Pseudomonas
Encyclopedia : P : PS : PSE : Pseudomonas
The bacterial genus Pseudomonas includes plant pathogenic bacteria such as P. syringae (various pathovars), the opportunistic human pathogen P. aeruginosa, the ubiquitous soil bacterium P. putida, and some species that are known to cause problems in dairy products. However, the actions of this group of bacteria are mainly considered neutral to man. They are considered to be metabolically diverse agents of spoilage and degradation. In recent times, members of the Pseudomonas have been used as biocontrol agents.
Members of Pseudomonas are Gram-negative, aerobic (able to consume oxygen) rods. Most are flagellated so they can move around. Most produce a slime layer that cannot be phagocytosed, and which aids in the production of surface-colonising biofilms. P. fluorescens is easily recognised as it secretes large amounts of a fluorescent, yellow-green siderophore under iron-limited conditions. Many Pseudomonadaceae are capable of producing these fluorescent pigments called pyoverdines. Growth of Pseudomonads is usually accompanied by a "fruity" odor compared to Escherichia coli.
Pseudomonas have the ability to metabolise a variety of diverse nutrients. Combined with the ability to form biofilms, they are thus able to able to survive in a variety of unexpected places. For example, they have been found in areas where pharmaceuticals are prepared. A simple carbon source, such as soap residue or cap liner-adhesives is a suitable place for the Pseudomonads to thrive. Other unlikely places where they have been found include antiseptics such as quaternary ammonium compounds and bottled mineral water. Most Pseudomonas spp. are naturally resistant to penicillin and related beta-lactam antibiotics, but a number are sensitive to piperacillin, imipenem, tobramycin, or ciprofloxacin.
This ability to thrive in harsh conditions is a result of their hardy cell wall that contains porins. Their resistance to most antibiotics is attributed to the efflux pumps call ABC transporters which pump out some antibiotics before they are able to act.
The Pseudomonads can also grow in the human ear canal causing pain and a discharge. It can be treated with Ciprofloxacin and Gentisone HC ear drops though this treatment is not receommended for children.
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