Mi, L., Wang, G., Jin, J., Sui, Y., Liu, J. and Liu, X. 2012. Comparison of microbial community structures in four Black soils along a climatic gradient in northeast China. Can. J. Soil Sci. 92: 543–549. Surveys of microorganisms across climatic gradients provide important information about their biodiversity and spatial distribution, which is linked to fundamental ecological functions. The present study investigated the bacterial communities, including total and culturable communities, and fungal communities in Black soils collected from Lishu (lat. 43°20′N, long. 124°28′E), Dehui (lat. 44°12′N, long. 125°33′E), Hailun (lat. 47°26′N, long. 126°38′E) and Beian (lat. 48°17′N, long. 127°15′E) in northeast China. Bacterial and fungal communities were evaluated by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) banding patterns of partial 16S rDNA and fungal rDNA internal transcribed spacer regions (ITS), respectively. Bacterial and fungal diversity, based on the number of DGGE bands, were similar among the locations, but cluster analysis of banding patterns showed distinct microbial communities along the climatic gradient. A closer relationship was found among soil bacterial (total and culturable) and fungal communities in neighboring locations than those at greater distance, which suggested that the spatial distribution of microbial community existed in the Black Soil Zone. Comparison of DGGE profiles among the four locations showed that the changes of fungal community and culturable bacterial community were greater than that of bacterial community, suggesting that fungal community and culturable bacterial community are more suitable to study microbial biogeographic distribution in Black soils.