THE PREFERENCE PRIORITY OF Bacillus subtilis IN UPTAKING FREE DNA DURING THE NATURAL TRANSFORMATION

Abstract

Although genetic material is vertically transferred between generations via sexual or asexual reproduction, similarities in some chromosome and gene parts of unrelated organisms provide important clues for another way of transfer. The mobility of genetic information among different organisms, known as horizontal gene transfer (HGT) has immediate or delayed effects on the recipient host. One of the most notable mechanisms of HGT is natural transformation (NT), a process in which cells take free DNA from the extracellular environment and incorporate it into their chromosomes by homologous recombination. NT is widely conserved in many bacterial species as it can promote to spread of resistance genes. Although it is known that many organisms rely on HGT, there is limited information about how they decide which particular genetic material to horizontally transfer. Here, I have investigated the preference priority among different gene sources presented under certain stress conditions for Bacillus subtilis possessing NT ability. To test this, two DNA specimens (E and C) with different sequence contents of the same length were presented to B. subtilis under different stress environments (BK, BC, BE and BCE). The hypothesis was evaluated according to the analysis of the results of colonial formations on selective plates (pE, pC and pCE). The obtained data presented a strong positive correlation that the bacteria have preference priority during NT depending on a stimulator. The tendency of the bacteria to uptake useful DNA fragments in a specific environment can be suggested. For instance, the majority of colonies grow on pE plates rather than the pC and pCE when the transformation media includes erythromycin (Eryt) as an inducer. Although the data significantly overlaps with the idea claiming that the bacteria have a preference priority to uptake free DNAs during NT, further investigations are needed to support the present data and for better understanding of the phenomenon.