Extracellular vesicles play a much greater role in horizontal gene transfer in the ocean than previously assumed.
Extracellular vesicles play a much greater role in horizontal gene transfer in the ocean than previously assumed.
There is a lively exchange of genetic information between the numerous microorganisms in the oceans. This so-called horizontal gene transfer (HGT) is crucial for the evolution of many organisms and is, for example, also the most important mechanism for the spread of antibiotic resistance in bacteria. Until now, it was assumed that direct contacts between cells, free DNA or viruses were primarily responsible for the exchange of genes. A study led by Susanne Erdmann from the Max Planck Institute for Marine Microbiology in Bremen now shows that so-called extracellular vesicles are also very important for the transfer of genetic information in the sea and thus for the life of its smallest inhabitants.
Viruses, GTAs, EVs: Tiny and Numerous
Most viruses are tiny. Up to 10 million of them can be found in every drop of seawater. They can not only pack up their own genetic material (their genome), but also parts of their host's DNA – i.e. the DNA of the organism they have infected – and transport it into other cells.
Studying viruses is challenging. Seawater samples have to be filtered through filters with a pore size of only 0.2 µm (which is about 300 times less than the thickness of a human hair) to separate the viruses from the cells. In addition to viruses, these filtered samples also contain so-called gene transfer agents (GTAs) and extracellular vesicles (EVs). GTAs are virus-like particles that exclusively package host DNA, and EVs are small vesicles enveloped by a membrane that detach from the cell surface of the host. These EVs can contain a variety of molecules. In addition to enzymes, nutrients and RNA, they often transport fragments of DNA.
Read more at Max Planck Institute for Marine Microbiology
Image: For this study, the researchers from the Max Planck Institute in Bremen also collected water samples off the North Sea Island of Helgoland. (© Silvia Vidal/Max Planck Institute for Marine Microbiology)
