Pseudomonas fluorescens

Pseudomonas fluorescens is a gram-negative, oxidasepositives, rod-shaped bacterium of the genus Pseudomonas with polständigem scourge tufts. P. fluorescens secretes siderophores from named Pyoverdine ( = fluorescein), which fluoresce under UV light. The bacterium is aerobic and comes in soil, water and plants in front. P. fluorescens is one of the rarely isolated, human medically important Pseudomonas species. More important than in medicine has P. fluorescens but in soil biology and the spoilage of food.

Soil Biology

Some strains of P. fluorescens are important soil organisms, as they are able to suppress a number of plant pathogenic bacteria. In this way, natural suppressive soils may arise. This effect is due to the fact that these strains of P. fluorescens produce secondary metabolites as antibiotics, that it comes through the roots colonization by such strains in an induced systemic resistance of the plant, or that such strains are often very specific antagonists of certain pathogens.

Antibiotics

The genome of strain Pf -5 was completely sequenced. This 4 already known gene complexes were found that encode toxic secondary metabolites of fungi or Eipilze. These were to pyoluteorin, 2,4- diacetylphloroglucinol, pyrrolnitrin and hydrogen cyanide. In addition, three previously unknown gene complexes were detected, which may also encode secondary metabolites. It also gene complexes were found for non-ribosomal preparation and for receiving the pyoverdine siderophores (position and orientation soft but of which are already known gene complexes in other microorganisms from ). Since Pyoverdine are very potent siderophores, it can in pH - neutral to basic soils ( Fe 3 ions are poorly soluble ) come to an inhibition of phytopathogenic bacteria because they can take up to little Fe3 ions. Here, however, the boundaries, because the antibiotics are secondary metabolites, while the iron is needed in the primary metabolism. Yet here affects the primary metabolic inhibitory one on the growth of phytopathogenic bacteria. Similarly, it is likely to behave with pyochelin. The gene complexes for its production were also detected in strain Pf -5. Pyochelin is a strong Cu2 - and Zn2 chelator and could be as inhibitory effect on fungal growth by removal of these ions.

Induced systemic resistance

It is not known exactly how to interact with the bacteria to the roots of a plant, so that there is induced systemic resistance. However, the production of the secondary metabolite 2,4 - diacetylphloroglucinol seems to play an important role.

Spoilage of food

P. fluorescens can secrete proteolytic and lipolytic enzymes and lives aerobic and psychrotrophic. Therefore P. fluorescens along with Pseudomonas fragi and Pseudomonas putida one of the most common gram-negative, psychrotolerant bacteria, which are involved in the spoilage of milk. The secreted enzymes are heat stable and remain active even after pasteurization and ultra-high heat. Another problem in the processing of milk is the colonization by P. fluorescens after pasteurization. As a source of such colonizations the processing environment comes into question.

Medical importance

P. fluorescens is rarely found in blood products. This is due to the ability of the bacterium together, even at 4 ° C continues to grow ( Psychrophilie ). Thus, this germ is one of the two most frequent causes of sepsis after transfusion with blood keimverseuchtem.