Identification of Genes Involved in Swarming Behavior of Pseudomonas aeruginosa PA14 strain Using Non-redundant Transposon Insertion Mutant Library

Abstract

The present work describes the genetic regulators of swarming behavior in Pseudomonas aeruginosa strain PA14. Swarming motility is a collective coordinated group behavior exhibited by several pathogenic bacteria. Swarming in PA14 is an emergent behavior as a result of local interactions of individual bacteria and globally forming a well-structured dendritic pattern. Several studies have shown that in different bacteria swarming arises due to interaction with another individual, its surface environment and via sensing nutrient availability. All these factors integrate together and lead to genotypic and phenotypic changes in bacterial morphology and behavior. P. aeruginosa is a well-known opportunistic human pathogen; causes infection in cystic fibrosis, burn injured and diabetic foot ulcer patients. It can show swarming in 0.6 % agar concentration and under nutrient depletes condition. Several parameters including temperature, moisture, pH, drying period etc. influence swarming pattern in PA14. In some bacterial species, swarming motility has been linked to virulence and antibiotic resistance. But there are very few studies on swarming and it’s linked to virulence in P. aeruginosa. We have used PA14 NR transposon insertion mutant library comprising 5987 mutants and screen for all of them in order to find non- swarming mutants can also call as ‘swarming promoting factors’. This study has found around 281 transposon mutants exhibiting swarming negative phenotype; 129 among them are newly identified in the screening. These set of genes belong to all the functional classes with the exception in non-coding RNA class; it comprises not only motility and attachment genes but also includes diverse sets of genes such as biosynthesis of amino acids, nucleotides, and cofactors, transcriptional regulators, transporters and two component regulators; 42 of them are hypothetical and unknown.