The association between Queensland fruit flies (Dacus Tryoni) and their alimentary tract microflora, including dinitrogen-fixing bacteria

Murphy, Kathleen (1992). The association between Queensland fruit flies (Dacus Tryoni) and their alimentary tract microflora, including dinitrogen-fixing bacteria PhD Thesis, School of Molecular and Microbial Sciences, University of Queensland. doi:10.14264/uql.2016.438

       
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Author Murphy, Kathleen
Thesis Title The association between Queensland fruit flies (Dacus Tryoni) and their alimentary tract microflora, including dinitrogen-fixing bacteria
School, Centre or Institute School of Molecular and Microbial Sciences
Institution University of Queensland
DOI 10.14264/uql.2016.438
Publication date 1992-01-01
Thesis type PhD Thesis
Supervisor David Teakle
Ian MacRae
Total pages 246
Language eng
Subjects 0605 Microbiology
Formatted abstract
The Queensland fruit fly (Dacus tryoni) has established an association with bacteria belonging to species of the family Enterobacteriaceae. When isolates of associated bacteria were assayed for dinitrogen-fixing activity by the acetylene reduction (AR) method, 5 of 27 from fruit surfaces and 3 of 26 from the alimentary tracts of field-collected flies gave a positive result. These bacteria were members of the species Klebsiella oxytoca, K. pneumoniae and Enterobacter cloacae. As the microflora of subtropical dacine flies is usually dominated by a single species, a small proportion of wild D. tryoni may be colonized by bacteria able to fix atmospheric nitrogen. 

To determine the ability of colonizing bacteria to grow diazotrophically in vivo, young laboratory-raised D. tryoni were allowed to feed once, overnight, on heavy growth of K. oxytoca F15C, a field-collected fly isolate expressing nitrogenase activity between 2 and 16 nmol ethylene produced h-1 mg-1 dry wt of cells. AR activity associated with these flies was recorded from 4 days after feeding, peaked about 4 days later, then declined to zero over the next 12 to 18 days. Nitrogenase activity associated with D. tryoni ranged from 15 to 839 nmol ethylene produced g-1 live wt h-1 over incubation periods from 2 to 6 h. Sugar fed flies which had received no supplementary feeding were also associated with AR activity. Autochthonous dinitrogen-fixing bacteria present in the laboratory environment can colonize the fly's alimentary tract then grow diazotrophically. When yeast hydrolysate was fed to flies associated with AR activity, dinitrogen fixation by alimentary tract bacteria was reduced by 90 % in 2.5 h and had ceased within 24 h. A direct (15N2) assay of the insect/diazotroph association showed that between 0.485 and 1.427 µg of fixed dinitrogen per day was incorporated in situ by bacteria colonizing the alimentary tract of D. tryoni. Benefits afforded to the host insect by the association may include the maintenance of a stable bacterial population as either a dietary supplement for growth factors and amino acids or a protection against the establishment of pathogens. 

Surveys of the microflora of laboratory-raised D. tryoni indicated that the average population was about 10 million bacteria per fly and confirmed that a single species of the Enterobacteriaceae, usually either K. oxytoca or E. cloacae, was predominant.   ........................................................................................
Keyword Fruit flies
Additional Notes Spine title: Queensland fruit flies and their alimentary tract microflora.

Document type: Thesis
Collection: UQ Theses (RHD) - UQ staff and students only
 
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