Final answer:
Bacterial cells convert environmental DNA into single-stranded form to prevent its degradation by nucleases, enabling the incorporation of new genetic material into the cell's genome.
Step-by-step explanation:
Why does a bacterial cell make environmental DNA single-stranded?
After a bacterial cell takes up environmental DNA, it converts this DNA into a single-stranded form. This process, known as transformation, is a mechanism of horizontal gene transfer. Typically, double-stranded foreign DNA within cells is susceptible to degradation by nucleases, which serve as a defense against viral infection. However, single-stranded DNA is less likely to be destroyed by these nucleases. Therefore, by converting the double-stranded DNA to a single strand, the bacterium enhances the survival of the genetic material within the cell. The single-stranded DNA can recombine into the bacterial genome, potentially providing the bacterium with new phenotypic properties, such as antibiotic resistance or virulence factors.
A bacterium may become pathogenic if it incorporates a toxin gene from another pathogenic bacterium. Plasmid DNA, which are small loops of DNA that can confer new properties to the cell, may also be taken up by bacteria through transformation. This ability to acquire and incorporate genetic elements crucially impacts microbial communities, providing advantages in survival and adaptation.