Metal-macrofauna interactions determine microbial community structure and function in copper contaminated sediments

Peer reviewedPublisher PD

Stable Carbon Isotope Ratios of Lipid Biomarkers of Sulfate-Reducing Bacteria

We examined the potential use of natural-abundance stable carbon isotope ratios of lipids for determining substrate usage by sulfate-reducing bacteria (SRB). Four SRB were grown under autotrophic, mixotrophic, or heterotrophic growth conditions, and the δ(13)C values of their individual fatty acids (FA) were determined. The FA were usually (13)C depleted in relation to biomass, with Δδ(13)C((FA − biomass)) of −4 to −17‰; the greatest depletion occurred during heterotrophic growth. The exception was Desulfotomaculum acetoxidans, for which substrate limitation resulted in biomass and FA becoming isotopically heavier than the acetate substrate. The δ(13)C values of FA in Desulfotomaculum acetoxidans varied with the position of the double bond in the monounsaturated C(16) and C(18) FA, with FA becoming progressively more (13)C depleted as the double bond approached the methyl end. Mixotrophic growth of Desulfovibrio desulfuricans resulted in little depletion of the i17:1 biomarker relative to biomass or acetate, whereas growth with lactate resulted in a higher proportion of i17:1 with a greater depletion in (13)C. The relative abundances of 10Me16:0 in Desulfobacter hydrogenophilus and Desulfobacterium autotrophicum were not affected by growth conditions, yet the Δδ(13)C((FA − substrate)) values of 10Me16:0 were considerably greater during autotrophic growth. These experiments indicate that FA δ(13)C values can be useful for interpreting carbon utilization by SRB in natural environments