Brearley Francis Q, Scholes Julie D, Su See Lee
Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK.
Res Microbiol. 2005 Mar;156(2):184-90. doi: 10.1016/j.resmic.2004.09.003. Epub 2004 Dec 10.
It is known that many ectomycorrhizal (EcM) fungi are able to utilise complex organic sources of nitrogen. Two hypotheses were tested using isolates of tropical EcM fungi grown in vitro: (i) EcM fungi isolated from mineral soils of tropical rain forests are less able to utilise organic sources of nitrogen than mineral sources; and (ii) nitrogen isotope discrimination patterns follow those of the nitrogen source utilised. Pisolithus albus and Tomentella sp. represented tropical EcM fungi and they were grown along with Thelephora terrestris. All three species were able to utilise bovine serum albumen as a nitrogen source and P. albus produced the greatest biomass on this source of nitrogen. Nitrate was generally less well utilised than ammonium although all three species were able to grow on this nitrogen source. The nitrogen source which led to the greatest biomass also led to the highest fungal nitrogen concentration in P. albus and Tomentella sp., but not T. terrestris. All three species discriminated against (15)N when grown on BSA and NO(3) but there were interspecific differences in isotope discrimination when grown on NH(4). From a limited number of isolates, it was found that EcM fungi from tropical soils utilise protein nitrogen as well as mineral nitrogen and there can be considerable nitrogen isotope discrimination during the utilisation of all these nitrogen sources.
已知许多外生菌根（EcM）真菌能够利用复杂的有机氮源。使用在体外培养的热带EcM真菌分离物对两个假设进行了测试：（i）从热带雨林矿质土壤中分离出的EcM真菌利用有机氮源的能力低于矿质氮源；（ii）氮同位素分馏模式与所利用的氮源一致。白环柄菇和绒盖牛肝菌属代表热带EcM真菌，它们与土生棱柄盘菌一起培养。所有这三个物种都能够利用牛血清白蛋白作为氮源，白环柄菇在这种氮源上产生的生物量最大。尽管所有这三个物种都能够在这种氮源上生长，但硝酸盐的利用率通常低于铵盐。导致最大生物量的氮源也导致白环柄菇和绒盖牛肝菌属中真菌氮浓度最高，但土生棱柄盘菌并非如此。当在牛血清白蛋白和硝酸盐上生长时，所有这三个物种都对15N有分馏现象，但在铵盐上生长时，同位素分馏存在种间差异。从有限数量的分离物中发现，来自热带土壤的EcM真菌既利用蛋白质氮也利用矿质氮，并且在利用所有这些氮源的过程中可能存在相当大的氮同位素分馏。
