| Abstract: | The structural characteristics of well-formed anaerobic granular sludges were examined using scanning electron microscopy and light microscopy of thin sections. Transverse sections were found to consist of randomly orientated filaments of Methanothrix soehngenii. These were tightly packed with little space between the individual filament sheaths, revealing a ‘honeycomb’ appearance. Sections cut from wax-embedded granules were stained using a number of histochemical procedures. Detailed examination of the overall structure of the granules was possible, revealing the presence of filamentous bundles of Methanothrix surrounded by a matrix found to be carbohydrate in nature. Interpretation of serial sections through the depth of the granule allowed for the construction of a diagrammatic illustration of the internal structure. A relationship between the measured diameter of these microcolonies of Methanothrix and the distance from the centre of the granule was established. Together these results enabled a proposal to be made as to the possible mechanisms involved in the growth of granules. This supports previous suggestions relating to the involvement of Methanothrix and bacterial polymers. |
