteria in the center, while experiments with fluorescent amino acids showed they were alive.
Phylogenetic analysis showed that only a few types of bacteria were found in Mono Lake within these colonies. The team also cultured the choano colonies with latex microspheres. The bacteria didn’t just float passively and get trapped; they actively entered or were allowed to enter, for their own benefit, the choano’s, or both.
“No one has ever described choanoflagellate with a stable physical interaction with bacteria. We’ve seen choanos reacting to small bacterial molecules floating in the water, or choanos eating bacteria, but there’s never been a case of a potential symbiosis. Or in this case, a microbiome,” King said.
Original research
Hake KH, West PT, McDonald K, Laundon D, Reyes-Rivera J, Garcia De Las Bayonas A, Feng C, Burkhardt P, Richter DJ, Banfield JF, King N. 0. (2024). A large colonial choanoflagellate from Mono Lake harbors live bacteria. mBio 0:e01623-24, DOI:10.1128/mbio.01623-24