AME 26:195-199 (2001)  -  doi:10.3354/ame026195

ABSTRACT: In an attempt to visualize the polysaccharide capsule of bacterioplankton in a more economic way than transmission electron microscopy offers, we modified a light microscopy method. By using a negative staining technique, bacterial capsules >150 nm in dimension can be enumerated. This method was used to determine the contribution of capsulated bacteria to the total bacterial community in 3 different water masses of the Faroe-Shetland Channel (North Atlantic), and the open and the coastal North Sea. The contribution of capsulated bacteria to the total bacterioplankton community, integrated over the water column, was 7% in the North Atlantic, and 17 and 27% in the open and the coastal North Sea, respectively. Generally, a strong decline with depth in the contribution of capsulated bacteria to the total number of bacteria was found for the water column of the North Atlantic. There, the contribution of capsulated bacteria decreased from about 30% at 10 m depth to 6% at 100 m depth and ranging from 0.4 to 4% between 100 and 1300 m depths.

KEY WORDS: Bacteria · Capsule · Polysaccharide