Pseudomonas fluorescens
Encyclopedia
Pseudomonas fluorescens is a common Gram-negative
, rod-shaped bacterium. It belongs to the Pseudomonas
genus
; 16S rRNA analysis has placed P. fluorescens in the P. fluorescens group within the genus, to which it lends its name.
, and can be found in the soil and in water. It is an obligate aerobe
, but certain strains are capable of using nitrate
instead of oxygen
as a final electron acceptor
during cellular respiration
.
Optimal temperatures for growth of Pseudomonas fluorescens are 25-30 degrees Celsius
. It tests positive for the oxidase test
.
Pseudomonas fluorescens is also a nonsaccharolytic bacteria.
Heat
-stable lipases and protease
s are produced by Pseudomonas fluorescens and other similar pseudomonads. These enzymes cause milk to spoil, by causing bitterness, casein
breakdown, and ropiness due to production of slime
and coagulation
of protein
s.
: ψευδο 'false') and monas (Latin
: monas, fr. Greek
: μονάς/μονάδα 'a single unit'). The word was used early in the history of microbiology
to refer to germ
s. The name 'fluorescens' refers to the microbe's secretion of a soluble fluorescent pigment called pyoverdin (formerly called fluorescein
), which is a type of siderophore
.
or Pythium
, as well as some phytophagous nematodes.
It is not clear exactly how the plant growth-promoting properties of P. fluorescens are achieved; theories include:
To be specific, certain P. fluorescens isolates produce the secondary metabolite 2,4-diacetylphloroglucinol
(2,4-DAPG), the compound found to be responsible for antiphytopathegenic and biocontrol properties in these strains. The phl gene cluster encodes factors for 2,4-DAPG biosynthesis, regulation, export, and degradation. Eight genes, phlHGFACBDE, are annotated in this cluster and conserved organizationally in 2,4-DAPG-producing strains of P. fluorescens. Of these genes, phlD encodes a type III polyketide synthase, representing the key biosynthetic factor for 2,4-DAPG production. PhlD shows similarity to plant chalcone synthases and has been theorized to originate from horizontal gene transfer. But phylogenetic and genomic analysis has revealed that the entire phl gene cluster is ancestral to P. fluorescens, many strains have lost the capacity, and it exists on different genomic regions among strains.
There is experimental evidence to support all of these theories, in certain conditions; a good review of the topic is written by Haas and Defago.
The strain referred to as Pf-CL145A has proved itself a promising solution to the invasive Dreissena( zebra and quagga) mussels. The strain of the bacteria produces toxins that destroy the digestive system of the mussels and produces a >90% kill rate.
Several strains of "P. Fluorescens", such as Pf-5 and JL3985, have developed a natural resistance to ampicillin
and streptomycin
. These antibiotics are regularly used in biological research as a selective pressure tool to promote plasmid
expression.
(an antibiotic
) can be produced, which has been found to be useful in treating skin, ear, and eye disorders.
Mupirocin free acid and its salts and esters are agents currently used in creams, ointments, and sprays as a treatment of Methicillin-resistant Staphylococcus aureus
(MRSA) infection.
P. fluorescens demonstrates hemolytic activity and, as a result, has been known to infect blood transfusions.
It is also used in milk to make yogurt.
United States Patents: 6489358, 4873012, 6156792
ized saline flushes being used with cancer patients.
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...
, rod-shaped bacterium. It belongs to the Pseudomonas
Pseudomonas
Pseudomonas is a genus of gammaproteobacteria, belonging to the family Pseudomonadaceae containing 191 validly described species.Recently, 16S rRNA sequence analysis has redefined the taxonomy of many bacterial species. As a result, the genus Pseudomonas includes strains formerly classified in the...
genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
; 16S rRNA analysis has placed P. fluorescens in the P. fluorescens group within the genus, to which it lends its name.
General characteristics
P. fluorescens has multiple flagella. It has an extremely versatile metabolismMetabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
, and can be found in the soil and in water. It is an obligate aerobe
Obligate aerobe
An obligate aerobe is an aerobic organism that requires oxygen to grow. Through cellular respiration, these organisms use oxygen to oxidize substances, like sugars or fats, in order to obtain energy. During respiration, they use oxygen as the terminal electron acceptor...
, but certain strains are capable of using nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...
instead of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
as a final electron acceptor
Electron acceptor
An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. It is an oxidizing agent that, by virtue of its accepting electrons, is itself reduced in the process....
during cellular respiration
Cellular respiration
Cellular respiration is the set of the metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate , and then release waste products. The reactions involved in respiration are catabolic reactions that involve...
.
Optimal temperatures for growth of Pseudomonas fluorescens are 25-30 degrees Celsius
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
. It tests positive for the oxidase test
Oxidase test
The oxidase test is a test used in microbiology to determine if a bacterium produces certain cytochrome c oxidases. It uses disks impregnated with a reagent such as N,N,N′,N′-tetramethyl-p-phenylenediamine or N,N-Dimethyl-p-phenylenediamine , which is also a redox indicator...
.
Pseudomonas fluorescens is also a nonsaccharolytic bacteria.
Heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
-stable lipases and protease
Protease
A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein....
s are produced by Pseudomonas fluorescens and other similar pseudomonads. These enzymes cause milk to spoil, by causing bitterness, casein
Casein
Casein is the name for a family of related phosphoprotein proteins . These proteins are commonly found in mammalian milk, making up 80% of the proteins in cow milk and between 60% and 65% of the proteins in human milk....
breakdown, and ropiness due to production of slime
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
and coagulation
Coagulation
Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...
of 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...
s.
The name
The word Pseudomonas means 'false unit', being derived from the Greek words pseudo (GreekAncient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
: ψευδο 'false') and monas (Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
: monas, fr. Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
: μονάς/μονάδα 'a single unit'). The word was used early in the history of microbiology
Microbiology
Microbiology is the study of microorganisms, which are defined as any microscopic organism that comprises either a single cell , cell clusters or no cell at all . This includes eukaryotes, such as fungi and protists, and prokaryotes...
to refer to germ
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...
s. The name 'fluorescens' refers to the microbe's secretion of a soluble fluorescent pigment called pyoverdin (formerly called fluorescein
Fluorescein
Fluorescein is a synthetic organic compound available as a dark orange/red powder soluble in water and alcohol. It is widely used as a fluorescent tracer for many applications....
), which is a type of siderophore
Siderophore
Siderophores are small, high-affinity iron chelating compounds secreted by grasses and microorganisms such as bacteria and fungi...
.
Genome sequencing projects
The genomes of P. fluorescens strains SBW25, Pf-5 and PfO-1 have been sequenced.Biocontrol properties
Some P. fluorescens strains (CHA0 or Pf-5, for example) present biocontrol properties, protecting the roots of some plant species against parasitic fungi such as FusariumFusarium
Fusarium is a large genus of filamentous fungi widely distributed in soil and in association with plants. Most species are harmless saprobes, and are relatively abundant members of the soil microbial community. Some species produce mycotoxins in cereal crops that can affect human and animal health...
or Pythium
Pythium
Pythium is a genus of parasitic oomycete. Most species are plant parasites, but Pythium insidiosum is an important pathogen of animals...
, as well as some phytophagous nematodes.
It is not clear exactly how the plant growth-promoting properties of P. fluorescens are achieved; theories include:
- the bacteria might induce systemic resistance in the host plant, so it can better resist attack by a true pathogen
- the bacteria might outcompete other (pathogenic) soil microbes, e.g., by siderophoreSiderophoreSiderophores are small, high-affinity iron chelating compounds secreted by grasses and microorganisms such as bacteria and fungi...
s, giving a competitive advantage at scavenging for iron - the bacteria might produce compounds antagonistic to other soil microbes, such as phenazinePhenazinePhenazine , also called azophenylene, dibenzo-p-diazine, dibenzopyrazine, and acridizine, is a dibenzo annulated pyrazine and the parent substance of many dyestuffs, such as the eurhodines, toluylene red, indulines and safranines.-Synthesis:A classic method for the synthesis of phenazine is the...
-type antibiotics or hydrogen cyanide
To be specific, certain P. fluorescens isolates produce the secondary metabolite 2,4-diacetylphloroglucinol
2,4-Diacetylphloroglucinol
2,4-Diacetylphloroglucinol is a natural phenol found in specific strains of the Gram-negative bacterium Pseudomonas fluorescens. This compound is found to be responsible for the antiphytopathogenic and biocontrol properties in these strains....
(2,4-DAPG), the compound found to be responsible for antiphytopathegenic and biocontrol properties in these strains. The phl gene cluster encodes factors for 2,4-DAPG biosynthesis, regulation, export, and degradation. Eight genes, phlHGFACBDE, are annotated in this cluster and conserved organizationally in 2,4-DAPG-producing strains of P. fluorescens. Of these genes, phlD encodes a type III polyketide synthase, representing the key biosynthetic factor for 2,4-DAPG production. PhlD shows similarity to plant chalcone synthases and has been theorized to originate from horizontal gene transfer. But phylogenetic and genomic analysis has revealed that the entire phl gene cluster is ancestral to P. fluorescens, many strains have lost the capacity, and it exists on different genomic regions among strains.
There is experimental evidence to support all of these theories, in certain conditions; a good review of the topic is written by Haas and Defago.
The strain referred to as Pf-CL145A has proved itself a promising solution to the invasive Dreissena( zebra and quagga) mussels. The strain of the bacteria produces toxins that destroy the digestive system of the mussels and produces a >90% kill rate.
Several strains of "P. Fluorescens", such as Pf-5 and JL3985, have developed a natural resistance to ampicillin
Ampicillin
Ampicillin is a beta-lactam antibiotic that has been used extensively to treat bacterial infections since 1961. Until the introduction of ampicillin by the British company Beecham, penicillin therapies had only been effective against Gram-positive organisms such as staphylococci and streptococci...
and streptomycin
Streptomycin
Streptomycin is an antibiotic drug, the first of a class of drugs called aminoglycosides to be discovered, and was the first antibiotic remedy for tuberculosis. It is derived from the actinobacterium Streptomyces griseus. Streptomycin is a bactericidal antibiotic. Streptomycin cannot be given...
. These antibiotics are regularly used in biological research as a selective pressure tool to promote plasmid
Plasmid
In microbiology and genetics, a plasmid is a DNA molecule that is separate from, and can replicate independently of, the chromosomal DNA. They are double-stranded and, in many cases, circular...
expression.
Medical Properties
By culturing Pseudomonas fluorescens, MupirocinMupirocin
Mupirocin is an antibiotic originally isolated from Pseudomonas fluorescens NCIMB 10586, developed by Beecham....
(an antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
) can be produced, which has been found to be useful in treating skin, ear, and eye disorders.
Mupirocin free acid and its salts and esters are agents currently used in creams, ointments, and sprays as a treatment of Methicillin-resistant Staphylococcus aureus
Methicillin-resistant Staphylococcus aureus
Methicillin-resistant Staphylococcus aureus is a bacterium responsible for several difficult-to-treat infections in humans. It is also called multidrug-resistant Staphylococcus aureus and oxacillin-resistant Staphylococcus aureus...
(MRSA) infection.
P. fluorescens demonstrates hemolytic activity and, as a result, has been known to infect blood transfusions.
It is also used in milk to make yogurt.
United States Patents: 6489358, 4873012, 6156792
Disease
P. fluorescens is an unusual cause of disease in humans, and usually affects patients with compromised immune systems (e.g., patients on cancer treatment). From 2004 to 2006, there was an outbreak of P. fluorescens in the United States, involving 80 patients in six states. The source of the infection was contaminated heparinHeparin
Heparin , also known as unfractionated heparin, a highly sulfated glycosaminoglycan, is widely used as an injectable anticoagulant, and has the highest negative charge density of any known biological molecule...
ized saline flushes being used with cancer patients.