Browsing by Author "Greenwood, Matthew Peter"

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    Drivers of gut microbiome diversity in commercially mass-reared black soldier flies
    (Stellenbosch : Stellenbosch University, 2021-12) Greenwood, Matthew Peter; Rhode, Clint; Stellenbosch University. Faculty of AgriSciences. Dept. of Genetics.
    ENGLISH ABSTRACT: The black soldier fly, Hermetia illucens, is a focal species for industrial and commercial mass-rearing owing to the ability of its larvae to convert large quantities of organic waste material into high-value protein, lipid, and chitin biomass. Recent studies have indicated that specific gut bacteria can modulate the bioconversion potential of H. illucens larvae. In turn, it is increasingly recognised that information regarding the diversity and composition of larval gut microbial communities (i.e., the microbiome) may be valuable for the prediction, directed improvement, and maintenance of phenotypic performance in these rearing systems. However, the development of strategies to effectively exploit microbiome data in practice will rely on understanding of the factors that dictate microbiome establishment, persistence, identity, and function. Therefore, the aim of this study was to determine the extent to which environmental and host genetic variation shape H. illucens gut microbial communities and, consequently, impact relationships between the microbiome and economically important larval traits. To disentangle the effects of host genetics and environment on microbiome establishment, larvae from two different strains were reared on four feed substrates in a crossed experimental design under otherwise controlled conditions. The gut bacterial communities of larvae were profiled using a 16S rDNA next-generation sequencing approach. Between-group comparisons of gut microbial diversity and composition revealed significant effects of diet, host genetic background, and an interaction between these factors on microbiome establishment. Moreover, by inferring the metabolic profiles of gut communities, it was demonstrated that the effects of diet likely drive microbiome divergence at the functional level. Correlation and variance partitioning analyses supported a subsequent impact of microbiome divergence on the fat and protein accumulation rates of larvae and suggested that the influence of diet on gut microbial communities was most relevant to phenotypic outcomes. Recognising that further interactions between immunity-related host gene expression patterns and diet may be implicated in shaping microbiome profile divergence, the transcriptional activity of two larval antimicrobial peptide genes was also assessed. Expression patterns for one of these genes, a cecropin-like peptide factor, was both affected by diet and significantly associated with differentiation in microbiome composition between larval groups. Together, these results are largely concordant with findings in other model systems and demonstrate that complex interactions between host regulatory networks and environmental variation shapes the diversity, identity, and functional capacity of the H. illucens microbiome. In resolving putative microbiome- trait effects associated with change in larval gut microbial profiles, this work indicates that black soldier fly biology and microbial ecology are tightly intertwined, and bolsters prior suggestions that knowledge of larval microbiome constitutes a viable avenue for phenotypic improvement in industry.