Soil degradation in sub-Saharan Africa can lead to the loss of nutrients as well as the changes in diverse soil microbes which have many life-supporting functions for the growth of plants. However, the influence of soil degradation due to the cultivation on soil microbes is unclear in this area. Understanding the changes in microbial community structures is important to evaluate the human impacts. We collected soils from three neighbouring natural and farm sites in Zambia, sub-Saharan Africa. After the measurement of basic soil properties, DNA was extracted from them and analyzed with 16S rRNA sequencing. Then, Tax4Fun in R software was used to investigate life-supporting functions of the bacterial communities. Overall, 196-1066 OTUs were found in 54 soil samples (97% similarity). Shannon diversity indices in natural soils were lower than those in farm soils though the natural ones were rich in carbon and nitrogen contents. The increased bacterial diversities in farms tended to diversify nitrogen-cycle-related genes, indicating the bacteria might have adjusted to the low carbon and nitrogen contents. We may need to dissociate the loss of bacterial functions and the loss of soil carbon and nitrogen, in some areas in sub-Saharan Africa, although we need further investigation.