Aeromonas veronii and the leech Hirudo
Characteristics of the symbiont/pathogen
Aeromonas veronii is a gram-negative, rod shaped bacteria [1] and has a genome size of about 4551783 base pairs [2]. It belongs to the Kingdom of bacteria, the phylum of proteobacteria, the class gammaproteobacteria, the order Aeromonadales, the family Aeromonadaceae, and the genus Aeromonas [2].
Characteristics of the host
A. veronii typically inhabits the digestive tract of, and shares in a symbiotic relationship with a number of differnt organisms of the genus Hirudo. Hirudo are a genus of leeches which are used for medicinal purposes and while there are many different species of Hirudo which A. veronii inhabit, this page will focus mainly on the relationship between A. veronii and H. medicinalis. A. veronii are most commonly found in the digestive tracts of the medicinal leech Hirudo medicinalis (3). This particular leech is widely used to prevent complications after surgery by alleviating potentially harmful blood clots (3). A. veroniican also be found residing in humans and other vertebrates, and may also inhabit fresh water environments (3).
Host-Symbiont Interaction
A. veronii and H. medicinalis share in a mutualistic relationship. It is thought that A. veronii and other Aeromonas species which live in the gut of H. medicinalis help the medicinal leech to break down and digest its blood meals (4). A. veronii is typically found as a pure culture existing in the gut of H. medicinalis and A. veronii can be transmitted vertically from one generation to the next (5). This transmission is thouhgt to occur when the eggs of the hermaphroditic H. medicinalis adult, hatch inside of their cocoon, which is full fluids which are abundant with A. veronii, and feed on the cocoon from which they came (5).
Molecular Insights into the Symbiosis
There have been many differnt studies done on the symbiotic partnership of A. veronii and H. medicinalis. Many of the studies have centered around how to better understand the specifics of the relationship between the two organsims and how their relationship may adversely affect the medicinal uses of the leech which A. veronii inhabits. This symbiotic partnership has also been exstensivley studied because H. medicinalis is a simple model organisms which scientists can use to better understand the nature of symbiotic relationships (5). Scientists have use comperative anlaysis and culture independent techniques to aid in these studies.
Ecological and Evolutionary Aspects
What is the evolutionary history of the interaction? Do particular environmental factors play a role in regulating the symbiosis?
Recent Discoveries
Describe two findings on the symbiosis published within the last two years.
References
[1] Mencacci, Anotella, Elio Cenci, Rosanna Mazolla, Senia Farinelli, Frencesco D’Alo, Mariolina Vitali, and Francesco Bistoni. 2003. “Aeromonas veronii biovar veronii septicaemia and acute suppurative cholangitis in a patient with hepatitis B.” Journal of Medical Microbiology 52: 727-730.
[2] http://www.genome.jp/kegg-bin/show_organism?org=avr
[3] Laufer, Alison S., Siddall, Mark E. and Graf, Joreg. 2008. “Characterization of the digestive-tract microbiota of Hirudo orientalis, a European medicinal leech. Antimicrobial Agents and Chemotherapy 74:6151-6154
Edited by [Gabrielle Woodford], students of Grace Lim-Fong
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