Gloeobacter

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Gloeobacter
Scientific classification Red Pencil Icon.png
Domain: Bacteria
Phylum: Cyanobacteria
Class: Cyanophyceae
Order: Gloeobacterales
Cavalier-Smith
Family: Gloeobacteraceae
Komárek et Anagnostidis
Genus: Gloeobacter
Rippka, Waterbury, & Cohen-Bazire, 1974 [1]
Species

Gloeobacter is a genus of cyanobacteria. It is the sister group to all other cyanobacteria. [2] Gloeobacter is unique among cyanobacteria in not having thylakoids, which are characteristic for all other cyanobacteria and chloroplasts. Instead, the light-harvesting complexes (also called phycobilisomes), that consist of different proteins, sit on the inside of the plasma membrane among the (cytoplasm). Subsequently, the proton gradient in Gloeobacter is created over the plasma membrane, where it forms over the thylakoid membrane in cyanobacteria and chloroplasts. [2]

Contents

The whole genome of G. violaceus (strain PCC 7421) and of G. kilaueensis have been sequenced. Many genes for photosystem I and II were found missing, likely related to the fact that photosynthesis in these bacteria does not take place in the thylakoid membrane as in other cyanobacteria, but in the plasma membrane. [3] [4]

Description

Gloeobacter violaceus produces several pigments, including chlorophyll a, 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 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 imbedded in mucus. They divide over the width of the cell. Cells color gramnegative, and lack vancomycin resistance. They are not motile and do not glide. Growth ceases in complete darkness, so Gloeobacter is very likely obligatory photoautotrophic. [4]

Species and distribution

Gloeobacter violaceus was found on a limestone rock in the Swiss canton Obwalden. 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. [5] The species of Gloeobacter may have branched 280 million years ago. [4]

Anthocerotibacter panamensis, found in a sample of hornwort 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. [6] According to AlgaeBase this genus is also a member of the family Gloeobacteraceae. [7]

Related Research Articles

Chloroplast Plant organelle that conducts photosynthesis

A chloroplast is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in the energy-storage molecules ATP and NADPH while freeing oxygen from water in the cells. The ATP and NADPH is then used to make organic molecules from carbon dioxide in a process known as the Calvin cycle. Chloroplasts carry out a number of other functions, including fatty acid synthesis, much amino acid synthesis, and the immune response in plants. The number of chloroplasts per cell varies from one, in unicellular algae, up to 100 in plants like Arabidopsis and wheat.

Photosynthesis Biological process to convert light into chemical energy

Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in carbohydrate molecules, such as sugars and starches, which are synthesized from carbon dioxide and water – hence the name photosynthesis, from the Greek phōs, "light", and sunthesis, "putting together". In most cases, oxygen is also released as a waste product that stores three times more chemical energy than the carbohydrates. Most plants, algae, and cyanobacteria perform photosynthesis; such organisms are called photoautotrophs. Photosynthesis is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and supplies most of the energy necessary for life on Earth.

Symbiogenesis Evolutionary theory holding that eukaryotic organelles evolved through symbiosis with prokaryotes

Symbiogenesis, endosymbiotic theory, or serial endosymbiotic theory, is the leading evolutionary theory of the origin of eukaryotic cells from prokaryotic organisms. The theory holds that mitochondria, plastids such as chloroplasts, and possibly other organelles of eukaryotic cells are descended from formerly free-living prokaryotes taken one inside the other in endosymbiosis. The idea that chloroplasts were originally independent organisms that merged into a symbiotic relationship with other one-celled organisms dates back to the 19th century, when it was espoused by researchers such as Andreas Schimper.

Cyanobacteria Phylum of photosynthesising prokaryotes

Cyanobacteria, also known as Cyanophyta, are a phylum of Gram-negative bacteria that obtain energy via photosynthesis. The name cyanobacteria refers to their color, giving them their other name, "blue-green algae", though modern botanists restrict the term algae to eukaryotes and do not apply it to cyanobacteria, which are prokaryotes. They appear to have originated in freshwater or a terrestrial environment. Sericytochromatia, the proposed name of the paraphyletic and most basal group, is the ancestor of both the non-photosynthetic group Melainabacteria and the photosynthetic cyanobacteria, also called Oxyphotobacteria.

Plastid Plant cell organelles that perform photosynthesis and store starch

The plastid is a membrane-bound organelle found in the cells of plants, algae, and some other eukaryotic organisms. They are considered to be intracellular endosymbiotic cyanobacteria. Examples include chloroplasts, chromoplasts, and leucoplasts.

Thylakoid Membrane enclosed compartments in chloroplasts and cyanobacteria

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 thylakoids frequently form stacks of disks referred to as grana. Grana are connected by intergranal/stromal thylakoids, which join granum stacks together as a single functional compartment.

Unicellular organism Organism that consists of only one cell

A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Unicellular organisms fall into two general categories: prokaryotic organisms and eukaryotic organisms. All prokaryotes are unicellular and are classified into bacteria and archaea. Many eukaryotes are multicellular, but many are unicellular such as protozoa, unicellular algae, and unicellular fungi. Unicellular organisms are thought to be the oldest form of life, with early protocells possibly emerging 3.8–4.0 billion years ago.

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 are found in the thylakoid membranes of plants, algae, and cyanobacteria. These membranes are located inside the chloroplasts of plants and algae, and in the cytoplasmic membrane of photosynthetic bacteria. There are two kinds of photosystems: PSI and PSII.

Photosystem I Second protein complex in photosynthetic light reactions

Photosystem I is one of two photosystems in the photosynthetic light reactions of algae, plants, and cyanobacteria. Photosystem I is an integral membrane protein complex that uses light energy to catalyze the transfer of electrons across the thylakoid membrane from plastocyanin to ferredoxin. Ultimately, the electrons that are transferred by Photosystem I are used to produce the moderate-energy hydrogen carrier NADPH. The photon energy absorbed by Photosystem I also produces a proton-motive force that is used to generate ATP. PSI is composed of more than 110 cofactors, significantly more than Photosystem II.

Phycobilisome Light-energy harvesting structure in cyanobacteria and red algae

Phycobilisomes are light harvesting antennae of photosystem II in cyanobacteria, red algae and glaucophytes. It was lost in the plastids of green algae/ plants (chloroplasts).

Photosynthetic reaction centre

A photosynthetic reaction center is a complex of several proteins, pigments and other co-factors that together execute the primary energy conversion reactions of photosynthesis. Molecular excitations, either originating directly from sunlight or transferred as excitation energy via light-harvesting antenna systems, give rise to electron transfer reactions along the path of a series of protein-bound co-factors. These co-factors are light-absorbing molecules (also named chromophores or pigments) such as chlorophyll and pheophytin, as well as quinones. The energy of the photon is used to excite an electron of a pigment. The free energy created is then used, via a chain of nearby electron acceptors, for a transfer of hydrogen atoms (as protons and electrons) from H2O or hydrogen sulfide towards carbon dioxide, eventually producing glucose. These electron transfer steps ultimately result in the conversion of the energy of photons to energy stored in relatively weak chemical bonds.

Archaeplastida Clade of eukaryotes containing land plants and some algae

The Archaeplastida are a major group of eukaryotes, comprising the photoautotrophic red algae (Rhodophyta), green algae, land plants, and the minor group glaucophytes. It also includes the non-photosynthetic lineage Rhodelphidia, a predatorial (eukaryotrophic) flagellate that is sister to the Rhodophyta, and probably the microscopic picozoans. The Archaeplastida have chloroplasts that are surrounded by two membranes, suggesting that they were acquired directly through a single endosymbiosis event by feeding on a cyanobacterium. All other groups which have chloroplasts, besides the amoeboid genus Paulinella, have chloroplasts surrounded by three or four membranes, suggesting they were acquired secondarily from red or green algae. Unlike red and green algae, glaucophytes have never been involved in secondary endosymbiosis events.

Photosynthetic reaction centre protein family

Photosynthetic reaction centre proteins are main protein components of photosynthetic reaction centres (RCs) of bacteria and plants. They are transmembrane proteins embedded in the chloroplast thylakoid or bacterial cell membrane.

Light-dependent reactions Photosynthetic reactions

In photosynthesis, the light-dependent reactions take place on the thylakoid membranes. The inside of the thylakoid membrane is called the lumen, and outside the thylakoid membrane is the stroma, where the light-independent reactions take place. The thylakoid membrane contains some integral membrane protein complexes that catalyze the light reactions. There are four major protein complexes in the thylakoid membrane: Photosystem II (PSII), cytochrome b6f complex, Photosystem I (PSI), and ATP synthase. These four complexes work together to ultimately produce ATP and NADPH.

Plastoglobulins is a family of proteins prominent found in lipid globules in plastids of flowering plants. It shows sequence similarities to the PAP/fibrillin family. PGL and similar proteins can be found in most algae, cyanobacteria and plants, but no other life forms; it suggests a role for PGL in oxygenic photosynthesis.

Ycf9 protein domain Plastid protein involved in photosynthesis

In molecular biology, the PsbZ (Ycf9) is a protein domain, which is low in molecular weight. It is a transmembrane protein and therefore is located in the thylakoid membrane of chloroplasts in cyanobacteria and plants. More specifically, it is located in Photosystem II (PSII) and in the light-harvesting complex II (LHCII). Ycf9 acts as a structural linker, that stabilises the PSII-LHCII supercomplexes. Moreover, the supercomplex fails to form in PsbZ-deficient mutants, providing further evidence to suggest Ycf9's role as a structural linker. This may be caused by a marked decrease in two LHCII antenna proteins, CP26 and CP29, found in PsbZ-deficient mutants, which result in structural changes, as well as functional modifications in PSII.

<i>Gloeomargarita lithophora</i> Species of bacterium

Gloeomargarita lithophora is a cyanobacterium, and is the proposed sister of the endosymbiotic plastids in the Eukaryote Archaeplastida. Gloeomargarita's ancestor would have ended up in an ancestral Archaeplastid through a singular Endosymbiotic event some ~1400 million years ago.

A plastid is a membrane-bound organelle found in plants, algae and other eukaryotic organisms that contribute to the production of pigment molecules. Most plastids are photosynthetic, thus leading to color production and energy storage or production. There are many types of plastids in plants alone, but all plastids can be separated based on the number of times they have undergone endosymbiotic events. Currently there are three types of plastids; primary, secondary and tertiary. Endosymbiosis is reputed to have led to the evolution of eukaryotic organisms today, although the timeline is highly debated.

Marine primary production

Marine primary production is the chemical synthesis in the ocean of organic compounds from atmospheric or dissolved carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through chemosynthesis, which uses the oxidation or reduction of inorganic chemical compounds as its source of energy. Almost all life on Earth relies directly or indirectly on primary production. The organisms responsible for primary production are called primary producers or autotrophs.

Photoautotrophs are organisms that use light energy and inorganic carbon to produce organic materials. Eukaryotic photoautotrophs absorb energy through the chlorophyll molecules in their chloroplasts while prokaryotic photoautotrophs use chlorophylls and bacteriochlorophylls present in their cytoplasm. All known photoautotrophs perform photosynthesis. Examples include plants, algae, and cyanobacteria.

References

  1. Komárek J, Kaštovský J, Mareš J, Johansen JR (2014). "Taxonomic classification of cyanoprokaryotes (cyanobacterial genera) 2014, using a polyphasic approach" (PDF). Preslia. 86: 295–335.
  2. 1 2 Antonia Herrero, Enrique Flores (2008). The Cyanobacteria: Molecular Biology, Genomics and Evolution. Horizon. p. 3. ISBN   978-1-904455-15-8.
  3. Nakamura Y, Kaneko T, Sato S, et al. (2003). "Complete genome structure of Gloeobacter violaceus PCC 7421, a cyanobacterium that lacks thylakoids". DNA Res. 10 (4): 137–45. doi: 10.1093/dnares/10.4.137 . PMID   14621292.
  4. 1 2 3 Saw JH, Schatz M, Brown MV, Kunkel DD, Foster JS, Shick H, et al. (2013). "Cultivation and Complete Genome Sequencing of Gloeobacter kilaueensis sp. nov., from a Lava Cave in Kīlauea Caldera, Hawai'i". PLOS ONE. 8 (10): e76376. Bibcode:2013PLoSO...876376S. doi: 10.1371/journal.pone.0076376 . PMC   3806779 . PMID   24194836.
  5. B.E. Schirrmeister; M. Gugger; P.C.J. Donoghue (2015). "Cyanobacteria and the Great Oxidation Event: evidence from genes and fossils". Palaeontology. 58 (5): 1–17. doi:10.1111/pala.12178. PMC   4755140 . PMID   26924853.
  6. New cyanobacteria species spotlights early life. On: ScienceDaily, May 15, 2021
  7. AlgaeBase: Anthocerotibacter F.-W.Li, 2021