FimL Regulates cAMP Synthesis in Pseudomonas aeruginosa

Pseudomonas aeruginosa, a ubiquitous bacteria found in diverse ecological niches, is an important cause of acute infections in immunocompromised individuals and chronic infections in patients with Cystic Fibrosis. One signaling molecule required for the coordinate regulation of virulence factors associated with acute infections is 3′, 5′-cyclic adenosine monophosphate, (cAMP), which binds to and activates a catabolite repressor homolog, Vfr. Vfr controls the transcription of many virulence factors, including those associated with Type IV pili (TFP), the Type III secretion system (T3SS), the Type II secretion system, flagellar-mediated motility, and quorum sensing systems. We previously identified FimL, a protein with histidine phosphotransfer-like domains, as a regulator of Vfr-dependent processes, including TFP-dependent motility and T3SS function. In this study, we carried out genetic and physiologic studies to further define the mechanism of action of FimL. Through a genetic screen designed to identify suppressors of FimL, we found a putative cAMP-specific phosphodiesterase (CpdA), suggesting that FimL regulates cAMP levels. Inactivation of CpdA increases cAMP levels and restores TFP-dependent motility and T3SS function to fimL mutants, consistent with in vivo phosphodiesterase activity. By constructing combinations of double and triple mutants in the two adenylate cyclase genes (cyaA and cyaB), fimL, and cpdA, we show that ΔfimL mutants resemble ΔcyaB mutants in TM defects, decreased T3SS transcription, and decreased cAMP levels. Similar to some of the virulence factors that they regulate, we demonstrate that CyaB and FimL are polarly localized. These results reveal new complexities in the regulation of diverse virulence pathways associated with acute P. aeruginosa infections

Loneliness among people with substance use problems: a narrative systematic review

Issues: Despite the serious implications of loneliness on health and wellbeing, little is understood about this experience across people with substance use problems. This systematic review aimed to examine: (i) correlates and predictors of loneliness; (ii) theories underpinning loneliness; (iii) methods employed to measure loneliness; and (iv) loneliness interventions for people with substance use problems. Approach: Empirical sources were identified from key databases for all publications preceding February 2019. Overall, 41 studies met the eligibility criteria and were included in the review. Key Findings: Findings from this review suggest that loneliness is related to poor physical and mental health, substance use, the quality of relationships, stigma and perception of ill treatment by others. Although cognitive theories have proposed cognitive patterns underlying the onset and maintenance of loneliness, they had not been investigated in relation to measurement or intervention efforts. Just one loneliness measure (UCLA Loneliness Scale) is valid for use with this population. Finally, only a single loneliness intervention had been trialled and was not found to be efficacious in reducing loneliness for people with substance use problems. Implications: Understanding possible links between loneliness and substance use and how to alleviate loneliness is important for this population in terms of their wellbeing and recovery. Conclusion: Loneliness is prevalent and experienced as problematic among people with substance use problems. Future research should focus on employing longitudinal designs, using validated, multidimensional measures of loneliness and on developing and trialling loneliness interventions that meet the specific needs of people with substance use problems