<i>N</i> -acetylglucosamine utilization and impact on antibiotic susceptibility, oxidative stress tolerance, and swimming in <i>Stenotrophomonas maltophilia</i>

<i>N</i>-acetylglucosamine (GlcNAc) is an amino sugar that serves as a structural component, nutrient source, and signal molecule in bacteria. In this study, we sought to identify the genes involved in GlcNAc utilization in <i>Stenotrophomonas maltophilia</i> and to evaluate the impact of GlcNAc utilization on antibiotic susceptibility, oxidative stress tolerance, and swimming motility. The roles of the <i>nagPIBAF</i> operon, <i>nagK</i>, and <i>nagA2</i> in GlcNAc utilization were investigated through mutant construction and growth assays. NagPsm and NagF mediated GlcNAc transport across the inner membrane, while NagK phosphorylated GlcNAc in the cytoplasm. NagA and NagA2 exhibited functional redundancy as <i>N</i>-acetylglucosamine-6-phosphate deacetylases, and NagB functioned as a glucosamine-6-phosphate deaminase. The <i>nagPIBAF</i> operon was repressed by NagI and derepressed in response to GlcNAc-6P. Antibiotic susceptibility and oxidative stress tolerance were assessed by E-test and menadione IC₅₀, respectively. Among the clinical isolates tested, 71.4% (5/7) and 57.1% (4/7) of the strains showed increases in MIC values for colistin and ceftazidime (CAZ) of 1.3 to 2.6 times and 1.3 to 2 times, respectively. Furthermore, GlcNAc utilization enhanced swimming motility but had little effect on oxidative stress tolerance. Overall, the <i>nagPIBAF</i> operon, <i>nagK</i>, and <i>nagA2</i> contribute to GlcNAc utilization, which in turn can increase resistance to CAZ and colistin and promote swimming motility in some clinical isolates of <i>S. maltophilia</i>.IMPORTANCE<i>N</i>-acetylglucosamine (GlcNAc) is widely used as a dietary supplement due to its proposed cartilage-protective and anti-inflammatory properties. In bacteria, however, GlcNAc functions as a structural component of peptidoglycan and lipopolysaccharide, as a signal molecule, and as a nutrient source. <i>Stenotrophomonas maltophilia</i> is a gram-negative opportunistic pathogen associated with nosocomial infections, particularly in cystic fibrosis (CF) patients. The abundance of amino sugars derived from mucin degradation is present in the CF lung. Utilization of GlcNAc can reprogram bacterial metabolism, leading to pleiotropic effects on physiology and stress tolerance. We were therefore interested in how bacteria adapt their physiology and stress tolerance when residing in GlcNAc-rich infection niches. Here, we investigated GlcNAc utilization and its impact on physiology and stress tolerance in <i>S. maltophilia</i>.