Answer:
The DNA of the bacteria is present in a circular form which can be housed inside the irregularly shaped nucleoid without membrane. The nucleoid contains other biomolecules like proteins, enzymes and RNA along with DNA.
The bacterial DNA is present in the center of the cell as its central location enables it to reach the to all parts of the cell which could facilitate the cell functions easily. Since DNA controls all the functions of the nucleus, therefore, it's central location is necessary to the cell.