Kunichika Nakamiya

Degradation of 1,4-dioxane and cyclic ethers by an isolated fungus.

ABSTRACT By using 1,4-dioxane as the sole source of carbon, a 1,4-dioxane-degrading microorganism was isolated from soil. The fungus, termed strain A, was able to utilize 1,4-dioxane and many kinds of cyclic ethers as the sole source of carbon and was identified as Cordyceps sinensis from its 18S rRNA gene sequence. Ethylene glycol was identified as a degradation product of 1,4-dioxane by the use of deuterated 1,4-dioxane-d8 and gas chromatography-mass spectrometry analysis. A degradation pathway involving ethylene glycol, glycolic acid, and oxalic acid was proposed, followed by incorporation of the glycolic acid and/or oxalic acid via glyoxylic acid into the tricarboxylic acid cycle.

Diphenylarsinic acid produces behavioral effects in mice relevant to symptoms observed in citizens who ingested polluted well water.

Citizens in an area of Kamisu City, Ibaraki, Japan had exhibited unusual health problems, and pollution of well water by diphenylarsinic acid (DPAA) was found in the area. We examined the effects of DPAA on various behaviors in mice. DPAA was administered to mice through free intake of drinking water for 27 weeks (subchronic exposure) or 57 weeks (chronic exposure), and behavior was examined during exposure. DPAA at 30-100 ppm increased ambulatory activity and the response rate of the shuttle type discrete conditioned avoidance response of mice. DPAA reduced coordination ability on the fixed rod at 100 ppm. DPAA at 7.5-15 ppm also reduced coordination on the rotating rod, although these doses of DPAA did not affect coordination on the fixed rod. Chronic exposure to 7.5-15 ppm of DPAA produced anti-anxiety-like effects in the elevated plus maze test, whereas subchronic exposure to 100 ppm of DPAA produced anxiogenic-like effects. Neither subchronic nor chronic exposure to 7.5-100 ppm of DPAA affected learning ability and/or memory, as evaluated using the passive avoidance response. Exposure to 15-30 ppm of DPAA for 52 weeks did not alter weights of the cerebrum and cerebellum or amounts of neuron marker protein TUJ-1 or astrocyte marker protein glial fibrillary acidic protein in the cerebellum of mice. Behavioral effects observed in mice seem relevant to symptoms observed in patients from Kamisu City.

Microbial production and vaporization of mono-(2-ethylhexyl) phthalate from di-(2-ethylhexyl) phthalate by microorganisms inside houses.

Laboratory workers were bothered by an irritation that caused coughing during the cultivation of microorganisms that degraded di-(2-ethylhexyl) phthalate (DEHP). The authors found that mono-(2-ethylhexyl) phthalate (MEHP), a known cause of asthma, was released during the degradation of DEHP. At its highest production and vaporization rate, the amount was almost equal to that of the DEHP starting material. It appeared that transport into the atmosphere depended on its adsorption on dust particles. The authors attempted to cultivate several microorganisms from house materials, especially those composed of rotting polyvinyl chloride. And microorganisms produced MEHP in the culture medium. In addition, MEHP was produced from DEHP by several stock microorganisms. Thus, MEHP could easily be produced from DEHP by microorganisms in the environment. In Japan, there are many cases of asthma with unknown causes. If MEHP is one of causes, then preventive measures against some cases of asthma could be taken.

Isolation and properties of a 2-chlorovinylarsonic acid-degrading microorganism

2-Chlorovinylarsonic acid (CVAOA) is a stable abiotic metabolite of lewisite 1 that has been identified in lewisite dumps. There have been no reports of microbial degradation of CVAOA, so we isolated and examined CVAOA-degrading microorganisms. CVAOA contains arsine, which is toxic to microbial growth. We therefore used the simple organic chemical, ethylene, as a sole carbon source in initial screening for suitable microbes. We isolated several microorganisms from sewage sludge and soil. Two strains, NK0505 and NK0506, could be grown on CVAOA as the sole carbon source and were identified by 16S rRNA sequencing as Nocardia carnea NK0505 and Rhodococcus opacus NK0506. Because N. carnea NK0505 was slightly more active in degrading CVAOA, we used it for further degradation studies. Strain NK0505 utilized about 90% of CVAOA (50 ppm) within 5 days; at higher concentrations of CVAOA no degradation occurred over a 10-day period. We identified 1-chloro-1,2-dihydroxyethane, ethylene glycol, glycolic acid, and arsenic acid as degradation products of CVAOA. Epoxy formation on alkylarsine was not confirmed. CVAOA is probably further metabolized via these compounds in the tricarboxylic acid cycle. Strain NK0505 could also degrade but-3-enylarsonic acid, trichloroethylene, isoprene, and 1,3-butadiene, but utilization of tetrachloroethylene and acetylene did not occur.