Fruit host-dependent fungal communities in the microbiome of wild Queensland fruit fly larvae

Abstract

Bactrocera tryoni (Froggatt), the Queensland fruit fly (Qfly), is a highly polyphagous tephritid fly that is widespread in Eastern Australia. Qfly physiology is closely linked with its fungal associates, with particular relationship between Qfly nutrition and yeast or yeast-like fungi. Despite animal-associated fungi typically occurring in multi-species communities, Qfly studies have predominately involved the culture and characterisation of single fungal isolates. Further, only two studies have investigated the fungal communities associated with Qfly, and both have used culture-dependant techniques that overlook non-culturable fungi and hence under-represent, and provide a biased interpretation of, the overall fungal community. In order to explore a potentially hidden fungal diversity and complexity within the Qfly mycobiome, we used culture-independent, high-throughput Illumina sequencing techniques to comprehensively, and holistically characterized the fungal community of Qfly larvae and overcome the culture bias. We collected larvae from a range of fruit hosts along the east coast of Australia, and all had a mycobiome dominated by ascomycetes. The most abundant fungal taxa belonged to the genera Pichia (43%), Candida (20%), Hanseniaspora (10%), Zygosaccharomyces (11%) and Penicillium (7%). We also characterized the fungal communities of fruit hosts, and found a strong degree of overlap between larvae and fruit host communities, suggesting that these communities are intimately inter-connected. Our data suggests that larval fungal communities are acquired from surrounding fruit flesh. It is likely that the physiological benefits of Qfly exposure to fungal communities is primarily due to consumption of these fungi, not through syntrophy/symbiosis between fungi and insect ‘host’.

Metagenomic Survey of the Highly Polyphagous Anastrepha ludens Developing in Ancestral and Exotic Hosts Reveals the Lack of a Stable Microbiota in Larvae and the Strong Influence of Metamorphosis on Adult Gut Microbiota

“…Thus, the degree of plasticity of the gut microbiota among fruit fly species is a topic that deserves further attention. Interestingly, in the case of B. tryoni the existence of a high similarity between mycobiome in larvae and their respective host fruit source was documented ( Majumder et al, 2020a ), suggesting that these fungal communities are closely interconnected, which is in direct contrast with what occurs with bacteria.…”

Dynamics of the Queensland Fruit Fly Microbiome through the Transition from Nature to an Established Laboratory Colony

“…65175) for 30 s, and rinsed 3 times in 1 M sterile phosphate-buffered saline (1× PBS) again for 30 s. The PBS from the 2nd and 3rd washes were kept and 100 µL spread plated on to five types of microbial growth medium (de Man, Rogosa and Sharpe Agar [MRSA], Tryptone Soya Agar [TSA], Macconkey Agar, Potato Dextrose Agar [PDA] and yeast-dextrose agar (YDA])) (Sigma-Aldrich, St. Louis, MO, USA) to check the performance of the sterilization method. All plates were incubated at 32 • C and 35 • C for 24 to 48 h [11,26,39,40]. Immediately after sterilisation, the gut of the adult flies was dissected using a stereomicroscope (Leica MZ6 stereo-microscope, Leica ® , Wetzlar, Germany).…”

“…The data were then normalised as the percentage of relative abundance, and are henceforth referred to as the OTU table (Supplementary Data S1). All the measurements of bacterial relative abundance, at different developmental stages, and between generations in colonies, reared on different diets, were plotted in Prism 8 (version 8.0.1(145), GraphPad software, Inc. San Diego, CA, USA) as used previously in Majumder et al (2019, 2020a,b,c) [11,26,40,44]. The Illumina sequence data were deposited into and made publicly available in the NCBI database under Bioproject PRJNA717989.…”

“…The OTU table was imported into Primer-E v7 for analysis as described in Clarke and Ainsworth, 1993; Sutcliffe et al, 2017, Majumder et al, 2019, 2020a, b, c [11,26,34,40,44,52]. The DIVERSE function was used to generate univariate biodiversity metrics, species richness and the Shannon and Simpson biodiversity indices.…”

“…Given the importance of the microbiome to insect health, it is important to understand how the microbiome changes during the domestication of the Qfly. Some studies of the Qfly bacterial microbiome are available, characterising the bacteria associated with wild and domesticated larvae [11,26,[38][39][40], pupae [11,26,41] and adult flies [11,26,[42][43][44]. However, dynamics of the changes occurring in the Qfly microbiome in the transition from nature to artificial rearing have not been characterised.…”