Research Director: Dr. Koki Horikoshi
(Professor, Faculty of Engineering, Tokyo Institute of Technology / Chief Scientist, RIKEN)
Research Term: 1984-1989


The Horikoshi superbugs project conducted a world-wide search for bacteria that thrive under extreme conditions of pH, salinity, and temperature. Interesting specimens found during this search were studied regarding their DNA, RNA, proteins, lipids, polysaccharides as well as tolerance mechanisms, metabolic pathways, and gene expressions.

Research Results

Unique triangular bacterium: A very unique microorganism was discovered living in Japanese saltern soil at a temperature of 37 oC and a salinity 8-times that of sea water. This extremely halophilic archaebacterium – Haloarcula japonicus – is triangular in shape and moves using flagella.

Solvent-tolerant bacterium: A variant strain of Pseudomonas putida (IH-2000), an aerobic gram-negative rod, was discovered which is capable of growing in culture media containing more than 50% (v/v) toluene or high concentrations of cyclohexane, xylene, styrene, and heptanol.

Thermophilic bacteria: A number of novel thermophilic bacteria were isolated from Japanese hot springs and surrounding soils. Thermostable enzymes recovered from such strains including β-glucosidase, trehalase, pullulanase, heparinase and chondroitinase were characterized and developed for commercial use. In many cases, the genes encoding these enzymes were cloned in E. coli and their complete nucleotide sequence was determined.

Alkalophilic bacteria: Several new alkalophilic bacteria were isolated, including two selenium resistant strains capable of growth in a highly alkaline medium containing more than 1% selenite.

Methanogenic Archaebacteria: Several new species of halo-, alkalo-, and thermophilic and psychrotolerant methanogenic Archaecbacteria were isolated and characterized.

Basic analysis of genes: The ori regions of the DNA of several species of bacteria have shown a new consensus sequence in bacterial plasmids and in the phage lambda.

Thermal properties of superbacteria: The thermal properties of superbacteria have been studied using heat leakage scanning calorimetry, a useful technique for studying the structures, stabilities, and conformational changes of macromolecules without separations into each constituent fraction.

Magnetite-producing bacteria: A better understanding of how small (150-250 nm) magnetic particles are produced by magnetotactic bacteria has been obtained by simulating magnetite synthesis in vitro using the enzyme urease.


·Ancient triangular microorganism from a highly saline environment



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