Biofilm Formation and Cell Surface Properties among Pathogenic and Nonpathogenic Strains of the Bacillus cereus Group (original) (raw)
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Applied Microbiology and Biotechnology, 2011
Microbial biofilms contribute to biofouling in a wide range of processes from medical implants to processed food. The extracellular polymeric substances (EPS) are implicated in imparting biofilms with structural stability and resistance to cleaning products. Still, very little is known about the structural role of the EPS in Gram-positive systems. Here, we have compared the cell surface and EPS of surface-attached (biofilm) and free-floating (planktonic) cells of Bacillus cereus, an organism routinely isolated from within biofilms on different surfaces. Our results indicate that the surface properties of cells change during biofilm formation and that the EPS proteins function as non-specific adhesions during biofilm formation. The physicochemical traits of the cell surface and the EPS proteins give us an insight into the forces that drive biofilm formation and maintenance in B. cereus.
Phenotypic and functional characterization of Bacillus anthracis biofilms
Biofilms, communities of micro-organisms attached to a surface, are responsible for many chronic diseases and are often associated with environmental reservoirs or lifestyles. Bacillus anthracis is a Gram-positive, endospore-forming bacterium and is the aetiological agent of pulmonary, gastrointestinal and cutaneous anthrax. Anthrax infections are part of the natural lifecycle of many ruminants in North America, including cattle and bison, and B. anthracis is thought to be a central part of this ecosystem. However, in endemic areas in which humans and livestock interact, chronic cases of cutaneous anthrax are commonly reported. This suggests that biofilms of B. anthracis exist in the environment and are part of the ecology associated with its lifecycle. Currently, there are few data that account for the importance of the biofilm mode of life in B. anthracis, yet biofilms have been characterized in other pathogenic and non-pathogenic Bacillus species, including Bacillus cereus and Ba...
Influence of physiological cell stages on biofilm formation by< i> Bacillus cereus of dairy origin
International Dairy Journal, 2011
The effect of initial physiological stages, i.e., sessile, vegetative, and spore (SP), of Bacillus cereus on its biofilm formation potential was investigated. Enhanced biofilm formation was observed in diluted tryptic soy broth in comparison with milk menstruum. Growth rate constants of the biofilm growth curve (BGC) indicated that SP was the most efficient cell stage to initiate and form a biofilm. Comparative evaluation of the BGC and suspension growth curve revealed that former's lag phase corresponded to latter's log phase (4e16 h). Through being surface adhered and in lag phase, these cells might be more resistant to cleaning. Moreover, the greater SP percentage in spore initiated biofilm than spore initiated suspension presents an obvious food safety threat. These findings suggest a noteworthy effect of initial cell stages on biofilm formation potential of B. cereus and may be helpful in designing/scheduling more efficient interventions to minimize associated health hazards.
Hydrophobicity and specific biofilm features of Bacillus cereus spores subjected to pH stresses
African Journal of Microbiology Research, 2016
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.
Biofilm formation displays intrinsic offensive and defensive features of Bacillus cereus
2019
Background: Biofilm formation is a strategy of many bacterial species to adapt to a variety of stresses and has become a part of infections, contaminations or beneficial interactions. We previously observed that B. cereus ATCC 14579 (CECT148), formed a thick biomass of cells firmly adhered to abiotic surfaces. Results: In this study, we combined two strong techniques, RNAseq and iTRAQ mass spectrometry, to demonstrate the profound physiological changes that permit Bacillus cereus to switch from a floating to a sessile lifestyle, to undergo further maturation of the biofilm, and to differentiate into offensive or defensive populations. The rearrangement of nucleotides, sugars, amino acids and energy metabolism lead to changes promoting reinforcement of the cell wall, activation of ROS detoxification strategies or secondary metabolite production, all oriented to defend biofilm cells from external aggressions. However, floating cells maintain a fermentative metabolic status along with ...
Role of Cell Surface Structures in Biofilm Formation by <i>Escherichia coli</i>
Food and Nutrition Sciences, 2015
This study aims to understand the relationship between capabilities of Escherichia coli strains to form biofilm and serotype groups expressed on cell surface. Sixteen strains of E. coli were originally isolated from different food processing lines in different Moroccan cities. Strains serotyped based on their O (somatic), H (flagellar), and K (capsular) surface antigen profiles using different antiserums. Biofilm assays carried out in 96-well microtiter dishes using the method of O'Toole et al. Our results show that no clear relation observed between origin and serotype groups. In the other hand, we observed that not all studied strains were able to form biofilm. Furthermore, combination of antigens H40 and K11 appears to be involved in biofilm formation. In fact, the H antigen seems to be implicated in the placement of the bacterial cells near the surface and the K antigen may play a role in physicochemical interactions between bacteria and inert surface.
Biofilms of a Bacillus subtilis hospital isolate protect Staphylococcus aureus from biocide action
PloS one, 2012
The development of a biofilm constitutes a survival strategy by providing bacteria a protective environment safe from stresses such as microbicide action and can thus lead to important health-care problems. In this study, biofilm resistance of a Bacillus subtilis strain (called hereafter ND(medical)) recently isolated from endoscope washer-disinfectors to peracetic acid was investigated and its ability to protect the pathogen Staphylococcus aureus in mixed biofilms was evaluated. Biocide action within Bacillus subtilis biofilms was visualised in real time using a non-invasive 4D confocal imaging method. The resistance of single species and mixed biofilms to peracetic acid was quantified using standard plate counting methods and their architecture was explored using confocal imaging and electronic microscopy. The results showed that the ND(medical) strain demonstrates the ability to make very large amount of biofilm together with hyper-resistance to the concentration of PAA used in m...
International Journal of Food Microbiology, 2015
Biofilm formation of Bacillus cereus reference strains ATCC 14579 and ATCC 10987 and 21 undomesticated food isolates was studied on polystyrene and stainless steel as contact surfaces. For all strains, the biofilm forming capacity was significantly enhanced when in contact with stainless steel (SS) as a surface as compared to polystyrene (PS). For a selection of strains, the total CFU and spore counts in biofilms were determined and showed a good correlation between CFU counts and total biomass of these biofilms. Sporulation was favoured in the biofilm over the planktonic state. To substantiate whether iron availability could affect B. cereus biofilm formation, the free iron availability was varied in BHI by either the addition of FeCl 3 or by depletion of iron with the scavenger 2,2-Bipyridine. Addition of iron resulted in increased air-liquid interface biofilm on polystyrene but not on SS for strain ATCC 10987, while the presence of Bipyridine reduced biofilm formation for both materials. Biofilm formation was restored when excess FeCl 3 was added in combination with the scavenger. Further validation of the iron effect for all 23 strains in microtiter plate showed that fourteen strains (including ATCC10987) formed a biofilm on PS. For eight of these strains biofilm formation was enhanced in the presence of added iron and for eleven strains it was reduced when free iron was scavenged. Our results show that stainless steel as a contact material provides more favourable conditions for B. cereus biofilm formation and maturation compared to polystyrene. This effect could possibly be linked to iron availability as we show that free iron availability affects B. cereus biofilm formation.