Molecular regulation of virulence in Legionella pneumophila

Abstract

Legionella pneumophila is a gram‐negative bacteria found in natural and anthropogenic aquatic environments such as evaporative cooling towers, where it reproduces as an intracellular parasite of cohabiting protozoa. If L. pneumophila is aerosolized and inhaled by a susceptible person, bacteria may colonize their alveolar macrophages causing the opportunistic pneumonia Legionnaires' disease. L. pneumophila utilizes an elaborate regulatory network to control virulence processes such as the Dot/Icm Type IV secretion system and effector repertoire, responding to changing nutritional cues as their host becomes depleted. The bacteria subsequently differentiate to a transmissive state that can survive in the environment until a replacement host is encountered and colonized. In this review, we discuss the lifecycle of L. pneumophila and the molecular regulatory network that senses nutritional depletion via the stringent response, a link to stationary phase‐like metabolic changes via alternative sigma factors, and two‐component systems that are homologous to stress sensors in other pathogens, to regulate differentiation between the intracellular replicative phase and more transmissible states. Together, we highlight how this prototypic intracellular pathogen offers enormous potential in understanding how molecular mechanisms enable intracellular parasitism and pathogenicity.

Cell-SELEX for aptamer discovery and its utilization in constructing electrochemical biosensor for rapid and highly sensitive detection of Legionella pneumophila serogroup 1

“…Legionella pneumophila ( L. pneumophila ), a Gram-negative pathogenic bacterium, is prevalent in both natural and artificial hot and humid environments, such as streams, lakes, fountains, cooling towers, hot showers, and plumbing systems. This bacterium serves as a significant causative agent of Pontiac fever and Legionnaires’ disease, leading to respiratory infection and pneumonia, causing multisystem damage in humans 1 , 2 . As a water-borne pathogen capable of spreading through inhalation of aerosols, it poses substantial threats to immunocompromised individuals, particularly in hospital environments.…”

Nitric oxide signaling through three receptors regulates virulence, biofilm formation, and phenotypic heterogeneity of Legionella pneumophila

“…The Lqs system is integrated into and crosstalks with other regulatory systems of L. pneumophila , such as sensor histidine kinase-response regulator two-component systems ( 22 , 39 ) and the cyclic di-guanosine monophosphate (c-di-GMP) signaling network ( 40 ) ( Fig. 1A ).…”