Bacteria-Killing Viruses Discovered in Abundance Across the World’s Oceans

by John Kerin ‘20

The surface of most of the Earth’s oceans contains, on average, 10 million viruses per milliliter of water. (Source: Wikimedia Commons)

The surface of most of the Earth’s oceans contains, on average, 10 million viruses per milliliter of water. (Source: Wikimedia Commons)

A new evolutionary lineage of viruses has been found in samples of seawater from many of the world’s oceans. This new group of viruses was recently named “Autolykiviridae,” after a Greek mythological character known for his ability to evade capture (1). They differ from the well-catalogued viruses that scientists expect to see when studying the surface of the Earth’s oceans, which is the primary reason that these abundant viruses went undiscovered until recently.

Several characteristics set these new viruses apart from the previously isolated viruses from seawater. Firstly, the viruses in this new group do not have a viral “tail” that is typical of viruses in this kind of environment. Secondly, the tail-less viruses take longer to kill bacteria than previously known ocean-borne viruses (1). This is the main reason why they went undetected for so long, as scientists would finish their study of culture samples before the viruses had a chance to hint at their presence by killing bacteria.

When compared to the tailed counterparts, this new group of viruses has a genome that is only twenty-five percent as long. Despite this, they can kill on average thirty-four hosts in four different Vibrio bacterial species, while tailed viruses can only kill one to two hosts in a single species (2). The fact that these viruses can do so much more with so much less leaves many questions to be answered in future studies.

The discovery of these hidden-in-plain-sight viruses is also important in that it illustrates deficiencies in how we are examining nature. “We already knew that viruses are very important there,” says Kathryn Kauffman, the post-doctorate leader of the MIT study that discovered the viruses (1). “There,” referring to the surface of the ocean, typically contains ten million viruses per milliliter of water. These tail-less viruses have been shown to be seventeen times more infective than their tailed counterparts, which further substantiates why Kauffman calls these viruses important to the ecology of the ocean’s surface.

Aside from advancing the scientific community’s understanding of the ocean’s biology, the discovery has been an excellent example of how researchers must pay long and careful attention to their work. The potential to miss interesting and significant new discoveries is higher than one might think.


(1) Massachusetts Institute of Technology. “New type of virus found in the ocean: The unusual characteristics of these abundant, bacteria-killing viruses could lead to evolutionary insights.” ScienceDaily. ScienceDaily, 24 January 2018. <>.

(2) Kathryn M. Kauffman, Fatima A. Hussain, Joy Yang, Philip Arevalo, Julia M. Brown, William K. Chang, David VanInsberghe, Joseph Elsherbini, Radhey S. Sharma, Michael B. Cutler, Libusha Kelly & Martin F. Polz. A major lineage of non-tailed dsDNA viruses as unrecognized killers of marine bacteriaNature, 2018 DOI: 10.1038/nature25474