Photosynthetic Bacteria

Photosynthetic bacteria are those bacteria that can prepare their own food by fixing the CO₂ present in the environment. These bacteria can convert light energy into chemical energy and use it for their metabolism.

CO₂ + H₂O ➝ C₆H₁₂O₆ + O₂

Examples:

Cyanobacteria

Why these bacteria are photosynthetic?

These bacteria contain chlorophyll pigments that are called as bacteriochlorophyll. These bacteriochlorophyll absorbs the longer wavelength light and converts it into chemical energy. These bacteria use oxygen to accept the free electron from the electron transport chain.

Classification:

There are two types of photosynthetic bacteria.

Oxygenic bacteria:

These bacteria use oxygen to accept the electron from ETC (Electron Transport Chain). These bacteria live in aerobic condition and release oxygen in the environment. Cyanobacteria are the oxygenic photosynthetic bacteria that prepare their food from the environment.

They are blue-green in colour and lives in water and moist places. They usually form a green layer around the water bodies.

An-oxygenic bacteria:

These bacteria don’t use oxygen for the acceptance of electron. These bacteria allow sulfur to accept the electron in the end of ETC. These bacteria release sulfur in the environment. They usually live in anaerobic conditions. Purple sulfur bacteria are the an-oxygenic bacteria that are present in anaerobic condition.

CO₂ + H₂S  ➝ C₆H₁₂O₆ + S

These bacteria are usually purple and green in colour. These bacteria are present in the soil.

Importance:

These bacteria are very important as

• They produce free oxygen that is present in the environment. This oxygen is readily available for human beings.
• The an-oxygenic bacteria consume the hydrogen sulfide from the soil and secrete sulfur into the environment that is used by plants.
• They can be used as good bio-fertilizer as they increase the fertility of the soil.