Characterization of the bacterial gut fauna of Phlebotomus papatasi: culture dependent vs. culture independent techniques

Abstract

Characterizing the gut bacteria of sand flies is essential not only to identify their influence on host biology, but also to investigate any potential impact on the establishment and development of Leishmania infection, which occurs in the vectors' gut. Gut bacteria may also provide a new avenue to arthropod-borne disease control if a bacterial species typically found in the sand fly can be genetically modified to produce anti-parasitic molecules, thereby producing a vector refractory to disease transmission. This study characterized the gut bacterial community of laboratory reared Phlebotomus papatasi, using both a culture based approach and a culture independent approach involving analysis of a 16S ribosomal RNA (rRNA) gene sequence library. The guts of several field flies were also included in the analysis.

These experiments identified 26 species of bacteria in sand fly guts, affiliated with four bacterial phyla: Actinobacteria, Proteobacteria, Firmicutes and Bacteroidetes. Laboratory reared flies were predominated by Leifsonia spp., regardless of the method of analysis used. Interestingly, Leifsonia has not been previously reported in the gut of sand flies. Moreover, bacteria of the genera Ochrobactrum, Stenotrophomonas and Bacillus, previously reported in sand flies from different geographical locations, were also recovered in this study, suggesting the presence of obligate fly-bacterial associations. Bacteria identified that are affiliated with the genera Achromobacter, Wolbachia, Leifsonia and Bacillus may be particularly significant due to their ability to deliver transgenes as shown in previous studies. Consequently, they could be considered in the control of Leishmania via paratransgenesis. Results from these experiments support the premise that culture independent approaches are generally more efficient for characterizing bacterial communities. Both the type and diversity of bacteria identified in this study strongly emphasize the significance of the bacteria inhabiting the gut of sand flies. These findings underscore the value of further research aimed at clearly understanding the role of specific bacterial species, and identifying ways in which they may modulate the functions of the vector, the life cycle of the parasite or even disease establishment in hosts.