Bikont
Encyclopedia
A Bikont is a eukaryotic
cell with two flagella, as its name suggests. It is a division of eukaryote
s.
s into a single unit: the genes for thymidylate synthase
(TS) and dihydrofolate reductase
(DHFR) encode a single
protein
with two functions.
The genes are separately translated in unikont
s.
(a eukaryotic cell with a single flagellum) was the ancestor of opisthokonts (Animals, Fungi, and related forms) and Amoebozoa
, and a bikont was the ancestor of Archaeplastida
(Plants and relatives), Excavata, Rhizaria
, and Chromalveolata
. Cavalier-Smith has suggested that Apusozoa
, which are typically considered incertae sedis
, are in fact bikonts.
Relationships within the bikonts are not yet clear. Cavalier-Smith has grouped the Excavata and Rhizaria into the Cabozoa
and the Archaeplastida
and Chromalveolata into the Corticata
, but at least one other study has suggested that the Rhizaria
and Chromalveolata form a clade
.
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...
cell with two flagella, as its name suggests. It is a division of eukaryote
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...
s.
Enzymes
Another shared trait of bikonts is the fusion of two geneGene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s into a single unit: the genes for thymidylate synthase
Thymidylate synthase
Thymidylate synthetase is the enzyme used to generate thymidine monophosphate , which is subsequently phosphorylated to thymidine triphosphate for use in DNA synthesis and repair....
(TS) and dihydrofolate reductase
Dihydrofolate reductase
- Function :Dihydrofolate reductase converts dihydrofolate into tetrahydrofolate, a methyl group shuttle required for the de novo synthesis of purines, thymidylic acid, and certain amino acids...
(DHFR) encode a single
protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
with two functions.
The genes are separately translated in unikont
Unikont
Unikonts are members of the Unikonta, a taxonomic group proposed by Thomas Cavalier-Smith.It includes amoebozoa, opisthokonts, and Apusozoa.-Clade:...
s.
Relationships
Some research suggests that a unikontUnikont
Unikonts are members of the Unikonta, a taxonomic group proposed by Thomas Cavalier-Smith.It includes amoebozoa, opisthokonts, and Apusozoa.-Clade:...
(a eukaryotic cell with a single flagellum) was the ancestor of opisthokonts (Animals, Fungi, and related forms) and Amoebozoa
Amoebozoa
The Amoebozoa are a major group of amoeboid protozoa, including the majority that move by means ofinternal cytoplasmic flow. Their pseudopodia are characteristically blunt and finger-like,...
, and a bikont was the ancestor of Archaeplastida
Archaeplastida
The Archaeplastida are a major group of eukaryotes, comprising the red and green algae and the land plants, together with a small group called the glaucophytes. The plastids of all of these organisms are surrounded by two membranes, suggesting they developed directly from endosymbiotic...
(Plants and relatives), Excavata, Rhizaria
Rhizaria
The Rhizaria are a species-rich supergroup of unicellular eukaryotes. This supergroup was proposed by Cavalier-Smith in 2002. They vary considerably in form, but for the most part they are amoeboids with filose, reticulose, or microtubule-supported pseudopods...
, and Chromalveolata
Chromalveolate
Chromalveolata is a eukaryote supergroup first proposed by Thomas Cavalier-Smith as a refinement of his kingdom Chromista, which was first put forward in 1981. Chromalveolata was proposed to represent the result of a single secondary endosymbiosis between a line descending from a bikont and a red...
. Cavalier-Smith has suggested that Apusozoa
Apusozoa
The Apusozoa are a phylum comprising several genera of flagellate protozoa. They are usually around 5-20 μm in size, and occur in soils and aquatic habitats, where they feed on bacteria...
, which are typically considered incertae sedis
Incertae sedis
, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
, are in fact bikonts.
Relationships within the bikonts are not yet clear. Cavalier-Smith has grouped the Excavata and Rhizaria into the Cabozoa
Cabozoa
In the classification of eukaryotes , Cabozoa was a taxon proposed by Cavalier-Smith.It was a putative clade comprising the Rhizaria and Excavata. More recent research tends to place the Rhizaria with the Alveolata and heterokonts instead of the Excavata, however....
and the Archaeplastida
Archaeplastida
The Archaeplastida are a major group of eukaryotes, comprising the red and green algae and the land plants, together with a small group called the glaucophytes. The plastids of all of these organisms are surrounded by two membranes, suggesting they developed directly from endosymbiotic...
and Chromalveolata into the Corticata
Corticata
Corticata , in the classification of eukaryotes , is a clade suggested by Cavalier-Smith to encompass the eukaryote supergroups of the following two groups:...
, but at least one other study has suggested that the Rhizaria
Rhizaria
The Rhizaria are a species-rich supergroup of unicellular eukaryotes. This supergroup was proposed by Cavalier-Smith in 2002. They vary considerably in form, but for the most part they are amoeboids with filose, reticulose, or microtubule-supported pseudopods...
and Chromalveolata form a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
.