Faculty and research guide

Laboratory of Environmental Microbiology

Naoto Ogawa

Soil contains more than 100 million microorganisms per gram, with thousands or tens of thousands of varieties. In this laboratory, we aim to contribute to the resolution of environmental puzzles, by clarifying the functions and ecology of these microorganisms. We are therefore pursuing the following challenging research and analysis.

「An analysis of the mechanisms of microorganism breakdown of aromatic compounds」
Microorganisms have an extraordinary ability to break down chemicals. Although aromatic chloride compounds, such as PCB, chlorobenzene in organic solvents, and the pesticide 2,4-D are man-made chemical substances, and they are persistent in the environment once released, microorganisms have developed the ability to break down these chemical substances. We clarify this process, evaluate Nature’s capacity for cleaning up the environment, and study ways of using microorganisms to restore it. Our chief target is the breakdown process of aromatic compounds such as chlorocatechols (Fig. 1) and chlorobenzoic acids. These are the intermediate metabolites commonly appearing in the process whereby microorganisms break down man-made compounds. The analysis we are advancing deals with the expression regulation mechanism (Fig. 2) and the relationship between the structure and functions of metabolism-related genes. Furthermore, we are doing research on the gene expression of decomposition bacteria in the soil and other places in the environment.

1/ Chloroaniline
2/ Chlorophenol
3/ Chlorophenoxyacetic acid
4/ Chloronaphthalene
5/ Chlorosalicylic acid
6/ Chlorotoluene
7/ Chlorobenzoic acid
8/ Chlorobenzene
9/ Chlorocatechol
10/Chlorocatechol ortho-cleavage pathway
11/ β-ketoadipic acid
12/ TCA cycle

Fig. 1 Decomposition path of various aromatic chloride compounds (Reineke 1998)

1/ Identification of the inducing substance by understanding the expression regulation and binding factors in the promoter region
2/ Expression of the inducing substance by a group of genes involved in decomposition
3/ Conversion of chlorocatechol by chlorocatechol 1,2-dioxygenase
4/ Pattern recognition
5/ Gene for the expression regulation factor
6/ Promoter region of a group of genes involved in decomposition
7/ Expression of a group of genes involved in the decomposition of chlorocatechol

Fig. 2 Expression regulation mechanism of the LysR-type regulation factor CbnR in a group of genes involved in the decomposition of chlorocatechol