# Z‑Amino Acids Present Innovative Antimicrobial and Antibiofilm Properties against Methicillin-Susceptible and -Resistant Staphylococcus aureus

## TL;DR

Z-amino acids, especially Z-Gln, show strong antimicrobial and antibiofilm effects against S. aureus with low toxicity to human cells.

## Contribution

Z-amino acids are introduced as novel antimicrobial agents effective against both planktonic and biofilm-associated S. aureus.

## Key findings

- Z-Gly and Z-Gln rapidly depolarize S. aureus membranes, increasing permeability.
- Z-amino acids inhibit biofilm formation at 1× MIC and disperse mature biofilms at 2× MIC.
- Z-Gln shows minimal toxicity to mammalian cells at effective concentrations.

## Abstract

One of the challenges associated with bacteria is their
ability
to form biofilms that can grow on medical equipment, resulting in
more severe and persistent infections. Unfortunately, most antibiotics
are optimized for planktonic bacteria, and their therapeutic window
is limited when targeting biofilms. Eradicating biofilms typically
requires concentrations that are much higher than the minimum inhibitory
concentration (MIC), increasing the concern about cytotoxicity toward
mammalian cells. In this study, benzyloxycarbonyl-protected amino
acids (Z-amino acids), for the first time, were analyzed for both
antimicrobial and antibiofilm activity against Staphylococcus
aureus (S. aureus),
a strain prevalent in surgical infections. It was determined that
Z-amino acids, especially Z-glycine (Z-Gly), exhibited fast antimicrobial
properties against S. aureus, causing
early depolarization and leading to enhanced membrane permeability.
Severe membrane disruption of S. aureus after treatment with Z-glutamine (Z-Gln) was confirmed microscopically.
Additionally, Z-amino acids effectively inhibited biofilm formation
at 1× MIC and dispersed mature biofilms at 2× MIC. Notably,
Z-Gln had the most favorable antimicrobial activity profile with minimal
toxicity toward mammalian cells at both 1× and 2× MIC. These
concentrations were effective against both planktonic and biofilm-associated
bacteria while maintaining at least 80% viability of osteoblast cells
after a 24 h exposure. These Z-amino acids also exhibited similar
toxicity toward epithelial cells (e.g., BEAS-2B cells), indicating
a consistent safety profile against different cell types. These findings
suggest that Z-amino acids, particularly Z-Gln, show promise as a
new therapeutic agent that targets both planktonic and biofilm-associated
infections.