Investigating the Potential Virulence of Legionella antarctica as a Human Pathogen through Comparative Genomic Analysis

Abstract

Our original objective was to experimentally evaluate the infection potential of L. antarctica in human macrophage models using THP-1 and alveolar macrophages. However, due to delayed bacterial sample availability, the study shifted to a comparative genomic analysis using the National Center for Biotechnology Information (NCBI) BLAST to investigate potential virulence genes. Legionella pneumophila causes a severe pneumonia known as Legionnaires’ disease by infecting and replicating within human macrophages. Its intracellular survival depends on key virulence factors, including: Dot/Icm Type IV secretion system – injects bacterial proteins into host cells Type IV Effector proteins – manipulate host cellular pathways to promote replication Surface adhesion proteins – aid in host attachment, motility, and infection. Research Question Does L. antarctica possess virulence genes similar to those found in L. pneumophila?Legionella pneumophila is the primary cause of Legionnaires' disease and infects human macrophages through specialized virulence factors, including the Dot/Icm Type IV secretion system, effector proteins, and surface proteins. However, many environmental Legionella species remain understudied. Legionella antarctica is a recently identified cold-adapted species isolated from Antarctic freshwater sediments and later detected in Texas. This study used comparative genomics to determine whether L. antarctica contains homologs of major virulence-associated proteins found in Legionella pneumophila. Protein sequences from L. pneumophila were retrieved from NCBI and analyzed using BLASTp against the L. antarctica genome. Ten virulence-associated proteins were examined, including Type IV secretion structural proteins, effector proteins, and surface proteins. Results demonstrated conservation of multiple structural proteins but reduced similarity among several effectors and surface proteins, suggesting that L. antarctica may possess partial virulence machinery while remaining less adapted for human infection. These findings contribute to understanding environmental Legionella evolution and potential public health risks..We would like to thank the Office of Sponsored Projects for the Undergraduate Faculty-Montored Grant which sponsored this research