Identification of differentially expressed Legionella genes during its intracellular growth in Acanthamoeba

Abstract

Legionella grows intracellularly in free-living amoeba as well as in mammalian macrophages. Until now, the overall gene expression pattern of intracellular Legionella in Acanthamoeba was not fully explained. Intracellular bacteria are capable of not only altering the gene expression of its host, but it can also regulate the expression of its own genes for survival. In this study, differentially expressed Legionella genes within Acanthamoeba during the 24 h intracellular growth period were investigated for comparative analysis. RNA sequencing analysis revealed 3,003 genes from the intracellular Legionella . Among them, 115 genes were upregulated and 1,676 genes were downregulated more than 2 fold compared to the free Legionella . Gene ontology (GO) analysis revealed the suppression of multiple genes within the intracellular Legionella , which were categorized under ‘ATP binding’ and ‘DNA binding’ in the molecular function domain. Gene expression of alkylhydroperoxidase, an enzyme involved in virulence and anti-oxidative stress response, was strongly enhanced 24 h post-intracellular growth. Amino acid ABC transporter substrate-binding protein that utilizes energy generation was also highly expressed. Genes associated with alkylhydroperoxidase, glucose pathway, and Dot/Icm type IV secretion system were shown to be differentially expressed. These results contribute to a better understanding of the survival strategies of intracellular Legionella within Acanthamoeba .

Legionella pneumophila — The causative agent of Legionnaires’ disease

“…Legionella is a Gram-negative, facultative aerobic and intracellular waterborne bacterium present in natural aquatic environments, such as lakes, rivers and groundwater, but at low concentrations [22] . The widespread distribution of Legionella bacteria is attributed to their ability to proliferate within diverse types of niches, including live in planktonic form, infect and replicate within protozoan hosts as well as coexist within multi-organismal biofilms developed on the surfaces of water systems [23,24] .…”

Budowa IV systemu sekrecji Legionella pneumophilai jego znaczenie w patogenezie

“…Białko DotB jest zaangażowane w sekrecję białek efektorowych za pomocą systemu Dot/Icm [47]. Ekspresja genów kodujących białka DotB oraz DotC zwiększa się po upływie 24 godzin od infekcji komórek Acanthamoeba castellanii przez L. pneumophila [48]…”

Conceptual model to inform Legionella–amoebae control, including the roles of extracellular vesicles in engineered water system infections

“…Overall, this begs the question, has L. pneumophila , like other amoeba-resisting pathogens ( Schmitz-Esser et al., 2010 ), evolved not only to grow and control host cells (using a large fraction of its genome to do so [( Burstein et al., 2016 )]), but is it also adapted to persist within EVs or even generate host EVs to extend its transmissive phase? Recent transcriptomics is helping us to understand the differentially expressed Legionella genes within their infected amoebal hosts ( Quan et al., 2020 ; Chauhan et al., 2023 ). Such techniques have yet to be applied to EVs production and within these vesicles.…”