MUTUALISTIC INTERACTIONS IN THE BIODEGRADATION OF THE BROMINATED FLAME RETARDANTS BIS(BROMOMETHYL)PROPANOL (TBNPA) AND DIBROMONEOPENTYL-GLYCOL (DBNPG)

Noa Balaban 1 Alicia Taylor 2 Anat Bernstein 1 Faina Gelman 3 Zeev Ronen 1
1Environmental Hydrology and Microbiology, Zuckerberg Institute for Water Research, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion, Israel
2Plant & Microbial Biology, University of California, Berkely, California, USA
3Geochemistry, Geological Survey of Israel, Jerusalem, Israel

Brominated organic compounds are widespread pollutants in air, water, soil and sediments. The two brominated flame retardants TBNPA and DBNPG are abundantly found in the groundwater underlying the industrial site Neot Hovav, Israel. An enriched aerobic microbial consortium from the contaminated groundwater with DBNPG was found to successfully degrade both compounds. Nevertheless, a supplement of yeast-extract was found to be essential..

Our work focused on understanding the role of yeast-extract in the biodegradation process, and to isolate a single bacterial strain with the ability to degrade both compounds. From the TBNPA consortium, five isolates were identified: Pseudomonas aeruginosa; Delftia tsuruhatensis; Pseudomonas citronellolis, Microbacterium paraoxydans; and Sphngobacterium siyangense. Four strains were isolated from the DBNPG consortium and identified as: Pseudomonas citronellolis; Gordonia sihwensis; Shinella zoogloeoides; and Microbacterium oxydans. Individual isolates proved unsuccessful in degrading the compounds, with the addition of yeast extract, whereas certain combinations succeeded, albeit at a slower rate than the original consortium. Identification of the two bacterial communities through MiSeq next-generation sequencing revealed the presence of genuses like Paracoccus; Brevundimonas; Pseudomonas; Delftia; Sphingobacterium; Flavobacterium; and Ochrobactrum, suggesting that the enrichments are far more diverse than what was cultured. Haloacid dehalogenase gene, dehI, was detected in the consortium but its role in degradation has not been resolved yet.

The role of yeast-extract and the compounds in biomass growth was also examined. Preliminary experiments show that the addition of only vitamins results in degradation. Resting cultures of both communities (without yeast extract) successfully degraded both compounds rapidly, without additional biomass growth. From these results we conclude that the bacterial communities cannot utilize solely DBNPG and TBNPA for biomass growth, and a supplementation is required.









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