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In this study, we isolated Pseudomonas sp. strain HB01 from a soil sample contaminated with brominated pollutants, and found that it degraded -hexabromocyclododecane (-HBCD). The strain degraded 81% of 1 mM -HBCD within 5 d of culture. Furthermore, it demonstrated biodegradation of structurally related (bromo) alkanes. To the best of our knowledge, this is the first report that outlines the isolation of a bacterial strain that degrades -HBCD.Key words: hexabromocyclododecane; brominated flame retardants; Pseudomonas; biodegradation; -HBCD Brominated flame retardants (BFRs) are routinely added to various consumer products to aid in the reduction of fire-related injury and property damage. Hexabromocyclododecane (HBCD) is an additive BFR present in extruded and expanded polystyrene foams (over 85% of total volume), and it forms a common component of the insulation materials used in the building and upholstery industries.1) Approximately 16,700 tons of HBCD were produced worldwide in 2001, and thus it is now identified as a high productionvolume chemical.2) Recently, a great deal of concern over risk of HBCD has arisen, as monitoring studies have demonstrated that HBCD pollution has expanded, and that residual levels in both the environment and vertebrates at higher levels in the food chain have increased over the last decade.3) Furthermore, several studies suggest toxic effects of HBCD on mammals. 2,3)In 2007, HBCD was defined as a persistent, bioaccumulative, and toxic (PBT) chemical. 4) Despite this, no suitable alternatives are presently available. Moreover, high concentrations of HBCD are also often detected in test samples, including sediment and fish that are collected within close proximity of production and handling sites.5) Thus the development of a microbial degradation system can be a solution to aid in the reduction of HBCD levels released into the environment. In the present study, we aimed to isolate a bacterial strain that is able to degrade HBCD.Technical HBCD consists of a mixture of three diastereomers, , and forms of 1,2,5,6,9,10-HBCD (Fig. 1).6) -HBCD forms the major component of the technical product (75-89%), while -HBCD and -HBCD are present in lower amounts (10-13% and 1-12% respectively).3) Hence we focused on -HBCD in this study. For screening of microorganisms that demonstrate potential -HBCD degradation activity, enrichment culture was performed as described previously, 7) with the exception of using 0.1% -HBCD (a kind gift from Manac Co., Ltd., Fukuyama, Japan) rather than 2,4,6-tribromophenol. For the culture of bacteria, a single colony was first inoculated into 10 ml of medium A (1.0 g of glucose, 5.0 g of polypeptone, 5.0 g of yeast extract, and 10 g of NaCl per liter, pH 7.0) in a 100-ml conical flask, after adding 100 ml of 100 mM -HBCD solution dissolved in dimethyl sulfoxide. The inoculants were then incubated by placing the flasks on a reciprocal shaker and shaking them at 150 rpm at 28 C, and -HBCD was recovered by ether extraction, as described previously.7) For rapid analys...