Vampirovibrio chlorellavorus

''Vampirovibrio chlorellavorus'' is a 0.6 µm pleomorphic cocci with a gram negative cell wall,I. Esteve, R. Guerrero, E. Montesinos, and C. Abellà. "Electron Microscope Study of the Interaction of Epibiontic Bacteria with Chromatium minus in Natural Habitats." Microbial Ecology 9 (Apr 1983): 57-64. doi:10.1007/BF02011580 and is one of the few known predatory bacteria.Ricardo Guerrero, Lynn Margulis, ''et al''. "Predatory Prokaryotes: Predation and Primary Consumption Evolved in Bacteria." Evolution and Microbiology 83 (1986): 2138-142. Proceedings of the National Academy of Sciences of the United States of America. U.S. National Library of Medicine. doi:10.1073/pnas.83.7.2138 Unlike many bacteria, ''Vampirovibrio chlorellavorus'' is an obligate parasite, attaching to the cell wall of green algae of the genus ''Chlorella''. ''Vampirovibrio'' originates from the Serbian ( Cyrillic: ). meaning vampire (due to the nature of sucking out cellular contents of its prey) 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 meaning "to devour" (''Chlorella''-devouring)."Vampirovibrio." List of Prokaryotic Names with Standing in Nomenclature. Web.

Classification

The bacterium, first described by Gromov and Mamkayeva in 1972, was originally classified in the genus '' Bdellovibrio''."Vampirovibrio Chlorellavorus Gromov & Mamkayeva, 1980." WoRMS - World Register of Marine Species - Vampirovibrio Chlorellavorus Gromov & Mamkayeva, 1980. World Register of Marine Species, 2014 It was then reclassified as its own genus ''Vampirovibrio'' in 1980 after being excluded from the genus ''Bdellovibrio'' for some essential discrepancies. The most significant difference was that members of ''Bdellovibrio'' are extracellular parasites, both residing and dividing in the periplasmic space in its host, whereas ''Vampirovibrio'' is epibiotic, attaching to the cell wall of green algae in the genus ''Chlorella''. It was also thought that the bacterium utilized a thin, uncovered flagellum for motility. However, it was later discovered that the bacterium was non-motile, further differentiating it from members of ''Bdellovibrio''.

Further research however suggests that the latest classification of ''V. chlorellavorus'' is still incorrect. By analyzing the genome of ''V. chlorellavorus'', Soo and Hugenholtz determined that the organism was more accurately a Cyanobacteria rather than a Proteobacteria. Using 16S rRNA analysis, scientists have estimated that this bacterium most closely belongs to the SM1D11 lineage of bacteria, which has now been classified as the order Vampirovibrionales.Marie-Eve Monchamp, Piet Spaak, Francesco Pomati
Long Term Diversity and Distribution of Non-photosynthetic Cyanobacteria in Peri-Alpine Lakes
In: Front Microbiol., volume 9, No. 3344, 2019 Jan 14. doi:10.3389/fmicb.2018.03344, , PMID 30692982 ''Vampirovibrio chlorellavorus'' was formerly regarded as related to the family Bdellovibrionacae, which has been described as ''Bdellovibrio'' and like organisms or BALOs. However, when compared to other Cyanobacteria, ''Vampirovibrio'' is non-photosynthetic and seems to belong to Melainabacteria, from Greek root words meaning “nymph of dark waters.”. It was later decided that phylum Cyanobacteria, class Melainabacteria, order Vampirovibrionales, and family Vampirovibrionaceae more accurately classified the organism, although Melainabacteria is now described as a phylum in its own right, distinct from Cyanobacteria.

Preliminary Characterization

''Vampirovibrio chlorellavorus'' is a gram-negative obligate aerobic and epibiotic parasitic bacterium with a curved comma shape.Hugenholtz, P., and Soo, R.M. 2015. Recent summary of research on Vampirovibrio chlorellavorus that was also partially discussed at the March 2015 Department of Energy Joint Genome Institute Genomics of Energy and Environment Meeting. Personal correspondence. The bacterium attaches to the surface of green algae of the genus ''Chlorella''. ''V''. ''chlorellavorus'' is an extracellular parasite and remains attached to the cell wall. Once attached to its host, ''V. chlorellavorus'' divides by binary fission, destroying its host in the process by “sucking out” all of the cellular contents via peripheral vacuoles much like a vampire (hence the name ''Vampirovibrio''). ''V. chlorellavorus'' leaves behind only the cell wall and cytoplasmic membrane of ''Chromatium'' along with a few intracytoplasmic inclusions. ''V. chlorellavorus'' will not grow in axenic cultures, depending on access to living cells of its preferred algae host, ''Chlorella vulgaris'' for reproduction. The ''Vampirovibrio'' life cycle consists of: prey location, attachment, ingestion, binary division, and release.

Discovery and Isolation

Gromov and Mamkaeva first isolated ''Bdellovibrio chlorellavorus'' in a lysis experiment with the algae ''Chlorella vulgaris'' from Ukrainian reservoir waters from a mass culture of ''Chlorella Beijer'' in 1966. In a later experiment, the scientists were then able to cultivate ''B. chlorellavorus'' together with ''Chlorella vulgaris'' at 24 degrees Celsius and pH 6.8 in a liquid agar solution under fluorescent lighting (at an average of 2100 lux).

Genomics

Dr. Hugenholtz and colleagues from the University of Queensland in Australia, have completed shotgun sequencing of lyophilized cells of ''V. chlorellavourus'' strain Gromov B, Mamkaeva K. 1980. Proposal of a new genus ''Vampirovibrio'' for chlorellavorus bacteria previously assigned to ''Bdellovibrio''. Mikrobiologia 49:165–167. in culture with ''Chlorella vulgaris.'' Subsequently, Soo and Hugenholtz's team performed a genomic reconstruction in 2014 from a culture previously deposited into the NCBI collection in 1978 and were able to make a general metabolic reconstruction of the genome They found that ''V. chlorellavorus'' uses
type IV secretion system
(T4SS), similar to that of ''Agrobacterium tumefaciens'' for host invasion, which is conserved in all three copies of the ''V. chlorellavorus'' genome.Hugenholtz, P. 2015. Back from the dead, the curious tale of the predatory cyanobacterium Vampirovibrio chlorellavorus. March 2015 DOE JGI Genomics of energy and environment meeting. Web. To locate its prey, ''V. chlorellavorus'' seems to be equipped with possible genes for aerotaxis and light activated kinase (moving towards light), suggesting that it might be motile as was originally thought. To digest its algal prey, ''V. chlorellavorus'' has over 100 hydrolytic enzymes including proteases and peptidases. From the results of Soo and her team's genomic analysis, ''V. chlorellavorus'' has approximately 26 contigs, 2.91 Mbp, an average GC content of 51.4%, and 2 circular plasmids. In keeping with its description as non-photosynthetic and parasitic microorganism, ''V. chlorellavorus'' does not have its own genes for photosynthesis or carbon fixation. ''V. chlorellavorus'' is however capable of synthesizing its own nucleotides, certain cofactors and vitamins, and 15 different amino acids. Its bacterial genome also includes coding for a complete glycolysis pathway as well as an electron transport chain.

Research and Implications

''Vampirovibrio'' or ''Bdellovibrio'' may be used to help control harmful populations of bacteria due to their predatory nature. In an experiment where ''Bdellovibrio'' were added to a shrimp tank to consume populations of bacteria, the target bacterial populations declined by up to 44%. However the ''Bdellovibrio'' population declined as well after consuming most of the available bacteria. Therefore, use of ''Bdellovibrio'' as an inhibitor of other bacteria shows potential, but may be limited to certain cases as ''Bdellovibrio'' prefers certain strains, such as gram-negative bacteria. In a subsequent experiment, chickens, highly susceptible to cecal or gut infections, were used in an experiment in which scientists purposely infected chickens with a pathogenic form of ''Salmonella enterica''. The chicken were then exposed to ''Bdellovibrio bacteriovorus'', after which a reduction in inflammation and other harmful changes in the chickens’ ceca were observed as a result of decreased ''Salmonella'' populations. The success of this experiment suggest there is significant potential for ''Bdellovibrio'' in bioremediation. Since ''Vampirovibrio chlorellavorus'' has not been cultured in recent years, it is possible to learn about its future research applications by learning about the methods in which ''Bdellovibrio'' and like organisms, or BALOs, are used to control pathogenic bacteria.

References

External links

"Phil Hugenholtz at the 2015 DOE JGI Genomics of Energy & Environment Meeting"Dr. Hugenholtz' website featuring his current areas of researchInformation about V. chlorellavorus by its strain number ATCC 29753Soo
et al., 2015. Back from the dead; the curious tale of the predatory cyanobacterium Vampirovibrio chlorellavorus

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Bacteria
Parasites of plants