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The Department of Plant Pathology and Microbiology
Robert H. Smith Faculty of Agriculture, Food and Environment
The Hebrew University of Jerusalem

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Bacteria-tephritid fruit flies symbioses

It is commonly thought of multicellular organisms as of biological units, or as populations composed of individuals. However, most (if not all) bear associated bacterial communities that perform functions essential for their well-being – or in other terms functions that may impact upon their fitness. Insects are practical models to study such interactions as they are small, numerous and may sustain less complex bacterial communities than larger organisms. Moreover, certain insects, like many tephritid fruit flies are important agricultural pests and their bacterial communities may offer novel opportunities for controlling the insect.

Our research on tephritid fruit flies has yielded a symbiotic association - with the Yuval lab of Entomology (http://departments.agri.huji.ac.il/entomology/boaz_yuval/index.html).

The diverse gut community of Ceratitis capitata, the Mediterranean fruit fly

The Mediterranean fruit fly (the medfly) is a widely distributed, polyphagous fly. Its larva grows within many kinds of fruits causing great losses.  

The medfly’s gut community is large and diverse. Our previous work has shown that it mainly harbours vertically transmitted Enterobacteriaceae that fix atmospheric nitrogen and cause fruit rot. Adding gut symbionts from field flies to sterile males produced in mass-rearing facilities for biocontrol purposes increased their mating efficiency.

Our research goals

We would like to understand how the microbial community of the medfly is selected – how the environment affects the insect’ microbial community and the functions it harbours; what is the importance of these functions under particular ecological settings; what are the barriers to transgenerational transmission and how are novel symbionts acquired. Finally, we would like to know what the roles of the fruit in these processes are. 

Recent and ongoing research

Figures

Top left: An adult Ceratitis capitata, the Mediterranean fruit fly. Top right: An adult Bactrocera olea, the olive fly. Bottom right:  Bacterial masses (red) in the gut of a field-caught adult Mediterranean fruit fly. Bacteria were stained with a 16S rRNA fluorescent probe. Gut cells are stained green. Bottom left: Rot in infested fruits originates from pectinolytic bacteria deposited during oviposition.

The unique association of Bactrocera olea, the olive fly with a gut symbiont

Bactrocera olea, the olive fly is a major pest of olives. It is one of a few insects that are able to overcome the chemical defences in green olives, enabling larval development.  The adult fly forages on plant leaves, honeydew and bird faeces, all providing unbalanced diets and rather poor nitrogen sources. 

The bacterial community of the olive fly is restricted

So far, little is known on the bacterial community of the olive fly. It seems to harbour one dominant symbiont, Candidatus Erwinia dacicola and a secondary Enterobacter spp. Our work has started to decipher the contributions of the symbionts to the fly’s life cycle.

Our research goals

We would like to unravel the interactions of the olive fly with its symbionts at the larval and the adult stages. More specifically, do the symbionts contribute to the fly’s nutrition? Do they support its growth in olives? Is there a difference between green (immature) and black (mature) fruits? What are the symbiont’s dynamics during the fly’s life cycle and how diverse is the clade? How are the mechanisms of symbiont transmission?

 Recent and ongoing research

Figures

Left: An adult Bactrocera olea female laying eggs in a green olive.Right : an olive fly larva in a green olive.