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Malaysian mosquitocidal soil bacterium (Bacillus thuringiensis) strains with selective hemolytic and lectin activity
V D Nadarajah1, S H Chai, S M Mohammed
1Human Biology Section, International Medical University, Kuala Lumpur, Malaysia. vishnadevi_nadarajah@imu.edu.my
Abstract:
The objective of this study is to determine the role of carbohydrates on the toxic effect of parasporal inclusion proteins isolated from Malaysian mosquitocidal Bacillus thuringiensis (Bt) strains on erythrocytes (human and rat). Dose response analyses on the effect of these parasporal inclusions on human and rat erythrocytes suggest that toxin action is selective depending on bacterial strains and source of erythrocytes. Results from this study suggest Bt toxin is a lectin which recognizes specific plasma membrane glycoconjugate receptor(s) with a terminal residue of either D-mannose (Man), N-acetyl-D-galactosamine (GalNAc), N-acetyl-D-glucosamine (GlcNAc) or even a combination of these monosaccharides.
Insights
Mosquitocidal Bacillus thuringiensis (Bt) toxins act as lectins, targeting specific carbohydrate receptors on erythrocyte cell membranes. This selectivity depends on the bacterial strain and erythrocyte source, influencing toxicity.
Area of Science:
- Biochemistry
- Molecular Biology
- Toxicology
Background:
- Mosquitocidal Bacillus thuringiensis (Bt) produces parasporal inclusion proteins with insecticidal properties.
- The precise mechanism of Bt toxin interaction with host cells, particularly erythrocytes, remains incompletely understood.
- Carbohydrates are known to play critical roles in cellular recognition and interaction.
Purpose of the Study:
- To investigate the role of carbohydrates in the toxic effects of Malaysian Bt parasporal proteins on human and rat erythrocytes.
- To determine if Bt toxins exhibit lectin-like activity and identify specific carbohydrate moieties involved in receptor binding.
Main Methods:
- Dose-response analyses were performed using parasporal inclusion proteins from Malaysian Bt strains.
- Human and rat erythrocytes were exposed to varying concentrations of Bt toxins.
- Characterization of toxin-erythrocyte interactions focused on identifying specific carbohydrate receptor recognition.
Main Results:
- Bt toxin toxicity on erythrocytes was found to be selective, varying with bacterial strain and erythrocyte origin (human vs. rat).
- Evidence suggests Bt toxins function as lectins, binding to specific glycoconjugate receptors on the erythrocyte plasma membrane.
- The identified receptors involve terminal D-mannose, N-acetyl-D-galactosamine, N-acetyl-D-glucosamine, or combinations thereof.
Conclusions:
- Malaysian mosquitocidal Bt toxins exhibit lectin activity, recognizing specific erythrocyte surface carbohydrate structures.
- The selectivity of Bt toxin action is mediated by the interaction with terminal monosaccharides like D-mannose and N-acetyl-D-glucosamine/galactosamine.
- Understanding these carbohydrate-glycoconjugate interactions is crucial for elucidating Bt toxicity mechanisms.
