Hydrophobicity and specific biofilm features of Bacillus cereus spores subjected to pH stresses

Abstract

Bacillus cereus is a foodborne pathogen that often persists on food processing surfaces due the formation of spores and biofilms. Spores of 12 selected B. cereus strains from genotypes that recurred in a pasteurized milk processing line were investigated in this study, for their surface and biofilm characteristics. The main objective was to have an insight into their persistence strategies. Spore surface hydrophobicity and acid-base properties, were assessed using the microbial adhesion to solvents (MATS) method. To determine how hydrophobicity was affected by cleaning procedures, this property was measured when spores were submitted to alkali or acidic stresses mimicking those of cleaning-in-place (CIP) procedures. Biofilms formation on stainless steel coupons by pH-treated spores was investigated in three culture media and imaged by using environmental scanning electron microscopy (ESEM). Results showed that spores were either hydrophilic or moderately hydrophobic. Alkali-stress reduced spore surface hydrophobicity, whereas acidic shock increased it. More limited hydrophobicity changes following alkaline stress suggest alkali adaptation of spores. In addition, spores submitted to pH-stresses produced specific biofilm features on stainless steel as shown by ESEM imaging. Alkali tolerance and the biofilm lifestyle are strategies that permit B. cereus recurrent genotypes to persist in the milk processing line. Overall, this study gives an insight into hydrophobicity and specific biofilm features of B. cereus spores submitted to chemical cleaning.

Biodegradation of polyethylene (PE), polypropylene (PP), and polystyrene (PS) microplastics by floc-forming bacteria, Bacillus cereus strain SHBF2, isolated from a commercial aquafarm

“…The hydrophobicity of the same bacterial species showed more than 90% hydrophobicity for xylene, and hexane hydrocarbons which is noticeably higher than the SHBF2 strain of the present study (Xie et al, 2023). The reason for this contrasting behavior from the same species has been answered by the study of Fadila, (2016) where they got 12 grouped strains of B. cereus that had different hydrophobicity for xylene, hexane, ether, and chloroform hydrocarbons. Interestingly, all of the strains showed lower hydrophobicity than the strain of the present study.…”

Microorganism Carrier-Surface Method as an Efficient Model for Microscopic Characterization of Biofilm Structure and Dispersion in Dairy Associated Spore-Forming Bacteria

“…The protection of strains within biofilms formed inside pipe milking systems has been described as a survival strategy for B. cereus recurrent genotypes that have been shown to persist on equipment surfaces in a dairy plant, for several years [34]. In order to better understand their persistence strategies, the spore surface and biofilm characteristics of this recurring B. cereus were characterized [35]. Interesting findings were that cleaning procedures (cleaning-in-palce, CIP system) may affect the spore surface hydrophobicity and hydrophilic spores were best able to withstand chemical cleaning, and form specific biofilm features on stainless steel surfaces (Fig.…”