Degradation of DDT by γ-hexachlorocyclohexane dehydrochlorinase LinA.

1,1,1-Trichloro-2,2-bis(4-chlorophenyl)-ethane (DDT) is the first synthetic insecticide and one of the most widely used pesticides. The use of DDT has been banned, but it remains one of the most notorious environmental pollutants around the world. In this study, we found that γ-hexachlorocyclohexane (γ-HCH) dehydrochlorinase LinA from a γ-HCH-degrading bacterium, Sphingobium japonicum UT26, converts DDT to 1,1-dichloro-2,2-bis(4-chlorophenyl)-ethylene (DDE). Because of the weak DDT degradation activity of LinA, we could not detect such activity in UT26 cells expressing LinA constitutively. However, the linA-deletion mutant of UT26 harboring a plasmid for the expression of LinA, in which LinA was expressed at a higher level than UT26, showed the DDT degradation activity. This outcome highlights the potential for constructing DDT-degrading sphingomonad cells through elevated LinA expression.

Isolation of Aspergillus oryzae mutants producing low levels of 2,4,6-trichloroanisole.

Musty or moldy off-odor in sake severely reduces its quality. Such off-odor is caused by 2,4,6-trichloroanisole (TCA), a compound that is produced by Aspergillus oryzae during sake production by O-methylating the precursor 2,4,6-trichlorophenol (TCP). TCP suppresses the growth of fungi, including A. oryzae, although TCA does not. Therefore, strains that are unable to convert TCP to TCA should be sensitive to TCP in the medium. Nevertheless, A. oryzae with a disrupted O-methyltransferase gene (ΔomtT) grew in a medium containing TCP. In agar medium, we observed no growth difference between the ΔomtT strain and a non-disrupted transformant; however, a significant growth delay was observed with the ΔomtT strain grown in liquid medium containing 0.5 µg/mL of TCP. This strain was more sensitive to low concentrations of TCP, suggesting that omtT contributes to the conversion (detoxification) of TCP in liquid culture. We generated A. oryzae RIB 40 mutants by ultraviolet irradiation and then cultured them in liquid medium containing TCP to obtain strains that did not produce moldy odor. The slow-growing strains were cultured in agar plates and then used to make koji with added TCP. We obtained three strains with lower TCA-producing ability and with sufficient hydrolase activities for sake brewing.

Molecular probes for fluorescence image-guided cancer surgery.

In cancer surgery, complete surgical resection of tumor lesions is critical to optimize the outcome. However, it is sometimes difficult to distinguish the boundary between tumor and normal tissues, and residual tumor tissue can result in cancer recurrence. Intraoperative imaging with fluorescent molecular probes can assist surgeons to visualize tumor lesions and their boundaries during surgery. Here, we review molecular probes for fluorescence image-guided cancer surgery, focusing especially on recent developments in high-performance tumor-imaging probes and the strategies used for their design.