RESUMO
Infections of the lung cause observable sickness thought to be secondary to inflammation. Signs of sickness are crucial to alert others via behavioral-immune responses to limit contact with contagious individuals. Gram-negative bacteria produce exopolysaccharide (EPS) that provides microbial protection; however, the impact of EPS on sickness remains uncertain. Using genome-engineered Pseudomonas aeruginosa (P. aeruginosa) strains, we compared EPS-producers versus non-producers and a virulent Escherichia coli (E. coli) lung infection model in male and female mice. EPS-negative P. aeruginosa and virulent E. coli infection caused severe sickness, behavioral alterations, inflammation, and hypothermia mediated by TLR4 detection of the exposed lipopolysaccharide (LPS) in lung TRPV1+ sensory neurons. However, inflammation did not account for sickness. Stimulation of lung nociceptors induced acute stress responses in the paraventricular hypothalamic nuclei by activating corticotropin-releasing hormone neurons responsible for sickness behavior and hypothermia. Thus, EPS-producing biofilm pathogens evade initiating a lung-brain sensory neuronal response that results in sickness.
Assuntos
Infecções por Escherichia coli , Escherichia coli , Pulmão , Polissacarídeos Bacterianos , Infecções por Pseudomonas , Pseudomonas aeruginosa , Animais , Feminino , Masculino , Camundongos , Biofilmes , Escherichia coli/fisiologia , Hipotermia/metabolismo , Hipotermia/patologia , Inflamação/metabolismo , Inflamação/patologia , Pulmão/microbiologia , Pulmão/patologia , Pneumonia/microbiologia , Pneumonia/patologia , Pseudomonas aeruginosa/fisiologia , Células Receptoras Sensoriais , Polissacarídeos Bacterianos/metabolismo , Infecções por Escherichia coli/metabolismo , Infecções por Escherichia coli/microbiologia , Infecções por Escherichia coli/patologia , Infecções por Pseudomonas/metabolismo , Infecções por Pseudomonas/microbiologia , Infecções por Pseudomonas/patologia , Nociceptores/metabolismoRESUMO
Many bacteria use the second messenger cyclic diguanylate (c-di-GMP) to control motility, biofilm production and virulence. Here, we identify a thermosensory diguanylate cyclase (TdcA) that modulates temperature-dependent motility, biofilm development and virulence in the opportunistic pathogen Pseudomonas aeruginosa. TdcA synthesizes c-di-GMP with catalytic rates that increase more than a hundred-fold over a ten-degree Celsius change. Analyses using protein chimeras indicate that heat-sensing is mediated by a thermosensitive Per-Arnt-SIM (PAS) domain. TdcA homologs are widespread in sequence databases, and a distantly related, heterologously expressed homolog from the Betaproteobacteria order Gallionellales also displayed thermosensitive diguanylate cyclase activity. We propose, therefore, that thermotransduction is a conserved function of c-di-GMP signaling networks, and that thermosensitive catalysis of a second messenger constitutes a mechanism for thermal sensing in bacteria.