Fatty Acid Biomarkers of Symbionts and Unusual Inhibition of Tetracosapolyenoic Acid Biosynthesis in Corals (Octocorallia)

Seven zooxanthellae-free species of octocorals (the genera Acanthogorgia, Acabaria, Chironephthya, Echinogorgia, Menella, Ellisella, and Bebryce) and two zooxanthellate octocorals (the genera Paralemnalia and Rumphella) were examined to elucidate their fatty acid (FA) composition. Arachidonic (about 40% of the total FA) and palmitic acids were predominant in all the species studied. Seven furan FA (F-acids) (up to 9.7%) were identified in the azooxanthellate octocorals. The main F-acids were 14,17-epoxy-15-methyldocosa-14,16-dienoic and 14,17-epoxy-15,16-dimethyldocosa-14,16-dienoic acids. In all specimens of Bebryce studeri, C_25–28 demospongic FA (about 20%) were identified. These FA reflect the presence of a symbiotic sponge in B. studeri and can be used as the specific markers for other corals. A significant difference (P < 0.01) between azooxanthellate and zooxanthellate corals was found for odd-chain and methyl-branched saturated FA, 18:1n-7, and 7-Me-16:1n-10; that indicated the presence of an advanced bacterial community in azooxanthellate corals. The zooxanthellate species were distinguished by significant amounts of 18:3n-6, 18:4n-3, and 16:2n-7 acids, which are proposed as the markers of zooxanthellae in soft corals. Contrary to the normal level of 24:5n-6 (9.4%) and 22:4n-6 (0.6%), unexpected low concentrations of 24:5n-6 (0.4%) accompanied by a high content of 22:4n-6 (up to 11.9%) were detected in some specimens. The presence of an unknown factor in octocorals, specific for n-6 PUFA, which inhibited elongation of 22:4n-6 to 24:4n-6, is conjectured.     

Improvement of growth of Eucalyptus globulus and soil biological parameters by amendment with sewage sludge and inoculation with arbuscular mycorrhizal and saprobe fungi

Sewage sludge is widely used as an organic soil amendment to improve soil fertility. We investigated the effects of sewage sludge (SS) application on certain biological parameters of Eucalyptus globulus Labill. The plant was either uninoculated or inoculated with saprobe fungi (Coriolopsis rigida and Trichoderma harzianum) or arbuscular mycorrhizal (AM) fungi (Glomus deserticola and Gigaspora rosea). Sewage sludge was applied to the surface of experimental plots at rates of 0, 2, 4, 6 and 8 g 100 g^− 1 of soil. Inoculation with both AM and saprobe fungi in the presence of SS was essential for the promotion of plant growth. The AM, saprobe fungi and SS significantly increased dry shoot weight. The AM fungi induced a significant increase in Fluorescein diacetate (FDA) activity but did not increase β-glucosidase activity. Addition of SS to AM-inoculated soil did not affect either FDA or α-glucosidase activities in plants from soil that was either uninoculated or inoculated with the saprobe fungi. SS increased β-glucosidase activity when it was applied at 4 g 100 g^− 1. SS negatively affected AM colonization as well as the mycelium SDH activity for both mycorrhizal fungi. SS increased Eucalyptus shoot biomass and enhanced its nutrient status. Inoculation of the soil with G. deserticola stimulated significant E. globulus growth and increases in shoot tissue content of N, P, K, Ca, Mg and Fe. Dual inoculation with G. deserticola and either of the saprobe fungi had positive effects on K, Ca, Mg and Fe contents. The application of 8 g 100 g^− 1 of SS had no positive effects on plant nutrition. The experimental setup provided a suitable tool for evaluating SS in combination with saprobe and AM fungi as a biological fertiliser for its beneficial effects on E. globulus plant growth.