1. Biocontrol via Nutrient Competition and Siderophores

P. putida can protect plants against pathogens without relying on toxic or antibiotic substances. Instead, it uses a strategy based on nutrient competition, especially for iron.

• Siderophores like pyoverdine are secreted to tightly bind iron from the environment, making it unavailable to competing microorganisms (including plant pathogens), thereby suppressing their growth.

• Notably, P. putida B2017 does not produce common antibiotics like pyocyanin or pyrrolnitrin, but still exhibits biocontrol activity due to pyoverdine production (Daura-Pich et al., 2020).

  
  

2. Plant Growth Promotion and Rhizosphere Colonization

P. putida is a well-known Plant Growth-Promoting Rhizobacteria (PGPR) that helps plants grow better by:

• Mobilizing nutrients (e.g., phosphorus solubilization, nitrogen metabolism).

• Inducing systemic resistance in plants against bacterial, viral, and fungal pathogens (Park et al., 2011).

• Efficiently colonizing the rhizosphere (plant root environment) due to genes promoting motility, chemotaxis, and biofilm formation (Molina et al., 2020).

These abilities allow P. putida to coexist with plants, creating a beneficial plant-microbe relationship.

3. Environmental Bioremediation and Stress Tolerance

Thanks to its metabolic versatility, P. putida can degrade a wide variety of toxic pollutants, including hydrocarbons, solvents, and xenobiotics. This makes it a powerful tool in bioremediation (cleaning up contaminated environments).

• It possesses catabolic genes for the breakdown of aromatic compounds, heavy metals, and other industrial pollutants (Udaondo et al., 2016).

• The strain KT2440 is widely used as a model for industrial biotechnology due to its non-pathogenic nature and ability to survive under stress conditions such as high salinity and oxidative stress (Nelson et al., 2002).

  
  

4. Production of Antimicrobial Compounds (Strain-Specific)

While not all P. putida strains produce antimicrobial compounds, certain isolates do exhibit this trait:

• Strains like W15Oct28 and BW11M1 produce putisolvins (cyclic lipopeptides), bacteriocins, tailocins, and other hydrophobic antimicrobial compounds that are active against Staphylococcus aureus, P. aeruginosa, and P. syringae (Ye et al., 2014); (Ghequire et al., 2016).

• These antimicrobial compounds often work under specific environmental conditions such as low iron availability, adding a layer of ecological control to their use.

  
  

5. Capsule Formation and Biofilm Development

P. putida can form a polysaccharide capsule that helps in:

• Surface adhesion (critical for root colonization and biofilm development).

• Protection against environmental stresses, such as desiccation and immune responses in the case of exposure to a host (Kachlany & Ghiorse, 2009).

Biofilm formation is also important for both plant interactions and survival in industrial settings.