Researchers have discovered new species of marine bacteria in the deep ocean microenvironment, including a previously unknown strain with unique characteristics. The discovery, published in the journal eLife, expands our understanding of the physiological mechanisms of deep-sea bacteria of the genus Planctomycetes.
The new strain of bacteria, named Poriferisphaera hetertotropicis, was discovered using transmission electron microscopy. It turned out to be the only known species of its class that uses budding to reproduce. This provides strong evidence that the new species is actively involved in nitrogen assimilation and lives with a chronic virus that facilitates nitrogen metabolism.
Nitrogen cycling by bacteria is an important process for life on Earth. Nitrogen is released to build nucleic acids, amino acids and proteins – the building blocks of life. Previous studies of the Planctomycetes family of bacteria have focused on strains living in freshwater and shallow ocean environments because of the difficulty of sampling and culturing deep-sea strains.
To study the new bacterium, the researchers collected sediment samples from a deep-sea cold spring and stimulated their growth by adding an antibiotic and nitrogen. This identified a previously unknown strain called ZRK32, which grew faster than the others. Genetic analysis showed that it belonged to the bacterial genus Poriferisphaera and the name Poriferisphaera hetertotropicis was proposed for this new species.
Experiments showed that Poriferisphaera hetertotropicis grows better in nutrient-rich medium and reproduces by budding. The addition of nitrogen in the form of nitrate or ammonia increases the growth of these bacteria, while the addition of nitrogen in the form of nitrite suppresses their growth.
Interestingly, adding ammonia to the nutrient medium causes the new strain to secrete a bacteriophage, a type of virus that infects the bacteria. This bacteriophage, called phage-ZRK32, is able to dramatically increase the growth of Poriferisphaera hetertotropicis and other marine bacteria by promoting nitrogen metabolism.
This discovery is of great importance to our understanding of deep-sea ecosystems and the role of bacteria in the nitrogen cycle. It also emphasizes the importance of further research on the deep ocean microenvironment and its potential impact on climate processes and life on Earth.