Master of Science (MS)
Semester of Degree Completion
William A. Weiler
The validity of the genus Siderocapsa, a group of unicellular iron-depositing bacteria, has been a subject of debate for many years. Lack of photomicroscopic and cultural studies has kept this group in taxonomic obscurity. Bacteria were collected from the Campus pond, Eastern Illinois University, Charleston, Illinois, by a submerged slide/coverslip technique. These bacteria were identified as Siderocapsa major according to the description of Molisch (1909). Scanning electron microscopy of Siderocapsa major microcolonies has shown cells (0.5 by 1.15 μm), in a clear central well (2-6 μm), surrounded by an amorphous material which accumulates with the age of the colony. Most authors have failed to explain how they have concluded that the material sequestered by Siderocapsa microcolonies is iron and/or manganese. Preliminary work employing the Prussian blue Reaction (and modifications) failed to demonstrate the presence of iron in the capsules around these bacteria. X-ray microanalysis also failed to demonstrate the presence of iron. However significant amounts of manganese were found to be present in the extra-cellular material.
Some investigators have suggested that Siderocapsa microcolonies are artifacts and the result of rod-shaped bacteria that have become entrapped in the well of a Sphaerotilus natans holdfast whose filament has become dislodged. Scanning electron microscopy has shown that the size and morphology of the holdfast of Sphaerotilus-Leptothrix members does not correspond to the size of the deposit around the Siderocapsa microcapsule. In addition, statistical analysis has shown a definite developmental pattern relating the total number of cells in the microcapsule to the total amount of material deposited.
The author concludes, from material observed here, that the Siderocapsa microcolonies are discretely different entities from members of the Sphaerotilus-Leptothrix group but may be related to other heterotrophic bacteria.
Swanson, Ray W., "Siderocapsa Major-- Fact or Artifact?" (1979). Masters Theses. 3120.