A competence-regulated toxin-antitoxin system in Haemophilus influenzae

Area of Science:

• Microbiology
• Bacterial genetics
• Molecular biology

Background:

• Natural competence enables bacteria to uptake environmental DNA for nutrients and genetic information.
• In Haemophilus influenzae, DNA uptake genes are regulated by CRP and Sxy transcription factors.
• Competence is triggered by the absence of preferred carbon sources and nucleotide precursors.

Purpose of the Study:

• To investigate the function of the HI0659 gene in Haemophilus influenzae competence.
• To characterize the competence-regulated toxin-antitoxin operon (toxTA) and its role in bacterial physiology.
• To analyze the prevalence and impact of toxTA operon variations in bacterial strains.

Main Methods:

• Gene deletion and mutant analysis to assess the role of HI0659 and HI0660.
• RNA-sequencing (RNA-seq) for transcript analysis and promoter identification.
• Comparative genomics to determine the frequency of toxTA operon presence and deletion.

Main Results:

• HI0659 encodes the antitoxin of a toxTA operon, likely acquired via horizontal gene transfer.
• Deletion of the toxin gene (HI0660) restored DNA uptake in antitoxin mutants.
• The full toxTA operon was found in a minority of strains, with frequent deletions observed.
• RNA-seq revealed an internal promoter within toxT, repressed by the antitoxin.
• Unopposed toxin expression may cause mRNA cleavage, arresting or killing competent cells.

Conclusions:

• The competence-regulated toxTA system in H. influenzae influences DNA uptake and cell viability.
• High frequencies of toxT and toxTA deletions suggest potential milddeleterious effects or a role in regulating protein synthesis and nucleotide recycling.
• The study provides a valuable RNA-seq dataset for further research into competence regulation.