Glacial lakes cover large areas of northern Europe and North America. These freshwater systems represent important habitats accommodating diverse microbial communities. Here, 27 lakes in northern Germany, Poland and Finland were surveyed for the presence of aerobic anoxygenic phototrophic (AAP) bacteria during the summer seasons of 2008 and 2009. Using infrared epifluorescence microscopy, AAP bacteria were found to represent from 2 to 12% of total bacteria in surface layers of the studied lakes. The AAP abundance was correlated with total bacterial numbers, total phosphorus and chlorophyll concentration. The size fractionation analyses indicated that a significant portion of AAP cells was attached to particles. Our findings suggest that AAP bacteria represent a significant component of the microbial community in the studied lakes. KEY WORDS: Lakes · Aerobic photosynthetic bacteria · AAP bacteria · Bacteriochlorophyll a · PhotoheterotrophyResale or republication not permitted without written consent of the publisher