''Gloeobacter'' is a genus of
cyanobacteria
Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...
. It is the
sister group
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree.
Definition
The expression is most easily illustrated by a cladogram:
Taxon A and ...
to all other photosynthetic
cyanobacteria
Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...
.
''Gloeobacters order, Gloeobacterales, is unique among cyanobacteria in not having
thylakoid
Thylakoids are membrane-bound compartments inside chloroplasts and cyanobacterium, cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. Thylakoids consist of a #Membrane, thylakoid membrane surrounding a #Lumen, ...
s, which are characteristic for all other cyanobacteria and
chloroplast
A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...
s. Instead, the
light-harvesting complex
In biology, a light-harvesting complex or LHC is an aggregate consisting of proteins bound with chromophores (chlorophylls and carotenoids) that play a key role in photosynthesis. LHCs are arrayed around photosynthetic reaction centers in both pl ...
es (also called
phycobilisome
Phycobilisomes are light-harvesting antennae that transmit the energy of harvested photons to photosystem II and photosystem I in cyanobacteria and in the chloroplasts of red algae and glaucophytes. They were lost during the evolution of the ...
s), that consist of different proteins, sit on the inside of the
plasma 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 interior of a cell from the outside environment (the extr ...
(among the
cytoplasm
The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...
). Subsequently, the
proton gradient
An electrochemical gradient is a gradient of electrochemical potential, usually for an ion that can move across a membrane. The gradient consists of two parts:
* The chemical gradient, or difference in solute concentration across a membrane.
...
in ''Gloeobacter'' is created across the plasma membrane, whereas it forms across the thylakoid membrane in cyanobacteria and chloroplasts.
The whole genome of ''G. violaceus'' (strain PCC 7421) and of ''G. kilaueensis'' have been sequenced. Many genes for
photosystem
Photosystems are functional and structural units of protein complexes involved in photosynthesis. Together they carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons. Photosystems ...
I and II were found missing, likely related to the fact that
photosynthesis
Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...
in these bacteria does not take place in the
thylakoid membrane
Thylakoids are membrane-bound compartments inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen. Chloroplast thyl ...
as in other cyanobacteria, but in the
plasma 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 interior of a cell from the outside environment (the extr ...
.
There is also a genome for ''G. morelensis''.
Description
''Gloeobacter violaceus'' produces several pigments, including
chlorophyll a
}
Chlorophyll ''a'' is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light, and it is a poor absorber of green and near-green portions of the spectrum. Chlorop ...
,
β-carotene, oscillol diglycoside, and
echinenone. The purple coloration is due to the relatively low chlorophyll content. ''G. kilaueensis'' grows with a few other bacteria as a purple-colored
biofilm
A biofilm is a Syntrophy, syntrophic Microbial consortium, community of microorganisms in which cell (biology), cells cell adhesion, stick to each other and often also to a surface. These adherent cells become embedded within a slimy ext ...
around 0.5 mm thick. Cultivated colonies are dark purple, smooth, shiny, and raised. ''G. kilaueensis'' is mostly unicellular, capsule-shaped, about 3.5×1.5 μm, and embedded in mucus. They divide over the width of the cell. Cells color
gramnegative, and lack
vancomycin
Vancomycin is a glycopeptide antibiotic medication used to treat certain bacterial infections. It is administered intravenously ( injection into a vein) to treat complicated skin infections, bloodstream infections, endocarditis, bone an ...
resistance. They are not
motile
Motility is the ability of an organism to move independently using metabolic energy. This biological concept encompasses movement at various levels, from whole organisms to cells and subcellular components.
Motility is observed in animals, mi ...
and do not glide. Growth ceases in complete darkness, so ''Gloeobacter'' is very likely obligatory
photoautotrophic
Photoautotrophs are organisms that can utilize light energy from sunlight, and elements (such as carbon) from inorganic compounds, to produce organic materials needed to sustain their own metabolism (i.e. autotrophy). Such biological activities ...
.
Species and distribution
''Gloeobacter violaceus'' was found on a limestone rock in the Swiss canton
Obwalden
Canton of Obwalden or Obwald ( ; ; ; ) is one of the Canton of Switzerland, 26 cantons forming the Switzerland, Swiss Confederation. It is composed of seven municipalities and the seat of the government and parliament is in Sarnen. It is traditio ...
.
''G. kilaueensis'' occurred within a lava cave at the Kilauea-caldera on Hawaii. It grew there at a temperature around 30 °C at very high humidity, with moisture condensing and dripping off the biofilm.
''Gloeobacter'' could have split off from the other cyanobacteria between 3.7 and 3.2 billion years ago. The species of ''Gloeobacter'' may have branched 280 million years ago.
Phylogeny
Notes:
* GTDB has three more metagenome-only genera under Gloeobacteraceae, each with one species containing one genome.
* ''Aphanocapsa lilacina'' was published in 2016 to genus ''Aphanocapsa''. The
protologue
A species description is a formal scientific description of a newly encountered species, typically articulated through a scientific publication. Its purpose is to provide a clear description of a new species of organism and explain how it differ ...
is found in a copyrighted book, with no free online copies as of May 2025.
Related groups
''Anthocerotibacter panamensis'', found in a sample of
hornwort
Hornworts are a group of non-vascular Embryophytes (land plants) constituting the division Anthocerotophyta (). The common name refers to the elongated horn-like structure, which is the sporophyte. As in mosses and liverworts, hornworts have a ...
from a rainforest in Panama, also lacks thylakoids. It has very few of the genes that are required to perform photosynthesis, but is still able to perform it, very slowly. It may have been split from ''Gloeobacter'' about 1.4 Ga ago. This genus is officially a member of family Anthocerotibacteraceae within order Gloeobacterales.
GTDB
The Genome Taxonomy Database (GTDB) is an online database that maintains information on a proposed nomenclature of prokaryotes, following a phylogenomic approach based on a set of conserved single-copy proteins. In addition to resolving paraphyl ...
RS226 concurs in assigning ''
Anthocerotibacter'' to
Gloeobacterales
Gloeobacterales is an order of cyanobacteria. Two of its members, '' Gloeobacter'' and '' Anthocerotibacter'', diverged 1.4 billion years ago. Members of this order differ from other cyanobacteria in that they have no thylakoids, yet like other c ...
, but is not yet aware of the name "Anthocerotibacteraceae" for the family; it instead calls the family "FY9".
GDTB Search: Anthocerotibacter
/ref>
See also
* List of bacteria genera
This article lists the genera of the bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, ...
* List of bacterial orders
This article lists the orders of the Bacteria. The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI)
and the phylogeny is based on 16 ...
References
{{Taxonbar, from=Q5571156
Cyanobacteria genera
Cyanobacteria