Pseudomonas aeruginosa is more accustomed as an arising adept antibody of analytic relevance. Several altered epidemiological studies announce antibacterial attrition is accretion in analytic isolates.
The associates of the brand authenticate a abundant accord of metabolic diversity, and appropriately are able to colonise a advanced ambit of niches. Their affluence of ability in vitro and availability of an accretion amount of Pseudomonas ache genome sequences has fabricated the brand an accomplished focus for accurate research; the best advised breed cover P. aeruginosa in its role as an adept animal pathogen, the bulb antibody P. syringae, the clay bacillus P. putida, and the bulb advance announcement P. fluorescens.
Because of their boundless accident in baptize and in bulb seeds such as dicots, the pseudomonads were empiric aboriginal in the history of microbiology. The all-encompassing name Pseudomonas created for these bacilli was authentic in rather ambiguous agreement by Walter Migula in 1894 and 1900 as a brand of Gram-negative, rod-shaped and polar-flagella bacilli with some sporulating species, the closing account was after accepted incorrect and was due to refractive granules of assets materials. Despite the ambiguous description, the blazon species, Pseudomonas pyocyanea (basonym of Pseudomonas aeruginosa), accepted the best descriptor.
Characteristics of Pseudomonas
Members of the genus display the following defining characteristics:
Rod shaped
Gram-negative
One or more polar flagella, providing motility
Aerobic
Non–spore forming
positive catalase test
positive oxidase test.
Other characteristics which tend to be associated with Pseudomonas species (with some exceptions) include secretion of pyoverdine, a fluorescent yellow-green siderophore under iron-limiting conditions. Certain Pseudomonas species may also produce additional types of siderophore, such as pyocyanin by Pseudomonas aeruginosa and thioquinolobactin by Pseudomonas fluorescens,. Pseudomonas species also typically give a positive result to the oxidase test, the absence of gas formation from glucose, glucose is oxidised in oxidation/fermentation test using Hugh and Leifson O/F test, beta hemolytic (on blood agar), indole negative, methyl red negative, Voges–Proskauer test negative, and citrate positive.
Use
As biocontrol agents
Since the mid 1980s, certain members of the Pseudomonas genus 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 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: that the bacteria might induce systemic resistance in the host plant, so it can better resist attack by a true pathogen; the bacteria might out compete 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. There is experimental evidence to support all of these theories.
Other notable Pseudomonas species with biocontrol properties include P. chlororaphis, which produces a phenazine-type antibiotic active agent against certain fungal plant pathogens, and the closely related species P. aurantiaca which produces di-2,4-diacetylfluoroglucylmethane, a compound antibiotically active against Gram-positive organisms.
As bioremediation agents
Some members of the genus Pseudomonas 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:
P. alcaligenes, which can degrade polycyclic aromatic hydrocarbons.
P. mendocina, which is able to degrade toluene.
P. pseudoalcaligenes is able to use cyanide as a nitrogen source.
P. resinovorans can degrade carbazole.
P. veronii has been shown to degrade a variety of simple aromatic organic compounds.
P. putida has the ability to degrade organic solvents such as toluene. At least one strain of this bacterium is able to convert morphine in aqueous solution into the stronger and somewhat expensive to manufacture drug hydromorphone (Dilaudid).
Strain KC of P. stutzeri is able to degrade carbon tetrachloride.
Food spoilage agents
As a result of their metabolic diversity, ability to grow at low temperatures and ubiquitous nature, many Pseudomonas spp. can cause food spoilage. Notable examples include dairy spoilage by P. fragi, mustiness in eggs caused by P. taetrolens and P. mudicolens, and P. lundensis, which causes spoilage of milk, cheese, meat, and fish.
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