Domain: Bacteria; Phylum: Proteobacteria; Class: Gammaproteobacteria; Order: Enterobacterales; family: Enterbacteriaceae; Genus: Hamiltonella
Description and Significance
Describe the appearance, habitat, etc. of the organism, and why you think it is important.
H. defensa is a host-restricted, mutualist symbiont which is conditionally beneficial. Its main purpose is protecting aphids from braconid wasp parasitoids. It is an endosymbiont of aphids, so it lives inside these sap-sucking insects. This bacterium is important because it has the unique ability to defend its aphid host from this invasive parasitoid.
Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence?
Hamiltonella defensa has an extremely dynamic genome. It is relatively small, only 2.1 Mb. It encodes 2,100 protein-coding genes, has a relatively large number of pseudogenes, and is littered with mobile DNA, insertion sequences, and phage remnants. Horizontal gene transfer plays a role in its dynamic genome.
Cell Structure, Metabolism and Life Cycle
Interesting features of cell structure; how it gains energy; what important molecules it produces.
Ecology and Pathogenesis
Habitat; symbiosis; biogeochemical significance; contributions to environment.
If relevant, how does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.
Chevignon, Germain et al. “Culture-Facilitated Comparative Genomics of the Facultative Symbiont Hamiltonella defensa.” Genome Biology and Evolution vol. 10,3 (2018): 786-802. doi.:10.1093/gbe/evy036
Degnan, Patrick H et al. “Hamiltonella defensa, genome evolution of protective bacterial endosymbiont from pathogenic ancestors.” Proceedings of the National Academy of Sciences of the United States of America vol. 106,22 (2009): 9063-8. doi:10.1073/pnas.0900194106
Dykstra, Hannah R et al. “Factors Limiting the Spread of the Protective Symbiont Hamiltonella defensa in Aphis craccivora Aphids.” Applied and Environmental Microbiology, vol. 80,18 (2014): 5818-27. doi:10.1128/aem.01775-14.
Moran, Nancy A et al. “Evolutionary relationships of three new species of Enterobacteriaceae living as symbionts of aphids and other insects.” Applied and environmental microbiology vol. 71,6 (2005): 3302-10. doi:10.1128/AEM.71.6.3302-3310.2005
Page authored by Isabella Valli, student of Prof. Jay Lennon at IndianaUniversity.