Lon protease has multifaceted biological functions in Acinetobacter baumannii .

Acinetobacter baumannii is a Gram-negative opportunistic pathogen known to survive harsh environmental conditions and is a leading cause of hospital-acquired infections. Specifically, multicellular communities, known as biofilms, of A. baumannii can withstand desiccation and survive on hospital surfaces and equipment. Biofilms are bacteria embedded in a self-produced extracellular matrix composed of proteins, sugars and/or DNA. Bacteria in a biofilm are protected from environmental stress, including antibiotics, providing them with selective advantage for survival. Though some gene products are known to play roles in this developmental process in A. baumannii , mechanisms and signaling remain mostly unknown. Here, we find that Lon protease in A. baumannii impacts biofilm development and has other important physiological roles, including motility and cell envelope. Lon proteases are found in all domains of life participating in regulatory processes and maintaining cellular homeostasis. These data reveal the importance of Lon protease in influencing key A. baumannii processes to survive stress and maintain viability. IMPORTANCE Acinetobacter baumannii is an opportunistic pathogen and leading cause of hospital-acquired infections. A. baumannii is difficult to eradicate and manage, as this bacterium is known to robustly survive desiccation and quickly gain antibiotic resistances. We sought to investigate biofilm formation in A. baumannii since much remains unknown about it in this bacterium. Biofilms, which are multicellular communities of bacteria, are surface-attached and difficult to eliminate from hospital equipment and implanted devices. Our research identifies a multi-faceted physiological role of the conserved bacterial protease Lon in A. baumannii These roles include biofilm formation, motility and viability. This work broadly impacts and expands the biology of A. baumannii , which will in turn permit us to find effective ways to eliminate it.