Korea Unveils Identity of 30-Year-Old 'Mystery' Marine Microorganism

Deep-sea 'Cleaner' Sar202 Bacteria Successfully Cultured in Laboratory for the First Time
Research Team Led by Professor Cho Jangcheon of Inha University Published in Nature Communications on the 22nd of Last Month
New 'Neck' Structure Identified, Genetic Analysis Completed

Domestic researchers have succeeded for the first time in artificially culturing microorganisms that decompose various organic materials in the deep sea in the laboratory.

The National Research Foundation of Korea announced on the 5th that Professor Jangcheon Cho's research team at Inha University succeeded in the laboratory cultivation and genome decoding of SAR202 bacteria, which account for up to 30% of deep-sea microbial communities.

About one million microorganisms inhabit one milliliter (ml) of seawater, mediating the circulation of carbon and energy and thereby regulating the Earth's climate. Since the 1990s, metagenomic analysis has revealed the diversity of marine microorganisms, but most microorganisms could not be cultured in the laboratory, limiting the understanding of their actual nature.

The research team collected seawater from the West Sea to create a medium suitable for growing microorganisms, injected microbial cells, and cultured them in the dark for one month. As a result, they obtained 24 SAR202 strains from the West Sea samples and secured the entire genome sequence through genomic analysis. These strains were identified through metagenomic analysis in the Bermuda region in the 1990s but remained mysterious microorganisms whose actual characteristics were unknown. Metagenome refers to all genomes present in nucleic acids directly extracted from the environment without culturing organisms.

The research team confirmed that SAR202 bacteria divide approximately once every three days in the laboratory, growing very slowly, and that exposure to light stops their growth and causes death. Instead of the flagella, a common bacterial motility organelle, they possess archaella motility genes characteristic of Archaea, suggesting that they may have acquired many genes from Archaea. They also carry various organic matter decomposition genes in their genome and were confirmed to grow in the laboratory using various organic substances such as fucose, rhamnose, and fuconate.

From this, the research team concluded that SAR202 bacteria are expected to play a role in cleaning deep-sea organic matter by utilizing various decomposition genes present in their genome. The cultured SAR202 bacteria were named Lucifugimonas marina, meaning "marine bacteria that dislike light." Furthermore, SAR202 bacteria correspond to a new order in the biological classification system, leading to the establishment of a new order called Lucifugimonadales.

Professor Cho stated, “We have cultured SAR202 bacteria, which microbiologists worldwide have long sought to identify, from domestic seas, paving the way for breakthroughs in marine microbial research. We plan to verify the functions of numerous organic matter decomposition genes present in SAR202 bacteria through follow-up studies.”

This research achievement was published in the international journal Nature Communications on the 22nd of last month.

This content was produced with the assistance of AI translation services.