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Paenibacillus larvae enolase as a virulence factor in honeybee larvae infection
Karina Antúnez1, Matilde Anido, Daniela Arredondo
1Departamento de Microbiología, Instituto de Investigaciones Biológicas Clemente Estable, Avda. Italia 3318, C.P. 11600, Montevideo, Uruguay. karina@iibce.edu.uy
Abstract:
Paenibacillus larvae is a gram-positive spore-forming bacteria, causative agent of American Foulbrood (AFB), a severe disease affecting larvae of the honeybee Apis mellifera. In an attempt to detect potential virulence factors secreted by P. larvae, we identified an enolase among different secreted proteins. Although this protein is a cytosolic enzyme involved in glycolytic pathways, it has been related to virulence. The aim of the present work was to evaluate its role during the infection of honeybee larvae. Toxicity assays showed that enolase was highly toxic and immunogenic to honeybee larvae. Its production was detected inside P. larvae vegetative cells, on the surface of P. larvae spores and secreted to the external growth medium. P. larvae enolase production was also confirmed in vivo, during the infection of honeybee larvae. This protein was able to hydrolyze milk proteins as described for P. larvae, suggesting that could be involved in larval degradation, maybe through the plasmin(ogen) system. These results suggest that P. larvae enolase may have a role in virulence and could contribute to a general insight about insect-pathogen interaction mechanisms.
Insights
Paenibacillus larvae enolase is toxic to honeybee larvae and is found on bacterial cells, spores, and secreted during infection. This suggests enolase is a virulence factor in American Foulbrood (AFB).
Area of Science:
- Microbiology
- Insect Pathology
- Biochemistry
Background:
- Paenibacillus larvae causes American Foulbrood (AFB), a destructive honeybee larval disease.
- Enolase, typically a glycolytic enzyme, has been implicated in bacterial virulence.
- The role of P. larvae enolase in AFB pathogenesis was previously unknown.
Purpose of the Study:
- To investigate the role of enolase secreted by Paenibacillus larvae in honeybee larval infection.
- To determine the toxicity and immunogenicity of P. larvae enolase.
- To elucidate the localization and potential function of P. larvae enolase during infection.
Main Methods:
- Toxicity and immunogenicity assays on honeybee larvae.
- Detection of enolase production in P. larvae vegetative cells, spores, and secreted medium.
- In vivo confirmation of enolase production during larval infection.
- Enzyme activity assays to assess protein hydrolysis.
Main Results:
- P. larvae enolase demonstrated high toxicity and immunogenicity towards honeybee larvae.
- Enolase was found within P. larvae cells, on spore surfaces, and secreted into the growth medium.
- Enolase production was confirmed in vivo during honeybee larval infections.
- The enzyme exhibited milk protein hydrolysis activity, similar to P. larvae.
Conclusions:
- Paenibacillus larvae enolase is a significant virulence factor in American Foulbrood.
- Enolase contributes to larval degradation, potentially via the plasmin(ogen) system.
- This study enhances understanding of insect-pathogen interactions and AFB mechanisms.
