Abundance and diversity of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)-metabolizing bacteria in UXO-contaminated marine sediments.
Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) is a toxic explosive known to be resistant to biodegradation. In this study, we found that sediment collected from two unexploded ordnance (UXO) disposal sites (UXO-3, UXO-5) and one nearby reference site (midref) in Hawaii contained anaerobic bacteria capable of removing HMX. Two groups of HMX-removing bacteria were found in UXO-5: group I contained aerotolerant anaerobes and microaerophiles, and group II contained facultative anaerobes. In UXO-3 and midref sediments, HMX-metabolizing bacteria were strictly anaerobic (group III and group IV). Using 16S rRNA sequencing, group I was assigned to a novel phylogenetic cluster of Clostridiales, and groups II and III were related to Paenibacillus and Tepidibacter of Firmicutes, respectively. Group IV bacteria were identified as Desulfovibrio of Deltaproteobacteria. Using [UL-(14)C]-HMX, group IV isolates were found to mineralize HMX (26.8% in 308 d) as determined by liberated (14)CO(2), but negligible mineralization was observed in groups I-III. Resting cells of isolates metabolized HMX to N(2)O and HCHO via the intermediary formation of 1-nitroso-octahydro-3,5,7-trinitro-1,3,5,7-tetrazocine together with methylenedinitramine. These experimental findings suggest that HMX biotransformation occurred either via initial denitration followed by ring cleavage or via reduction of one or more of the N-NO(2) group(s) to the corresponding N-NO bond(s) prior to ring cleavage.
Zhao
Jian-Shen
JS
Biotechnology Research Institute, National Research Council of Canada, Montreal, QC, Canada.
Manno
Dominic
D
Hawari
Jalal
J
D001392:Azocines / Q000378:metabolism*; D001421:Bacteria, Anaerobic / Q000145:classification* / Q000302:isolation & purification / Q000378:metabolism*; D001711:Biotransformation; D004783:Environmental Microbiology; D019015:Geologic Sediments / Q000032:analysis / Q000382:microbiology*; D006254:Hawaii; D006256:Hazardous Waste / Q000032:analysis*; D006573:Heterocyclic Compounds, 1-Ring / Q000378:metabolism*; D008386:Marine Biology; D013045:Species Specificity
D001392:Azocines; D006256:Hazardous Waste; D006573:Heterocyclic Compounds, 1-Ring; C007950:octogen