# Genome-wide high-throughput transposon mutagenesis unveils key factors for acidic pH adaptation of Corynebacterium diphtheriae

## TL;DR

This study identifies genes that help the bacteria C. diphtheriae survive in acidic environments, like those inside host cells.

## Contribution

The study reveals the Ktr potassium transport system as a novel factor for C. diphtheriae's acidic pH adaptation.

## Key findings

- The Ktr system helps C. diphtheriae maintain pH balance and grow under acidic conditions.
- Deleting the ktrBA genes reduced growth at pH 5, but not survival in macrophages.
- Restoring ktrBA expression reversed the growth defect in acidic conditions.

## Abstract

Corynebacterium diphtheriae, a notable pathogen responsible for the life-threatening disease diphtheria, encounters harsh intracellular environments within the host, particularly within macrophages where acidic conditions prevail. To elucidate the genetic and molecular mechanisms underlying its acid stress response, we employed a Transposon Directed Insertion-site Sequencing approach. This comprehensive study identified crucial genes and pathways facilitating C. diphtheriae’s survival at low pH. In subsequent experiments, the Ktr potassium transport system was identified as a putative key factor for maintaining pH homeostasis and growth under acidic stress. A ktrBA deletion strain exhibited significantly reduced growth at pH 5, which could be restored by ktrBA expression in trans. The deletion strain showed unchanged uptake and survival in macrophages compared to the wild-type, indicating that the Ktr system is not crucial for the survival of C. diphtheriae in phagocytes. These findings advance our understanding of C. diphtheriae’s pathophysiology, further delineating the intricate survival strategies of C. diphtheriae in hostile environments.