Signature fatty acids provide tools for determination of the distribution and interactions of mycorrhizal fungi in soil

Abstract

Mycorrhizal fungi form extensive mycelia in soil and play significant roles in most soil ecosystems. The estimation of their biomasses is thus of importance in order to understand their possible role in soil nutrient processes. For arbuscular mycorrhizal (AM) fungi the signature fatty acid 16:1ω5 provides a new and promising tool for the estimation of AM fungal biomass in soil and roots. For ectomycorrhizal fungi 18:2ω6,9 dominates among the fatty acids and can be used as an indicator of mycelial biomass of these fungi in soil in experimental systems. In biomass estimation primarily the phospholipid fatty acids (PLFAs) are suitable. Through the use of specific PLFAs it is possible to study interactions between mycorrhizal mycelia and bacteria in soil as well as between AM fungal mycelia and mycelia of saprophytic and parasitic fungi in soil and in roots. AM fungi, in particular, store a large proportion of their energy as lipids and by using the signature fatty acids it is possible to determine the relation between membrane and storage lipids, which could be an indication of energy storage levels. Various aspects of how the fatty acid signatures can be used for studies related to questions of biomass distribution and nutritional status of mycorrhizal fungi are discussed.

Organic matter dynamics along a salinity gradient in Siberian steppe soils

“…We applied a principal component analysis (PCA) to the relative distribution of all 17 PLFAs to identify clusters of correlated PLFAs, which presumably derive from identical microbial functional groups. The assignment of individual PLFAs to certain microbial groups based on the PCA was in agreement with the literature (Frostegård et al, 2011;Olsson, 1999;Ruess and Chamberlain, 2010;Zelles, 1999). Thus, the following PLFAs were used to distinguish functional microbial groups: 18 : 2ω6,9 and 18 : 1ω9c as markers for saprotrophic fungi (SapFungi), 16 : 1ω5c to identify arbuscular mycorrhizal fungi (AMF), i15 : 0, a15 : 0, i16 : 0, i17 : 0, and a17 : 0 were related to gram-positive bacteria, 10Me16 : 0 characterized actinomycetes (Actino), 16 : 1ω7c and 18 : 1ω7c identified gram-negative bacteria, and 14 : 0, 15 : 0, 17 : 0, and 18 : 0 related to nonspecific bacteria (NonspBact).…”

“…These studies suggest that the content of water-soluble salts in the soils of the studied transect is large enough to provoke the flocculation of OM and mineral components and the formation of stable mineral-organic associations. Moreover, Nelson and Oades (1998) showed that the solubility of Na + -coated OM is larger than that of OM coated with Ca 2+ . Thus, particularly in the non-sodic Solonchaks where Ca 2+ is a dominant cation in the soil solution (Fig.…”

“…Both parameters exert a decisive impact on the dispersion of clay and OM. Numerous studies showed that the desorption of OM from clay particles increases with SAR, while a rise in EC or the proportion of divalent cations counterbalances the dispersing effect of Na + by inducing flocculation (Mavi et al, 2012;Nelson and Oades, 1998;Setia et al, 2014). High soil pH is likewise assumed to increase losses of organic C (OC) through solubilization of OM (Pathak and Rao, 1998).…”

Changes in Ecosystem Carbon Following Afforestation of Native Sand Prairie

“…Recovery of fatty acids from microbial cells is higher with this procedure compared with other methods since it includes more than just phospholipids and avoids extraction efficiency issues with removal of intact phospholipids from microbial cells within the soil. This method also gives a more complete picture of fungal fatty acids, particularly those from arbuscular mycorrhizal fungi (Olsson, 1999;Grigera et al, 2007). Fatty acid methyl esters were assayed by gas chromatography using an internal standard, methyl-nonadecanoate (0.05 mg mL -1 ), and converted to nmol FAME g -1 soil (Grigera et al, 2006).…”

Increases in Soil Aggregation Following Phosphorus Additions in a Tropical Premontane Forest are Not Driven by Root and Arbuscular Mycorrhizal Fungal Abundances

“…The neutral lipid fatty acid (NLFA) 16:1ω5 has been shown to be a good signature of extra-radical AMF (Olsson et al, 1997;Olsson, 1999;Olsson and Johansen, 2000). Therefore, we extracted neutral lipid fatty acids from 5.0 g of soil following the protocol of van Aarle and Olsson (2003).…”