☆ 4.7 Article Proceedings Paper

Inactivation of chemical and heat-resistant spores of Bacillus and Geobacillus by nitrogen cold atmospheric plasma evokes distinct changes in morphology and integrity of spores

FOOD MICROBIOLOGY (2015)

Journal

FOOD MICROBIOLOGY

Volume 45, Issue -, Pages 26-33

Publisher

ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD

DOI: 10.1016/j.fm.2014.03.018

Keywords

Food safety; Plasma treatment; CAP; Disinfectants; Spores; Bacillus cereus

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Abstract

Bacterial spores are resistant to severe conditions and form a challenge to eradicate from food or food packaging material. Cold atmospheric plasma (CAP) treatment is receiving more attention as potential sterilization method at relatively mild conditions but the exact mechanism of inactivation is still not fully understood. In this study, the biocidal effect by nitrogen CAP was determined for chemical (hypochlorite and hydrogen peroxide), physical (UV) and heat-resistant spores. The three different sporeformers used are Bacillus cereus a food-borne pathogen, and Bacillus atrophaeus and Geobacillus stearothermophilus that are used as biological indicators for validation of chemical sterilization and thermal processes, respectively. The different spores showed variation in their degree of inactivation by applied heat, hypochlorite, hydrogen peroxide, and UV treatments, whereas similar inactivation results were obtained with the different spores treated with nitrogen CAP. G. stearothermophilus spores displayed high resistance to heat, hypochlorite, hydrogen peroxide, while for UV treatment B. atrophaeus spores are most tolerant. Scanning electron microscopy analysis revealed distinct morphological changes for nitrogen CAP-treated B. cereus spores including etching effects and the appearance of rough spore surfaces, whereas morphology of spores treated with heat or disinfectants showed no such changes. Moreover, microscopy analysis revealed CAP-exposed B. cereus spores to turn phase grey conceivably because of water influx indicating damage of the spores, a phenomenon that was not observed for non-treated spores. In addition, data are supplied that exclude UV radiation as determinant of antimicrobial activity of nitrogen CAP. Overall, this study shows that nitrogen CAP treatment has a biocidal effect on selected Bacillus and Geobacillus spores associated with alterations in spore surface morphology and loss of spore integrity. (C) 2014 Elsevier Ltd. All rights reserved.

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Proteomic response and molecular regulatory mechanisms of Bacillus cereus spores under ultrasound treatment

Ruiling Lv, Donghong Liu, Wenjun Wang, Enbo Xu, Tian Ding, Xingqian Ye, Jianwei Zhou

Summary: This study found that ultrasound treatment led to significant changes in the proteome of Bacillus cereus spores, mainly related to metabolism and cell processes pathways. Particularly, the expression of key proteins involved in the phosphorylation reaction of spores and tricarboxylic acid cycle were significantly decreased, affecting the nutrient metabolism of the spores. Additionally, down-regulation of fatty acid synthetase expression and promotion of fatty acid metabolism were observed after ultrasound treatment, resulting in decreased fatty acid content in spores.

ULTRASONICS SONOCHEMISTRY (2021)