AUTHOR=Li Pengfei , Vassiliadis Dane , Ong Sze Ying , Bennett-Wood Vicki , Sugimoto Chihiro , Yamagishi Junya , Hartland Elizabeth L. , Pasricha Shivani 

TITLE=Legionella pneumophila Infection Rewires the Acanthamoeba castellanii Transcriptome, Highlighting a Class of Sirtuin Genes

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=10

YEAR=2020

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2020.00428

DOI=10.3389/fcimb.2020.00428

ISSN=2235-2988

ABSTRACT=<p><italic>Legionella pneumophila</italic> is an environmental bacterium that has evolved to survive predation by soil and water amoebae such as <italic>Acanthamoeba castellanii</italic>, and this has inadvertently led to the ability of <italic>L. pneumophila</italic> to survive and replicate in human cells. <italic>L. pneumophila</italic> causes Legionnaire's Disease, with human exposure occurring via the inhalation of water aerosols containing both amoebae and the bacteria. These aerosols originate from aquatic biofilms found in artifical water sources, such as air-conditioning cooling towers and humidifiers. In these man-made environments, <italic>A. castellanii</italic> supports <italic>L. pneumophila</italic> intracellular replication, thereby promoting persistence and dissemination of the bacteria and providing protection from external stress. Despite this close evolutionary relationship, very little is known about how <italic>A. castellanii</italic> responds to <italic>L. pneumophila</italic> infection. In this study, we examined the global transcriptional response of <italic>A. castellanii</italic> to <italic>L. pneumophila</italic> infection. We compared <italic>A. castellanii</italic> infected with wild type <italic>L. pneumophila</italic> to <italic>A. castellanii</italic> infected with an isogenic Δ<italic>dotA</italic> mutant strain, which is unable to replicate intracellularly. We showed that <italic>A. castellanii</italic> underwent clear morphological and transcriptional rewiring over the course of <italic>L. pneumophila</italic> infection. Through improved annotation of the <italic>A. castellanii</italic> genome, we determined that these transcriptional changes primarily involved biological processes utilizing small GTPases, including cellular transport, signaling, metabolism and replication. In addition, a number of sirtuin-encoding genes in <italic>A. castellanii</italic> were found to be conserved and upregulated during <italic>L. pneumophila</italic> infection. Silencing of sirtuin gene, <italic>sir6f</italic> (ACA1_153540) resulted in the inhibition of <italic>A. castellanii</italic> cell proliferation during infection and reduced <italic>L. pneumophila</italic> replication. Overall our findings identified several biological pathways in amoebae that may support <italic>L. pneumophila</italic> replication and <italic>A. castellanii</italic> proliferation in environmental conditions.</p>