Bdellovibrio

Bdellovibrio
	Central slice through a cryotomogram of an intact Bdellovibrio bacteriovorus cell. Scale bar 200 nm
Scientific classification
Domain:	Bacteria
Phylum:	Bdellovibrionota
Class:	Bdellovibrionia
Order:	Bdellovibrionales
Family:	Bdellovibrionaceae
Genus:	Bdellovibrio
Type species
	Bdellovibrio bacteriovorus ; Stolp & Starr 1963
Species
	B. bacteriovorus ; B. reynosensis;

Last updated April 23, 2024

Bdellovibrio is a genus of Gram-negative, obligate aerobic bacteria. One of the more notable characteristics of this genus is that members can prey upon other Gram-negative bacteria and feed on the biopolymers, e.g. proteins and nucleic acids, of their hosts. They have two lifestyles: a host-dependent, highly mobile phase, the "attack phase", in which they form "bdelloplasts" in their host bacteria; and a slow-growing, irregularly shaped, host-independent form.^[1]

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 periplasmic space. The Bdellovibrio bacterium then forms a structure called a bdelloplast. This bdelloplast is created as the host cell is modified to become spherical in shape. Inside the bdelloplast, the singular large flagellum of the predatory Bdellovibrio is lost. The host cell is then rapidly killed allowing the passage of molecules from the interior of the host cytoplasm through to the periplasm freely, and the periplasm dwelling Bdellovibrio to feed.^[2] Using some of these molecules the Bdellovibrio creates a protective environment by reinforcing the peptidoglycan cell wall of the host in which it now dwells using amidases and transpeptidases. After around 4hrs, depending on ambient temperature, the Bdellovibrio has increased in size dramatically through this nourishment. It divides to replicate and then leaves via a final lysis of the host's cell wall and membranes. The newly emerging Bdellovibrio use their newly grown powerful flagella to swim away and find the next suitable host. Because of this intermittent bdelloplast stage, and momentary parasitic phase (15-20 mins), Bdellovibrio could be considered bacterial predators or parasites.

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 life cycle. The Bdellovibrio attaches to a Gram-negative bacterium after contact, and penetrates into the prey's periplasmic space. Once inside, elongation occurs and progeny cells are released within 4 hours. Bellovibrio-cycle.svg — *Bdellovibrio* life cycle. The *Bdellovibrio* attaches to a Gram-negative bacterium after contact, and penetrates into the prey's periplasmic space. Once inside, elongation occurs and progeny cells are released within 4 hours.

Bdellovibrio cells can swim as fast as 160 μm/s, or over 100 times their body-length per second. It swims using a single sheathed polar flagellum with a characteristic dampened filament waveform. Bdellovibrio attacks other Gram-negative bacteria by attaching itself to the prey cell's outer membrane and peptidoglycan layer, after which it creates a small hole in the outer membrane. The Bdellovibrio cell then enters the host periplasmic space. It remains reversibly attached to it for a short "recognition" period.

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]

Related Research Articles

<span class="mw-page-title-main">Gram stain</span> Investigative procedure in microbiology

Gram stain, is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. It may also be used to diagnose a fungal infection. The name comes from the Danish bacteriologist Hans Christian Gram, who developed the technique in 1884.

In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall.

Gram-negative bacteria are bacteria that unlike gram-positive bacteria do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is their cell envelope, which consists of a thin peptidoglycan cell wall sandwiched between an inner (cytoplasmic) membrane and an outer membrane. These bacteria are found in all environments that support life on Earth.

Peptidoglycan or murein is a unique large macromolecule, a polysaccharide, consisting of sugars and amino acids that forms a mesh-like layer (sacculus) that surrounds the bacterial cytoplasmic membrane. The sugar component consists of alternating residues of β-(1,4) linked N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). Attached to the N-acetylmuramic acid is an oligopeptide chain made of three to five amino acids. The peptide chain can be cross-linked to the peptide chain of another strand forming the 3D mesh-like layer. Peptidoglycan serves a structural role in the bacterial cell wall, giving structural strength, as well as counteracting the osmotic pressure of the cytoplasm. This repetitive linking results in a dense peptidoglycan layer which is critical for maintaining cell form and withstanding high osmotic pressures, and it is regularly replaced by peptidoglycan production. Peptidoglycan hydrolysis and synthesis are two processes that must occur in order for cells to grow and multiply, a technique carried out in three stages: clipping of current material, insertion of new material, and re-crosslinking of existing material to new material.

The periplasm is a concentrated gel-like matrix in the space between the inner cytoplasmic membrane and the bacterial outer membrane called the periplasmic space in gram-negative bacteria. Using cryo-electron microscopy it has been found that a much smaller periplasmic space is also present in gram-positive bacteria, between cell wall and the plasma membrane. The periplasm may constitute up to 40% of the total cell volume of gram-negative bacteria, but is a much smaller percentage in gram-positive bacteria.

The cell envelope comprises the inner cell membrane and the cell wall of a bacterium. In gram-negative bacteria an outer membrane is also included. This envelope is not present in the Mollicutes where the cell wall is absent.

The bacterial outer membrane is found in gram-negative bacteria. Gram-negative bacteria form two lipid bilayers in their cell envelopes - an inner membrane (IM) that encapsulates the cytoplasm, and an outer membrane (OM) that encapsulates the periplasm.

A bacterium, despite its simplicity, contains a well-developed cell structure which is responsible for some of its unique biological structures and pathogenicity. Many structural features are unique to bacteria and are not found among archaea or eukaryotes. Because of the simplicity of bacteria relative to larger organisms and the ease with which they can be manipulated experimentally, the cell structure of bacteria has been well studied, revealing many biochemical principles that have been subsequently applied to other organisms.

Bacteria are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria play a vital role in many stages of the nutrient cycle by recycling nutrients and the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of dead bodies; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Bacteria also live in mutualistic, commensal and parasitic relationships with plants and animals. Most bacteria have not been characterised and there are many species that cannot be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.

Vampirococcus is an informally described genus of ovoid Gram-negative bacteria, but the exact phylogeny remains to be determined. This predatory prokaryote was first described in 1983 by Esteve et al. as small, anaerobic microbe about 0.6 μm wide before being given the name of Vampirococcus in 1986 by Guerrero et al. This prokaryote is a freshwater obligate predator that preys specifically on various species of the photosynthetic purple sulfur bacterium, Chromatium. As an epibiont, Vampirococcus attaches to the cell surface of their prey and "sucks" out the cytoplasm using a specialized cytoplasmic bridge. They are commonly mentioned as an example of epibionts when discussing strategies employed by bacterial predators. This microbe still has yet to be classified based on genomic sequencing or 16S rRNA because it cannot be sustained long enough outside its natural environment to isolate a pure culture.

Micavibrio aeruginosavorus is a species of epibiotic predatory bacteria. Unlike Bdellovibrio, Micavibrio do not invade the periplasmic space of their prey, but feed by attaching themselves to its surface.

Bacterial morphological plasticity refers to changes in the shape and size that bacterial cells undergo when they encounter stressful environments. Although bacteria have evolved complex molecular strategies to maintain their shape, many are able to alter their shape as a survival strategy in response to protist predators, antibiotics, the immune response, and other threats.

Outer membrane vesicles (OMVs) are vesicles released from the outer membranes of Gram-negative bacteria. While Gram-positive bacteria release vesicles as well those vesicles fall under the broader category of bacterial membrane vesicles (MVs). OMVs were the first MVs to be discovered, and are distinguished from outer inner membrane vesicles (OIMVS), which are gram-negative baterial vesicles containing portions of both the outer and inner bacterial membrane. Outer membrane vesicles were first discovered and characterized using transmission-electron microscopy by Indian Scientist Prof. Smriti Narayan Chatterjee and J. Das in 1966-67. OMVs are ascribed the functionality to provide a manner to communicate among themselves, with other microorganisms in their environment and with the host. These vesicles are involved in trafficking bacterial cell signaling biochemicals, which may include DNA, RNA, proteins, endotoxins and allied virulence molecules. This communication happens in microbial cultures in oceans, inside animals, plants and even inside the human body.

Bacteriovorax is a genus containing a single species of bacterium in the family Bacteriovoracaceae, Bacteriovorax stolpii. It is a predator that feeds on larger Gram-negative bacteria. These prey bacteria tend to live in enteric environments and have similar lipopolysaccharide structures. Bacteriovorax stolpii recognizes its prey by outer membrane protein receptors, which explains why Gram-positive bacteria that lack outer membranes do not serve as prey. They prey on bacteria by invading the interperiplasmic space where they feed, grow, and reproduce. Bacteriovorax stolpii used to be classified in the genus Bdellovibrio because of similar morphologies and lifestyle characteristics, however they were recognized as a new genus through phylogenetic analysis.

The type 2 secretion system is a type of protein secretion machinery found in various species of Gram-negative bacteria, including many human pathogens such as Pseudomonas aeruginosa and Vibrio cholerae. The type II secretion system is one of six protein secretory systems commonly found in Gram-negative bacteria, along with the type I, type III, and type IV secretion systems, as well as the chaperone/usher pathway, the autotransporter pathway/type V secretion system, and the type VI secretion system. Like these other systems, the type II secretion system enables the transport of cytoplasmic proteins across the lipid bilayers that make up the cell membranes of Gram-negative bacteria. Secretion of proteins and effector molecules out of the cell plays a critical role in signaling other cells and in the invasion and parasitism of host cells.

<i>Vampirovibrio chlorellavorus</i> Gram-negative bacteria, algae predator

Vampirovibrio chlorellavorus is a 0.6 µm pleomorphic cocci with a gram negative cell wall, and is one of the few known predatory bacteria. Unlike many bacteria, V. chlorellavorus is an obligate parasite, attaching to the cell wall of green algae of the genus Chlorella. The name Vampirovibrio originates from the Serbian vampir. meaning vampire and vibrio referring to the bacterial genus of curved rod bacterium. Chlorellavorus is named for the algal host of the bacterium (Chlorella) and the Latin voro meaning "to devour" (Chlorella-devouring).

Resistance-nodulation-division (RND) family transporters are a category of bacterial efflux pumps, especially identified in Gram-negative bacteria and located in the cytoplasmic membrane, that actively transport substrates. The RND superfamily includes seven families: the heavy metal efflux (HME), the hydrophobe/amphiphile efflux-1, the nodulation factor exporter family (NFE), the SecDF protein-secretion accessory protein family, the hydrophobe/amphiphile efflux-2 family, the eukaryotic sterol homeostasis family, and the hydrophobe/amphiphile efflux-3 family. These RND systems are involved in maintaining homeostasis of the cell, removal of toxic compounds, and export of virulence determinants. They have a broad substrate spectrum and can lead to the diminished activity of unrelated drug classes if over-expressed. The first reports of drug resistant bacterial infections were reported in the 1940s after the first mass production of antibiotics. Most of the RND superfamily transport systems are made of large polypeptide chains. RND proteins exist primarily in gram-negative bacteria but can also be found in gram-positive bacteria, archaea, and eukaryotes.

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Renee Elizabeth Sockett is a professor and microbiologist in the School of Life Sciences at the University of Nottingham. She is a world-leading expert on Bdellovibrio bacteriovorus, a species of predatory bacteria.

References

↑ Lovering, Andrew L.; Sockett, R. Elizabeth (2021-04-12). "Microbe Profile: Bdellovibrio bacteriovorus: a specialized bacterial predator of bacteria". Microbiology. 167 (4): 001043. doi: 10.1099/mic.0.001043 . ISSN 1350-0872. PMC 8289219 . PMID 33843574.
↑ Rittenberg SC, Shilo M (April 1970). "Early host damage in the infection cycle of Bdellovibrio bacteriovorus". Journal of Bacteriology. 102 (1): 149–60. doi:10.1128/jb.102.1.149-160.1970. PMC 284981 . PMID 4908670.
1 2 Hobley L, Lerner TR, Williams LE, Lambert C, Till R, Milner DS, et al. (November 2012). "Genome analysis of a simultaneously predatory and prey-independent, novel Bdellovibrio bacteriovorus from the River Tiber, supports in silico predictions of both ancient and recent lateral gene transfer from diverse bacteria". BMC Genomics. 13: 670. doi: 10.1186/1471-2164-13-670 . PMC 3539863 . PMID 23181807.
↑ Koval SF, Hynes SH, Flannagan RS, Pasternak Z, Davidov Y, Jurkevitch E (January 2013). "Bdellovibrio exovorus sp. nov., a novel predator of Caulobacter crescentus". International Journal of Systematic and Evolutionary Microbiology. 63 (1): 146–151. doi: 10.1099/ijs.0.039701-0 . PMID 22368169.
↑ Shemesh, Y. (2003). "Small eats big: Ecology and diversity of Bdellovibrio and like organisms, and their dynamics in predator-prey interactions" (PDF). Agronomie. 23 (5–6): 433–439. doi:10.1051/agro:2003026. S2CID 17194037.
↑ Madigan, Michael T. (7 January 2011). Brock Biology of Microorganisms (Global ed.). Pearson Education. ISBN 978-0-321-73551-5.
↑ Strauch, E.; Beck, S.; Appel, B. (2007). "Bdellovibrio and like organisms: Potential sources for new biochemicals and therapeutic agents?". Predatory Prokaryotes. Microbiology Monographs. Vol. 4. p. 131. doi:10.1007/7171_2006_055. ISBN 978-3-540-38577-6.
↑ Chen, H.; Williams, H.N. (2012). "Sharing of prey: Co-infection of a bacterium by a virus and a prokaryotic predator". mBio. 3 (2): e00051-12. doi:10.1128/mBio.00051-12. PMC 3345577 . PMID 22511350.
↑ Rendulic S, Jagtap P, Rosinus A, Eppinger M, Baar C, Lanz C, Keller H, Lambert C, Evans KJ, Goesmann A, Meyer F, Sockett RE, Schuster SC (January 2004). "A predator unmasked: Life cycle of Bdellovibrio bacteriovorus from a genomic perspective". Science. 303 (5658): 689–692. doi:10.1126/science.1093027. PMID 14752164. S2CID 38154836.
↑ Tudor, J. J.; McCann, M. P. (2007). "Genomic analysis and molecular biology of predatory prokaryotes". Predatory Prokaryotes. Microbiology Monographs. Vol. 4. p. 153. doi:10.1007/7171_056. ISBN 978-3-540-38577-6.

External links

"Type-strain of Bdellovibrio bacteriovorus at Bac Dive". The Bacterial Diversity Metadatabase.

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[1] Lovering, Andrew L.; Sockett, R. Elizabeth (2021-04-12). "Microbe Profile: Bdellovibrio bacteriovorus: a specialized bacterial predator of bacteria". Microbiology. 167 (4): 001043. doi: 10.1099/mic.0.001043 . ISSN 1350-0872. PMC 8289219 . PMID 33843574.

[2] Rittenberg SC, Shilo M (April 1970). "Early host damage in the infection cycle of Bdellovibrio bacteriovorus". Journal of Bacteriology. 102 (1): 149–60. doi:10.1128/jb.102.1.149-160.1970. PMC 284981 . PMID 4908670.

[Hobley_2012-3] 1 2 Hobley L, Lerner TR, Williams LE, Lambert C, Till R, Milner DS, et al. (November 2012). "Genome analysis of a simultaneously predatory and prey-independent, novel Bdellovibrio bacteriovorus from the River Tiber, supports in silico predictions of both ancient and recent lateral gene transfer from diverse bacteria". BMC Genomics. 13: 670. doi: 10.1186/1471-2164-13-670 . PMC 3539863 . PMID 23181807.

[4] Koval SF, Hynes SH, Flannagan RS, Pasternak Z, Davidov Y, Jurkevitch E (January 2013). "Bdellovibrio exovorus sp. nov., a novel predator of Caulobacter crescentus". International Journal of Systematic and Evolutionary Microbiology. 63 (1): 146–151. doi: 10.1099/ijs.0.039701-0 . PMID 22368169.

[5] Shemesh, Y. (2003). "Small eats big: Ecology and diversity of Bdellovibrio and like organisms, and their dynamics in predator-prey interactions" (PDF). Agronomie. 23 (5–6): 433–439. doi:10.1051/agro:2003026. S2CID 17194037.

[brock-6] Madigan, Michael T. (7 January 2011). Brock Biology of Microorganisms (Global ed.). Pearson Education. ISBN 978-0-321-73551-5.

[strauch-7] Strauch, E.; Beck, S.; Appel, B. (2007). "Bdellovibrio and like organisms: Potential sources for new biochemicals and therapeutic agents?". Predatory Prokaryotes. Microbiology Monographs. Vol. 4. p. 131. doi:10.1007/7171_2006_055. ISBN 978-3-540-38577-6.

[chen2012-8] Chen, H.; Williams, H.N. (2012). "Sharing of prey: Co-infection of a bacterium by a virus and a prokaryotic predator". mBio. 3 (2): e00051-12. doi:10.1128/mBio.00051-12. PMC 3345577 . PMID 22511350.

[9] Rendulic S, Jagtap P, Rosinus A, Eppinger M, Baar C, Lanz C, Keller H, Lambert C, Evans KJ, Goesmann A, Meyer F, Sockett RE, Schuster SC (January 2004). "A predator unmasked: Life cycle of Bdellovibrio bacteriovorus from a genomic perspective". Science. 303 (5658): 689–692. doi:10.1126/science.1093027. PMID 14752164. S2CID 38154836.

[Tudor-10] Tudor, J. J.; McCann, M. P. (2007). "Genomic analysis and molecular biology of predatory prokaryotes". Predatory Prokaryotes. Microbiology Monographs. Vol. 4. p. 153. doi:10.1007/7171_056. ISBN 978-3-540-38577-6.

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