Data di Pubblicazione:
2014
Citazione:
MICROBIAL ECOLOGY OF THE SPOTTED WING FLY DROSOPHILA SUZUKII / V.f. Vacchini ; supervisor: D. Daffonchio ; coordinator: D. Daffonchio. Università degli Studi di Milano, 2014 Dec 18. 27. ciclo, Anno Accademico 2014. [10.13130/vacchini-violetta-francesca_phd2014-12-18].
Abstract:
Abstract
Symbiotic relationships between arthropods and microorganisms are widespread in nature. In the last years these interactions are received considerable attention, as many microorganisms may play relevant roles in the biology and lifecycle of insects (Dale and Moran, 2006; Moran et al., 2008). In this perspective, researchers are directing many efforts to depict the interactions that shape the symbiosis. Furthermore, considering the importance that microorganisms play for their hosts, the modification of the microbiome structure in the insect body could support the development of sustainable strategies, alternative to chemical pesticides. To achieve the development of these methods, the knowledge and the identification of the symbionts associated to the pest of interest, is a mandatory requirement.
Recent studies documented the evidence of stable associations between acetic acid bacteria (AAB) and insects characterized by a sugar-based diet. These include Diptera, Hymenoptera and Hemiptera orders (Crotti et al., 2010). It was reported that AAB are essential in the modulation of the immune homeostasis as well as metabolism and larval development. These capacities have been demonstrated in Drosophila (Ryu et al., 2008; Shin et al., 2011), but have been recently confirmed in other models, like Anopheles (Chouaia et al. 2012, Hughes et al., 2014).
Along with bacteria, drosophilid flies establish a mutualistic relationship with yeasts, in particular with those belonging to the Saccharomycetaceae family: these microorganisms represent the main nutritional source for the flies, as they provide proteins, vitamins and other nutrients. Yeasts are vectored by Drosophila, from which they are dispersed, favoring the colonization of new habitats (Christiaens et al., 2014). Moreover, they can affect the fly development and fitness in terms of susceptibility to parasitism (Anagnostou et al. 2010). Yeasts share the same environments with AAB, supporting the hypothesis of possible microbe-microbe interactions.
The aim of my PhD project was the characterization of the microbiome associated to the spotted wing fly Drosophila suzukii Matsumura (Diptera: Drosophilidae), an economically damaging pest of healthy soft summer fruits, rapidly spreading in many countries from South-East Asia (Lee et al., 2011). In particular, targets of the research were AAB and yeasts symbionts.
Results revealed that AAB were a major component of D. suzukii bacterial community. Members of Gluconobacter, Gluconacetobacter and Acetobacter genera were the main representatives, as shown by culture-dependent (isolation by using specific media, dereplication with ITS-PCR and isolate identification through partial 16S rRNA gene sequencing) and -independent analyses (16S rRNA barcoding and Denaturing Gradient Gel Electrophoresis-PCR). The investigation was performed on specimens of different developmental stages (larvae, pupae and adults), reared on two feeding substrates (fruit or an artificial diet).
The plasmid pHM2(Gfp) was introduced by electroporation in three selected AAB isolates, Gluconobacter oxydans DSF1C.9A, Acetobacter tropicalis BYea.1.23 and Acetobacter indonesiensis BTa1.1.44 to label them with Green fluorescent protein (Gfp). After oral administration to the insects, Gfp-tagged strains were visualized in the host by fluorescence microscopy. The symbionts were able to successfully reach and colonize the epithelium of the insect crop, proventriculus and midgut. Tests performed on bacterial cultures grown in liquid media showed that several AAB isolates are able to produce an extracellular matrix in which the cells are entrapped and that presumably is implicated in the bacterial adhesion to the insect epithelia and maintenance in the digestive system.
Tipologia IRIS:
Tesi di dottorato
Keywords:
-ACETIC ACID BACTERIA
-YEASTS
-DROSOPHILA SUZUKII
-VOLATILE COMPOUNDS
-KILLER TOXINS
Elenco autori:
V.F. Vacchini
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