Most microbes divide asexually but they have sex pilus which they use to transfer their genes to other bacteria. This process is called horizontal gene transfer(HGT). This is very important for evolution of any bacteria.
For example most of the antibiotic resistant genes are transferred by this mechanism and these bacteria survive even when antibiotics are used against them.
In this case soil microbe a must undergone the process of transformation with multiple bacteria species which is common in soil bacteria therefore after analyses long stretches of genes from multiple species of other soil microbial species are discovered.
As most microbes reproduce asexually, "species" are defined by differences in their DNA sequences. when the genome of soil microbe a is analyzed, long stretches of genes from multiple species of other soil microbial species are discovered. This indicates that the microbes present in the soil underwent transformation and transfection. Transformation, shown in the image, is the process of the prokaryotic nucleus taking up the foreign DNA from other microbes present in the environment. Tranfection is like transformation but for the eukaryotic cells.
