Gracilicutes is a controversial taxon in Bacterial taxonomy

Bacterial taxonomy

Bacterial taxonomy is the taxonomy, i.e. the rank-based classification, of bacteria.In the scientific classification established by Carl von Linné, each species has to be assigned to a genus , which in turn is a lower level of a hierarchy of ranks .In the currently accepted classification...

.

Traditionally Gram staining

Gram staining

Gram staining is a method of differentiating bacterial species into two large groups ....

 results were most commonly used as a classification tool, consequently until the advent of molecular phylogeny

Molecular phylogeny

Molecular phylogenetics is the analysis of hereditary molecular differences, mainly in DNA sequences, to gain information on an organism's evolutionary relationships. The result of a molecular phylogenetic analysis is expressed in a phylogenetic tree...

, the Kingdom Prokaryotae (as the domain Bacteria was known then) was divided into four divisions,

• Gracilicutes (gram negative)
• Firmacutes [sic] (gram positive, subsequently corrected to Fimicutes)
• Mollicutes (gram variable, e.g. Mycoplasma)
• Mendocutes (uneven gram stain, "methanogenic bacteria" now known as the Archaea)

This classification system was abandoned in favour the molecular phylogeny bacterial megaclassification

Bacterial phyla

The bacterial phyla are the major lineages of the domain Bacteria.In the scientific classification established by Carl von Linné, each bacterial strain has to be assigned to a species , which is a lower level of a hierarchy of ranks...

 started by C. Woese.

This taxon was revived in 2006 by Cavalier-Smith as a infrakindgom containing the phyla Spirochaetae, Sphingobacteria

Sphingobacteria (phylum)

Sphingobacteria is a division , created by Cavalier-Smith, which contains the classes Chlorobea, Fibrobacteres, Bacteroidetes and Flavobacteria....

, Planctobacteria

Planctobacteria

Planctobacteria is a taxon created by Cavalier-Smith, specifically a division Historically bacteria were considered plants consequently the usage of "division" over "phylum" was brought over when the kindgom Monera was established. The bacteriological code has since imposed that the rank should be...

, and Proteobacteria

Proteobacteria

The Proteobacteria are a major group of bacteria. They include a wide variety of pathogens, such as Escherichia, Salmonella, Vibrio, Helicobacter, and many other notable genera....

. However, this taxon is not accepted by the scientific community at large which follows the molecular phylogeny view.

It is a Gram-negative

Gram-negative

Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...

 clade that branched off from other bacteria just before the evolutionary loss of the outer membrane or capsule, and just after the evolution of flagella.

Relationships

The following graph shows Cavalier-Smith's version of the tree of life, indicating the status of Gracilicutes

Gracilicutes

Gracilicutes is a controversial taxon in Bacterial taxonomy.Traditionally Gram staining results were most commonly used as a classification tool, consequently until the advent of molecular phylogeny, the Kingdom Prokaryotae was divided into four divisions,*...

.

Legend: [A] Gram-negative Gram-negative Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...  with a peptidoglycan Peptidoglycan Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of bacteria , forming the cell wall. The sugar component consists of alternating residues of β- linked N-acetylglucosamine and N-acetylmuramic acid...  cell wall Cell wall The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...  like Chlorosome Chlorosome A Chlorosome is a photosynthetic antenna complex found in green sulfur bacteria and some green filamentous anoxygenic phototrophs . They differ from other antenna complexes by their large size and lack of protein matrix supporting the photosynthetic pigments... e. [B] Oxygenic Photosynthesis Photosynthesis Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can... , Omp85 and four new catalase Catalase Catalase is a common enzyme found in nearly all living organisms that are exposed to oxygen, where it catalyzes the decomposition of hydrogen peroxide to water and oxygen... s. [C] Glycobacterial revolution: outer membrane with insertion of lipopolysaccharide Lipopolysaccharide Lipopolysaccharides , also known as lipoglycans, are large molecules consisting of a lipid and a polysaccharide joined by a covalent bond; they are found in the outer membrane of Gram-negative bacteria, act as endotoxins and elicit strong immune responses in animals.-Functions:LPS is the major... s, hopanoids Hopanoids Hopanoids are natural pentacyclic compounds based on the chemical structure of hopane. Their primary function is to improve plasma membrane strength and rigidity in bacteria. In eukaryotes cholesterol serves a similar function... , diaminopimelic acid Diaminopimelic acid Diaminopimelic acid is an amino acid, representing an epsilon-carboxy derivative of lysine.DAP is a characteristic of certain cell walls of some bacteria. When provided, they exhibit normal growth. When in deficiency, they still grow but with the inability to make new cell wall proteoglycan.This... , ToIC and TonB TonB-dependent receptors TonB-dependent receptors is a family of beta-barrel proteins from the outer membrane of Gram-negative bacteria. The TonB complex senses signals from outside the bacterial cell and transmits them via two membranes into the cytoplasm, leading to transcriptional activation of target genes.In... . [D] Phycobilin Phycobilin Phycobilins are chromophores found in cyanobacteria and in the chloroplasts of red algae, glaucophytes and some cryptomonads...  chromophores. [E] Flagella Flagellum A flagellum is a tail-like projection that protrudes from the cell body of certain prokaryotic and eukaryotic cells, and plays the dual role of locomotion and sense organ, being sensitive to chemicals and temperatures outside the cell. There are some notable differences between prokaryotic and... . [F] Four sections: an amino acid Amino acid Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...  in HSP60 HSP60 Heat shock proteins are generally responsible for preventing damage to proteins in response to high levels of heat. Heat shock proteins are classified into six major families based on their molecular mass: small HSPs, HSP40, HSP60, HSP70, HSP90, and HSP110...  and FtsZ FtsZ FtsZ is a protein encoded by the ftsZ gene that assembles into a ring at the future site of the septum of bacterial cell division. This is a prokaryotic homologue to the eukaryotic protein tubulin. FtsZ has been named after "Filamenting temperature-sensitive mutant Z". The hypothesis was that cell...  and a domain in RNA polymerase RNA polymerase RNA polymerase is an enzyme that produces RNA. In cells, RNAP is needed for constructing RNA chains from DNA genes as templates, a process called transcription. RNA polymerase enzymes are essential to life and are found in all organisms and many viruses... s β and σ. [G] Endospores. [H] Gram-positive Gram-positive Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink...  Bacteria: hypertrophy of the wall peptidoglycan Peptidoglycan Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of bacteria , forming the cell wall. The sugar component consists of alternating residues of β- linked N-acetylglucosamine and N-acetylmuramic acid... , sortasa enzyme Enzyme Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...  and a loss of the outer membrane. [I] Glycerol Glycerol Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...  1-P dehydrogenase Dehydrogenase A dehydrogenase is an enzyme that oxidises a substrate by a reduction reaction that transfers one or more hydrides to an electron acceptor, usually NAD+/NADP+ or a flavin coenzyme such as FAD or FMN.-Examples:... . [J] Proteasome Proteasome Proteasomes are very large protein complexes inside all eukaryotes and archaea, and in some bacteria.  In eukaryotes, they are located in the nucleus and the cytoplasm.  The main function of the proteasome is to degrade unneeded or damaged proteins by proteolysis, a chemical reaction that breaks...  and phosphatidylinositol Phosphatidylinositol Phosphatidylinositol is a negatively charged phospholipid and a minor component in the cytosolic side of eukaryotic cell membranes.... . [K] Neomura Neomura Neomura is a clade composed of the two domains of life of Archaea and Eukaryota. The group was first proposed by Thomas Cavalier-Smith and its name means "new walls"; so called because it is thought to have evolved from Bacteria, and one of the major changes was the replacement of peptidoglycan...  revolution: Replacement of peptidoglycan Peptidoglycan Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of bacteria , forming the cell wall. The sugar component consists of alternating residues of β- linked N-acetylglucosamine and N-acetylmuramic acid...  by glycoprotein Glycoprotein Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending... s and lipoprotein Lipoprotein A lipoprotein is a biochemical assembly that contains both proteins and lipids water-bound to the proteins. Many enzymes, transporters, structural proteins, antigens, adhesins, and toxins are lipoproteins... s. [L] Reverse DNA gyrase DNA gyrase DNA gyrase, often referred to simply as gyrase, is an enzyme that relieves strain while double-stranded DNA is being unwound by helicase. This causes negative supercoiling of the DNA...  and ether Ether Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...  lipid isoprenoids. [M] Phagocytosis.