Alteration of Carbon Isotope Ratios by Eight Ustilago Species on Defined Media

Will, Oscar H.; Tieszen, Larry L.; Gerlach, Tamara; Kellen, Mark

doi:10.1086/337761

Cited by 8 publications

(12 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similarly, when ecosystems are transformed from C 3 -dominant vegetation to C 4 -dominant vegetation, the relative abundance of stable C isotopes in the soil is roughly maintained and is similar to that in the original vegetation, suggesting that only minor changes due to microbial transformations occur (5, 43). Nevertheless, more detailed measurements of C isotopic distributions have revealed patterns that suggest that significant discrimination by microbes occurs during soil formation; these patterns include the consistent enrichment of 13 C often observed with increasing depth in soil profiles (34) and the relative enrichment observed in the CO 2 produced from soil respiration compared with canopy measurements (12, 13).More directly, recent studies of fungi indicate that significant isotopic effects can be apparent when fungal tissues are compared to their presumed plant substrates (20,22,24,25,27,44,45), and a consistent difference in isotopic fractionation between mycorrhizal and saprotrophic basidiomycetes has also been found in the field (22,25,27). Given the importance of fungi in terrestrial ecosystems (15,35,40), the implications of isotopic discrimination associated with fungal C processing are of great consequence for isotope-based nutrient cycling models.…”

mentioning

confidence: 98%

“…Given the importance of fungi in terrestrial ecosystems (15,35,40), the implications of isotopic discrimination associated with fungal C processing are of great consequence for isotope-based nutrient cycling models. The question remains as to whether fractionation patterns observed in the field result from intrinsic fungal processing or are due to substrate effects (20,44,45).In this work we documented intrinsically determined isotopic fractionation in fungi and studied the basis for a newly discovered isotopic discrimination mechanism that is sensitive to differences in C 3 -and C 4 -derived sugars during their catabolism. We concentrated on three basidiomycete species chosen for their contrasting fractionation patterns and ecophysiological roles in pine-dominated ecosystems.…”

mentioning

confidence: 99%

“…More directly, recent studies of fungi indicate that significant isotopic effects can be apparent when fungal tissues are compared to their presumed plant substrates (20,22,24,25,27,44,45), and a consistent difference in isotopic fractionation between mycorrhizal and saprotrophic basidiomycetes has also been found in the field (22,25,27). Given the importance of fungi in terrestrial ecosystems (15,35,40), the implications of isotopic discrimination associated with fungal C processing are of great consequence for isotope-based nutrient cycling models.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Differential C Isotope Discrimination by Fungi during Decomposition of C₃- and C₄-Derived Sucrose

Henn

Chapela

2000

Appl Environ Microbiol

View full text Add to dashboard Cite

Stable isotope analysis is a major tool used in ecosystem studies to establish pathways and rates of C exchange between various ecosystem components. Little is known about isotopic effects of many such components, especially microbes. Here we report on the discovery of an unexpected pattern of C isotopic discrimination by basidiomycete fungi with far-reaching consequences for our understanding of isotopic processing in ecosystems where these microbes mediate material transfers across trophic levels. We measured fractionation effects on three ecologically relevant basidiomycete species under controlled laboratory conditions. Sucrose derived from C 3 and C 4 plants is fractionated differentially by these microbes in a taxon-specific manner. The differentiation between mycorrhizal and saprotrophic fungi observed in the field by others is not explained by intrinsic discrimination patterns. Fractionation occurs during sugar uptake and is sensitive to the nonrandom distribution of stable isotopes in the sucrose molecule. The balance between respiratory physiology and fermentative physiology modulates the degree of fractionation. These discoveries disprove the assumption that fungal C processing does not significantly alter the distribution of stable C isotopes and provide the basis for a reevaluation of ecosystem models based on isotopic evidence that involve C transfer across microbial interfaces. We provide a mechanism to account for the observed differential discrimination effects.In the last decade, the analysis of stable C isotopes has emerged as a major tool to trace and quantify C transfers across trophic levels in a variety of ecosystems (10, 21, 28). Two major premises concerning stable C isotopes in the environment are frequently assumed. First, it is known that the mechanism of CO 2 uptake from the atmosphere and incorporation of CO 2 into plant organic matter through photosynthesis result in characteristic isotopic ratios, which distinguish C 3 plants from C 4 plants (37). Second, it is frequently assumed that the effects of other biological transformations on the natural distribution of stable C isotopes are relatively insignificant compared to the photosynthesis-determined isotopic discrimination (17,18,41,42). These two assumptions are at the core of isotope-based models of ecosystem function and global nutrient cycling.While much refinement in knowledge has occurred with respect to photosynthetic pathways under various ecological conditions (11, 37), other equally important processes, such as decomposition, have remained mostly unexplored with respect to their isotopic discrimination effects, although they are critical for understanding ecosystem C flows. Previous studies have shown that microbial metabolic processes can be associated with characteristic fractionation patterns at the subcellular scale (1, 7), but the discrimination effects are often masked at the whole-organism level, resulting in the assumption that, overall, C isotopic discrimination due to microbial processing is not significant (Ͻ1...

show abstract

mentioning

confidence: 98%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Differential C Isotope Discrimination by Fungi during Decomposition of C₃- and C₄-Derived Sucrose

Henn

Chapela

2000

Appl Environ Microbiol

View full text Add to dashboard Cite

show abstract

“…Nevertheless, the effect of fungal interfaces on isotopic transformations in terrestrial ecosystems is poorly understood. Recent studies indicate that fractionation of stable isotopes of C by fungi is common in nature (8,12,14,18) and in culture (11,30,31). Since this fractionation can result in an alteration of isotope distributions in microbially respired CO 2 and in organic matter that has accumulated in the ecosystem (11), fractionation effects due to fungal processing can be expected to be significant at an ecosystem level.…”

mentioning

confidence: 99%

Growth-Dependent Stable Carbon Isotope Fractionation by Basidiomycete Fungi: δ ¹³ C Pattern and Physiological Process

Henn

Gleixner

Chapela

2002

Appl Environ Microbiol

View full text Add to dashboard Cite

We grew 11 basidiomycetes in axenic culture to characterize their physiological capacities to fractionate stable C isotopes. Generally, ␦ 13 C values of the fungal biomass were (i) enriched in 13 C relative to the growth medium, (ii) variable among the isolates, and (iii) dependent on the growth rate and growth stage of the fungi. We found a multiphasic dynamic of fractionation for Cryptoporus volvatus and Marasmius androsaceus during various growth stages. The first phase, P1, corresponded to the exponential growth stage and was characterized by an increasing enrichment in 13 C content of the fungal biomass relative to the growth medium ranging between 4.6 and 6.9‰. The second phase, P2, exhibited a continual depletion in 13 C of the fungal biomass, with the ␦ 13 C values of the fungal biomass asymptotically returning to the ␦ 13 C value of the growth medium at inoculation. The expression of the various fractionation phases was dependent on the amount of low-concentration micronutrients and growth factors added to the growth medium. The onset of P2 occurred at reduced concentrations of these elements. All of the sugars in the growth medium (sucrose, maltose, and glucose) were utilized for growth, indicating that the observed fractionation was not an artifact derived from the preferential use of 13 C-rich maltose, which was found at low concentrations in the growth medium. In this study, we establish a framework with which to explore the impact of physiological fractionations by fungal interfaces on natural distributions of stable C isotopes.Fungi form a ubiquitous interface mediating nutrient movements in terrestrial ecosystems (5,23,24,28). In this role, fungi should be expected to affect the natural distribution of stable C isotopes. Nevertheless, the effect of fungal interfaces on isotopic transformations in terrestrial ecosystems is poorly understood. Recent studies indicate that fractionation of stable isotopes of C by fungi is common in nature (8,12,14,18) and in culture (11,30,31). Since this fractionation can result in an alteration of isotope distributions in microbially respired CO 2 and in organic matter that has accumulated in the ecosystem (11), fractionation effects due to fungal processing can be expected to be significant at an ecosystem level.Research on forest fungi across the Northern Hemisphere (6, 7, 12-15, 18, 29) has consistently suggested an isotopic fractionation pattern in which ectomycorrhizal (EM) and saprotrophic (SAP) sporocarps (mushrooms) display, on average, characteristically different isotopic signatures for both C and N. This "EM/SAP divide" (12) is predominantly determined by substrate effects (7, 12), but there is also evidence of an additional physiological component that appears to be insensitive to these substrate effects or to differences between EM and SAP functional groups (12).Here we investigate the dynamics and determinants of C isotopic fractionation for 11 basidiomycetes that represent EM and SAP fungi under controlled substrate conditions. For two representativ...

show abstract

Assessing Functions of Soil Microbes with Isotopic Measurements

Hobbie

Soil Biology

View full text Add to dashboard Cite

Alteration of Carbon Isotope Ratios by Eight Ustilago Species on Defined Media

Cited by 8 publications

References 21 publications

Differential C Isotope Discrimination by Fungi during Decomposition of C₃- and C₄-Derived Sucrose

Differential C Isotope Discrimination by Fungi during Decomposition of C₃- and C₄-Derived Sucrose

Growth-Dependent Stable Carbon Isotope Fractionation by Basidiomycete Fungi: δ ¹³ C Pattern and Physiological Process

Assessing Functions of Soil Microbes with Isotopic Measurements

Contact Info

Product

Resources

About

Alteration of Carbon Isotope Ratios by Eight Ustilago Species on Defined Media

Cited by 8 publications

References 21 publications

Differential C Isotope Discrimination by Fungi during Decomposition of C3- and C4-Derived Sucrose

Differential C Isotope Discrimination by Fungi during Decomposition of C3- and C4-Derived Sucrose

Growth-Dependent Stable Carbon Isotope Fractionation by Basidiomycete Fungi: δ 13 C Pattern and Physiological Process

Assessing Functions of Soil Microbes with Isotopic Measurements

Contact Info

Product

Resources

About

Differential C Isotope Discrimination by Fungi during Decomposition of C₃- and C₄-Derived Sucrose

Differential C Isotope Discrimination by Fungi during Decomposition of C₃- and C₄-Derived Sucrose

Growth-Dependent Stable Carbon Isotope Fractionation by Basidiomycete Fungi: δ ¹³ C Pattern and Physiological Process