Bacterial Bounty

One of the most abundant kinds of marine cyanobacteria is continually releasing an unexpected bounty of protein- and genetic-material-packed vesicles into the ocean, notes a report in Science (2014, DOI: 10.1126/science.1243457). The photosynthetic organisms from the genus Prochlorococcus are responsible for up to 60% of all the chlorophyll a in some marine layers and have a global population that reaches 10²⁷ cells. While examining unusual spherical features in micrographs of the abundant organisms, a team led by Sallie W. Chisholm and Steven J. Biller of MIT discovered that the species release vesicles packed with biomaterial. They confirmed that the process also occurs in the ocean, noting that the vesicles are an unexpected source of marine carbon. One hypothesis for why the bacteria release the vesicles is that they serve as decoys for pathogenic viruses. Another is that the proteins in the vesicles are useful to species of marine microorganisms in symbiosis with Prochlorococcus. Additionally, the vesicles may enable genetic material to be shared among marine microorganisms.