Bacteria are prokaryotes and their cellular structure is a very simple one. Within the outer cell wall is a watery interior called cytoplasm. Ribosomes in the cytoplasm make all the protein in the bacterial cell and are regulated by mRNA.
The DNA in bacteria is not enclosed within a nucleus, instead it floats freely in the cytoplasm. The DNA has a double strand structure and in a majority of bacteria makes up only one chromosome. The complexity of the number of base pairs in the chromosome can vary from 100,000 in some to over 10 million in others.
The DNA is transcribed into RNA. The structure of base pairs in the DNA in a bacterium defines the mRNA which moving further in the chain defines the protein sequences. All activity in the cell is controlled by regulating the synthesis of proteins via the mRNA.
The control center for a bacterial cell is it's nuclear structure. It doesn't have a nucleus, which is the control center of plant and animal cells, so it uses the DNA. Within the DNA is genetic material that is duplicated and passes to daughter cells during reproduction.