Weird Symbiosis Between Marine Algae and Bacteria Discovered

Researchers at the University of California in Santa Cruz (UCSC) announce in a new study that they've identified an unusual type of symbiotic relationship between a species of single-celled marine algae and highly-specialized, nitrogen-fixing bacteria living in the ocean.

According to the group, this relationship may play an important role in oceanic fertilization, making it possible for other species to thrive and multiply as a result. Basically, this type of symbiosis takes up nitrogen from the atmosphere, and transforms it in a manner that enables other organisms to use it.

Details of the new investigation were published in this week's issue of the top journal Science.

UCSC marine scientist Jonathan Zehr is the one who first discovered the existence of the nitrogen-fixing microbes, back in 1998. The expert has been following up on that study ever since, gaining more and more data on how the microorganisms develop and live.

One of the particularities of these bacteria is that they have a rather small genome. Regardless, they are now known to be the most widespread nitrogen-fixing organisms in the world's oceans.

Although it belongs to a group called cyanobacteria, which comprises bacterial microorganisms capable of conducting photosynthesis, this particular species cannot carry out this conversion process on its own. Apparently, this capability did not emerge on account of the symbiotic relationship.

“The cyanobacterium is a nitrogen-fixer, so it provides nitrogen to the host cell [the algae], and the host cell provides needed carbon to the cyanobacterium, which is lacking the machinery to get its own,” Anne Thompson explains.

In other words, the close connection the microbe has with algae makes the emergence of the specialized genes required for photosynthesis unnecessary. Thompson was a lead author of the Science paper.

She holds an appointment as a researcher at the UCSC. The other lead author of the research paper is expert Rachel Foster, who is based at the Max Planck Institute for Marine Microbiology, Germany.

“Genomic analysis indicates that the partnership between these organisms in some ways models the one that led to the evolution of plant organelles,” concludes US National Science Foundation (NSF) Division of Environmental Biology (DEB) program director, Matt Kane.