Detonation‐produced nanodiamond, both as a powder (with adsorbed water) and especially when suspended in an aqueous colloid, can support the growth (both aerobic and anaerobic) of bacteria and fungi. These were isolated and identified by microbiological methods, optical and electron microscopy, as species of Penicillium, Purpureocillium, Beaveria, Trichoderma and Aspergillus genera. The C : N molar ratio of the developing fibers (comprising fungal mycelia with attached bacteria and entrapped nanodiamond) decreased from 25 to 11 between the 1st and 10th week of incubation (cf. 40 in initial nanodiamond, 4.6 typical for bacteria and 8.3 for fungi), and from 4 to <1 after the 12th week, as the lysis of microorganisms releases carbon as CO2 and nitrogen as NH4+ or NO3−. The nitrogen content of the colloid increased by an order of magnitude and more, due to fixation of N2 by nanodiamond under ambient conditions.The process requires water but not necessarily oxygen present.