Novel collective prey evasion response of Pseudomonas aeruginosa PAO1 to soil micropredator Myxococcus xanthus DK1622

Author

Joshua LummusFollow

Date of Award

Summer 7-31-2023

Degree Type

Thesis

Degree Name

Master of Science in Integrative Biology (MSIB)

Department

Biology

Committee Chair/First Advisor

Melanie Griffin

Major Professor

Ramya Rajagopalan

Second Committee Member

Andrew Haddow

Abstract

The search for alternative therapeutics is on the rise because of the threat of multi-drug resistant bacteria. Looking at the hunting strategy of soil-based bacterial micropredators is one avenue of exploration. Myxobacteria are soil predators with a wide prey range including Gram-negative and Gram-positive bacteria, fungi, and archaea. In our lab we discovered a distinct and novel anti-predation behavior in Pseudomonas aeruginosa strain 01. P. aeruginosa is an opportunistic and nosocomial pathogen responsible for 10% of all hospital acquired infections. P. aeruginosa is also an ESKAPE pathogen, which are leading causes of nosocomial infections throughout the world, and they are often multi-drug resistant. When standardized spots of micropredator Myxococcus xanthus DK1622 and prey were placed 1 millimeter apart on partial starvation media, most prey bacteria such as Escherichia coli K12 and Staphylococcus aureus displayed a three-log reduction in surviving cell counts following 48 hours of myxobacterial predation. However, under the same conditions PAO1 showed no reduction in surviving cells when compared to non-predation controls. Concurrently, we observed a retreat of prey cells at the junction between advancing M. xanthus front and the PAO1 spot, resembling a “fold”. This distinct evasion response was not observed in another P. aeruginosa strain, PA14, nor in other closely related pseudomonads we tested. Transposon mutants of the quorum sensing operon pqs and gene rsaL, did not possess the fold. Here we describe a novel predation resistance response observed in PAO1 and we aim to frame this predation response in the context of predation resistance responses seen in prey bacteria.