Bacterial Communities of Diverse Drosophila Species: Ecological Context of a Host–Microbe Model System

Drosophila melanogaster is emerging as an important model of non-pathogenic host–microbe interactions. The genetic and experimental tractability of Drosophila has led to significant gains in our understanding of animal–microbial symbiosis. However, the full implications of these results cannot be appreciated without the knowledge of the microbial communities associated with natural Drosophila populations. In particular, it is not clear whether laboratory cultures can serve as an accurate model of host–microbe interactions that occur in the wild, or those that have occurred over evolutionary time. To fill this gap, we characterized natural bacterial communities associated with 14 species of Drosophila and related genera collected from distant geographic locations. To represent the ecological diversity of Drosophilids, examined species included fruit-, flower-, mushroom-, and cactus-feeders. In parallel, wild host populations were compared to laboratory strains, and controlled experiments were performed to assess the importance of host species and diet in shaping bacterial microbiome composition. We find that Drosophilid flies have taxonomically restricted bacterial communities, with 85% of the natural bacterial microbiome composed of only four bacterial families. The dominant bacterial taxa are widespread and found in many different host species despite the taxonomic, ecological, and geographic diversity of their hosts. Both natural surveys and laboratory experiments indicate that host diet plays a major role in shaping the Drosophila bacterial microbiome. Despite this, the internal bacterial microbiome represents only a highly reduced subset of the external bacterial communities, suggesting that the host exercises some level of control over the bacteria that inhabit its digestive tract. Finally, we show that laboratory strains provide only a limited model of natural host–microbe interactions. Bacterial taxa used in experimental studies are rare or absent in wild Drosophila populations, while the most abundant associates of natural Drosophila populations are rare in the lab

The Drosophila melanogaster host model

The deleterious and sometimes fatal outcomes of bacterial infectious diseases are the net result of the interactions between the pathogen and the host, and the genetically tractable fruit fly, Drosophila melanogaster, has emerged as a valuable tool for modeling the pathogen–host interactions of a wide variety of bacteria. These studies have revealed that there is a remarkable conservation of bacterial pathogenesis and host defence mechanisms between higher host organisms and Drosophila. This review presents an in-depth discussion of the Drosophila immune response, the Drosophila killing model, and the use of the model to examine bacterial–host interactions. The recent introduction of the Drosophila model into the oral microbiology field is discussed, specifically the use of the model to examine Porphyromonas gingivalis–host interactions, and finally the potential uses of this powerful model system to further elucidate oral bacterial-host interactions are addressed

Beliefs that Condoms Reduce Sexual Pleasure—Gender Differences in Correlates Among Heterosexual HIV-Positive Injection Drug Users (IDUs)

Studies consistently find that negative condom beliefs or attitudes are significantly associated with less condom use in various populations, including HIV-positive injection drug users (IDUs). As part of efforts to reduce sexual risk among HIV-positive IDUs, one of the goals of HIV interventions should be the promotion of positive condom beliefs. In this paper we sought to identify the correlates of negative condom beliefs and examined whether such correlates varied by gender, using a subsample (those with an opposite-sex main partner; n = 348) of baseline data collected as part of a randomized controlled study of HIV-positive IDUs. In multivariate analyses, we found more significant correlates for women than for men. With men, perception that their sex partner is not supportive of condom use (negative partner norm) was the only significant correlate (Beta = −0.30; p < 0.01; R2 = 0.18). Among women, negative partner norm (Beta = −0.18; p < 0.05); having less knowledge about HIV, STD, and hepatitis (Beta = −0.16; p < 0.05); lower self-efficacy for using a condom (Beta = −0.40; p < 0.01); and more episodes of partner violence (Beta = 0.15; p < 0.05) were significantly associated with negative condom beliefs (R2 = 0.36). These findings suggest important gender-specific factors to consider in interventions that seek to promote positive condom beliefs among HIV-positive IDUs