Probiotic Enterococcus mundtii Isolate Protects the Model Insect Tribolium castaneum against Bacillus thuringiensis
Thorben Grau1, Andreas Vilcinskas1,2, Gerrit Joop1
1Institute for Insect Biotechnology, Justus-Liebig-University GiessenGiessen, Germany.
Abstract:
Enterococcus mundtii strains isolated from the larval feces of the Mediterranean flour moth Ephestia kuehniella show antimicrobial activity against a broad spectrum of Gram-positive and Gram-negative bacteria. The in vitro probiotic characterization of one isolate revealed a high auto-aggregation score, a hydrophilic cell surface, tolerance for low pH, no hemolytic activity, and susceptibility to all tested antibiotics. We used the red flour beetle Tribolium castaneum, an established model organism, for the in vivo characterization of one probiotic E. mundtii isolate from E. kuehniella larvae. Tribolium castaneum larvae were fed orally with the probiotic isolate or the corresponding supernatant and then infected with either the entomopathogen Bacillus thuringiensis or Pseudomonas entomophila. Larvae exposed to the isolate or the supernatant showed increased survival following infection with B. thuringiensis but not P. entomophila. Heat treatment or treatment with proteinase K reduced the probiotic effect of the supernatant. However, the increased resistance attracts a fitness penalty manifested as a shorter lifespan and reduced fertility. T. castaneum has, pending on further research, the potential as an alternative model for the pre-screening of probiotics.
Insights
Enterococcus mundtii from moth larvae show probiotic potential, enhancing survival in beetle models against certain bacteria. However, this protection comes at a cost to the beetle
Area of Science:
- Microbiology
- Insect Pathology
- Probiotics
Background:
- Enterococcus mundtii strains isolated from Ephestia kuehniella larval feces exhibit antimicrobial properties.
- Probiotic potential requires in vitro and in vivo characterization.
Purpose of the Study:
- To evaluate the probiotic characteristics of E. mundtii isolates.
- To assess the in vivo efficacy of E. mundtii in a Tribolium castaneum model.
- To investigate the impact of probiotic treatment on insect fitness.
Main Methods:
- In vitro probiotic assays including auto-aggregation, cell surface hydrophilicity, pH tolerance, and hemolytic activity.
- In vivo studies using Tribolium castaneum larvae fed E. mundtii isolates or supernatant, followed by infection with Bacillus thuringiensis or Pseudomonas entomophila.
- Analysis of supernatant components (heat treatment, proteinase K) and assessment of insect lifespan and fertility.
Main Results:
- E. mundtii demonstrated broad-spectrum antimicrobial activity in vitro.
- Oral administration of E. mundtii or its supernatant increased T. castaneum survival against B. thuringiensis but not P. entomophila.
- Probiotic effects were linked to heat-labile and proteinaceous components in the supernatant.
- Probiotic treatment resulted in reduced lifespan and fertility in T. castaneum.
Conclusions:
- Enterococcus mundtii possesses probiotic properties with potential applications in insect health.
- Tribolium castaneum serves as a viable model for pre-screening insect probiotics.
- Probiotic interventions may involve trade-offs between pathogen resistance and host fitness.
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