Fine structural studies of Rhodococcus species

Area of Science:

• Microbiology
• Cell Biology
• Bacteriology

Background:

• Actinomycetous bacteria, including Rhodococcus species, share common prokaryotic cell structures.
• Understanding the fine structural details of bacterial cell walls is crucial for taxonomy and potential applications.

Purpose of the Study:

• To describe and illustrate the fine structural aspects of Rhodococcus rhodochrous and R. equi using electron microscopy.
• To characterize the composition of the outer cell wall layers and capsular substances in these bacteria.

Main Methods:

• Cells of R. rhodochrous and R. equi were prepared using various electron cytochemical staining procedures.
• Electron microscopy was employed to visualize the fine structural details of the bacterial cells.
• Specific stains (Ruthenium red, Alcian blue-lanthanum, PATAg) were used to identify cellular components.

Main Results:

• The internal cell contents were consistent with typical prokaryotic cells.
• An electron-opaque, likely proteinaceous, substance was observed on the exterior of R. rhodochrous cell walls.
• Both species exhibited a capsular substance, presumed to be a mucopolysaccharide or mucopolysaccharide-protein complex.
• The capsular substance did not react with the PATAg stain, indicating an absence of vicinal glycol groups in polysaccharide macromolecules.

Conclusions:

• Rhodococcus rhodochrous and R. equi possess distinct cell wall and capsular structures.
• The outer layer of R. rhodochrous contains a proteinaceous component.
• The capsular substance is likely a mucopolysaccharide-based complex, differing in its polysaccharide structure from PATAg-reactive substances.