The most abundant photosynthetic bacterium in the oceans casts off many minute pieces of itself every day, amounting collectively to tonnes of material that potentially influences the global carbon cycle.

Many bacterial species release membrane-bound sacs called vesicles, which have not been well studied in natural ecosystems. Sallie Chisholm, Steven Biller and their colleagues at the Massachusetts Institute of Technology in Cambridge discovered vesicles in laboratory cultures of the microbe Prochlorococcus, and in samples from the Atlantic Ocean.

Analysis revealed that the laboratory vesicles contained proteins, DNA and RNA, and that each Prochlorococcus produced two to five vesicles per generation. The authors estimated that the Prochlorococcus sacs could be contributing 104 tonnes or more of fixed carbon to the ocean carbon cycle each day. Vesicles might serve to decoy attacking viruses away from the bacterium and aid in gene transfer.

Science 343, 183–186 (2014)