Ergosterol and fatty acids for biomass estimation of mycorrhizal fungi

Olsson, Pål Axel; Larsson, Lennart; Bago, Berta; Wallander, Håkan; Aarle, Ingrid M. van

doi:10.1046/j.1469-8137.2003.00810.x

Cited by 169 publications

(88 citation statements)

References 32 publications

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“…Ergosterol data were used to calculate the fungal biomass. For zygomycetes, a conversion factor of 3 mg ergosterol per gram biomass can be applied (Olsson et al, 2003). This implies that the amount of 0.5 mg of ergosterol that was measured per gram soil is equivalent to 167 mg Absidia biomass.…”

Section: Discussionmentioning

confidence: 99%

Mycophagous growth of Collimonas bacteria in natural soils, impact on fungal biomass turnover and interactions with mycophagous Trichoderma fungi

et al. 2008

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Bacteria of the genus Collimonas are widely distributed in soils, although at low densities. In the laboratory, they were shown to be mycophagous, that is, they are able to grow at the expense of living hyphae. However, so far the importance of mycophagy for growth and survival of collimonads in natural soil habitats is unknown. Using a Collimonas-specific real-time PCR assay, we show here that the invasion of field soils by fungal hyphae (Absidia sp.) resulted in a short-term, significant increase (average fourfold) of indigenous collimonads. No such responses were observed for other soil bacteria studied (Pseudomonas, Burkholderia, PCR-denaturing gradient gel electrophoresis patterns of total bacteria and Burkholderia). Hence, it appears that the stimulation of growth of Collimonas bacteria by fungal hyphae is not common among other soil bacteria. In the same field soils, Trichoderma, a fungal genus known for mycophagous (mycoparasitic) growth, increased upon introduction of Absidia hyphae. Hence, mycophagous growth by Collimonas and Trichoderma can occur in the same soils. However, in controlled experiments (sand microcosms), collimonads appeared to have a negative effect on mycophagous growth of a Trichoderma strain. The effect of mycophagous growth of collimonads on fungal biomass dynamics was studied in sand microcosms using the same Absidia sp. as a test fungus. The growth of collimonads did not cause a significant reduction in the Absidia biomass. Overall, the study indicates that mycophagous nutrition may be important for collimonads in natural soils, but the impact on fungal biomass turnover is likely to be minor.

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Section: Discussionmentioning

confidence: 99%

Mycophagous growth of Collimonas bacteria in natural soils, impact on fungal biomass turnover and interactions with mycophagous Trichoderma fungi

et al. 2008

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“…If these fungi are an important source of food for collimonads, then this should not be apparent from ergosterol measurements as AM fungi do not contain ergosterol (35).…”

Section: Discussionmentioning

confidence: 99%

Specific Detection and Real-Time PCR Quantification of Potentially Mycophagous Bacteria Belonging to the Genus Collimonas in Different Soil Ecosystems

Höppener-Ogawa

Leveau

Smant

et al. 2007

Appl Environ Microbiol

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The bacterial genus Collimonas has the remarkable characteristic that it grows at the expense of living fungal hyphae under laboratory conditions. Here, we report the first field inventory of the occurrence and abundance of Collimonas in soils (n ‫؍‬ 45) with naturally different fungal densities, which was performed in order to test the null hypothesis that there is a relationship between the presence of Collimonas and fungal biomass. Estimates of fungal densities were based on ergosterol measurements. Each soil was also characterized in terms of its physical and chemical properties and vegetation and management types. Culturable Collimonas was identified in plate-spread soil samples by its ability to clear colloidal chitin, in combination with a Collimonas-specific restriction fragment length polymorphism analysis of 16S rRNA PCR amplified from individual colonies. Using this approach, we found culturable collimonads only in (semi)natural grasslands. A real-time PCR assay for the specific quantification of Collimonas 16S rRNA in total soil DNA was developed. Collimonas was detectable in 80% of the soil samples, with densities up to 10 5 cells g ؊1 (dry weight) soil. The numbers of Collimonas cells per gram of soil were consistently lowest in fungus-poor arable soils and, surprisingly, also in fungus-rich organic layers of forest soils. When all soils were included, no significant correlation was observed between the number of Collimonas cells and ergosterol-based soil fungal biomass. Based on this result, we rejected our null hypothesis, and possible explanations for this were addressed.All described strains of the genus Collimonas are soil bacteria that have the capacity to grow at the expense of intact, living fungal hyphae (9). This property, termed mycophagy (7, 17, 27), has not been well examined for soil bacteria (7). In contrast, fungal mycophagy, which is better known as mycoparasitism, has been studied extensively (5, 6). This is especially the case for the mycoparasitic fungi (e.g., Trichoderma spp.) that are applied as biocontrol agents for plant-pathogenic soil fungi (19,31). Although the mechanisms of mycophagous growth of collimonads have yet to be elucidated, it is known that these bacteria share some properties with mycoparasitic fungi, such as the production of chitinases (9-11, 27), which are thought to be involved in the destabilization of the fungal cell wall (14, 18, 48). However, de Boer et al. reported that for collimonads chitinase activity alone could not explain mycophagous growth (9), and other factors (for example, other lytic enzymes and antibiotics) should be involved (9, 13, 45).Until now, collimonads have been quantified only for the acidic dune grassland soils from which they were originally isolated (11). In these soils, the numbers of collimonads ranged from 10 3 to 10 5 CFU per g (dry weight) soil. Enumeration was based on plate counts of chitin-degrading colonies on agar plates containing colloidal chitin. On such plates, Collimonas strains can be recognized as halo-producin...

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“…Consequently, conclusions concerning the effects of pH on the proportions of fungi and bacteria as decomposers may be compromised if biomarkers that also are indicative of ectomycorrhizae, such as ergosterol and PLFA 18:26,9, are used (35,48), potentially exaggerating the importance of saprotrophic fungi at low pH. The only mycorrhizae potentially present in the Hoosfield acid strip were arbuscular mycorrhizae, which do not contain ergosterol (49), and thus this factor should not have influenced our results.…”

Section: Vol 75 2009 Contrasting Ph Effects On Fungal and Bacterialmentioning

confidence: 93%

Contrasting Soil pH Effects on Fungal and Bacterial Growth Suggest Functional Redundancy in Carbon Mineralization

Rousk

Brookes

Bååth

2009

Appl Environ Microbiol

1,425

710

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The influence of pH on the relative importance of the two principal decomposer groups in soil, fungi and bacteria, was investigated along a continuous soil pH gradient at Hoosfield acid strip at Rothamsted Research in the United Kingdom. This experimental location provides a uniform pH gradient, ranging from pH 8.3 to 4.0, within 180 m in a silty loam soil on which barley has been continuously grown for more than 100 years. We estimated the importance of fungi and bacteria directly by measuring acetate incorporation into ergosterol to measure fungal growth and leucine and thymidine incorporation to measure bacterial growth. The growthbased measurements revealed a fivefold decrease in bacterial growth and a fivefold increase in fungal growth with lower pH. This resulted in an approximately 30-fold increase in fungal importance, as indicated by the fungal growth/bacterial growth ratio, from pH 8.3 to pH 4.5. In contrast, corresponding effects on biomass markers for fungi (ergosterol and phospholipid fatty acid [PLFA] 18:26,9) and bacteria (bacterial PLFAs) showed only a two-to threefold difference in fungal importance in the same pH interval. The shift in fungal and bacterial importance along the pH gradient decreased the total carbon mineralization, measured as basal respiration, by only about one-third, possibly suggesting functional redundancy. Below pH 4.5 there was universal inhibition of all microbial variables, probably derived from increased inhibitory effects due to release of free aluminum or decreasing plant productivity. To investigate decomposer group importance, growth measurements provided significantly increased sensitivity compared with biomass-based measurements.

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Ergosterol and fatty acids for biomass estimation of mycorrhizal fungi

Cited by 169 publications

References 32 publications

Mycophagous growth of Collimonas bacteria in natural soils, impact on fungal biomass turnover and interactions with mycophagous Trichoderma fungi

Mycophagous growth of Collimonas bacteria in natural soils, impact on fungal biomass turnover and interactions with mycophagous Trichoderma fungi

Specific Detection and Real-Time PCR Quantification of Potentially Mycophagous Bacteria Belonging to the Genus Collimonas in Different Soil Ecosystems

Contrasting Soil pH Effects on Fungal and Bacterial Growth Suggest Functional Redundancy in Carbon Mineralization

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