Biodegradation of pyridine by aerobic nocardioides sp. OS4 and denitrifying azoarcus evansii pF6 = 호기성 Nocardioides sp. OS4와 탈질 Azoarcus evansii pF6를 이용한 피리딘의 생물학적 분해

Abstract

A pyridine-degrading bacterial strain was isolated from the oxic zone of spent shale column. The microorganism was an aerobic and pleomorphic coryneform bacterium with LL-diaminopimelic acid in the cell wall. On the basis of its phylogenetic and chemotaxonomic characteristics, the strain was identified as Nocardioides sp. OS4. The pyridine was completely degraded and the growth yield was 0.30g cellㆍg$pyridine^{-1}$. This strain also degraded some compounds of the basic fraction of retort water and various other aromatic compounds. It was found that the total organic carbon in retort water could be decreased remarkably by inoculation of the strain. These results imply that microorganisms have significant role in the removal of organic pollutants by spent shale column and this strain could be used at the retort water-contaminated sites. The pathway of the pyridine degradation was investigated in the aerobic Nocardioides sp. OS4 and denitrifying Azoarcus evansii pF6. Hydroxy-intermediates apparently were not involved in pyridine metabolism by these strains. Pyridine induction of NAD-linked glutaric dialdehyde dehydrogenase and isocitrate lyase suggest that Azoarcus evansii pF6 used the N-C2 ring cleavage pathway to degrade pyridine. In case of Nocardioides sp. OS4, pyridine didn``t induced the glutarate-dialdehyde dehydrogenase, isocitratase, NAD-linked succinate-semialdehyde dehydrogenase, and formamidase. The results suggest that that the system for the metabolism of pyridine by Nocardioides sp. OS4 may not use the C2-C3 or N-C2 ring cleavage. In order to elucidate tolerance of the cells, fatty acid composition of the cells grown in the presence of pyridine was examined. When pyridine was used as a sole inhibitory substrate, the fatty acid composition of Nocardioides sp. OS4 was quite different from that in other readily available substrates. When compared with the fatty acid composition in a complex medium, the proportion of isopalmitic acid drastically ...