Vampirovibrio Chlorellavorus
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''Vampirovibrio chlorellavorus'' is a 0.6 μm pleomorphic
coccus Bacterial cellular morphologies are the shapes that are characteristic of various types of bacteria and often key to their identification. Their direct examination under a light microscope enables the classification of these bacteria (and archaea ...
with a
gram negative 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 that their cell envelope consists of ...
cell wall,
This book cites this research:
and is one of the few known predatory bacteria. These secondary sources cite this research:
Unlike many bacteria, ''V. chlorellavorus'' is an obligate parasite, attaching to the
cell wall A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...
of
green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...
of the genus ''
Chlorella ''Chlorella'' is a genus of about thirteen species of single- celled or colonial green algae of the division Chlorophyta. The cells are spherical in shape, about 2 to 10 μm in diameter, and are without flagella. Their chloroplasts contain t ...
''. The name ''Vampirovibrio'' originates from the Serbian (
Cyrillic The Cyrillic script ( ) is a writing system used for various languages across Eurasia. It is the designated national script in various Slavic, Turkic, Mongolic, Uralic, Caucasian and Iranic-speaking countries in Southeastern Europe, Ea ...
: ). meaning vampire (due to the nature of sucking out cellular contents of its prey) and ''
vibrio ''Vibrio'' is a genus of Gram-negative bacteria, which have a characteristic curved-rod (comma) shape, several species of which can cause foodborne infection or soft-tissue infection called Vibriosis. Infection is commonly associated with eati ...
'' referring to the bacterial genus of curved rod bacterium. ''Chlorellavorus'' is named for the algal host of the bacterium (''
Chlorella ''Chlorella'' is a genus of about thirteen species of single- celled or colonial green algae of the division Chlorophyta. The cells are spherical in shape, about 2 to 10 μm in diameter, and are without flagella. Their chloroplasts contain t ...
'') 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 intracellular parasites, both residing and dividing in the periplasmic space in its host, whereas ''Vampirovibrio'' is epibiotic, attaching to the
cell wall A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...
of
green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...
in the genus ''
Chlorella ''Chlorella'' is a genus of about thirteen species of single- celled or colonial green algae of the division Chlorophyta. The cells are spherical in shape, about 2 to 10 μm in diameter, and are without flagella. Their chloroplasts contain t ...
''. It was also originally thought that the bacterium utilized a
flagellum A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...
for motility. However, it was later discovered that the bacterium was non-motile, further differentiating it from members of ''Bdellovibrio''. By analyzing the genome of ''V. chlorellavorus'', Soo and Hugenholtz determined that the organism was more accurately a Cyanobacterium rather than a Proteobacterium. Using
16S rRNA 16S ribosomal RNA (or 16Svedberg, S rRNA) is the RNA component of the 30S subunit of a prokaryotic ribosome (SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure. The genes coding for it are referred to as ...
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. ''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.


Preliminary characterization

''Vampirovibrio chlorellavorus'' is a
gram-negative 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 that their cell envelope consists ...
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 The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...
of the genus ''
Chlorella ''Chlorella'' is a genus of about thirteen species of single- celled or colonial green algae of the division Chlorophyta. The cells are spherical in shape, about 2 to 10 μm in diameter, and are without flagella. Their chloroplasts contain t ...
''. ''V. chlorellavorus'' is an
extracellular This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices; for more specific and technical definitions ...
parasite Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...
and remains attached to the cell wall. Once attached to its host, ''V. chlorellavorus'' divides by
binary fission Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two values (0 and 1) for each digit * Binary function, a function that takes two arguments * Binary operation, a mathematical o ...
, 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 The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the cytoplasm, interior of a Cell (biology), cell from the extrac ...
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 Lysis ( ; from Greek 'loosening') is the breaking down of the membrane of a cell, often by viral, enzymic, or osmotic (that is, "lytic" ) mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a ...
experiment with the algae '' Chlorella vulgaris'' from Ukrainian reservoir waters from a mass culture of the algae in 1966. In a later experiment, the scientists were then able to cultivate ''B. chlorellavorus'' together with '' Chlorella vulgaris'' at and pH 6.8 in a liquid agar solution under fluorescent lighting (at an average of 2100 lux).


Culture status

The type strain of bacterium is deposited as a lyophilised co-culture with '' C. vulgaris'' in three culture collections (ATCC 29753; NCIB 11383; NCIMB 11383), but all attempts to revive these cultures have failed as of 2015. Live co-cultures have been established from samples collected in the USA, where this bacterium has greatly disrupted the growth of '' C. sorokiniana'' microalgae in outdoor bioreactors.


Genomics

Although the original lyophilized culture of ''V. chlorellavourus''Gromov B, Mamkaeva K. 1980. Proposal of a new genus ''Vampirovibrio'' for chlorellavorus bacteria previously assigned to ''Bdellovibrio''. Mikrobiologia 49:165–167. with ''C. vulgaris'' from Ukraine (deposited as NCIB 11383) could not be revived, it contained enough DNA. Dr. Hugenholtz and colleagues from the
University of Queensland The University of Queensland is a Public university, public research university located primarily in Brisbane, the capital city of the Australian state of Queensland. Founded in 1909 by the Queensland parliament, UQ is one of the six sandstone ...
in Australia performed
shotgun sequencing In genetics, shotgun sequencing is a method used for sequencing random DNA strands. It is named by analogy with the rapidly expanding, quasi-random shot grouping of a shotgun. The Sanger sequencing#Method, chain-termination method of DNA sequencin ...
of these projects. Subsequently, Soo and Hugenholtz's team reconstructed the genome from the shotgun reads and published their results in 2015. The bacterium's genome consists of 1 circular chromosome and 2 circular
plasmids A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria and ...
. The Soo team assembled not three whole molecules, but 26 contigs totaling 2.91 Mbp. The GC content was 51.4%. Soo et al. found that ''V. chlorellavorus'' uses a type IV secretion system (T4SS), similar to that of ''
Agrobacterium tumefaciens ''Agrobacterium tumefaciens'' (also known as ''Rhizobium radiobacter'') is the causal agent of crown gall disease (the formation of tumours) in over 140 species of eudicots. It is a rod-shaped, Gram-negative soil bacterium. Symptoms are cause ...
'' for host invasion, which is conserved in all three copies of the ''V. chlorellavorus'' genome. 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 A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products. They do ...
and peptidases. In keeping with its description as non-photosynthetic and parasitic microorganism, ''V. chlorellavorus'' does not have its own genes for photosynthesis or
carbon fixation Biological carbon fixation, or сarbon assimilation, is the Biological process, process by which living organisms convert Total inorganic carbon, inorganic carbon (particularly carbon dioxide, ) to Organic compound, organic compounds. These o ...
. ''V. chlorellavorus'' is however capable of synthesizing its own
nucleotides Nucleotides are Organic compound, organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both o ...
, certain cofactors and vitamins, and 15 different
amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the Proteinogenic amino acid, 22 α-amino acids incorporated into p ...
. Its bacterial genome also includes coding for a complete
glycolysis Glycolysis is the metabolic pathway that converts glucose () into pyruvic acid, pyruvate and, in most organisms, occurs in the liquid part of cells (the cytosol). The Thermodynamic free energy, free energy released in this process is used to form ...
pathway as well as an
electron transport chain An electron transport chain (ETC) is a series of protein complexes and other molecules which transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples th ...
. The genomes for the US bioreactor strains were published in 2020. No plasmids were found in these two strains. Vc_AZ_1 assembled into 11 contigs totaling 2.78 Mbp via metagenome, with 54.8% GC. Vc_AZ_2 assembled into 38 contigs totaling 2.98 Mbp via Hi-C, with 53.0% GC. GTDB splits RS226 currently-sequenced ''V. chlorellavorus'' genomes into four species-sized clusters. ''V. chlorellavorus'' includes Soo's type strain sequence. ''V. chlorellavorus''_A includes Vc_AZ_2. ''V. chlorellavorus''_B includes Vc_AZ_1. ''V. chlorellavorus''_D includes a few Swedish samples. Four additional unnamed species-sized clusters were identified in ''Vampirovibrio''.


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 29753

Soo
et al., 2015. Back from the dead; the curious tale of the predatory cyanobacterium //Vampirovibrio chlorellavorus// {{Taxonbar, from1=Q20721471, from2=Q20993378, from3=Q20993392, from4=Q20993405 Parasites of plants