Biology subjects

Domenech, A.

Publications and source records attributed to Domenech, A..

3 recordsLinked to original sources

bioRxiv2018

Antibiotic-induced cell chaining triggers pneumococcal competence by reshaping quorum sensing to autocrine signaling

Streptococcus pneumoniae can acquire antibiotic resistance by activation of competence and subsequent DNA uptake. Several antibiotics induce competence by disrupting protein-quality control or perturbing DNA replication. Here, we demonstrate that aztreonam (AZT) and clavulanic acid (CLA) also promote competence. We show that both compounds induce cell chain formation by targeting the D,D-carboxypeptidase PBP3. In support of the hypothesis that chain formation promotes competence, we demonstrate that an autolysin mutant (lytB) is hypercompetent. As competence is initiated by the binding of a small extracellular peptide (CSP) to a membrane-anchored receptor (ComD), we wondered if chain formation alters CSP diffusion and thereby sensing by ComD. Indeed, the presence of AZT or CLA affects competence synchronization by switching CSP-based quorum sensing to autocrine-like signaling, as CSP is retained to chained cells and no longer shared in a common pool. Together, these insights demonstrate the versatility of quorum sensing in integrating different stresses and highlight that certain antibiotics should be prescribed with care not to drive the spread of antibiotic resistance.

microbiology↗

bioRxiv2018

The Streptococcus pneumoniae Competence-Induced BriC Peptide Promotes Nasopharyngeal Colonization and Impacts Biofilm Development

Streptococcus pneumoniae (pneumococcus) is an opportunistic pathogen that causes otitis media, sinusitis, pneumonia, meningitis and sepsis. The progression to this pathogenic lifestyle is preceded by asymptomatic colonization of the nasopharynx. This colonization is associated with biofilm formation; the competence pathway influences the structure and stability of biofilms. However, the molecules that link the competence pathway to biofilm formation are unknown. Here, we describe a new competence-induced gene, called briC, and demonstrate that its product promotes biofilm development and stimulates colonization in a murine model. We show that expression of briC is induced by the master regulator of competence, ComE. Whereas briC does not substantially influence early biofilm development on abiotic surfaces, it significantly impacts later stages of biofilm development. Specifically, briC expression leads to increases in biofilm biomass and thickness at 72h. Consistent with the role of biofilms in colonization, briC promotes nasopharyngeal colonization in the murine model. The function of BriC appears to be conserved across pneumococci, as comparative genomics reveal that briC is widespread across isolates. Surprisingly, many isolates, including strains from clinically important PMEN1 and PMEN14 lineages, which are widely associated with colonization, encode a long briC promoter. This long form captures an instance of genomic plasticity and functions as a competence-independent expression enhancer that may serve as a precocious point of entry into this otherwise competence-regulated pathway. Moreover, overexpression of briC by the long promoter fully rescues the comE-deletion induced biofilm defect in vitro, and partially in vivo. These findings indicate that BriC may bypass the influence of competence in biofilm development and that such a pathway may be active in a subset of pneumococcal lineages. In conclusion, BriC is a part of the complex molecular network that connects signaling of the competence pathway to biofilm development and colonization.

microbiology↗

bioRxiv2016

High-throughput CRISPRi phenotyping in Streptococcus pneumoniae identifies new essential genes involved in cell wall synthesis and competence development

Genome-wide screens have discovered a large set of essential genes in the opportunistic human pathogen Streptococcus pneumoniae. However, the functions of many essential genes are still unknown, hampering vaccine development and drug discovery. Based on results from transposon-sequencing (Tn-Seq), we refined the list of essential genes in S. pneumoniae serotype 2 strain D39. Next, we created a knockdown library targeting 348 potentially essential genes by CRISPR interference (CRISPRi) and show a growth phenotype for 254 of them (73%). Using high-content microscopy screening, we searched for essential genes of unknown function with clear phenotypes in cell morphology upon CRISPRi-based depletion. We show that SPD1416 and SPD1417 (renamed to MurT and GatD, respectively) are essential for peptidoglycan synthesis, and that SPD1198 and SPD1197 (renamed to TarP and TarQ, respectively) are responsible for the polymerization of teichoic acid (TA) precursors. This knowledge enabled us to reconstruct the unique pneumococcal TA biosynthetic pathway. CRISPRi was also employed to unravel the role of the essential Clpproteolytic system in regulation of competence development and we show that ClpX is the essential ATPase responsible for ClpP-dependent repression of competence. The CRISPRi library provides a valuable tool for characterization of pneumococcal genes and pathways and revealed several promising antibiotic targets.

microbiology↗