Bacteriochlorophyll b is a pigment found in certain types of bacteria, particularly in the group known as purple bacteria. It plays a crucial role in photosynthesis, allowing these bacteria to capture light energy and convert it into chemical energy. Bacteriochlorophyll b absorbs light primarily in the infrared region, which is different from the chlorophyll found in plants. This pigment is similar in structure to chlorophyll a, but it has distinct properties that enable it to function effectively in low-light environments. Bacteriochlorophyll b is essential for the survival of these bacteria, as it helps them thrive in various ecological niches, including aquatic and anaerobic environments.