DIVERSITY AND HOST AFFINITY OF TROPICAL SEED-INFECTING BACTERIA

Abstract

Numerous symbiotic relationships are known to exist between seeds and microbes, including both fungi and bacteria. Relationships between seeds and fungi play a crucial role in the survival of pioneer tree species during the seed-dispersal, seed-bank, and seed-germination phases. Prior studies have shown that these fungi can influence the establishment of pioneer trees, which in turn influences forest succession and recovery from disturbance. The question arises if similar roles are played by bacterial interactions in the seeds of pioneer species. The purpose of this thesis was to determine the diversity, host specificity of the bacterial community found in the seeds of three pioneer species in Barro Colorado Island, Panama. Six strains of bacteria were identified using molecular analysis methods focusing on the 16S rRNA gene. One was Gram negative, and the others were Gram positive. Four genotypes were unique relative to previous studies of bacteria in these tropical seeds. This expands our knowledge of the diversity of seed-associated bacteria. Two genotypes were found previously in an ongoing study of these seeds. Here, our findings expand our understanding of their host range, as here they were identified from tree species in which they had not been observed before. In future work we propose testing the effects of these bacteria on seed germination and viability. For now this work contributes to ongoing studies to understand the diversity, distributions, and host specificity of tropical microbes associated with plants at different life stages. Such an understanding will inform fundamental aspects of tropical forest ecology.