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Apparent contradiction: psychrotolerant bacteria from hydrocarbon-contaminated arctic tundra soils that degrade diterpenoids synthesized by trees.

ABSTRACT: Resin acids are tricyclic terpenoids occurring naturally in trees. We investigated the occurrence of resin acid-degrading bacteria on the Arctic tundra near the northern coast of Ellesmere Island (82 degrees N, 62 degrees W). According to most-probable-number assays, resin acid degraders were abundant (10(3) to 10(4) propagules/g of soil) in hydrocarbon-contaminated soils, but they were undetectable (<3 propagules/g of soil) in pristine soils from the nearby tundra. Plate counts indicated that the contaminated and the pristine soils had similar populations of heterotrophs (10(6) to 10(7) propagules/g of soil). Eleven resin acid-degrading bacteria belonging to four phylogenetically distinct groups were enriched and isolated from the contaminated soils, and representative isolates of each group were further characterized. Strains DhA-91, IpA-92, and IpA-93 are members of the genus Pseudomonas. Strain DhA-95 is a member of the genus Sphingomonas. All four strains are psychrotolerant, with growth temperature ranges of 4 degrees C to 30 degrees C (DhA-91 and DhA-95) or 4 degrees C to 22 degrees C (IpA-92 and IpA-93) and with optimum temperatures of 15 to 22 degrees C. Strains DhA-91 and DhA-95 grew on the abietanes, dehydroabietic and abietic acids, but not on the pimaranes, isopimaric and pimaric acids. Strains IpA-92 and IpA-93 grew on the pimaranes but not the abietanes. All four strains grew on either aliphatic or aromatic hydrocarbons, which is unusual for described resin acid degraders. Eleven mesophilic resin acid degraders did not use hydrocarbons, with the exception of two Mycobacterium sp. strains that used aliphatic hydrocarbons. We conclude that hydrocarbon contamination in Arctic tundra soil indirectly selected for resin acid degraders, selecting for hydrocarbon degraders that coincidentally use resin acids. Psychrotolerant resin acid degraders are likely important in the global carbon cycle and may have applications in biotreatment of pulp and paper mill effluents.

SUBMITTER: Yu Z

PROVIDER: S-EPMC92436 | biostudies-literature | 2000 Dec

REPOSITORIES: biostudies-literature

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Apparent contradiction: psychrotolerant bacteria from hydrocarbon-contaminated arctic tundra soils that degrade diterpenoids synthesized by trees.

Yu Z Z Stewart G R GR Mohn W W WW

Applied and environmental microbiology 20001201 12

Resin acids are tricyclic terpenoids occurring naturally in trees. We investigated the occurrence of resin acid-degrading bacteria on the Arctic tundra near the northern coast of Ellesmere Island (82 degrees N, 62 degrees W). According to most-probable-number assays, resin acid degraders were abundant (10(3) to 10(4) propagules/g of soil) in hydrocarbon-contaminated soils, but they were undetectable (<3 propagules/g of soil) in pristine soils from the nearby tundra. Plate counts indicated that t ...[more]

PMID: 11097882

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Project description:We tested whether post-fire seedling establishment of common boreal tree and expanding shrub species at treeline and in Arctic tundra is facilitated by co-migration of boreal forest mycorrhizal fungi. Wildfires are anticipated to facilitate biome shifts at the forest-tundra ecotone by improving seedbed conditions for recruiting boreal species; at the same time fire alters the composition and availability of mycorrhizal fungi critical to seedling performance. To determine the role of root-associated fungi (RAF) in post-fire seedling recruitment and future biome shifts, we outplanted four dominant boreal tree and shrub species inoculated with one of three treatments at treeline and in tundra: burned boreal forest, unburned boreal forest, or a control treatment of sterilized inoculum. We compared survivorship, growth, and physiological performance of the seedlings in relation to mycorrhizal inoculum treatment and among host species, characterized the RAF communities based on ITS-rDNA sequencing of individual root tips sampled from surviving seedlings, and tested for correlations between RAF composition and the inoculation treatments, host species, and duration of the experiment. We explored correlations between RAF composition and seedling metrics. Both live and sterile autoclaved inoculation treatments had similar effects on seedling survivorship and growth for all species. RAF composition did not vary by treatment, suggesting that most colonization was due to local fungi. However, seedling traits and growth were correlated with RAF species composition, colonization, and the relative abundance of specific RAF taxa. Picea sp. performance in particular showed strong co-variation with RAF metrics. Our results suggest that mycorrhizal co-migration is not a primary limiting factor to boreal seedling recruitment because the experimental provision of inoculum did not affect seedling recruitment; yet, RAF did influence seedling performance, particularly resident RAF at treeline and in tundra, suggesting that mycorrhizal fungi are important to vegetation processes at the treeline-tundra ecotone.

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Apparent contradiction: psychrotolerant bacteria from hydrocarbon-contaminated arctic tundra soils that degrade diterpenoids synthesized by trees.

Publications

Apparent contradiction: psychrotolerant bacteria from hydrocarbon-contaminated arctic tundra soils that degrade diterpenoids synthesized by trees.

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