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Clostridium bifermentans serovar malaysia: characterization of putative mosquito larvicidal proteins
L Nicolas1, J F Charles, H de Barjac
1Institut Pasteur, Unité des Bactéries Entomopathogènes, Paris, France.
Abstract:
The toxicity of Clostridium bifermentans serovar malaysia to mosquito larvae is due to protein toxins, belonging to a novel class of insecticidal toxins. Toxic extracts contains three major proteins of 66, 18 and 16 kDa. The 18-kDa and 16-kDa proteins are probably involved in toxicity. They are synthesised during sporulation, concomitant with activity. They are absent from non-toxic strains of C. bifermentans and are present at very low levels in non-toxic C. bifermentans serovar malaysia cultures produced at 42 degrees C. The 66-kDa protein is present throughout the growth phases of C. bifermentans serovar malaysia, and an immunologically related 66-kDa protein is present in non-toxic C. bifermentans strains.
Insights
Clostridium bifermentans serovar malaysia produces novel insecticidal protein toxins responsible for mosquito larvae toxicity. These toxins, primarily 18-kDa and 16-kDa proteins synthesized during sporulation, are key to its larvicidal activity.
Area of Science:
- Microbiology
- Toxicology
- Insecticide Development
Background:
- Clostridium bifermentans serovar malaysia exhibits toxicity towards mosquito larvae.
- This toxicity is attributed to proteinaceous toxins, suggesting a novel insecticidal mechanism.
Purpose of the Study:
- To identify and characterize the specific protein toxins responsible for the insecticidal activity of Clostridium bifermentans serovar malaysia against mosquito larvae.
- To investigate the synthesis and expression patterns of these toxic proteins in relation to bacterial growth and sporulation.
Main Methods:
- Analysis of toxic extracts from Clostridium bifermentans serovar malaysia to identify major protein components.
- Comparison of protein profiles between toxic and non-toxic strains, as well as cultures produced under different temperature conditions.
- Correlation of protein presence and synthesis with observed larvicidal activity.
Main Results:
- Three major proteins of 66, 18, and 16 kDa were identified in toxic extracts.
- The 18-kDa and 16-kDa proteins were found to be synthesized during sporulation, coinciding with peak toxicity.
- These toxic proteins were absent in non-toxic strains and present at very low levels in non-toxic cultures of C. bifermentans serovar malaysia.
- A 66-kDa protein was present throughout growth, with an immunologically related protein found in non-toxic strains.
Conclusions:
- The insecticidal activity of Clostridium bifermentans serovar malaysia against mosquito larvae is mediated by novel protein toxins, likely the 18-kDa and 16-kDa species.
- The synthesis of these toxins is tightly linked to the sporulation phase of the bacteria.
- The presence of these specific proteins distinguishes toxic strains and is crucial for larvicidal efficacy.
