Inactivation Effect of Thymoquinone on Alicyclobacillus acidoterrestris Vegetative Cells, Spores, and Biofilms

Abstract

Alicyclobacillus acidoterrestris (A. acidoterrestris), a spore-forming bacterium, has become a main challenge and concern for the juices and acid beverage industry across the world due to its thermo-acidophilic characteristic. Thymoquinone (TQ) is one of the active components derived from Nigella sativa seeds. The objective of this study was to investigate antibacterial activity and associated molecular mechanism of TQ against A. acidoterrestris vegetative cells, and to evaluate effects of TQ on A. acidoterrestris spores and biofilms formed on polystyrene and stainless steel surfaces. Minimum inhibitory concentrations of TQ against five tested A. acidoterrestris strains ranged from 32 to 64 μg/mL. TQ could destroy bacterial cell morphology and membrane integrity in a concentration-dependent manner. Field-emission scanning electron microscopy observation showed that TQ caused abnormal morphology of spores and thus exerted a killing effect on spores. Moreover, TQ was effective in inactivating and removing A. acidoterrestris mature biofilms. These findings indicated that TQ is promising as a new alternative to control A. acidoterrestris and thereby reduce associated contamination and deterioration in the juice and acid beverage industry.

Molecular insight into thymoquinone mechanism of action against Mycobacterium tuberculosis

“…Notably, the observed significant upregulation of sigF suggests that TQ causes the exhaustion of energy resources in bacterial cells; thus, transcriptomic observations were consistent with metabolomic ones. The TQ mechanism of action described in this study is in agreement with previously reported damage to the cytoplasmic membrane ( Fan et al, 2021 ), and a decrease in intracellular ATP concentration ( Wang et al, 2021 ). It is worth noticing that the stability of TQ in bacterial broth was limited and, after 48 h, significantly lowered.…”

“…TQ’s antibacterial mechanism of action was studied in several bacterial species other than mycobacteria. It included the inhibition of cell adhesion to the glass slide surface ( Chaieb et al, 2011 ), production of reactive oxygen species ( Goel and Mishra, 2018 ), changes in the cell morphology, damage to the cytoplasmic membrane ( Fan et al, 2021 ), membrane depolarization, and decrease in intracellular ATP concentration ( Wang et al, 2021 ). However, there are no reports about the TQ mode of action in M. tuberculosis .…”

Inhibitory mechanism of quercetin on Alicyclobacillus acidoterrestris

“…This effect became more pronounced with higher quercetin concentrations, highlighting the impact on cell membrane permeability further. Fan et al (2021) investigated the impact of thymoquinone on the membrane integrity of A. acidoterrestris using laser scanning confocal microscopy and fluorescent dye PI and found negligible red fluorescence in the control group. However, upon treatment with 1 MIC thymoquinone, a modest amount of red fluorescence was observed, indicating the disruption of membrane integrity in certain cells.…”