AUTHOR=Fan Qiuxia , Liu Cheng , Gao Zhenpeng , Hu Zhongqiu , Wang Zhouli , Xiao Jianbo , Yuan Yahong , Yue Tianli 

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

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.679808

DOI=10.3389/fmicb.2021.679808

ISSN=1664-302X

ABSTRACT=<p><italic>Alicyclobacillus acidoterrestris</italic> (<italic>A. acidoterrestris</italic>), 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 <italic>Nigella sativa</italic> seeds. The objective of this study was to investigate antibacterial activity and associated molecular mechanism of TQ against <italic>A. acidoterrestris</italic> vegetative cells, and to evaluate effects of TQ on <italic>A. acidoterrestris</italic> spores and biofilms formed on polystyrene and stainless steel surfaces. Minimum inhibitory concentrations of TQ against five tested <italic>A. acidoterrestris</italic> 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 <italic>A. acidoterrestris</italic> mature biofilms. These findings indicated that TQ is promising as a new alternative to control <italic>A. acidoterrestris</italic> and thereby reduce associated contamination and deterioration in the juice and acid beverage industry.</p>