Bdellovibrio
Bdellovibrio | |
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Central slice through a cryotomogram of an intact Bdellovibrio bacteriovorus cell. Scale bar 200 nm
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Scientific classification | |
Domain: | Bacteria |
Phylum: | Bdellovibrionota |
Class: | Bdellovibrionia
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Order: | Bdellovibrionales |
Family: | Bdellovibrionaceae |
Genus: | Bdellovibrio |
Type species | |
Bdellovibrio bacteriovorus Stolp & Starr 1963
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Species | |
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Bdellovibrio is a
Bdellovibrio bacteriovorus
The most well studied of these is Bdellovibrio bacteriovorus, which is found almost exclusively in host dependent growth in nature. In this free swimming attack form after searching for prey using its pili, it burrows through the host outer membrane/ peptidoglycan cell wall and enters the
Bdellovibrio bacteriovorus was first described by Stolp and Petzold in 1962. In 2012 another member of the Bdellovibrio species was identified "Bdellovibrio tiberius" of the River tiber.[3] This species is more capable of host-independent growth.
Little is known of Bdellovibrio exovorus,[4] an extra-parasitic bdellovibrio, which cannot enter its prey, and does not form Bdelloplasts.
Appearance
Under a light microscope, host-dependent Bdellovibrio appears to be a comma-shaped motile rod that is about 0.3–0.5 by 0.5–1.4 μm in size with a barely discernible flagellum. Bdellovibrio show up as a growing clear plaque in an E. coli "lawn". Notably, Bdellovibrio has a sheath that covers its flagellum – a rare feature for bacteria. Flagellar motion stops once Bdellovibrio has penetrated its prey, and the flagella is then shed.
Host-independent Bdellovibrio appear amorphous, and larger than the predatory phase.
Culture conditions
B. bacteriovorus appears to be ubiquitous in nature and manmade habitats. They have been found in soil samples, rhizosphere of plant roots, rivers, oceans, sewage, intestines and feces of birds and mammals, and even in oyster shells and the gills of crabs.[5] B. bacteriovorus are able to thrive in almost any habitat, the general requirements are that there needs to be oxygen and some other Gram-negative bacteria present in its environment. Its optimal temperature is between 28-30 °C, making B. bacteriovorus a mesophile. Bdellovibrio is grown in the laboratory in its stationary HI (host-independent) phase at 29 °C on yeast peptone broth agar. Host-dependent (predatory) cultures are grown with a population of E. coli S-17 at 29 °C for 16 hrs.[3] They may also be cultured using YPSC (yeast extract, peptone, sodium acetate, calcium chloride) overlays or prey lysates.[citation needed]
Life cycle and parasitism
Bdellovibrio cells can swim as fast as 160 μm/s, or over 100 times their body-length per second. It swims using a
After the recognition period, it becomes irreversibly attached via the pole opposite the flagellum. Once inside the periplasm, the Bdellovibrio cell seals the membrane hole and converts the host cell to a spherical morphology, this is due to secretion of L,D transpeptidases which breaks the peptidoglycan apart, and therefore causes the cell to become amorphous. The two-cell complex formed is called a bdelloplast. The Bdellovibrio cell uses hydrolytic enzymes to break down the host cell molecules, which it uses to grow filamentously. When the host cell nutrients are exhausted, the filament septates to form progeny Bdellovibrios. The progeny become motile before they lyse the host cell and are released into the environment. The entire life cycle takes three to four hours, and produces an average of 3–6 progeny cells from a single E. coli, or up to 90 from larger prey such as filamentous E. coli.[7]
Targets of Bdellovibrio species, including Vibrio vulnificus, may undergo co-infection by Bdellovibrio and bacteriophage.[8] Although the Bdellovibrio rounding of prey is thought to be evolved to reduce co-infection of multiple Bdellovibrio, larger prey that do not round may be infected by multiple Bdello's.
Genomics
The genome of Bdellovibrio bacteriovorus HD100 was sequenced in 2004.[9] The HD100 genome is 3782950 nucleotides long, larger than expected given its small size.[10]
See also
References
- PMID 33843574.
- PMID 4908670.
- ^ PMID 23181807.
- PMID 22368169.
- S2CID 17194037.
- ISBN 978-0-321-73551-5.
- ISBN 978-3-540-38577-6.
- PMID 22511350.
- S2CID 38154836.
- ISBN 978-3-540-38577-6.
External links
- "Type-strain of Bdellovibrio bacteriovorus at Bac Dive". The Bacterial Diversity Metadatabase.