Solid-state CP/MAS ¹³C NMR analysis of bacterial and fungal cultures isolated from a soil incubated fith glucose

Abstract

Bacteria and fungi were isolated from a sample of the Meadows fine sandy loam, an Alfisol, and selectively cultured in nutrient solutions at 20°C for 5 days. The bacteria and fungi were collected, washed with deionized water, freeze dried and analysed using conventional and dipolar dephased solid state CP/MAS 13C n.m.r. spectroscopy. To obtain a quantitative estimate of the chemical composition of the bacterial and fungal carbon, a recycle delay of 3.0 s was required to allow complete relaxation between pulses, and the acquired signal intensities had to be corrected for the amount of signal relaxation which occurred during the contact time (i.e. T1pH effects). The bacterial materials contained more alkyl and carboxyl carbon but less O-alkyl and acetal carbon than the fungal materials. Comparison of the composition of the bacterial and fungal carbon with that of the native and residual substrate carbon contained in the clay and light fraction of a sample of Meadows fine sandy loam incubated with 13C-glucose indicated that the soil microbial population was dominated by fungi.