Researchers have discovered a new bacteriophage in the Mariana Trench, specifically from sediments 8,900 meters deep. This discovery reveals a previously unknown family of viruses in the deep sea and provides clues to understand the genomic characteristics and evolution of deep-sea viruses.
"The Mariana Trench is the deepest place on Earth, dropping nearly 11,000 meters (36,000 feet) at the lowest point on the Pacific Ocean floor. Even in this bottomless and freezing abyss, life still exists." Dr. Wang Min, a marine virologist at Ocean University of China in Qingdao, said: "Wherever there is life, there must be regulators at work." In this case, it refers to viruses.
In a recent study published in the journal Microbiology Spectrum, Wang Min and a team of international researchers reported that they isolated a new virus from sediments 8,900 meters (29,200 feet) deep. The virus is a type of bacteriophage, a virus that infects and replicates within bacteria, and bacteriophages are considered the most abundant life forms on Earth. "To our knowledge, this is the most deeply isolated phage known to exist in the global ocean," Wang said.
The newly discovered phage infects bacteria in the phylum Halomonas, which are commonly found in deep-sea sediments and hydrothermal vents, which are fountain-like openings on the ocean floor that release heated water. Wang said the research team's analysis of the viral genetic material revealed the existence of a previously unknown virus family in the deep sea and gained new insights into the diversity, evolution and genomic characteristics of deep-sea phages, as well as phage-host interactions.
In previous work, the researchers used metagenomic analysis to study viruses that infect bacteria from the class Oceanospirallales, which includes Halomonas. In the new study, Wang's research team looked for viruses in bacterial strains collected and isolated by a research team led by Dr. Zhang Yuzhong, a marine virologist at Ocean University of China in Qingdao. Zhang’s research explores microbial life in extreme environments, including the polar regions and the Mariana Trench.
Genomic analysis of the new virus, identified as vB_HmeY_H4907, showed that it is widely distributed in the ocean and is structurally similar to its host. The study points to new questions and areas of research focused on the survival strategies of viruses in harsh, cryptic environments - and how they co-evolve with their hosts. The new virus is lytic, meaning it can invade the host and replicate but does not typically kill bacterial cells. As cells divide, the virus's genetic material is copied and passed on.
In future studies, the research team plans to investigate the molecular mechanisms driving interactions between deep-sea viruses and their hosts, Wang said. They are also looking for other new viruses in extreme environments, "which will help broaden our understanding of the virus sphere," Wang said. "Extreme environments offer the best prospects for discovering new viruses."