A human respiratory tract-associated bacterium with an extremely small genome

Area of Science:

• Microbiology
• Genomics
• Human Pathogens

Background:

• Culture-independent microbiological analyses have revealed microbial diversity.
• Discovery of novel human pathogenic bacteria significantly different from known taxa remains rare.

Purpose of the Study:

• To present the complete genome sequence of a novel uncultured bacterium, IOLA, detected in the human respiratory tract.
• To characterize the unique genomic features of IOLA and its potential lifestyle and association with human respiratory infections.

Main Methods:

• Development of a protocol for selective amplification of extremely AT-rich genomes.
• Whole-genome sequencing of the uncultured bacterium IOLA.
• Bioinformatic analysis of the IOLA genome.
• Surveillance of clinical samples for IOLA detection.

Main Results:

• The complete genome sequence of IOLA was determined, measuring 303,838 bp with a 20.7% GC content.
• IOLA possesses the smallest and most AT-rich genome among known human-associated bacteria, comparable to insect endosymbionts.
• Gene content suggests an epicellular parasitic lifestyle, despite belonging to the order Rickettsiales.
• IOLA was predominantly detected in patients with respiratory bacterial infections and persisted for at least 15 months.

Conclusions:

• IOLA represents a novel human respiratory tract-associated bacterium.
• Its unique genomic characteristics challenge existing understanding of bacterial adaptation and parasitism.
• Further research is warranted to elucidate the pathogenic role and clinical significance of IOLA.