Gram-negative non-proteobacterial diseases
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Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mech ...
sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane. Gram-negative bacteria are found in virtually all environments on Earth that support life. The gram-negative bacteria include the
model organism A model organism (often shortened to model) is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workin ...
'' Escherichia coli'', as well as many
pathogenic bacteria Pathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often Probiotic, beneficial but others can cause infectious diseases. The n ...
, such as '' Pseudomonas aeruginosa'', '' Chlamydia trachomatis'', and '' Yersinia pestis''. They are a significant medical challenge as their outer membrane protects them from many
antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention of ...
s (including
penicillin Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using ...
),
detergent A detergent is a surfactant or a mixture of surfactants with cleansing properties when in dilute solutions. There are a large variety of detergents, a common family being the alkylbenzene sulfonates, which are soap-like compounds that are more ...
s that would normally damage the inner cell membrane, and lysozyme, an antimicrobial enzyme produced by animals that forms part of the
innate immune system The innate, or nonspecific, immune system is one of the two main immunity strategies (the other being the adaptive immune system) in vertebrates. The innate immune system is an older evolutionary defense strategy, relatively speaking, and is the ...
. Additionally, the outer leaflet of this membrane comprises a complex lipopolysaccharide (LPS) whose
lipid A Lipid A is a lipid component of an endotoxin held responsible for the toxicity of gram-negative bacteria. It is the innermost of the three regions of the lipopolysaccharide (LPS), also called endotoxin molecule, and its hydrophobic nature allows it ...
component can cause a toxic reaction when bacteria are lysed by immune cells. This toxic reaction may lead to low blood pressure, respiratory failure, reduced oxygen delivery, and lactic acidosis – manifestations of
septic shock Septic shock is a potentially fatal medical condition that occurs when sepsis, which is organ injury or damage in response to infection, leads to dangerously low blood pressure and abnormalities in cellular metabolism. The Third International Con ...
. Several classes of antibiotics have been designed to target gram-negative bacteria, including
aminopenicillin The aminopenicillins are a group of antibiotics in the penicillin family that are structural analogs of ampicillin (which is the 2-amino derivative of benzylpenicillin, hence the name). Like other penicillins and beta-lactam antibiotics, they co ...
s,
ureidopenicillin The ureidopenicillins are a group of penicillins which are active against ''Pseudomonas aeruginosa''. There are three ureidopenicillins in clinical use: *Azlocillin *Piperacillin *Mezlocillin They are mostly ampicillin derivatives in which the ...
s,
cephalosporin The cephalosporins (sg. ) are a class of β-lactam antibiotics originally derived from the fungus ''Acremonium'', which was previously known as ''Cephalosporium''. Together with cephamycins, they constitute a subgroup of β-lactam antibiotics ...
s, beta-lactam- betalactamase inhibitor combinations (e.g.
piperacillin-tazobactam Piperacillin/tazobactam, sold under the brand name Zosyn among others, is a combination medication containing the antibiotic piperacillin and the β-lactamase inhibitor tazobactam. The combination has activity against many Gram-positive and Gram- ...
), Folate antagonists,
quinolone Quinolone may refer to: * 2-Quinolone * 4-Quinolone * Quinolone antibiotic A quinolone antibiotic is a member of a large group of broad-spectrum bacteriocidals that share a bicyclic core structure related to the substance 4-quinolone. They ...
s, and carbapenems. Many of these antibiotics also cover gram-positive organisms. The drugs that specifically target gram-negative organisms include aminoglycosides, monobactams ( aztreonam) and ciprofloxacin.


Characteristics

Conventional gram-negative (LPS-diderm) bacteria display : * An inner cell membrane is present ( cytoplasmic) * A thin peptidoglycan layer is present (this is much thicker in
gram-positive bacteria In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bact ...
) * Has outer membrane containing lipopolysaccharides (LPS, which consists of
lipid A Lipid A is a lipid component of an endotoxin held responsible for the toxicity of gram-negative bacteria. It is the innermost of the three regions of the lipopolysaccharide (LPS), also called endotoxin molecule, and its hydrophobic nature allows it ...
, core
polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wa ...
, and
O antigen Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. They are composed of an O-antigen, an outer core, and an inner core all joined by a covalent bond, and are found in the outer ...
) in its outer leaflet and
phospholipid Phospholipids, are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue (usually a glycerol molecule). Marine phospholipids typ ...
s in the inner leaflet *
Porins Porins are beta barrel proteins that cross a cellular membrane and act as a pore, through which molecules can diffuse. Unlike other membrane transport proteins, porins are large enough to allow passive diffusion, i.e., they act as channels tha ...
exist in the outer membrane, which act like pores for particular molecules * Between the outer membrane and the cytoplasmic membrane there is a space filled with a concentrated gel-like substance called periplasm * The S-layer is directly attached to the outer membrane rather than to the peptidoglycan * If present,
flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...
have four supporting rings instead of two *
Teichoic acid Teichoic acids (''cf.'' Greek τεῖχος, ''teīkhos'', "wall", to be specific a fortification wall, as opposed to τοῖχος, ''toīkhos'', a regular wall) are bacterial copolymers of glycerol phosphate or ribitol phosphate and carbohydr ...
s or
lipoteichoic acid Lipoteichoic acid (LTA) is a major constituent of the cell wall of gram-positive bacteria. These organisms have an inner (or cytoplasmic) membrane and, external to it, a thick (up to 80 nanometer) peptidoglycan layer. The structure of LTA varies be ...
s are absent * Lipoproteins are attached to the polysaccharide backbone * Some contain Braun's lipoprotein, which serves as a link between the outer membrane and the peptidoglycan chain by a covalent bond * Most, with few exceptions, do not form spores


Classification

Along with cell shape, Gram staining is a rapid diagnostic tool and once was used to group species at the subdivision of Bacteria.
Historically History (derived ) is the systematic study and the documentation of the human activity. The time period of event before the invention of writing systems is considered prehistory. "History" is an umbrella term comprising past events as well ...
, the kingdom
Monera Monera (/məˈnɪərə/) (Greek - μονήρης (monḗrēs), "single", "solitary") is a biological kingdom that is made up of prokaryotes. As such, it is composed of single-celled organisms that lack a nucleus. The taxon Monera was first p ...
was divided into four divisions based on Gram staining: Firmacutes (+), Gracillicutes (−), Mollicutes (0) and Mendocutes (var.). Since 1987, the monophyly of the gram-negative bacteria has been disproven with molecular studies. However some authors, such as Cavalier-Smith still treat them as a
monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...
taxon (though not a
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
; his definition of monophyly requires a single common ancestor but does not require
holophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...
, the property that all descendants be encompassed by the taxon) and refer to the group as a subkingdom "Negibacteria".


Taxonomy

Bacteria are traditionally classified based on their Gram-staining response into the gram-positive and gram-negative bacteria. Having just one membrane the gram-positive bacteria are also known as
monoderm bacteria In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bact ...
, and gram-negative having two membranes are also known as diderm bacteria. It was traditionally thought that the groups represent lineages, i.e. the extra membrane only evolved once, such that gram-negative bacteria are more closely related to one another than to any gram-positive bacteria. While this is often true, the classification system breaks down in some cases, with lineage groupings not matching the staining result. Thus, Gram staining cannot be reliably used to assess familial relationships of bacteria. Nevertheless, staining often gives reliable information about the composition of the cell membrane, distinguishing between the presence or absence of an outer lipid membrane. Of these two structurally distinct groups of prokaryotic organisms, monoderm prokaryotes are thought to be ancestral. Based upon a number of different observations including that the gram-positive bacteria are the most sensitive to antibiotics and that gram-negative bacteria are, in general, resistant to them, it has been proposed that the outer cell membrane in gram-negative bacteria (diderms) evolved as a protective mechanism against antibiotic selection pressure. Some bacteria such as ''
Deinococcus ''Deinococcus'' (from the el, δεινός, ''deinos'', "dreadful, strange" and κόκκος, ''kókkos'', "granule") is in the monotypic family Deinococcaceae, and one genus of three in the order Deinococcales of the bacterial phylum ''Deinococ ...
'', which stain gram-positive due to the presence of a thick peptidoglycan layer, but also possess an outer cell membrane are suggested as intermediates in the transition between monoderm (gram-positive) and diderm (gram-negative) bacteria. The diderm bacteria can also be further differentiated between simple diderms lacking lipopolysaccharide (LPS); the archetypical diderm bacteria, in which the outer cell membrane contains lipopolysaccharide; and the diderm bacteria, in which the outer cell membrane is made up of mycolic acid (e. g. ''
Mycobacterium ''Mycobacterium'' is a genus of over 190 species in the phylum Actinomycetota, assigned its own family, Mycobacteriaceae. This genus includes pathogens known to cause serious diseases in mammals, including tuberculosis ('' M. tuberculosis'') and ...
''). The conventional LPS-''diderm'' group of gram-negative bacteria (e.g.,
Pseudomonadota Pseudomonadota (synonym Proteobacteria) is a major phylum of Gram-negative bacteria. The renaming of phyla in 2021 remains controversial among microbiologists, many of whom continue to use the earlier names of long standing in the literature. The ...
, Aquificota,
Chlamydiota The Chlamydiota (synonym Chlamydiae) are a bacterial phylum and class whose members are remarkably diverse, including pathogens of humans and animals, symbionts of ubiquitous protozoa, and marine sediment forms not yet well understood. All of th ...
,
Bacteroidota The phylum Bacteroidota (synonym Bacteroidetes) is composed of three large classes of Gram-negative, nonsporeforming, anaerobic or aerobic, and rod-shaped bacteria that are widely distributed in the environment, including in soil, sediments, and ...
,
Chlorobiota The green sulfur bacteria are a phylum of obligately anaerobic photoautotrophic bacteria that metabolize sulfur. Green sulfur bacteria are nonmotile (except ''Chloroherpeton thalassium'', which may glide) and capable of anoxygenic photosynthes ...
, "
Cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...
",
Fibrobacterota Fibrobacterota is a small bacterial phylum which includes many of the major rumen bacteria, allowing for the degradation of plant-based cellulose in ruminant animals. Members of this phylum were categorized in other phyla. The genus '' Fibrobac ...
, Verrucomicrobiota, Planctomycetota,
Spirochaetota A spirochaete () or spirochete is a member of the phylum Spirochaetota (), (synonym Spirochaetes) which contains distinctive diderm (double-membrane) gram-negative bacteria, most of which have long, helically coiled (corkscrew-shaped or ...
,
Acidobacteriota Acidobacteriota is a phylum of Gram-negative bacteria. Its members are physiologically diverse and ubiquitous, especially in soils, but are under-represented in culture. Description Members of this phylum are physiologically diverse, and can be ...
; "
Hydrobacteria Hydrobacteria is a taxon containing approximately one-third of prokaryote species, mostly gram-negative bacteria and their relatives. It was found to be the closest relative of an even larger group of Bacteria, Terrabacteria, which are mostly gram ...
") are uniquely identified by a few conserved signature indel (CSI) in the HSP60 ( GroEL) protein. In addition, a number of bacterial taxa (including Negativicutes, Fusobacteriota, Synergistota, and Elusimicrobiota) that are either part of the
phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature f ...
Bacillota (a monoderm group) or branches in its proximity are also found to possess a diderm cell structure. They lack the GroEL signature. The presence of this CSI in all sequenced species of conventional lipopolysaccharide-containing gram-negative bacterial phyla provides evidence that these phyla of bacteria form a
monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
and that no loss of the outer membrane from any species from this group has occurred.


Example species

The proteobacteria are a major superphylum of gram-negative bacteria, including ''
E. coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escher ...
'', ''
Salmonella ''Salmonella'' is a genus of rod-shaped (bacillus) Gram-negative bacteria of the family Enterobacteriaceae. The two species of ''Salmonella'' are ''Salmonella enterica'' and ''Salmonella bongori''. ''S. enterica'' is the type species and is fur ...
'', '' Shigella'', and other
Enterobacteriaceae Enterobacteriaceae is a large family (biology), family of Gram-negative bacteria. It was first proposed by Rahn in 1936, and now includes over 30 genera and more than 100 species. Its classification above the level of family is still a subject ...
, '' Pseudomonas'', '' Moraxella'', '' Helicobacter'', ''
Stenotrophomonas ''Stenotrophomonas'' is a genus of Gram-negative bacteria, comprising at least ten species. The main reservoirs of Stenotrophomonas are soil and plants. ''Stenotrophomonas'' species range from common soil organisms (''S. nitritireducens'') to o ...
'', ''
Bdellovibrio ''Bdellovibrio'' is a genus of Gram-negative, obligate aerobic bacteria. One of the more notable characteristics of this genus is that members can prey upon other Gram-negative bacteria and feed on the biopolymers, e.g. proteins and nucleic acid ...
'', acetic acid bacteria, '' Legionella'' etc. Other notable groups of gram-negative bacteria include the
cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...
, spirochaetes, green sulfur, and green non-sulfur bacteria. Medically relevant gram-negative cocci include the four types that cause a sexually transmitted disease (''
Neisseria gonorrhoeae ''Neisseria gonorrhoeae'', also known as ''gonococcus'' (singular), or ''gonococci'' (plural), is a species of Gram-negative diplococci bacteria isolated by Albert Ludwig Sigesmund Neisser, Albert Neisser in 1879. It causes the sexually transmit ...
''), a
meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or ...
('' Neisseria meningitidis''), and respiratory symptoms ('' Moraxella catarrhalis'', '' Haemophilus influenzae''). Medically relevant gram-negative bacilli include a multitude of species. Some of them cause primarily respiratory problems ('' Klebsiella pneumoniae'', ''
Legionella pneumophila ''Legionella pneumophila'' is a thin, aerobic, pleomorphic, flagellated, non-spore-forming, Gram-negative bacterium of the genus ''Legionella''. ''L. pneumophila'' is the primary human pathogenic bacterium in this group and is the causative age ...
'', '' Pseudomonas aeruginosa''), primarily urinary problems ('' Escherichia coli'', ''
Proteus mirabilis ''Proteus mirabilis'' is a Gram-negative, facultatively anaerobic, rod-shaped bacterium. It shows swarming motility and urease activity. ''P. mirabilis'' causes 90% of all ''Proteus'' infections in humans. It is widely distributed in soil and ...
'', '' Enterobacter cloacae'', '' Serratia marcescens''), and primarily gastrointestinal problems ('' Helicobacter pylori'', ''
Salmonella enteritidis ''Salmonella enterica'' subsp. ''enterica'' is a subspecies of ''Salmonella enterica'', the rod-shaped, flagellated, aerobic, Gram-negative bacterium. Many of the pathogenic serovars of the ''S. enterica'' species are in this subspecies, includi ...
'', '' Salmonella typhi''). Gram-negative bacteria associated with hospital-acquired infections include '' Acinetobacter baumannii'', which cause
bacteremia Bloodstream infections (BSIs), which include bacteremias when the infections are bacterial and fungemias when the infections are fungal, are infections present in the blood. Blood is normally a sterile environment, so the detection of microb ...
, secondary
meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or ...
, and
ventilator-associated pneumonia Ventilator-associated pneumonia (VAP) is a type of lung infection that occurs in people who are on mechanical ventilation breathing machines in hospitals. As such, VAP typically affects critically ill persons that are in an intensive care unit (I ...
in hospital intensive-care units.


Bacterial transformation

Transformation Transformation may refer to: Science and mathematics In biology and medicine * Metamorphosis, the biological process of changing physical form after birth or hatching * Malignant transformation, the process of cells becoming cancerous * Trans ...
is one of three processes for horizontal gene transfer, in which exogenous genetic material passes from bacterium to another, the other two being
conjugation Conjugation or conjugate may refer to: Linguistics * Grammatical conjugation, the modification of a verb from its basic form * Emotive conjugation or Russell's conjugation, the use of loaded language Mathematics * Complex conjugation, the chang ...
(transfer of genetic material between two bacterial cells in direct contact) and transduction (injection of foreign DNA by a
bacteriophage A bacteriophage (), also known informally as a ''phage'' (), is a duplodnaviria virus that infects and replicates within bacteria and archaea. The term was derived from "bacteria" and the Greek φαγεῖν ('), meaning "to devour". Bacteri ...
virus into the host bacterium). In transformation, the genetic material passes through the intervening medium, and uptake is completely dependent on the recipient bacterium. As of 2014 about 80 species of bacteria were known to be capable of transformation, about evenly divided between gram-positive and gram-negative bacteria; the number might be an overestimate since several of the reports are supported by single papers. Transformation has been studied in medically important gram-negative bacteria species such as '' Helicobacter pylori'', ''
Legionella pneumophila ''Legionella pneumophila'' is a thin, aerobic, pleomorphic, flagellated, non-spore-forming, Gram-negative bacterium of the genus ''Legionella''. ''L. pneumophila'' is the primary human pathogenic bacterium in this group and is the causative age ...
'', '' Neisseria meningitidis'', ''
Neisseria gonorrhoeae ''Neisseria gonorrhoeae'', also known as ''gonococcus'' (singular), or ''gonococci'' (plural), is a species of Gram-negative diplococci bacteria isolated by Albert Ludwig Sigesmund Neisser, Albert Neisser in 1879. It causes the sexually transmit ...
'', '' Haemophilus influenzae'' and '' Vibrio cholerae''. It has also been studied in gram-negative species found in soil such as ''
Pseudomonas stutzeri ''Pseudomonas stutzeri'' is a Gram-negative soil bacterium that is motile, has a single polar flagellum, and is classified as bacillus, or rod-shaped. While this bacterium was first isolated from human spinal fluid, it has since been found in man ...
'', ''
Acinetobacter baylyi ''Acinetobacter baylyi'' is a bacterial species of the genus ''Acinetobacter''. As with other species of Acinetobacter it is characterized by being a nonmotile, gram negative coccobacillus. It grows under aerobic conditions, is catalase positive ...
'', and gram-negative plant pathogens such as ''
Ralstonia solanacearum ''Ralstonia solanacearum'' is an aerobic non-spore-forming, Gram-negative, plant pathogenic bacterium. ''R. solanacearum'' is soil-borne and motile with a polar flagellar tuft. It colonises the xylem, causing bacterial wilt in a very wide rang ...
'' and '' Xylella fastidiosa''.


Role in disease

One of the several unique characteristics of gram-negative bacteria is the structure of the bacterial outer membrane. The outer leaflet of this membrane contains lipopolysaccharide (LPS), whose
lipid A Lipid A is a lipid component of an endotoxin held responsible for the toxicity of gram-negative bacteria. It is the innermost of the three regions of the lipopolysaccharide (LPS), also called endotoxin molecule, and its hydrophobic nature allows it ...
portion acts as an endotoxin. If gram-negative bacteria enter the circulatory system, LPS can trigger an
innate immune response The innate, or nonspecific, immune system is one of the two main immunity strategies (the other being the adaptive immune system) in vertebrates. The innate immune system is an older evolutionary defense strategy, relatively speaking, and is the ...
, activating the immune system and producing cytokines (hormonal regulators). This leads to inflammation and can cause a toxic reaction, resulting in fever, an increased respiratory rate, and low blood pressure. That is why some infections with gram-negative bacteria can lead to life-threatening
septic shock Septic shock is a potentially fatal medical condition that occurs when sepsis, which is organ injury or damage in response to infection, leads to dangerously low blood pressure and abnormalities in cellular metabolism. The Third International Con ...
. The outer membrane protects the bacteria from several
antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention of ...
s,
dye A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution an ...
s, and
detergent A detergent is a surfactant or a mixture of surfactants with cleansing properties when in dilute solutions. There are a large variety of detergents, a common family being the alkylbenzene sulfonates, which are soap-like compounds that are more ...
s that would normally damage either the inner membrane or the cell wall (made of peptidoglycan). The outer membrane provides these bacteria with resistance to lysozyme and
penicillin Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using ...
. The periplasmic space (space between the two cell membranes) also contains enzymes which break down or modify antibiotics. Drugs commonly used to treat gram negative infections include amino, carboxy and ureido penicillins ( ampicillin, amoxicillin, pipercillin, ticarcillin) these drugs may be combined with beta-lactamase inhibitors to combat the presence of enzymes that can digest these drugs (known as beta-lactamases) in the peri-plasmic space. Other classes of drugs that have gram negative spectrum include
cephalosporin The cephalosporins (sg. ) are a class of β-lactam antibiotics originally derived from the fungus ''Acremonium'', which was previously known as ''Cephalosporium''. Together with cephamycins, they constitute a subgroup of β-lactam antibiotics ...
s, monobactams ( aztreonam), aminoglycosides,
quinolone Quinolone may refer to: * 2-Quinolone * 4-Quinolone * Quinolone antibiotic A quinolone antibiotic is a member of a large group of broad-spectrum bacteriocidals that share a bicyclic core structure related to the substance 4-quinolone. They ...
s, macrolides,
chloramphenicol Chloramphenicol is an antibiotic useful for the treatment of a number of bacterial infections. This includes use as an eye ointment to treat conjunctivitis. By mouth or by injection into a vein, it is used to treat meningitis, plague, cholera, a ...
,
folate antagonists Antifolates are a class of antimetabolite medications that antagonise (that is, block) the actions of folic acid (vitamin B9). Folic acid's primary function in the body is as a cofactor to various methyltransferases involved in serine, methionine ...
, and carbapenems.


Orthographic note

The adjectives ''Gram-positive'' and ''Gram-negative'' derive from the surname of
Hans Christian Gram Hans Christian Joachim Gram (13 September 1853 – 14 November 1938) was a Danish bacteriologist noted for his development of the Gram stain, still a standard technique to classify bacteria and make them more visible under a microscope. Early l ...
, a Danish bacteriologist; as eponymous adjectives, their initial letter can be either capital ''G'' or lower-case ''g'', depending on which
style guide A style guide or manual of style is a set of standards for the writing, formatting, and design of documents. It is often called a style sheet, although that term also has multiple other meanings. The standards can be applied either for gene ...
(e.g., that of the
CDC The Centers for Disease Control and Prevention (CDC) is the National public health institutes, national public health agency of the United States. It is a Federal agencies of the United States, United States federal agency, under the United S ...
), if any, governs the document being written. This is further explained at '' Gram staining § Orthographic note''.


See also

*
Autochaperone In molecular biology, autotransporter proteins are proteins secreted out the Gram-negative bacteria. These beta helixes require a domain which is called the intramolecular autochaperone domain. It shows similarities with other intramolecular chape ...
* Gram-variable and gram-indeterminate bacteria *
OMPdb OMPdb is a dedicated database that contains beta barrel (β-barrel) outer membrane proteins from Gram-negative bacteria. Such proteins are responsible for a broad range of important functions, like passive nutrient uptake, active transport of large ...
(2011) *
Outer membrane receptor Outer membrane receptors, also known as TonB-dependent receptors, are a family of beta barrel proteins named for their localization in the outer membrane of gram-negative bacteria. TonB complexes sense signals from the outside of bacterial cells ...


References

*


Notes


External links


3D structures of proteins from inner membranes of Ellie Wyithe's gram-negative bacteria
{{Authority control Staining Bacteriology