Use of ergosterol, diaminopimelic acid and glucosamine contents of soils to monitor changes in microbial populations

Abstract

Ergosterol, diaminopimelic acid (DAP) and glucosamine contents were measured in stored (−50 kPa, 25°C), air-dried and substrate-amended (glucose, 1 % w/w) grassland and arable soils. Amounts ranged from 0.2 to 13.9 μg ergosterol. 12 to 311 μg DAP and 420 to 2070 μg glucosamine g −1 soil. The grassland soils had higher amounts of each compound than the arable soil. Generally, storage and air-drying reduced, whilst substrate-amendment increased, amounts of ergosterol and DAP in soil. Changes in amounts of glucosamine were not consistent between soils. Comparison with previously determined biomass contents from these same soil treatments gave ratios of ergosterol-to-mycelial C of 0.002–0.059, DAP-to-bacterial C of 0.3–2.6 and glucosamine-to-biomass C ratios of 2.2–6.7. Ergosterol was linearly correlated with fungal surface area in a common function for two of the soils (0.16 μg ergosterol cm −2 fungi) and DAP with bacterial surface area in each soil (1.6 μg DAP cm −2 bacteria), suggesting that ergosterol and DAP were specific to fungal and bacterial populations respectively. The novel finding that the ergosterol contents of these soils could be accounted for by the amount of fungi present, suggests that soil ergosterol content is a sensitive indicator of changes in fungal populations.