Photosynthetic bacteria are microorganisms that can convert light energy into chemical energy through the process of photosynthesis. Unlike plants, they do not have chloroplasts; instead, they contain pigments like bacteriochlorophyll, which allows them to capture sunlight. These bacteria play a crucial role in ecosystems by producing organic compounds and oxygen, contributing to the overall energy flow. There are two main types of photosynthetic bacteria: purple bacteria and green bacteria. Purple bacteria typically thrive in aquatic environments, while green bacteria are often found in anaerobic conditions. Both types are essential for nutrient cycling and can be used in various biotechnological applications, such as biofuels and wastewater treatment.