Pseudomonas

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Pseudomonas
P. aeruginosa colonies on an agar plate
Scientific classification Edit this classification
Domain: Bacteria
Phylum: Pseudomonadota
Class: Gammaproteobacteria
Order: Pseudomonadales
Family: Pseudomonadaceae
Genus: Pseudomonas
Migula 1894
Type species
Pseudomonas aeruginosa
Species

See text.

Synonyms
  • "Stutzerimonas" Lalucat et al. 2022[1]
  • Flavimonas Holmes et al. 1987
  • Chryseomonas Holmes et al. 1986
  • Serpens Hespell 1977 (Approved Lists 1980)

Pseudomonas is a genus of Gram-negative bacteria belonging to the family Pseudomonadaceae in the class Gammaproteobacteria. The 313 members of the genus[2][3] demonstrate a great deal of metabolic diversity and consequently are able to colonize a wide range of niches.[4] Their ease of culture in vitro and availability of an increasing number of Pseudomonas strain genome sequences has made the genus an excellent focus for scientific research; the best studied species include P. aeruginosa in its role as an opportunistic human pathogen, the plant pathogen P. syringae, the soil bacterium P. putida, and the plant growth-promoting P. fluorescens, P. lini, P. migulae, and P. graminis.[5][6]

Because of their widespread occurrence in water and plant seeds such as

flagellated bacteria with some sporulating species.[7][8] The latter statement was later proved incorrect and was due to refractive granules of reserve materials.[9] Despite the vague description, the type species, Pseudomonas pyocyanea (basonym of Pseudomonas aeruginosa), proved the best descriptor.[9]

Classification history

Like most bacterial genera, the pseudomonad

Monas, a nanoflagellated protist[9] (subsequently, the term "monad" was used in the early history of microbiology to denote unicellular organisms). Soon, other species matching Migula's somewhat vague original description were isolated from many natural niches and, at the time, many were assigned to the genus. However, many strains have since been reclassified, based on more recent methodology and use of approaches involving studies of conservative macromolecules.[10]

Recently, 16S rRNA sequence analysis has redefined the taxonomy of many bacterial species.[11] As a result, the genus Pseudomonas includes strains formerly classified in the genera Chryseomonas and Flavimonas.[12] Other strains previously classified in the genus Pseudomonas are now classified in the genera Burkholderia and Ralstonia.[13][14]

In 2020, a phylogenomic analysis of 494 complete Pseudomonas genomes identified two well-defined species (P. aeruginosa and P. chlororaphis) and four wider phylogenetic groups (P. fluorescens, P. stutzeri, P. syringae, P. putida) with a sufficient number of available proteomes.[15] The four wider evolutionary groups include more than one species, based on species definition by the Average Nucleotide Identity levels.[16] In addition, the phylogenomic analysis identified several strains that were mis-annotated to the wrong species or evolutionary group.[15] This mis-annotation problem has been reported by other analyses as well.[17]

Genomics

In 2000, the complete

genome sequence of a Pseudomonas species was determined; more recently, the sequence of other strains has been determined, including P. aeruginosa strains PAO1 (2000), P. putida KT2440 (2002), P. protegens Pf-5 (2005), P. syringae pathovar tomato DC3000 (2003), P. syringae pathovar syringae B728a (2005), P. syringae pathovar phaseolica 1448A (2005), P. fluorescens Pf0-1, and P. entomophila L48.[10]

By 2016, more than 400 strains of Pseudomonas had been sequenced.[18] Sequencing the genomes of hundreds of strains revealed highly divergent species within the genus. In fact, many genomes of Pseudomonas share only 50-60% of their genes, e.g. P. aeruginosa and P. putida share only 2971 proteins out of 5350 (or ~55%).[18]

By 2020, more than 500 complete Pseudomonas genomes were available in Genebank. A phylogenomic analysis utilized 494 complete proteomes and identified 297 core orthologues, shared by all strains.[15] This set of core orthologues at the genus level was enriched for proteins involved in metabolism, translation, and transcription and was utilized for generating a phylogenomic tree of the entire genus, to delineate the relationships among the Pseudomonas major evolutionary groups.[15] In addition, group-specific core proteins were identified for most evolutionary groups, meaning that they were present in all members of the specific group, but absent in other pseudomonads. For example, several P. aeruginosa-specific core proteins were identified that are known to play an important role in this species' pathogenicity, such as CntL, CntM, PlcB, Acp1, MucE, SrfA, Tse1, Tsi2, Tse3, and EsrC.[15]

Characteristics

Members of the genus display these defining characteristics:[19]

Other characteristics that tend to be associated with Pseudomonas species (with some exceptions) include secretion of

Voges–Proskauer test negative, and citrate positive.[citation needed
]

Pseudomonas may be the most common nucleator of ice crystals in clouds, thereby being of utmost importance to the formation of snow and rain around the world.[23]

Biofilm formation

All

white blood cells.[25] Exopolysaccharide production also contributes to surface-colonising biofilms that are difficult to remove from food preparation surfaces. Growth of pseudomonads on spoiling foods can generate a "fruity" odor.[citation needed
]

Antibiotic resistance

Most Pseudomonas spp. are naturally resistant to penicillin and the majority of related beta-lactam antibiotics, but a number are sensitive to piperacillin, imipenem, ticarcillin, or ciprofloxacin.[25] Aminoglycosides such as tobramycin, gentamicin, and amikacin are other choices for therapy.[citation needed]

This ability to thrive in harsh conditions is a result of their hardy

efflux pumps, which pump out some antibiotics before they are able to act.[citation needed
]

multidrug resistance by P. aeruginosa isolates requires several different genetic events that include acquisition of different mutations and/or horizontal transfer of antibiotic resistance genes. Hypermutation favours the selection of mutation-driven antibiotic resistance in P. aeruginosa strains producing chronic infections, whereas the clustering of several different antibiotic resistance genes in integrons favours the concerted acquisition of antibiotic resistance determinants. Some recent studies have shown phenotypic resistance associated to biofilm formation or to the emergence of small-colony-variants, which may be important in the response of P. aeruginosa populations to antibiotic treatment.[10]

Sensitivity to gallium

Although gallium has no natural function in biology, gallium ions interact with cellular processes in a manner similar to iron(III). When gallium ions are mistakenly taken up in place of iron(III) by bacteria such as Pseudomonas, the ions interfere with respiration, and the bacteria die. This happens because iron is redox-active, allowing the transfer of electrons during respiration, while gallium is redox-inactive.[28][29]

Pathogenicity

Animal pathogens

Infectious species include

nosocomial infections).[30] This pathogenesis may in part be due to the proteins secreted by P. aeruginosa. The bacterium possesses a wide range of secretion systems, which export numerous proteins relevant to the pathogenesis of clinical strains.[31] Intriguingly, several genes involved in the pathogenesis of P. aeruginosa, such as CntL, CntM, PlcB, Acp1, MucE, SrfA, Tse1, Tsi2, Tse3, and EsrC are core group-specific,[15]
meaning that they are shared by the vast majority of P. aeruginosa strains, but they are not present in other Pseudomonads.

Plant pathogens

P. syringae is a prolific

plant pathogen. It exists as over 50 different pathovars, many of which demonstrate a high degree of host-plant specificity. Numerous other Pseudomonas species can act as plant pathogens, notably all of the other members of the P. syringae subgroup, but P. syringae is the most widespread and best-studied.[citation needed
]

Fungus pathogens

mushrooms.[32] Similarly, P. agarici can cause drippy gill in cultivated mushrooms.[33]

Use as biocontrol agents

Since the mid-1980s, certain members of the genus Pseudomonas have been applied to cereal seeds or applied directly to soils as a way of preventing the growth or establishment of crop pathogens. This practice is generically referred to as

biocontrol. The biocontrol properties of P. fluorescens and P. protegens strains (CHA0 or Pf-5 for example) are currently best-understood, although 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 siderophores giving a competitive advantage at scavenging for iron; the bacteria might produce compounds antagonistic to other soil microbes, such as phenazine-type antibiotics or hydrogen cyanide. Experimental evidence supports all of these theories.[34]

Other notable Pseudomonas species with biocontrol properties include

Use as bioremediation agents

Some members of the genus are able to metabolise chemical pollutants in the environment, and as a result, can be used for bioremediation. Notable species demonstrated as suitable for use as bioremediation agents include:

Risks associated with pseudomonas

Pseudomonas is a genus of bacteria known to be associated with several diseases affecting humans, plants, and animals.

Humans & Animals

One of the most concerning strains of Pseudomonas is

blood poisoning, and urinary tract infections.[46] Pseudomonas aeruginosa is highly contagious and has displayed resistance to antibiotic treatments, making it difficult to manage effectively. Some strains of Pseudomonas are known to target white blood cells in various mammal species, posing risks to humans, cattle, sheep, and dogs alike.[47]

Fish

While Pseudomonas aeruginosa seems to be a pathogen that primarily affects humans, another strain known as Pseudomonas plecoglossicida poses risks to fish. This strain can cause gastric swelling and haemorrhaging in fish populations.[47]

Plants & Fungi

Various strains of Pseudomonas are recognized as pathogens in the plant kingdom. Notably, the Pseudomonas syringae family is linked to diseases affecting a wide range of agricultural plants, with different strains showing adaptations to specific host species. In particular, the virulent strain Pseudomonas tolaasii is responsible for causing blight and degradation in edible mushroom species.[47]

Detection of food spoilage agents in milk

One way of identifying and categorizing multiple bacterial organisms in a sample is to use ribotyping.

P. fluorescens, with 69% of these isolates possessing proteases, lipases, and lecithinases which contribute to degradation of milk components and subsequent spoilage.[49] Other Pseudomonas species can possess any one of the proteases, lipases, or lecithinases, or none at all.[49] Similar enzymatic activity is performed by Pseudomonas of the same ribotype, with each ribotype showing various degrees of milk spoilage and effects on flavour.[49] The number of bacteria affects the intensity of spoilage, with non-enzymatic Pseudomonas species contributing to spoilage in high number.[49]

Food spoilage is detrimental to the food industry due to production of volatile compounds from organisms metabolizing the various nutrients found in the food product.

Species

Pseudomonas comprises the following species,[52] organized into genomic affinity groups:[53][54][55][56][57][58][59]

P. aeruginosa Group

P. anguilliseptica Group

P. fluorescens Group

P. asplenii Subgroup

P. chlororaphis Subgroup

  • P. aurantiaca
    Nakhimovskaya 1948 (Approved Lists 1980)
  • P. aureofaciens Kluyver 1956 (Approved Lists 1980)
  • P. chlororaphis (Guignard and Sauvageau 1894) Bergey et al. 1930 (Approved Lists 1980)
  • P. piscium (Burr et al. 2010) Chen et al. 2018

P. corrugata Subgroup

P. fluorescens Subgroup

P. fragi Subgroup

P. gessardii Subgroup

P. jessenii Subgroup

P. koreensis Subgroup

P. mandelii Subgroup

P. protegens Subgroup

incertae sedis

P. linyingensis Group

P. lutea Group

P. massiliensis Group

P. oleovorans Group

P. oryzihabitans Group

P. pohangensis Group

P. putida Group

P. resinovorans Group

P. rhizosphaerae Group

P. straminea Group

P. stutzeri Group

P. syringae Group

incertae sedis

Species previously classified in the genus

Recently, 16S rRNA sequence analysis redefined the taxonomy of many bacterial species previously classified as being in the genus Pseudomonas.[11] Species removed from Pseudomonas are listed below; clicking on a species will show its new classification. The term 'pseudomonad' does not apply strictly to just the genus Pseudomonas, and can be used to also include previous members such as the genera Burkholderia and Ralstonia.

α proteobacteria:

P. rosea, P. vesicularis
.

β proteobacteria:

.

γ-β proteobacteria: P. boreopolis, P. cissicola, P. geniculata, P. hibiscicola, P. maltophilia, P. pictorum.

γ proteobacteria:

.

δ proteobacteria: P. formicans.

Phylogenetics

The following relationships between genomic affinity groups have been determined by phylogenetic analysis:[61][62]

Bacteriophages

There are a number of bacteriophages that infect Pseudomonas, e.g.

See also

  • Culture collection
    for a list of culture collections

Footnotes

References

  1. .
  2. .
  3. ^ "Genus Pseudomonas". LPSN.dsmz.de. Retrieved 4 April 2023. Partial citation, see Parte et al., 2020 for project reference
  4. ^ .
  5. .
  6. .
  7. ^ Migula, W. (1894) Über ein neues System der Bakterien. Arb Bakteriol Inst Karlsruhe 1: 235–238.
  8. ^ Migula, W. (1900) System der Bakterien, Vol. 2. Jena, Germany: Gustav Fischer.
  9. ^
    PMID 20553550
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  23. ^ Biello, David (February 28, 2008). "Do Microbes Make Snow?". Scientific American.
  24. PMID 12458153
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  28. ^ "Scientists Discover Clays to Fight Deadly Bacteria". www.infoniac.com. 2007-03-16. Retrieved 2008-11-20.
  29. ^ Smith, Michael (2007-03-16). "Gallium May Have Antibiotic-Like Properties". MedPage Today. Archived from the original on 2008-09-18.
  30. PMID 6405475
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  46. ^ "What Is Pseudomonas Aeruginosa?". WebMD. October 27, 2022. Retrieved 2023-08-07.
  47. ^ a b c Wood, Peter (2021-03-16). "Pseudomonas: How to Treat and Prevent in Commercial Water Systems". Wychwood Water Systems. Retrieved 2023-08-07.
  48. ^
    PMID 7529239
    .
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  62. . Note that the tree in this reference has the same topology, but looks different because it is unrooted.
  63. ^
    PMID 16256135. Archived from the original
    (PDF) on 2016-03-04. Retrieved 2015-08-27.
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