2006, pp 784-810

The Genera Beggiatoa and Thioploca

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Introduction

Filamentous sulfur-oxidizing bacteria of the genera Beggiatoa and Thioploca are some of the largest and most conspicuous bacteria in nature (Schulz and Jørgensen, 2001). Their white or yellow color, their filamentous morphology, the large width and length of their filaments, and their growth pattern in flocs and mats on sediment surfaces makes them highly conspicuous even to the unaided eye. The two genera are distinguished by a single morphological character: Thioploca filaments occur in bundles surrounded by a common sheath, whereas Beggiatoa filaments do not form this structure and occur as individual filaments. All Beggiatoa and Thioploca strains have the ability to oxidize sulfide to elemental sulfur that is stored as intracellular sulfur globules, which make the cells highly refractory and conspicuous under the microscope. This characteristic, together with the absence of photosynthetic pigments, has distinguished the genera Beggiatoa and Thioploca as filamentous memb