The quorum sensing regulator RhlR positively controls the expression of the type III secretion system in Pseudomonas aeruginosa PAO1.

Pseudomonas aeruginosa is an opportunist bacterium that causes acute and chronic infections. During acute infections, the type III secretion system (T3SS) plays a pivotal role in allowing the bacteria to translocate effectors such as ExoS, ExoT, and ExoY into host cells for colonization. Previous research on the involvement of quorum sensing systems Las and Rhl in controlling the T3SS gene expression produced ambiguous results.

Isolates from Water Samples of the Gulf of Mexico Show Similar Virulence Properties but Different Antibiotic Susceptibility Profiles than Clinical Isolates.

is an opportunistic pathogen found in a wide variety of environments, including soil, water, and habitats associated with animals, humans, and plants. From a One Health perspective, which recognizes the interconnectedness of human, animal, and environmental health, it is important to study the virulence characteristics and antibiotic susceptibility of environmental bacteria. In this study, we compared the virulence properties and the antibiotic resistance profiles of seven isolates collected from the Gulf of Mexico with those of seven clinical strains of .

strains belonging to phylogroup 3 frequently exhibit an atypical quorum sensing response: the case of MAZ105, a tomato rhizosphere isolate.

is a widespread γ-proteobacterium and an important opportunistic pathogen. The genetically diverse phylogroup 3 strains are characterized by producing the pore-forming ExlA toxin and by their lack of a type III secretion system. However, like all strains of this species, they produce several virulence-associated traits, such as elastase, rhamnolipids and pyocyanin, which are regulated by quorum sensing (QS).

Vfr or CyaB promote the expression of the pore-forming toxin operon in ATCC 9027 without increasing its virulence in mice.

is a wide-spread γ-proteobacterium that produces the biosurfactant rhamnolipid that has a great commercial value due to excellent properties of low toxicity and high biodegradability. However, this bacterium is an opportunist pathogen that constitutes an important health hazard due to its production of virulence-associated traits and its high antibiotic resistance. Thus, it is highly desirable to have a non-virulent strain for rhamnolipid production.