Commensal oralRothia mucilaginosaproduces enterobactin – a metal chelating siderophore

Abstract

<jats:title>Abstract</jats:title><jats:p>Next-generation sequencing studies of saliva and dental plaque from subjects in both healthy and diseased states have identified bacteria belonging to the <jats:italic>Rothia</jats:italic> genus as ubiquitous members of the oral microbiota. To gain a deeper understanding of molecular mechanisms underlying the chemical ecology of this unexplored group, we applied a genome mining approach that targets functionally important biosynthetic gene clusters (BGCs). All 45 genomes that were mined, representing <jats:italic>Rothia mucilaginosa, R. dentocariosa</jats:italic> and <jats:italic>R. aeria</jats:italic>, harbored a catechol-siderophore-like BGC. To explore siderophore production further we grew the previously characterized <jats:italic>R. mucilaginosa</jats:italic> ATCC 25296 in liquid cultures, amended with glycerol, which led to the identification of the archetype siderophore enterobactin by using tandem Liquid Chromatography Mass Spectrometry (LC/MS/MS), High Performance Liquid Chromatography (HPLC), and Nuclear Magnetic Resonance (NMR) spectroscopy. Normally attributed to pathogenic gut bacteria, <jats:italic>R. mucilaginosa</jats:italic> is the first commensal oral bacterium found to produce enterobactin. Co-cultivation studies including <jats:italic>R. mucilaginosa</jats:italic> or purified enterobactin revealed that enterobactin reduced growth of certain strains of cariogenic <jats:italic>Streptococcus mutans</jats:italic> and pathogenic strains of <jats:italic>Staphylococcus aureus</jats:italic>. Commensal oral bacteria were either unaffected by, reduced in growth, or induced to grow adjacent to enterobactin producing <jats:italic>R. mucilaginosa</jats:italic> or the pure compound. Taken together with <jats:italic>Rothia</jats:italic>’s known capacity to ferment a variety of carbohydrates and amino acids, our findings of enterobactin production adds an additional level of explanation to <jats:italic>R. mucilaginosa</jats:italic>’s colonization success of the oral cavity. Enterobactin is the strongest Fe(III)-binding siderophore known, and its role in oral health requires further investigation.</jats:p><jats:sec><jats:title>Importance</jats:title><jats:p>The communication language of the human oral microbiota is vastly underexplored. However, a few studies have shown that specialized small molecules encoded by BGCs have critical roles such as in colonization resistance against pathogens and quorum sensing. Here, by using a genome mining approach in combination with compound screening of growth cultures, we identified that the commensal oral community member <jats:italic>mucilaginosa</jats:italic> harbors a catecholate-siderophore BGC, which is responsible for the biosynthesis of enterobactin. The iron-scavenging role of enterobactin is known to have positive effects on the host’s iron pool and negative effects on host immune function, however its role in oral health remains unexplored. <jats:italic>R. mucilaginosa</jats:italic> was previously identified as an abundant community member in cystic fibrosis, where bacterial iron cycling plays a major role in virulence development. With respect to iron’s broad biological importance, iron-chelating enterobactin may explain <jats:italic>R. mucilaginosa</jats:italic>’s colonization success in both health and disease.</jats:p></jats:sec>

The Pneumococcal Iron Uptake Protein A (PiuA) Specifically Recognizes Tetradentate FeIIIbis- and Mono-Catechol Complexes

“…The two common commensal co-colonizers of the human nasopharynx, Haemophilus influenzae and Moraxella catarrhalis, do not synthesize siderophores under conditions of Fe starvation [69][70][71]. Further, although it was recently reported that Rothia mucilaginosa, a common commensal of the oral cavity, synthesizes Ent [72], it is unknown if Ent or Ent hydrolysis products are accessible to S. pneumoniae in this and other colonization sites. Based on the available information, we favor a model in which host-derived endogenous catecholamines or another bacterially derived, naturally occurring tetradentate siderophore(s), are the primary physiological substrates for PiuA.…”

Short-term effects of Chlorhexidine mouthwash and Listerine on oral microbiome in hospitalized patients

“…In a previous study (de Steenhuijsen Piters et al, 2016), the domination of Rothia was strongly associated with pneumonia. And iron-chelating enterobactin might explain Rothia mucilaginosa's successful oral colonization in both healthy and diseased individuals (Uranga et al, 2020). However, a recent literature showed that Rothia mucilaginosa abundance inversely correlated with sputum pro-inflammatory markers in chronic lung disease, which implies a beneficial role in the respiratory tract (Rigauts et al, 2022).…”

Protein and Microbial Biomarkers in Sputum Discern Acute and Latent Tuberculosis in Investigation of Pastoral Ethiopian Cohort

“…While there were no differences in overall aor b-diversity in sputum microbiomes among the cohorts, we identified statistically significant differences in abundance for the genera Rothia and Haemophilus, two oral microbiome community members, in the comparison of the PTB and LTBI datasets. Rothia mucilaginosa was recently reported to produce the siderophore enterobactin in the human oral niche (Uranga et al, 2020). Mtb is also a producer of siderophores (mycobactins), which are released to acquire iron from the host in infected lung tissue (De Voss et al, 2000).…”

“…Enhanced iron sequestration during an active host inflammatory response in PTB possibly diminishes the fitness and growth of Rothia species in the upper respiratory tract. This genus is a ubiquitous commensal organism of the oral cavity (Singh et al, 2019;Uranga et al, 2020). One may also speculate that the genus Haemophilus, increased in abundance in respiratory secretions of PTB compared to LTBI subjects, is due to its better adaptation to inflammatory conditions caused by the infection with Mtb.…”