Isotope Bioscience Laboratory, Ghent University, Gent, Belgium.
Rapid Commun Mass Spectrom. 2013 Jun 30;27(12):1367-79. doi: 10.1002/rcm.6586.
Bacteria and fungi are key protagonists of litter degradation in soils. Often they have to share common substrates, which has led to special interactions between both microbial groups. Due to the historical classification of bacteriology and mycology as two separate fields of microbial research, the understanding of their interactions in soils is scares, while it is crucial for a better understanding of nutrient recycling and carbon sequestration in soils. Therefore, a new approach to investigate fungal-bacterial interactions is proposed using stable isotope probing of their amino sugar biomarkers.
An agricultural soil, under different microbial inhibition treatments, was incubated for 21 days with (13)C-labeled plant residues. Residue respiration was determined by measuring the isotopic composition and concentration of the produced CO2, using an isotope ratio mass spectrometer coupled to a trace gas preparation unit. At several time points, amino sugars were extracted, after hydrolysis, from the incubated microcosms. Subsequently, (13)C-isotopic composition and concentration of the individual amino sugars was determined using liquid chromatography/isotope ratio mass spectrometry.
When the bacterial community was inhibited, fungi showed an increased capacity to metabolize added plant residues indicating an antagonistic effect of bacteria towards fungi. Furthermore, the fungal community was able to take benefit of a larger portion of the residue, which indicates that this antagonism was at least partially due to interference competition. On the other hand, the inhibition of the fungal community appeared to have a very negative effect on the capacity of bacteria to metabolize added plant residues. Therefore, the bacterial community could be considered as playing a parasitic type role towards fungi during litter degradation.
This newly developed methodology proved to be very useful for elucidating microbial interactions during plant residue degradation.
细菌和真菌是土壤中 litter 降解的关键主角。它们经常需要共享共同的基质，这导致了这两个微生物群体之间的特殊相互作用。由于细菌学和真菌学在历史上被归类为微生物研究的两个独立领域，因此对它们在土壤中的相互作用的理解很少，而这对于更好地理解土壤中的养分循环和碳固存至关重要。因此，提出了一种使用其氨基糖生物标志物的稳定同位素探测来研究真菌-细菌相互作用的新方法。
在不同的微生物抑制处理下，将农业土壤在含有（13）C 标记的植物残体的情况下培养 21 天。通过测量产生的 CO2 的同位素组成和浓度来确定残留呼吸，使用与痕量气体制备单元耦合的同位素比质谱仪。在几个时间点，从培养的微宇宙中提取水解后的氨基糖。随后，使用液相色谱/同位素比质谱仪测定各个氨基糖的（13）C-同位素组成和浓度。
当细菌群落受到抑制时，真菌显示出代谢添加的植物残体的能力增加，表明细菌对真菌具有拮抗作用。此外，真菌群落能够利用更多的残留物，这表明这种拮抗作用至少部分是由于干扰竞争。另一方面，真菌群落的抑制似乎对细菌代谢添加的植物残体的能力产生了非常负面的影响。因此，细菌群落可以被认为在 litter 降解过程中对真菌起到寄生作用。
这种新开发的方法证明对于阐明植物残体降解过程中的微生物相互作用非常有用。
