DENNIS KUNKEL MICROSCOPY / SCIENCE PHOTO LIBRARY DENNIS KUNKEL MICROSCOPY / SCIENCE PHOTO LIBRARY
Coloured scanning electron micrograph (SEM) of Pseudomonas fluorescens bacteria. These are Gram-negative, aerobic, rod-shaped bacteria. Pseudomonas fluorescens encompasses a group of common pseudomonads, which are nonpathogenic saprophytes that colonize soil, water and plant surfaces. A number of strains of P. fluorescens suppress plant diseases by protecting the seeds and roots from fungal infection. This effect is the result of production of a number of secondary metabolites including antibiotics, siderophores and hydrogen cyanide. Competitive exclusion of pathogens as the result of rapid colonization of the rhizosphere may also be an important factor in disease control. P. fluorescens strains produce a soluble, greenish fluorescent pigment (yellow-green siderophores), under conditions of low iron availability. It is primarily an obligate aerobe, however some strains can utilize nitrate (NO3) as an electron acceptor in place of oxygen (O2). It is motile by means of multiple polar flagella. Genetic techniques such as conjugation, transposition, and gene replacement are well established for this soil bacterium. P. fluorescens is used in bioremediation applications due to various strains have the inherent metabolic diversity to partially or completely degrade pollutants such as styrene, TNT and polycyclic aromatic hydrocarbons. Magnification: x2,600 when shortest axis printed at 25 millimetres.
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