PARENT SESSION

PH14 Biotransformation of Organics and Their Biological Effects
Exhibit Hall
8:00 AM - Thursday, 13 November 2003

(PH139) Kinetic studies of microbial degradation of CL-20 (Hexanitrohexaazaisowurtzitane).

Sizova, M¹, Panikov, N¹, Christodoulatos, C¹, ¹ Stevens Institute of Technology, Hoboken, NJ, USA

ABSTRACT- Hexanitrohexaazaisowurtzitane (CL-20 or HNIW) is currently under consideration for a wider military application by the Department of Defense (DoD). It is considered to be much less toxic to environment than similar nitramine explosives such as RDX and HMX. Anyway one of the urgent tasks is to develop an efficient technological procedure for removal of CL-20 from soils, surface and ground water, vegetation, etc. after its accidental release to natural environment. The bioremediation is known to be promising alternative to chemical detoxication; that is why the objective of our research was to find out whether CL-20 can be degraded by soil/aquatic microorganisms. The conventional enrichment technique as applied to soils, river waters and sewage sludge always gave some aerobic growth, concomitant CO2 formation and partial degradation of CL-20. However under careful examination, we have found that major source of utilizable C came from impurities in commercial HNIW preparations rather than from hexanitrohexaazaisowurtzitane per se. The essentially more vigorous degradation of CL-20 was observed under strictly anaerobic conditions. The bacteria capable to ferment CL-20 was isolated in pure culture and characterized in terms of cell morphology, physiology and taxonomic position as determined by sequencing of SSU (small subunit of 16S rRNA). It turned out to be new to science organisms which belong to -1-subgroup of Proteobacteria (probably forming new genus). The closest relative (94.3-94.9% of sequences similarity) was an uncultured eubacterium WD229 from soil polluted with polychlorinated biphenyl [Nogales et al. 2001. Appl. Environ. Microbiol. 67, 1874-188437]. It is a normal inhabitant of ultra-poor and pristine Sphagnum peatland, and intriguing question is why and how these bacteria can degrade such unusual recently synthesized compound.

Key words: degradation, anaerobic, 16SrRNA, kinetics