Differential growth of the fungus Absidia cylindrospora on ¹³C/¹⁵N‐labelled media

Abstract

Many studies utilise enrichment of stable isotopes as tracers to follow the interactions occurring within soil food webs and methods have been developed to enrich bacteria, soil fauna and plant litter, Here for the first time we attempt to enrich a soil fungus to 99 atom% with (13)C and (15)N stable isotopes. In this study our objectives were to (a) assess whether the saprotrophic zygomycete fungus Absidia cylindrospora could grow on a medium enriched to 99 atom% with (13)C-glucose and (15)N-ammonium chloride, (b) to determine the level of enrichment obtained, and (c) to examine the change in growth rate of this fungus while it was growing on the dually enriched medium. To achieve this, the fungus was grown on agar enriched with (13)C and (15)N to 99 atom% and its growth rate monitored. The results showed that A. cylindrospora would grow on the highly labelled growth medium, but that its rate of growth was affected compared with the rate on either natural abundance media or media highly enriched with a single isotope ((13)C or (15)N). The implications of these results is that although the fungus is able to utilise these heavier isotopes, the biochemical processes involved in growth are affected, and consideration should be given to these differences when using stable isotope tracers in, for example, soil food web studies.

Kinetic 15N-isotope effects on algal growth

“…The evidence is accumulating, however, that KIEs occur in bacteria, fungi, and yeast growing in media enriched with a heavy isotope781516. Recent applications of isotope labeling in metabolomics indicate that many enzymes may be susceptible to these effects5, and microorganism growth changes with increasing proportion of heavy isotopes in the media678.…”

Strategies in relative and absolute quantitative mass spectrometry based proteomics

“…Labeling of single amino acids like arginine and lysine or the replacement of all nitrogens for their heavy 15 N variant during cell growth reduce variances and ensure a precise quantification accuracy as cells are labeled in a very early step in the workflow. However, a limited number of different samples can be compared and metabolic labeling can cause a growth defect in some organisms (Crotty et al, 2011;Filiou et al, 2012). An alternative to this is chemical-based relative quantification such as the isobaric tags for relative and absolute quantitation (iTRAQ) or the tandem mass tags (TMT) that are fused to proteins or peptides after proteolytic digestion.…”

Protozoan Pulses Unveil Their Pivotal Position Within the Soil Food Web

“…Methods have been developed to enrich bacteria [38], fungi [12], earthworms [16], slugs [22] and plant litter [48], to trace the passage of 13 C and 15 N through soil ecosystems and act as an isotopic baseline [49]. Our aim of this study was to extend the methods developed to determine the uptake of bacterially derived C and N into the soil food web [13,38], using protozoa.…”