The Bactérie S of the Pseudomonas can be defined by:
- Bacilli with negative Gram, Catalase + and variable Oxydase (negative generally);
- Aerobic strict;
- Degrading the Glucose by aerobic or inert Breathing with respect to the Glucose. They do not attack sugars or attack them by oxydative and nonfermentative way;
- Generally mobile;
- Not very demanding, cultivating to 30 °C.
This kind however includes/understands more than one hundred of S Ubiquitaire S (whose Species-type Pseudomonas aeruginosa generally called Bacille is pyocyanic ) of many species are in the course of exclusion (of share progress of the Phylogénétique) and to reduce their number to an about sixty species.
Habitat
These bacteria, largely widespread in the environment, live in Saprophyte S in the ground and water. They are found on the plants, the foodstuffs, involving, sometimes, their deterioration Organoleptique S.They meet in the man or the animal, on the level of the nasal fossae. They constitute, for the majority, a Flore commensale. Some play a pathogenic part:
- At the plants (some species, of which Pseudomonas syringae , of which a stock keep silent of young chestnut trees per thousands since the beginning of the years 2000)
- In the man and the animal (with mainly Pseudomonas aeruginosa )
They occupy of the varied ecological niches, but are found more particularly in moist environments such as fresh water, the sea water, the thermal springs. They find in more minor amount in water rich in organic matters (in particular stagnant water) consequence of the competition between micro-organisms where the Pseudomonas are not most powerful.
In the human dwellings, they are found in the siphons of sink and water tanks of rain which, when that they are used for the watering of the plants, can cause diseases on the plants in particular the flowers (for the species phytopathogene).
Pathogenic role
At the man, the species Pseudomonas aeruginosa (also called bacillus pyocyanic) frequently intervenes like pathogenic opportunist. It is found in flora of transit on the skin and the mucous membrane and causes superinfections of wounds or burns. At individuals immunodépressifs it can be the cause of various cutaneous and visceral infections and even of Septicémie. It involves a particularly high risk of infections nosocomiales (contracted by the intermédaire of care in hospital medium).The other species Saprophyte S meet during opportunist infections exclusively among patients in immunodépression and in a more sporadic way.
Bacteriological characters
Microscopic morphology
Aspect : The Pseudomonas are negative Gram bacilli ends rights and very mobiles thanks to a polar Flagelle: ciliature monotriche, deprived of spores and capsules.Grouping : They appear most of the time isolated or in diplobacilles.
Characters of culture
Conditions of culture
The Pseudomonas are not very demanding germs, the vast majority of the species do not require any Growth factor and are able to use like only source of carbon and energy a broad spectrum of simple carbonaceous substrates and variés.They develop on all the usual mediums, even simplest.
It have also a great tolerance in the ranges of surrounding temperature, although having an optimal temperature of growth located between 30 and 35°C (Mésophile), it are able to push at temperatures between 4 and 42°C by slowing down to them Métabolisme. Their growth thus is not completely blocked by the cooled buildings and the incubators.
It resist many bacterial inhibiters, particularly with the chemical agents. They continue their development of the certain solutions disinfectants (in particular the Cétrimide) and are resistant to many antibiotics.
Culture media used
- nonselective Milieux
- ordinary Gélose
- Gélose BCP
- peptonée Eau
- selective Milieux
- Gélose cétrimide
- Milieu of King has
- Milieu of King B
Biochemical characters
Metabolism
All the species have a Oxydase.The degradation of the Glucose is carried out by the way of Entner-Doudoroff, this property is highlighted on medium Hugh-Leifson. They frequently have a Arginine dihydrolase allowing the degradation of the Arginine in anaérobiose.
Certain species can extract the Oxygène released by the reduction from the Nitrate S in Azote, and thus grow in anaérobiose; one speaks then about " Breathing nitrate" .
Production of pigments
Many representatives of this kind produce a pigment. Let us quote those used for the identification:- the Pyocyanin, blue pigment - green phenazinic, it is soluble in the Chloroforme and the Eau and is specific of P. aeruginosa .
-
the Pyoverdine, fluorescent, water soluble green synthesized by the Pseudomonas of the group fluorescens .
Species belonging to the kind Pseudomonas
List of the species which should be excluded from the kind Pseudomonas :
Sources and references
Internal bonds
External bonds:
- L P S NR
- http://www.genome.jp/kegg-bin/KEGG_Genome_map_top.pl?org_id=pae Genome of Pseudomonas aeruginosa PAO1 (to point on the gray bar)]
Literature:
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