In what could prove to be a seminal moment for research into systemic risks, researchers have discovered a new type of virus in the Mariana Trench, the deepest place on Earth.

The bacteria have been found from sediments at a depth of 8,900 meters. This discovery points to a previously unknown viral family in the deep ocean and offers insights into the genomic characteristics and evolution of deep-sea viruses.

The Mariana Trench descends almost 11,000 meters (36,000 feet) at its lowest point on the floor of the Pacific Ocean. 

In a study recently published in the journal Microbiology Spectrum, an international group of researchers report the discovery of a new virus isolated from sediment brought up from a depth of 8,900 meters (29,200 feet). 

The virus is a bacteriophage, or a virus that infects and replicates inside bacteria, and bacteriophages are believed to be the most abundant life forms on the planet. 

“To our best knowledge, this is the deepest known isolated phage in the global ocean,” said lead researcher Min Wang at the Ocean University of China.

The newly found phage infects bacteria in the phylum Halomonas, which are often found in sediments from the deep seas and from hydrothermal vents, geyser-like openings on the seafloor that release streams of heated water. 

Wang said the group’s analysis of the viral genetic material points to the existence of a previously unknown viral family in the deep ocean, as well as new insights into the diversity, evolution, and genomic features of deep-sea phages and phage-host interactions.

In previous work, the researchers have used metagenomic analysis to study viruses that infect bacteria in the order Oceanospirallales, which includes Halomonas. For the new study, Wang’s team looked for viruses in bacterial strains collected and isolated by a team led by marine virologist Dr Yu-Zhong Zhang, also at the Ocean University of China, in Qingdao. Zhang’s research explores microbial life in extreme environments, including polar regions and the Mariana Trench.

The genomic analysis of the new virus, identified as vB_HmeY_H4907, suggests that it is distributed widely in the ocean and has a similar structure to its host. Wang said the study points to new questions and research areas focused on the survival strategies of viruses in harsh, secluded environments—and how they co-evolve with their hosts. 

The new virus is lysogenic, which means it invades and replicates inside its host, but usually without killing the bacterial cell. As the cell divides, the viral genetic material is also copied and passed on.

In future studies, Wang said, the group plans to investigate the molecular machinery that drives interactions between deep-sea viruses and their hosts.