Ergosterol and fatty acids for biomass estimation of mycorrhizal fungi

• DOI: 10.1046/j.1469-8137.2003.00810.x
• Publication Date: 2003-06-12T08:19:10Z
• Authors: Pål Axel Olsson; Lennart Larsson; Bert Bago; Håkan Wallander; Ingrid M. Van Aarle
• Keywords: Ergosterol

Ergosterol has recently been used as a biomass indicator to compare the growth of different arbuscular mycorrhizal (AM) fungi (Hart & Reader, 2002a,b). Here, we show that ergosterol is not suitable biochemical marker for estimating AM and comparison between fungal taxa very difficult using any kind currently available marker. Because they are usually degraded rapidly after cell death because membrane area assumed be well correlated with biovolume microbial cells (Tunlid White, 1992), compounds, such sterols, attractive indicators microorganisms in environmental samples. Furthermore, sterols seem represent rather constant part biomass, constituting somewhere 5 15 mg g−1 most groups (Weete Gandhi, 1996). In particular, specific kingdom 1996) occurs mainly constituent. indicate soil (Grant West, 1986; Frostegård Bååth, 1996), pathogenic roots (Bindler et al., 1988), cereal grains (Seitz 1972), saprophytic decaying plant material (Newell 1988) ectomycorrhizal (Salmanowicz Nylund, 1988; Wallander 1997) (Ek 1994; Ekblad 1995). The occurrence generally restricted more advanced taxa, while primitive contain other Thus, it dominating sterol ascomycetes basidiomycetes. By contrast, picture complex within phylum Zygomycota where members Mucorales ergosterol, Mortierella desmosterol, but no 1999). similar way, newly identified Glomeromycota (Schüssler 2001), obligate symbionts forming mycorrhizas (AM), than ergosterol. No was detected several studies which gas chromatography-mass spectrometry (GC-MS) analysis carried out on spores or extraradical mycelium either Glomus Acaulospora species (Beilby Kidby, 1980; Beilby, Nordby 1981; Grandmougin-Ferjani 1999; Fontaine 2001) mature Gigaspora margarita (Grandmougin-Ferjani However, Frey al. (1992, 1994) colonised by intraradices GC-MS, noncolonised roots, proposed content hyphae this fungus 0.063 per g mycelium. More recently, Fujiyoshi (2000) found collected around had 0.63 Nevertheless, neither former two under vitro conditions, thus from contaminating could hardly avoided. slightest contamination may have significant effect results high many fungi. Despite fact shown absent occasions, performance liquid chromatography (HPLC) estimation means comparing various same studies, inocula equalising amount inoculum added. order ascertain whether can estimate at all, investigated monoxenically (in vitro) grown (Petri dish systems carrot root cultures) affect results. We G. developing medium monoxenic cultures (Olsson 2002) Gi. solid (Bago roots. contents both were estimated HPLC separation detection UV detector (Nylund Wallander, commonly method determination indicator. Other retained purified sample only detectable 280 nm conjugated pair double bonds 1992). A developed highly analysed tandem mass (GC-MS-MS; Larsson Saraf, also used. Irrespective method, (Table 1), accordance earlier studies. fatty acid 16 : 1ω5 biomarker 1995; Olsson, 1999), even make comparisons variation genera considerable (Graham use conversion factor each must first obtained, ideally cultures. large compound furthermore exemplified phospholipid (PLFA) 18 2ω6,9 Suillus spp. Paxillus involutus, contained amounts 2). conclude that: cannot glomalean fungi; regardless used, there always taxonomic-based differences signature compound. Ideally, would when aim species. thank Christina Pehrsson Custodia Cano technical assistance, Erland Bååth valuable suggestions.