The cell surface of Phytomonas davidi

Area of Science:

• Cell biology
• Parasitology
• Biochemistry

Background:

• Carbohydrates on the cell surface play crucial roles in biological processes.
• Understanding the surface composition of parasites like Phytomonas davidi is essential for studying host-parasite interactions.

Purpose of the Study:

• To investigate the presence and nature of carbohydrates on the surface of Phytomonas davidi.
• To analyze the surface charge of Phytomonas davidi cells and identify specific residues contributing to it.

Main Methods:

• Ultrastructural cytochemistry to locate surface carbohydrates.
• Lectins were used to induce agglutination based on specific carbohydrate binding.
• Cationic particle binding (colloidal iron, cationized ferritin) and cell electrophoretic mobility (EPM) were employed to assess surface charge.
• Neuraminidase treatment and chromatography (paper, gas-liquid) were used to detect and confirm sialic acid presence.

Main Results:

• Agglutination by lectins indicated the presence of mannose, N-acetylglucosamine, galactose, N-acetylgalactosamine, fucose, and sialic acid residues.
• Analysis of cationic particle binding and EPM suggested the presence of negatively charged residues on the cell surface.
• Neuraminidase treatment decreased EPM and cationic particle binding, supporting the presence of sialic acid.
• N-acetylneuraminic acid was detected, confirming the exposure of sialic acid residues.
• Agglutination by Limulus polyphemus lectin was enhanced after trypsinization, suggesting sialic acid residues might be masked or associated with proteins/lipids.

Conclusions:

• Sialic acid residues are exposed on the surface of Phytomonas davidi.
• These sialic acid residues contribute to the negative surface charge of the cells.
• The exact nature of these residues (glycolipids or masked) requires further investigation.