Biology subjects

Ntamubano, S.

Publications and source records attributed to Ntamubano, S..

4 recordsLinked to original sources

bioRxiv2026

Novel Streptococcus mitis subsp. mitis Picklauza buccal isolate from individual with idiopathic pulmonary fibrosis containing functional mobile qacG Gene.

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive lung disease characterized by immune dysregulation, fibrosis, and eventual respiratory failure. While the etiology of IPF remains unclear, accumulating evidence implicates the oral and airway microbiome in disease progression, with elevated Streptococcal burden linked to increased mortality. Whether specific taxa actively contribute to IPF pathophysiology or arise secondarily from the damaged lung environment remains unresolved. Here, we characterize "Picklauza," a streptococcal strain isolated from the buccal mucosa of an individual with IPF. Although its average nucleotide identity to a Streptococcus mitis reference genome was 93.855%, analysis with Streptoquod supported classification as Streptococcus mitis subsp. mitis. Genomic analysis identified a 109-amino-acid qacG homolog predicted to encode a small multidrug resistance (SMR)-family efflux transporter. The locus was located near genes associated with mobile genetic elements, raising the possibility of horizontal acquisition. The predicted QacG protein retained residues conserved in the extensively characterized SMR transporter EmrE, and RT-qPCR detected qacG transcripts under standard culture conditions. Nevertheless, Picklauza did not display increased tolerance to benzalkonium chloride, benzethonium chloride, or ethidium bromide compared with S. mitis NCTC 12261. Picklauza also differed from the reference strain in growth kinetics, carbon utilization, and antimicrobial susceptibility. PCR screening detected qacG homologs in three additional oral isolates from patients with IPF. Together, these findings identify a transcriptionally active, putatively mobile qacG homolog in oral streptococci while revealing a disconnect between gene carriage and QAC susceptibility under the conditions tested. This work highlights the need to validate predicted resistance determinants phenotypically and to investigate the mobility and conditional activity of SMR-family genes across genus boundaries in host-associated microbial communities.

microbiology↗

bioRxiv2026

Phenotypic characterization of Prevotella melaninogenica ATCC 25845

Prevotella melaninogenica is a Gram-negative bacterium that has been implicated in numerous disorders such as chronic obstructive pulmonary disease (COPD) and cystic fibrosis, and despite its abundance in the human microbiome, there is still limited knowledge on the fundamental physiology describing Prevotella melaninogenica. To properly advance Prevotella biology, it is critical to report and document such characterizations of Prevotella; therefore, the purpose of this study is to examine and define the phenotypic and growth characteristics of P. melaninogenica ATCC 25845. In this study, we found that Prevotella melaninogenica ATCC 25845 is a Gram-negative bacterium that is predominantly short and medium rod-shaped, with occasional filamentous rods. SEM imaging revealed that this filamentation may serve as division centers, points from which multiple daughter cells form. We also describe the antibiotic profile, which showed susceptibility to four classes and resistance to six classes of antibiotics. Carbon source growth kinetic characterization revealed a preference for carbohydrate sources.

microbiology↗

bioRxiv2026

Aerotolerant Capacity of the Lung Commensal Prevotella melaninogenica

Prevotella melaninogenica is a core member of the human oral and respiratory microbiomes, often representing more than 10% of microbial populations in both healthy and diseased lungs. Despite its prevalence in these oxygenated environments, P. melaninogenica has been historically classified as a strict obligate anaerobe, ostensibly unable to survive oxygen concentrations exceeding 0.05%. This creates a fundamental biological paradox, as the organism consistently persists in the lower respiratory tract where oxygen levels reach higher than what is tolerated by obligate anaerobes. In this study, we resolve this contradiction by evaluating the growth and tolerance of P. melaninogenica across intermediate oxygen concentrations of 2%, 5%, and 8%. Contrary to the long-standing classification, we demonstrate that P. melaninogenica maintains growth at 2% and 5% oxygen- a level significantly higher than previously reported for the genus- and exhibits robust aerotolerance in 21% O2. Transcriptional profiling via RNA-sequencing reveals that this survival is likely driven by the robust expression of oxidative stress defense and DNA repair machinery. Ultimately, these results provide the first evidence of the specialized mechanisms that enable Prevotella melaninogenica to adapt to and colonize the respiratory tract, providing a clearer understanding of its persistence in oxygen-exposed human niches. IMPORTANCEThis study provides a correction to the 100-year-old classification of Prevotella melaninogenica as a strict obligate anaerobe. We demonstrate that this key member of the human microbiome is capable of robust growth under oxygen levels previously thought to be lethal. By identifying transcriptional responses associated with growth and survival, we predict how Prevotella melaninogenica dominates the oxygenated niches of the respiratory tract. This work reveals the putative mechanisms driving the adaptive evolution of Prevotella melaninogenica and its role in human airway ecology.

microbiology↗

bioRxiv2025

Development of a basal media for carbon utilization assay and analysis of the starch utilization locus in Prevotella melaninogenica

Prevotella melaninogenica is a highly abundant member of the human respiratory microbiota, occupying a range of distinct niches from the oral cavity to the lower airways. Colonization within these nutrient diverse environments suggest a sophisticated metabolic system equipped to deal with large fluctuations in nutrient availability. However, the core physiology and metabolic profile of this bacteria remain largely uncharacterized. In this study, we developed a basal media conducive to assaying carbon utilization of P. melaninogenica and demonstrate the utilization of dietary carbohydrates with varied glycosidic bonds, including the starch mimic cyclodextrin. Furthermore, we identified the putative starch utilization system, highlighting the presence of three novel components which are absent from starch metabolism in the closely related Bacteroides genus. Together, these findings provide the first characterization of the nutritional profile and central metabolic capacity of P. melaninogenica, offering crucial insight into how this bacterium adapts to and thrives within ecologically distinct niches. IMPORTANCEThis work significantly advances our understanding of the metabolic capabilities of Prevotella melaninogenica, a common yet largely unexplored member of the respiratory microbiota. By mapping key aspects of its predicted starch utilization locus, we lay the foundation for future studies on microbial adaptation and persistence in the respiratory tract.

microbiology↗