  Bacteria are known to exchange genetic information by horizontal gene
transfer. Since the frequency of homologous recombination depends on the
similarity of recombining segments, several studies examined whether this could
lead to the emergence of subspecies. Most of them used simulations of fixed
size Wright-Fisher populations, in which the genetic drift should be taken into
account. Here, we use non-linear Markov chains to describe a bacterial
population evolving under mutation and recombination processes. We consider a
population as a space of genomes and a probability measure on it. Thus, the
genetic drift is not assumed. We prove that under these conditions the
emergence of subspecies is impossible, so the genetic drift is a necessary
driving force of bacterial speciation.
