Ostyn, L. | Search bioRxiv

bioRxiv2023

Genome-Scale Modeling of Rothia mucilaginosa Reveals Insights into Metabolic Capabilities and Therapeutic Strategies for Cystic Fibrosis

BackgroundCystic fibrosis (CF) is an inherited genetic disorder caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, resulting in the production of sticky and thick mucosal fluids. This leads to an environment that facilitates the colonization of various microorganisms, some of which can cause acute and chronic lung infections, while others may have a positive influence on the disease process. Rothia mucilaginosa, an oral commensal, is relatively abundant in the lungs of CF patients. Recent studies have unveiled the anti-inflammatory properties of R. mucilaginosa using in vitro three-dimensional (3-D) lung epithelial cell cultures and in vivo mouse models relevant to chronic lung diseases. Apart from a potentially beneficial anti-inflammatory role in chronic lung diseases, R. mucilaginosa has been associated with severe infections. This dual nature highlights the bacteriums complexity and diverse impact on health and disease. However, its metabolic capabilities and genotype-phenotype relationships remain largely unknown. ResultsTo gain insights into the cellular metabolism and genetic content of R. mucilaginosa, we developed the first manually curated genome-scale metabolic model, iRM23NL. Through growth kinetic experiments and high-throughput phenotypic microarray testings, we defined its complete catabolic phenome. Subsequently, we assessed the models effectiveness in accurately predicting growth behaviors and utilizing multiple substrates. We used constraint-based modeling techniques to formulate novel hypotheses that could expedite the development of antimicrobial strategies. More specifically, we detected putative essential genes and assessed their effect on metabolism under varying nutritional conditions. These predictions could offer novel potential antimicrobial targets without laborious large-scale screening of knock-outs and mutant transposon libraries. ConclusionOverall, iRM23NL demonstrates a solid capability to predict cellular phenotypes and holds immense potential as a valuable resource for accurate predictions in advancing antimicrobial therapies. Moreover, it can guide metabolic engineering to tailor R. mucilaginosas metabolism for desired performance.

systems biology↗

bioRxiv2018

Various evolutionary trajectories lead to loss of the tobramycin-potentiating activity of the quorum sensing inhibitor baicalin hydrate in Burkholderia cenocepacia biofilms

Combining antibiotics with potentiators that increase their activity is a promising strategy to tackle infections caused by antibiotic-resistant and -tolerant bacteria. As these potentiators typically do not interfere with essential processes of bacteria, it has been hypothesized that they are less likely to induce resistance than conventional antibiotics. However, evidence supporting this hypothesis is lacking. In the present study, we investigated whether Burkholderia cenocepacia J2315 biofilms develop resistance towards one such adjuvant, baicalin hydrate (BH), a quorum sensing inhibitor known to increase antibiotic-induced oxidative stress. Biofilms were repeatedly and intermittently treated with tobramycin (TOB) alone or in combination with BH for 24 h. After each cycle of treatment, the remaining cells were quantified using plate counting. After 15 cycles, biofilm cells were less susceptible to treatments with TOB and TOB+BH, compared to the start population, and the potentiating effect of BH towards TOB was lost. Whole genome sequencing was performed to probe which changes were involved in the reduced effect of BH and mutations in 14 protein-coding genes were identified (including mutations in genes involved in central metabolism and in BCAL0296, encoding an ABC transporter), as well as a partial deletion of two larger regions. No changes in the minimal inhibitory or minimal bactericidal concentration of TOB or changes in the number of persister cells were observed in the evolved populations. However, basal intracellular levels of reactive oxygen species (ROS) and ROS levels found after treatment with TOB were markedly decreased in the evolved populations. In addition, in evolved cultures with mutations in BCAL0296, a significantly reduced uptake of TOB was observed. Our results indicate that resistance towards antibiotic-potentiating activity can develop rapidly in B. cenocepacia J2315 biofilms and point to changes in central metabolism, reduced ROS production, and reduced TOB uptake as potential mechanisms.\n\nImportanceBacteria show a markedly reduced susceptibility to antibiotics when growing in a biofilm, which hampers effective treatment of biofilm-related infections. The use of potentiators that increase the activity of antibiotics against biofilms has been proposed as a solution to this problem, but it is unclear whether resistance to these potentiators could develop. Using an experimental evolution approach, we convincingly demonstrate that Burkholderia cenocepacia biofilms rapidly develop resistance towards the tobramycin-potentiating activity of baicalin hydrate. Whole genome sequencing revealed that there are different mechanisms that lead to this resistance, including mutations resulting in metabolic changes, changes in production of intracellular levels of reactive oxygen species, and differences in transporter-mediated tobramycin uptake. Our study suggests that this form of combination therapy is not evolution-proof and highlights the usefulness of experimental evolution to identify mechanisms of resistance and tolerance in biofilm-grown bacteria.

microbiology↗