Microscopic Bubbles Baffle Ocean Scientists:
The most abundant photosynthetic organism in the world throws countless small sacs in the oceans , which could be having a dramatic impact on marine ecosystems , according to a new study. These sprouts contain microbial proteins and genetic material , which may influence the growth of other marine microbes and even protect against viruses.
The oceans are the largest ecosystem in the world , and unicellular cyanobacteria organisms that obtain their energy through photosynthesis – are the keystone group . A type of cyanobacteria, Prochlorococcus is the most abundant in the world, numbering in the billions of billions of billions photosynthetic organism . These tiny organisms account for about 10 % of all photosynthesis on Earth, forming the base of the food chain and provides the atmosphere with oxygen . Researchers at the Massachusetts Institute of Technology (MIT ) , led by biological oceanographer Sallie Chisholm found that cyanobacteria may play an even greater role in the ecosystem than previously thought .
The team reports that Chisholm cyanobacteria secrete small vesicles, membrane-enclosed sacs into the surrounding ocean. Chisholm first observed vesicles in 2008 when one of his graduate students , Anne Thompson , spotted small buds on the surface of Prochlorococcus under an electron microscope. ” The vesicles , which called them” Chisholm recalled, ” like little bubbles. ” A couple of years later, MIT postdoctoral Steven Biller proposed that these vesicles may be vesicles, based on their resemblance to the vesicles of other species. This was confirmed by isolation of the vesicles and further examination under the electron microscope. The vesicles were at least as abundant as the bacteria themselves .
These initial observations were made in bacteria grown in the laboratory and may not necessarily apply to wild microbes. Therefore, Biller tactics , collecting hundreds of liters of seawater off the coast of Massachusetts, and from the Sargasso Sea near Bermuda. Vesicles found in these samples as those of laboratory cultures . Analysis of the contents of the blebs revealed a variety of biological molecules : proteins, DNA , and RNA . DNA sequencing revealed that it was a variety of microbes , not only Prochlorococcus . Therefore, these vesicles appear to be a general feature of the marine microorganisms .
Because they are so abundant , and because they contain various biomolecules, these vesicles are a major source of organic carbon , nitrogen, and phosphorus in which other organisms can feed . Indeed , Chisholm and colleagues showed that no other photosynthetic bacteria, can grow using vesicles of cyanobacteria as their sole carbon source . ” That’s kind of neat ,” says Marvin Whiteley , a microbiologist at the University of Texas, Austin, who was not involved in the study. “What really changes the way we think about marine ecosystems and how they are created and how nutrients are provided . ”
Another important consequence of this finding is that , in the words of Biller, “It’s kind of asking a lot more questions than it answers . ” Perhaps the new bigger question is why the bacteria produce these vesicles in the first place . The authors offer some hypotheses . First, cyanobacteria live benefit from other types of bacteria . Vesicles provide food for other bacteria encourage this living arrangement . Moreover, because the vesicles containing the DNA, can facilitate the exchange of genetic material between individual bacteria , a process known as horizontal gene transfer . The last and perhaps most interesting , the vesicles may help defend against viruses. Chisholm group showed that when known to attack virus cyanobacteria are mixed with vesicles , the virus will bind to vesicles and to infect them appear as if the vesicles were living cells. Therefore, the authors speculate that these vesicles may function as cellular decoys , distracting the virus from infecting cyanobacteria .
Whatever their purpose , these vesicles show that we still have much to learn about life in the oceans. ” We did not set out to study this,” Chisholm says, “but Prochlorococcus is always putting things in front of us to study.