The colorless part of the cell surrounded by plasma membrane is called cytoplasm. The parts of cytoplasm are:
(i) Ribosomes: 70S ribosomes are located freely in the cytoplasm of the cell. It is made up of proteins and RNA. It contains 30-50% protein and 50-70% RNA. Each bacterium contains 10,000-20,000 ribosomes. It synthesizes proteins for cells.
(ii) Chromatophore : Cytoplasm of bacteria contains hollow spherical chromatophore. It contains bacteriochlorophyll. It helps in photosynthesis.
(iii) Volutin : The cytoplasm of young bacterial cells contains small granular volutin. With the increase of age, it turns into cell cavity. It stores food for cells and transports phosphate.
(iv) Cell cavity: Cell cytoplasm contains small cell cavities. It is filled with cell sap.
(v) Mesosomes : The plasma membrane folds inward to form a sac-like structure. It is called mesosome. Mesosomes are called chondroids. It helps in breathing. It carries out DNA replication and forms the cell wall during cell division. Gram positive bacteria have mesosomes.
(vi) Plasmid: Extra-chromosomal circular double-stranded DNA located in the cytoplasm of the cell is called plasmid. It is self-reproducing. It carries several types of genes. Fertility factor (F-factor), Resistance factor (R-factor), Nitrogen fixing genes (Nif-genes) etc. It acts as a carrier in genetic engineering.