NEWLY DISCOVERED ROLES FOR PHOTOSYNTHETIC PLANKTON
IN MARINE ECOSYSTEMS
Bacterial vesicles are gaining increasing attention for their roles in pathogenesis, … Biller et al. in this paper provide evidence that membrane vesicles ∼100 nm in diameter are released by marine cyanobacteria and are a major feature of marine ecosystems.
Studies of cultures of Prochlorococcus show that vesicles are continually released by this cyanobacterium and are abundant in the marine environment. These vesicles have properties changing the way we think about genetic and biogeochemical exchange among plankton and the dissolved organic carbon pool in marine ecosystems.
- Marine microbes play a key role in global nutrient cycling.
- Although they account for less than 1% of the photosynthetic biomass on Earth, phytoplankton contribute at least half of the world’s primary production.
- In open oceans between ∼45°N and ∼40°S, cyanobacteria of the genus Prochlorococcus dominate the phytoplankton.
- Prochlorococcus is the smallest free-living phototroph; its genome (of approx. 2000 genes) is subject to miniaturization; and distinct ecotypes are adapted to the strong gradients of light and nutrients in the surface ocean.
- Prochlorococcus are thought to be the most abundant photosynthetic organism on Earth and are responsible for at least 50% of atmospheric oxygen.
- Kingdom: Bacteria > Phylum: Cyanobacteria >
Order: Synechococcales > Family: Synechococcaceae >
Genus: Prochlorococcus Chisholm et al., 1992
Multipurpose vesicles produced by the cyanobacterium Prochlorococcus may play functional roles in defending against viral attack, interactions between heterotrophs and Prochlorococcus, and horizontal gene transfer. This is a schematic presentation and is not to scale. CREDIT: P. HUEY/Science
The cyanobacterium Prochlorococcus releases membrane vesicles.
(A) Scanning electron micrograph of Prochlorococcus shows the presence of numerous small spherical features (vesicles, indicated by arrows) near the cells. Scale bar, 1 μm. (B) Purified Prochlorococcus vesicles as seen by negative-stain TEM. Scale bar, 100 nm. (C) Thin-section electron micrographs confirm that Prochlorococcus vesicles are circular, membrane-enclosed features lacking notable internal structure. Scale bar, 100 nm.
Based on Bacterial Vesicles in the Ocean, a report by David Scanlan and on Carbon Budding in the Ocean, an editorial summary by Caroline Ash (Science, AAAS) – both about Bacterial Vesicles in Marine Ecosystems by Steven J. Biller, Florence Schubotz, Sara E. Roggensack„ Anne W. Thompson, Roger E. Summons, Sallie W. Chisholm || Published in Science 10 January 2014: Vol. 343 no. 6167 pp. 183-186 ||