Journal Article

The c‐di‐AMP signaling system influences stress tolerance and biofilm formation of Streptococcus mitis

Simm, Roger, Rørvik, Gro Herredsvela, Edvardsen, Per Kristian Thorén, Naemi, Ali‐Oddin

2021

Overview

Streptococcus mitis is a commensal bacterial species of the oral cavity, with the potential for opportunistic pathogenesis. For successful colonization, S. mitis must be able to adhere to surfaces of the oral cavity and survive and adapt to frequently changing environmental conditions. Cyclic‐di‐AMP (c‐di‐AMP) is a nucleotide second messenger, involved in the regulation of stress responses and biofilm formation in several bacterial species. Cyclic‐di‐AMP is produced by diadenylate cyclases and degraded by phosphodiesterases. We have previously shown that in S. mitis, one diadenylate cyclase (CdaA) and at least two phosphodiesterases (Pde1 and Pde2) regulate the intracellular concentration of c‐di‐AMP. In this study, we utilized S. mitis deletion mutants of cdaA, pde1, and pde2 to analyze the role of c‐di‐AMP signaling in various stress responses, biofilm formation, and adhesion to eukaryotic cells. Here, we demonstrate that the Δpde1 mutant displayed a tendency toward increased susceptibility to acetic acid at pH 4.0. Deletion of cdaA increases auto‐aggregation of S. mitis but reduces biofilm formation on an abiotic surface. These phenotypes are more pronounced under acidic extracellular conditions. Inactivation of pde1 or pde2 reduced the tolerance to ciprofloxacin, and UV radiation and the Δpde1 mutant was more susceptible to Triton X‐100, indicating a role for c‐di‐AMP signaling in responses to DNA damage and cell membrane perturbation. Finally, the Δpde2 mutant displayed a tendency toward a reduced ability to adhere to oral keratinocytes. Taken together, our results indicate an important role for c‐di‐AMP signaling in cellular processes important for colonization of the mouth. Using mutants of Streptococcus mitis for genes encoding cyclic di‐adenosine turnover proteins, we tested the role of c‐di‐AMP signaling in properties important for persistent colonization of the oral cavity. We show that the c‐di‐AMP signaling system influences biofilm formation, tolerance to cell envelope stress, and DNA damage. Our data also suggest that the c‐di‐AMP signaling system may have a role in the ability of S. mitis to tolerate organic acid stress and adhere to eukaryotic cells.

• Publisher: John Wiley & Sons, Inc,John Wiley and Sons Inc,Wiley
• Subject: Acetic acid / Acetic Acid - pharmacology / acid stress / Adaptation, Physiological - physiology / AMP / Antibiotics / Bacteria / Bacterial Adhesion - physiology / biofilm / Biofilms / Biofilms - growth & development / Cell Line, Tumor / Cell membranes / Cellular stress response / Ciprofloxacin / Ciprofloxacin - pharmacology / Colonization / Cyclic AMP - metabolism / Cyclic Nucleotide Phosphodiesterases, Type 1 - genetics / Cyclic Nucleotide Phosphodiesterases, Type 1 - metabolism / Cyclic Nucleotide Phosphodiesterases, Type 2 - genetics / Cyclic Nucleotide Phosphodiesterases, Type 2 - metabolism / c‐di‐AMP / Deletion / Deletion mutant / DNA damage / Environmental changes / Environmental conditions / Experiments / Gene Deletion / Gene Expression Regulation, Bacterial - genetics / Glycerol / Humans / Immune system / Inactivation / Keratinocytes / Keratinocytes - microbiology / Mouth - microbiology / Mutants / Nucleotides / Octoxynol - pharmacology / Oral cavity / Original / Pathogenesis / Perturbation / Phenotypes / Phosphorus-Oxygen Lyases - genetics / Phosphorus-Oxygen Lyases - metabolism / Radiation / Second Messenger Systems - physiology / Signalling systems / Streptococcus infections / Streptococcus mitis / Streptococcus mitis - growth & development / Streptococcus mitis - metabolism / Stress, Physiological - physiology / Ultraviolet radiation / β‐lactam antibiotics