Research

1. Urban Microbial Ecology in sewage and waterway

The mechanisms underlying the formation of new ecosystems are a fundamental unsolved question in ecology.
Sewage systems are newly expanding aquatic environments in urban areas.
Recent studies have shown that sewage pipes are microbial habitats similar to ponds, lakes, or oceans.

Our main goal is testing the dispersal limitation hypothesis in sewer pipe to understand the underlying mechanisms of microbial ecosystem formation.
We also try to understand the fate of antibiotic resistance genes in urban sewage environment.
These studies would elucidate new paradigms that exist in the artificial ecosystems.

2. Bacterial Heavy Metal Resistance System in Microbial Ecology

Mercury is highly toxic and has no beneficial role for living organisms.
However, some bacteria possess systems that are resistant to this toxic metal.
The best-characterized bacterial biotransformation of mercury is reduction by the mer resistance determinants found on plasmids and transposons in both Gram-positive and -negative bacteria.
　 TnMERI1, a class II mercury resistance transposon, was first identified in a Gram-positive Bacillus megaterium MB1 strain isolated from sediment in Minamata Bay Japan, the site of an infamous mercury poisoning disaster.
However, our study revealed that TnMERI1-like class II transposons are distributed worldwide, including among environmental Bacilli strains isolated from non-contaminated sites.
This observation provoked a variety of questions related to bacterial dissemination, horizontal gene transfer, bacterial settlement in microbial communities, and potential significance for bioremediation.
Our laboratory aimed to address these questions using both molecular and ecological approaches.

3. Biodiversity and multifunctionality in microbial ecology

4. Dissolved DNA & Horizontal Gene Transfer in aquatic environment