Cycloclasticus: A Genus of Marine Polycyclic Aromatic Hydrocarbon Degrading Bacteria
Cycloclasticus is a genus of marine bacteria that specializes in the aerobic breakdown of polycyclic aromatic hydrocarbon (PAH) compounds including naphthalene, phenanthrene, and pyrene. This bacterial genus contains a single validly described species, Cy
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K. N. Timmis (ed.), Handbook of Hydrocarbon and Lipid Microbiology, DOI 10.1007/978-3-540-77587-4_128, # Springer-Verlag Berlin Heidelberg, 2010
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Cycloclasticus: A Genus of Marine Polycyclic Aromatic Hydrocarbon Degrading Bacteria
Abstract: Cycloclasticus is a genus of marine bacteria that specializes in the aerobic breakdown of polycyclic aromatic hydrocarbon (PAH) compounds including naphthalene, phenanthrene, and pyrene. This bacterial genus contains a single validly described species, Cycloclasticus pugetii. Cycloclasticus is recognized as the predominant genus of PAH-degrading bacteria in many marine sediments. Cycloclasticus strains are widely distributed in marine sediments in contaminated coastal areas as well as in deep-sea mid-oceanic sediments of the Atlantic and Pacific Oceans.
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Introduction
Cycloclasticus was named as a genus of marine polycyclic aromatic hydrocarbon (PAH)degrading bacteria in the 1990s (Dykesterhouse et al., 1995). The genus name refers to its ‘‘ring-breaking’’ activity, i.e., its ability to degrade the PAH ring to form simpler products. The type species Cycloclasticus pugetii was isolated from Puget Sound in Washington State using enrichment cultures containing naphthalene and phenanthrene as sole added carbon sources. These enrichment cultures were set up as a series of dilutions using marine sediments as inocula that were diluted to extinction. Other isolates of the genus have been reported from other locations. Don Button’s laboratory isolated ‘‘C. oligotrophicus’’ from Alaskan coastal waters (Button et al., 1993). Subsequently, another species, ‘‘Cycloclasticus spirillensis’’ was named for a strain isolated from a marine polychaete burrow in an intertidal mudflat in Maine (Chung and King, 2001).
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Morphology, Phylogeny, and Taxonomy
Cells of C. pugetii, the type species of the genus, are relatively small rod-shaped bacteria that measure about 0.5 mm in diameter by 1–2 mm in length (Dykesterhouse et al., 1995; Geiselbrecht, 2002). Cells stain as gram-negative and are motile by a single polar flagellum. They are members of the Gammaproteobacteria. Their closest relatives phylogenetically are methylotrophic bacteria. The closest match based on 16S rRNA gene sequence was to the methanotroph, Methylomonas methanica, which showed an 89% sequence similarity to C. pugetii. The phylogenetic position of Cycloclasticus relative to other hydrocarbonaclastic Gammaproteobacteria is illustrated in > Chapter 6, Vol. 3, Part 1. C. pugetii uses a variety of PAH compounds including naphthalene, phenanthrene, anthracene and, in addition, biphenyl as sole carbon sources for growth. Cycloclasticus strains are obligately aerobic, oxidase positive, and catalase positive. The two other species of Cycloclasticus have not yet been validly named. ‘‘Cycloclasticus oligotrophicus’’ was not initially known to be a PAH-catabolizing bacterium but instead was recognized as an oligotrophic bacterium that grew on media containing very low concentrations of nutrients in a chemostat. Further work s
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