Bdellovibrio
A Microbial Biorealm page on the genus Bdellovibrio
Classification
Higher order taxa
Kingdom: Bacteria Phylum: Proteobacteria Class: Deltaproteobacteria Order: Bdellovibrionales Family: Bdellovibrionaceae Genus: Bdellovibrio
Species: Bdellovibrio bacteriovorus
Species
B. bacteriovorus; B. starrii; B. stolpii
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NCBI: Taxonomy |
Description and significance
Bdellovibrio is a genus of small, highly motile, vibrio shaped, monoflagellated, gram negative bacteria of the class delta-proteobacteria with the ability to parasitize and kill other gram negative bacteria[1]. This includes many pathogens, a few of the genera being: Alcaligenes, Campylobacter, Erwinia, Escherichia, Helicobacter, Pseudomonas, Salmonella, Legionella, and Shigella1. Bdellovibrio have what is described as a biphasic lifestyle with a motile, free-living “hunting” phase and an intra-cellular parasitizing growth phase [1],[2]. The intra-cellular phase of Bdellovibrio is restricted to the periplasm, where the prey’s physiology is modified to suit the predator, forming a distinctive bdelloplast[5]. Wild type Bdellovibrio are obligate parasites and must live out part of their lives in a host or die[4]; however, researchers have been able to artificially culture certain strains of Bdellovibrio on rich media in the lab. Bdellovibrio are normally grown in E. coli prey cultures in the lab, and colonies are isolated from plaques in confluent lawns of prey culture, similar to viruses[2]. The most widespread species, Bdellovibrio Bacteriovorus, inhabits a wide range of environments such as freshwater, brackish water, seawater, sewage, water pipes, animal intestines and other water reservoirs[3],[8].
Genome structure
The genome of B. bacterivorus has been recently published in 2004 by Rendulic et al. and has revealed a number of characteristics of, and mechanisms employed in its predatory lifestyle[4]. After initial discovery by Hans Stolp in 1963 and a period of enthusiastic biochemical and physiological research, the effort substantially dropped. It wasn’t until recently with the advent of molecular genetics and sequencing that work on Bdellovibrio has picked up[6]. Sequencing of the HD(Host-Dependent)100 strain yielded a large 3.85Mb genome which was surprising considering the small size of the bacterium (0.2 to 0.5 μm by 0.5 to 2.5 μm)[4],[6]. The genome is devoid of any plasmids and contains only a single IS element and one prophage[4]. The G/C content of the genome was also fairly constant among all genes which indicates that no lateral gene transfers have occurred in recent times[7], despite being in constant contact with prey genomes containing high G/C content[4],[6].
Cell structure and metabolism
B. bacteriovorus is a gram-negative rod shaped bacterium that is highly motile. On average, B. bacteriovorus is 0.2 to 0.5 μm by 0.5 to 2.5 μm in size. It thrives on the degradation products of the host’s proteins and nucleic acids. The bacterium is comprised of a helical filament of flagellum that is contained within a membrane sheath; this membrane sheath is then surrounded by a basal sheath.
The life cycle of B. bacteriovorus includes five stages. First, the bacterium attaches itself to the host's outer membrane using a hook-like extension which breaks down the outer cell wall through the release of certain enzymes. This is followed by penetration into the periplasm and the repair of damage done to the cell membrane. Once the bacterium is inside the periplasm, it introduces hydrolytic enzymes into the host cytoplasm. This increases the bacterium’s food supply by making the inner membrane of the host cell “leaky.” The bacterium then grows and once it has exhausted all the resources in the host’s cell, it divides into as many as 15 motile cells. The weakened host cell lyses, releasing progeny B. bacteriovirus bacteria, which are then ready to find new prey to attack. This life cycle takes up to three to four hours.
Ecology
This bacterium is commonly found in water of different qualities including some water treatment plants. It can also be found in man-made habitats, the rhizosphere of plant roots, and soil. It has also been observed to reside in the intestinal tract of certain mammals where it reduces pathogens in the intestines. B. bacteriovorus is useful in the purification of waste water because it decreases gram-negative bacterial counts.
Current Research
The genome of Bdellovibrio has been recently sequenced and researchers found out that it contains roughly 3.8 megabases of DNA, which makes it similar to the size of E. coli. Bdellovibrio controls biofilms and in turn is also able to control pathogens. This bacteria might be useful in future medical advances, if gram-negative pathogens would need to be reduced in the body.
References
Bacteria Genomes BDELLOVIBRIO BACTERIOVORUS. (2006, August 30). 2Can Support Portal: Genomes- All Genomes. Retrieved November 3, 2006, from http://www.ebi.ac.uk/2can/genomes/genomes.html?http://www.ebi.ac.uk/2can/genomes/bacteria/Bdellovibrio_bacteriovorus.html
Bacterial Nomenclature Up-to-Date. (2004). DSMZ- the German Resource Centre for Biological Material. Retrieved November 3, 2006, from http://www.dsmz.de/microorganisms/bacterial_nomenclature_info.php?genus=Bdellovibrio&show_all_details=1
Bdellovibrio bacteriovorus. (2006). MEROPS- the peptidase database. Retrieved November 3, 2006, from MEROPS database: http://merops.sanger.ac.uk/cgi-bin/speccards?sp=sp002161&type=P
Bdellovibrio genome sequenced. (2006). Genome Biology Research News. Retrieved November 3, 2006, from http://genomebiology.com/researchnews/ default.asp?arx_id=gb-spotlight-20040130-01
Fox, J. F. (2006). Bdellovibrio make fast food of gram-negative bacteria . In Microbe Magazine. Retrieved December 10, 2006, from http://www.asm.org/ microbe/index.asp?bid=44300
Lambert, C., Smith, M. C. M., & Sockett, R. E. (2003, February). A novel assay to monitor predator-prety interaction for Bdellovibrio bacteriovorus 109 J reveals a role for methylaccepting chemotaxis proteins in predation. Environmental Biology, 5(2), 127. Abstract retrieved November 3, 2006, from http://www.blackwell-synergy.com/links/doi/10.1046/ j.1462-2920.2003.00385.x
Shemesh, Y., Davidov, Y., Koval, S., & Edouard, J. (2003). [Review of the scientific experiment Small eats big: ecology and diversity of Bdellovibrio and like organisms, and their dynamics in predator-prey interactions]. EDP Sciences, 23, 433-439. Retrieved November 3, 2006, from http://www.edpsciences.org/articles/agro/pdf/2003/05/A3505.pdf?access=ok
Schwudke, D., Linscheid, M., Strauch, E., Appel, B., Zahringer, U., Moll, H., et al. (2003, July 25). The Obligate Predatory Bdellovibrio bacteriovorus Possesses a Neurtal Lid A Containing {-D-Mannoses That Replace Phosphate Residues. Biol. Chem, 278(30), 27502-27512. Retrieved November 10, 2006, from jbc ONLINE database: http://www.jbc.org/cgi/content/full/278/30/27502
Edited by Swetha Desai, Krystina Eikeseth, Janice Silva, and Derron Simmonds- students of Dr. Kirk Bartholomew
