Selection of hyperadherent mutants in Pseudomonas putida biofilms

Area of Science:

• Microbiology
• Bacterial Genetics
• Biofilm Formation

Background:

• Genetic factors influencing bacterial biofilm formation are known, but mutations promoting sessile life are less understood.
• Pseudomonas putida KT2440 is a model organism for studying bacterial adaptation.

Purpose of the Study:

• To isolate and characterize mutants of Pseudomonas putida KT2440 with enhanced biofilm formation.
• To identify the genetic basis for increased sessile growth and complex biofilm development.

Main Methods:

• Random transposon mutagenesis was used to generate mutants.
• Phenotypic analysis included colony morphology, extracellular polymeric substance production, and swarming motility.
• Sequence analysis identified the specific mutations responsible for the observed phenotype.

Main Results:

• A mutant exhibiting significantly increased biofilm formation was isolated.
• This mutant displayed altered colony morphology, enhanced swarming, and increased extracellular polymeric substance production.
• The complex phenotype resulted from two mutations: a transposon insertion disrupting an outer membrane lipoprotein and a point mutation in lapG, affecting LapA adhesin turnover.

Conclusions:

• The study identifies specific genetic alterations that promote enhanced biofilm formation in Pseudomonas putida.
• The findings suggest that selection for hyperadherent mutants may occur during prolonged sessile growth.
• Understanding these genetic mechanisms provides insights into bacterial adaptation and biofilm development.