Environment–host–parasite interactions in mass-reared insects

Herren, Pascal; Hesketh, Helen; Meyling, Nicolai V.; Dunn, Alison M.

doi:10.1016/j.pt.2023.04.007

Cited by 6 publications

(2 citation statements)

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“…The ability of P. pentosaceus to produce and excrete antimicrobial secondary metabolites such as pediocins ( 65 , 66 ) might play an important role in shaping the insect microbiota dynamics by favoring probiotic gut colonization and avoiding pathogen proliferation ( 45 ). The mechanisms related to pediocin production in the gut environment of the yellow mealworm still need to be investigated, taking into consideration the gut pH ( 67 ) and the mass-rearing environmental conditions that might affect the insect microbiota dynamics ( 68 ). Further studies should also consider the impact of the probiotics on the whole life cycle of T. molitor , as earlier reported ( 25 , 45 ).…”

Section: Discussionmentioning

confidence: 99%

Minor impact of probiotic bacteria and egg white on Tenebrio molitor growth, microbial composition, and pathogen infection

Savio,

Herren,

Rejasse

et al. 2024

Front. Insect Sci.

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The industrial rearing of the yellow mealworm (Tenebrio molitor) for feed and food purposes on agricultural by-products may expose larvae and adults to entomopathogens used as biocontrol agents in crop production. Bacterial spores/toxins or fungal conidia from species such as Bacillus thuringiensis or Metarhizium brunneum could affect the survival and growth of insects. Therefore, the aim of this study was to investigate the potential benefits of a wheat bran diet supplemented with probiotic bacteria and dried egg white on larval development and survival and its effects on the gut microbiome composition. Two probiotic bacterial species, Pediococcus pentosaceus KVL B19-01 and Lactiplantibacillus plantarum WJB, were added to wheat bran feed with and without dried egg white, as an additional protein source, directly from neonate larval hatching until reaching a body mass of 20 mg. Subsequently, larvae from the various diets were exposed for 72 h to B. thuringiensis, M. brunneum, or their combination. Larval survival and growth were recorded for 14 days, and the bacterial microbiota composition was analyzed using 16S rDNA sequencing prior to pathogen exposure and on days 3 and 11 after inoculation with the pathogens. The results showed increased survival for T. molitor larvae reared on feed supplemented with P. pentosaceus in the case of co-infection. Larval growth was also impacted in the co-infection treatment. No significant impact of egg white or of P. pentosaceus on larval growth was recorded, while the addition of Lb. plantarum resulted in a minor increase in individual mass gain compared with infected larvae without the latter probiotic. On day 14, B. thuringiensis was no longer detected and the overall bacterial community composition of the larvae was similar in all treatments. On the other hand, the relative operational taxonomic unit (OTU) abundance was dependent on day, diet, and probiotic. Interestingly, P. pentosaceus was present throughout the experiments, while Lb. plantarum was not found at a detectable level, although its transient presence slightly improved larval performance. Overall, this study confirms the potential benefits of some probiotics during the development of T. molitor while underlining the complexity of the relationship between the host and its microbiome.

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Section: Discussionmentioning

confidence: 99%

Minor impact of probiotic bacteria and egg white on Tenebrio molitor growth, microbial composition, and pathogen infection

Savio,

Herren,

Rejasse

et al. 2024

Front. Insect Sci.

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“…Some of these entomopathogens are used as biological control agents against T. molitor in stored grains [ 23 , 24 ] but at the same time, entomopathogens can also cause lethal or sublethal diseases in insects mass-reared for food and feed leading to economic losses in production systems [ 21 ]. Currently, there is a dearth of knowledge on how CO 2 concentrations affect host-pathogen interactions in both mass-reared and wild insects [ 25 ]. Improving our understanding of the effects of CO 2 on entomopathogens and their interactions with insect hosts will help to guide decisions of whether CO 2 should be considered a relevant factor to include for insect-pathogen interaction experiments and in the design of insect mass rearing facilities.…”

Section: Introductionmentioning

confidence: 99%

Effect of CO2 Concentrations on Entomopathogen Fitness and Insect-Pathogen Interactions

Herren,

Dunn,

Meyling

et al. 2024

Microb Ecol

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Numerous insect species and their associated microbial pathogens are exposed to elevated CO2 concentrations in both artificial and natural environments. However, the impacts of elevated CO2 on the fitness of these pathogens and the susceptibility of insects to pathogen infections are not well understood. The yellow mealworm, Tenebrio molitor, is commonly produced for food and feed purposes in mass-rearing systems, which increases risk of pathogen infections. Additionally, entomopathogens are used to control T. molitor, which is also a pest of stored grains. It is therefore important to understand how elevated CO2 may affect both the pathogen directly and impact on host-pathogen interactions. We demonstrate that elevated CO2 concentrations reduced the viability and persistence of the spores of the bacterial pathogen Bacillus thuringiensis. In contrast, conidia of the fungal pathogen Metarhizium brunneum germinated faster under elevated CO2. Pre-exposure of the two pathogens to elevated CO2 prior to host infection did not affect the survival probability of T. molitor larvae. However, larvae reared at elevated CO2 concentrations were less susceptible to both pathogens compared to larvae reared at ambient CO2 concentrations. Our findings indicate that whilst elevated CO2 concentrations may be beneficial in reducing host susceptibility in mass-rearing systems, they may potentially reduce the efficacy of the tested entomopathogens when used as biological control agents of T. molitor larvae. We conclude that CO2 concentrations should be carefully selected and monitored as an additional environmental factor in laboratory experiments investigating insect-pathogen interactions.

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