Turkish Gall Extract Disrupts Staphylococcus aureus Biofilms at Multiple Stages

A plant-derived extract from Turkish gall shows potent antibacterial and anti-biofilm activity against Staphylococcus aureus, according to a study published in Annals of Microbiology. The research, conducted on the reference strain S. aureus ATCC 6538, reports that the extract kills bacteria at low concentrations and interferes with the genetic program that allows the pathogen to build its protective biofilm, a structure that shields bacteria from antibiotics and disinfectants.

S. aureus is a common foodborne pathogen and a frequent cause of clinical infections. It forms dense biofilms by adhering to surfaces of objects or the human body, and these communities markedly reduce the bactericidal efficacy of conventional treatments. The new study set out to investigate the inhibitory effect of Turkish gall extract on S. aureus biofilm formation and the molecular mechanisms behind it.

The measured activity was substantial. The minimum inhibitory concentration (MIC) of the extract was 56.25 micrograms per milliliter, and the minimum bactericidal concentration (MBC) was 112.5 micrograms per milliliter, indicating that the extract both halts growth and kills the bacterium at only a twofold higher dose. Following treatment with the extract, the researchers observed significant increases in extracellular alkaline phosphatase (AKP) and nucleic acid content, findings that point to disruption of the bacterial cell wall and membrane integrity. Leakage of these intracellular components is a classic sign that the envelope enclosing the cell has been compromised, a process that can lead directly to bacterial death.

The study also probed how the extract affects biofilm development at the transcriptional level using quantitative real-time PCR. During the initial adhesion stage, when individual cells first attach to a surface, expression of the sarA gene was significantly downregulated.

The icaADB gene cluster was significantly downregulated, while icaR, a negative regulator of the operon, was upregulated. This dual effect would reduce production of the adhesive matrix and slow the consolidation of a mature biofilm, indicating that the extract acts on biofilm development at multiple stages rather than a single point.

Taken together, the authors conclude that Turkish gall extract exhibits significant antibacterial activity against S. aureus and effectively suppresses its biofilm formation. They propose two complementary mechanisms: the extract may directly cause bacterial death by disrupting cell wall and membrane integrity, and it may interfere with initial adhesion and intercellular aggregation by altering the transcription of sarA and ica operon-related genes. This combination of killing activity and biofilm suppression is notable because biofilm-embedded cells are typically far harder to eradicate than free-floating planktonic bacteria.

The findings suggest that plant-derived extracts could offer new strategies for developing anti-biofilm agents, an area of growing interest as biofilm-related infections and contaminated surfaces in food and clinical settings remain difficult to control. Because the work was performed on a single reference strain in vitro, further studies would be needed to confirm the effect across diverse S. aureus isolates and in real-world applications. The authors position the study as providing a theoretical basis for such development rather than a ready-made treatment.

Subject of Research: Antibacterial and anti-biofilm activity of Turkish gall extract against Staphylococcus aureus

Article Title: Evaluation of the antibacterial activity of turkish gall extract against Staphylococcus aureus ATCC 6538

Article References: Wei, Y., Yu, S., Liu, Q., Ma, X., Gu, J., Lin, N., & Ma, X. (2026). Evaluation of the antibacterial activity of turkish gall extract against Staphylococcus aureus ATCC 6538. Annals of Microbiology. https://doi.org/10.1186/s13213-026-01863-9

Image Credits: AI Generated

DOI: 10.1186/s13213-026-01863-9

Keywords: Staphylococcus aureus, Turkish gall extract, biofilm, antibacterial activity, minimum inhibitory concentration, cell membrane disruption, sarA, ica operon, plant-derived antimicrobials, foodborne pathogen, qRT-PCR, Evaluation