Viability of culturable soil microorganisms during freeze storage

Abstract

Soil microbial populations are preferably studied by analysing fresh soil samples, but this may not always be feasible in field conditions. We therefore studied the effect of freeze storage (at -20°C, up to 44 months) on soil culturable microorganism viability. Most culturable soil bacteria were not affected by the prolonged freeze storage and freeze-thaw stress, but the viability of the fungus and sporulating bacillus populations significantly decreased after 8-12 months frozen. These changes did not, however, significantly affect the total culturable microorganism count, biodiversity index, or differences in biodiversity between soils. Therefore, freeze storage for up to 8 months may be allowed for analyses of culturable microbial population biodiversity, and longer times may be reasonably acceptable.