Characterization of diverse heterocyclic amine-degrading denitrifying bacteria from various environments.
Although, there have been many published bacterial strains aerobically degrading the heterocyclic amine compounds, only one strain to date has been reported to degrade pyrrolidine under denitrifying conditions. In this study, denitrifying bacteria degrading pyrrolidine and piperidine were isolated from diverse geological and ecological origins through selective enrichment procedures. Based on the comparative sequence results of 16S rRNA genes, 30 heterocyclic amine-degrading isolates were grouped into ten distinct phylotypes belonging to the genera Thauera, Castellaniella, Rhizobium, or Paracoccus of the phylum Proteobacteria. The representative isolates of individual phylotypes were characterized by phylogenetic, phenotypic and chemotaxonomical traits, and dissimilatory nitrite reductase gene (nirK and nirS). All isolates completely degraded pyrrolidine and piperidine under both aerobic and anaerobic conditions. The anaerobic degradations were coupled to nitrate reduction. A metabolic pathway for the anaerobic degradation of pyrrolidine was proposed on the basis of enzyme activities implicated in pyrrolidine metabolism from three isolates. The three key pyrrolidine-metabolizing enzymes pyrrolidine dehydrogenase, gamma-aminobutyrate/alpha-ketoglutarate aminotransferase, and succinic semialdehyde dehydrogenase, were induced by heterocyclic amines under denitrifying conditions. They were also induced in cells grown aerobically on heterocyclic amines, suggesting that the anaerobic degradation of pyrrolidine shares the pathway with aerobic degradation.
Bae
Hee-Sung
HS
Department of Biological Sciences, Korean Advanced Institute of Science of Technology (KAIST), Yuseong-gu, Daejeon, South Korea. hsbae@lsu.edu
Im
Wan-Taek
WT
Suwa
Yuichi
Y
Lee
James M
JM
Lee
Sung-Taik
ST
Chang
Young-Keun
YK
D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D020459:Genes, rRNA; D009566:Nitrates / Q000378:metabolism*; D009572:Nitrite Reductases / Q000235:genetics; D010641:Phenotype; D010802:Phylogeny; D010880:Piperidines / Q000378:metabolism*; D020560:Proteobacteria / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D011759:Pyrrolidines / Q000378:metabolism*; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics
D009566:Nitrates; D010880:Piperidines; D011759:Pyrrolidines; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; C032727:piperidine; D009572:Nitrite Reductases; C032519:pyrrolidine