Some Giant Sulphur Bacteria are so large as to be visible to

Some Giant Sulphur Bacteria are so large as to be visible to the naked eye. Nonetheless, they have been very difficult to cultivate and classify. Why?

Solution

Cultivate

Grow very slowly. Metabolism is based on lithotrophic utilization of sulphide oxidation coupled to nitrate reduction which is gives poor yields. In natural environments they grow in gradients where one end of filament is sulphide rich, the other end nitrate rich. Difficult to simulate in the lab.

Classify

Morphology has been used, but this is not linked to phylogeny. 16S rRNA hard to amplify due to containing an intron