Clostridium perfringens forms biofilms and spores that are a source of food contamination. In this study, the antibacterial activities of Lactobacillus plantarum culture supernatants (LP-S), LP-S fractions, and the plant-derived compound epigallocatechin gallate (EG) were evaluated. Specifically, their effects on the viability and biofilm-forming ability of C. perfringens were assessed. Moreover, the expression of quorum sensing-regulated genes associated with the pathogenesis of this microorganism and that of genes involved in biofilm formation was also investigated. The results showed that both EG and the LP-S exerted bactericidal activity against all C. perfringens strains tested. The minimal bactericidal concentration (MBC) of EG was 75 µg/mL for all strains but ranged from 61 to 121 µg of total protein per mL for LP-S. EG exerted only minor effects on biofilm formation, whereas LP-S, particularly its 10 and 30 K fractions, significantly reduced the biofilm-forming ability of all the strains. The antibiofilm activity of LP-S was lost following preincubation with proteases, suggesting that it was mediated by a proteinaceous molecule. The treatment of C. perfringens with either EG or LP-S did not change the transcript levels of two CpAL (C. perfringens quorum-sensing Agr-like system)-related genes, agrB and agrD, which are known to be involved in the regulation of biofilms, suggesting that LP-S exerted its biofilm inhibitory activity downstream of CpAL signaling. In summary, we demonstrated the bactericidal activity of EG and LP-S against C. perfringens and antibiofilm activity of LP-S at a subinhibitory dose. Our results suggested that these compounds can be further explored for food safety applications to control agents such as C. perfringens.
- MeSH
- Biofilms MeSH
- Clostridium perfringens * drug effects genetics MeSH
- Catechin analogs & derivatives pharmacology MeSH
- Culture Media, Conditioned * pharmacology MeSH
- Lactobacillus plantarum * metabolism MeSH
- Gene Expression Regulation, Bacterial drug effects MeSH
- Publication type
- Journal Article MeSH
The evolutionary "success" of the genus Brucella depends on the ability to persist both in the environment as well as inside of even activated macrophages of the animal host. For that, the Brucellae produce catalase and superoxide dismutase to defend against oxidative stress. Since the deletion of the mglA gene in the B. abortus S19 vaccine strain resulted not only in an increased tolerance to H2O2 but also in the induction of cytokines in macrophages, we here investigated the effect of oxidative stress (Fe2+ and H2O2) on the survival of B. abortus S19 and the isogenic B. abortus S 19 ∆mglA 3.14 deletion mutant in comparison with B. neotomae 5K33, Brucella strain 83/13, and B. microti CCM4915. These Brucellae belong to different phylogenetic clades and show characteristic differences in the mgl-operon. From the various Brucellae tested, B. abortus S19 showed the highest susceptibility to oxidative stress and the lowest ability to survive inside of murine macrophages. B. abortus S19 ∆mglA 3.14 as well as B. neotomae, which also belongs to the classical core clade of Brucella and lacks the regulators of the mgl-operon, presented the highest degree of tolerance to H2O2 but not in the survival in macrophages. The latter was most pronounced in case of an infection with B. 83/13 and B. microti CCM4915. The various Brucellae investigated here demonstrate significant differences in tolerance against oxidative stress and different survival in murine macrophages, which, however, do not correlate directly.
- MeSH
- Adenosine Triphosphate metabolism MeSH
- Genes, Bacterial MeSH
- Brucella abortus physiology MeSH
- Brucella classification physiology MeSH
- Cell Line MeSH
- Cytokines metabolism MeSH
- Species Specificity MeSH
- Macrophages immunology microbiology MeSH
- Microbial Viability MeSH
- Mutation MeSH
- Mice MeSH
- Oxidative Stress * MeSH
- Hydrogen Peroxide metabolism MeSH
- Colony Count, Microbial MeSH
- Iron metabolism MeSH
- Animals MeSH
- Check Tag
- Mice MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
Three different transformation strategies were tested and compared in an attempt to facilitate and improve the genetic transformation of Acremonium chrysogenum, the exclusive producer of the pharmaceutically relevant β-lactam antibiotic cephalosporin C. We investigated the use of high-voltage electric pulse to transform germinated conidia and young mycelium and compared these procedures with traditional PEG-mediated protoplast transformation, using phleomycin resistance as selection marker in all cases. The effect of the field strength and capacitance on transformation frequency and cell viability was evaluated. The electroporation of germinated conidia and young mycelium was found to be appropriate for transforming A. chrysogenum with higher transformation efficiencies than those obtained with the conventional protoplast-based transformation procedures. The developed electroporation strategy is fast, simple to perform, and highly reproducible and avoids the use of chemicals toxic to cells. Electroporation of young mycelium represents an alternative method for transformation of fungal strains with reduced or no sporulation, as often occurs in laboratory-developed strains in the search for high-yielding mutants for industrial bioprocesses.
- MeSH
- Acremonium drug effects genetics metabolism MeSH
- Drug Resistance, Bacterial MeSH
- Cephalosporins biosynthesis MeSH
- Electroporation methods MeSH
- Phleomycins pharmacology MeSH
- Microbial Viability MeSH
- Mycelium drug effects genetics metabolism MeSH
- Protoplasts physiology MeSH
- Spores, Fungal drug effects genetics metabolism MeSH
- Transformation, Genetic * MeSH
- Publication type
- Journal Article MeSH
- Comparative Study MeSH
Staphylococcus aureus may be a highly virulent human pathogen, especially when it is able to form a biofilm, and it is resistant to antibiotic. Infections caused by these bacteria significantly affect morbidity and mortality, primarily in hospitalized patients. Treatment becomes more expensive, more toxic, and prolonged. This is the reason why research on alternative therapies should be one of the main priorities of medicine and biotechnology. A promising alternative treatment approach is bacteriophage therapy. The effect of the anti-staphylococcal bacteriophage preparation Stafal® on biofilm reduction was assessed on nine S. aureus strains using both sonication with subsequent quantification of surviving cells on the catheter surface and evaluation of biofilm reduction in microtiter plates. It was demonstrated that the bacteriophages destroy planktonic cells very effectively. However, to destroy cells embedded in the biofilm effectively requires a concentration at least ten times higher than that provided by the commercial preparation. The catheter disc method (CDM) allowed easier comparison of the effect on planktonic cells and cells in a biofilm than the microtiter plate (MTP) method.
- MeSH
- Anti-Infective Agents * MeSH
- Bacteriological Techniques MeSH
- Biofilms * MeSH
- Humans MeSH
- Methicillin-Resistant Staphylococcus aureus growth & development isolation & purification virology MeSH
- Microbial Viability MeSH
- Colony Count, Microbial MeSH
- Staphylococcus Phages physiology MeSH
- Staphylococcal Infections microbiology MeSH
- Staphylococcus aureus growth & development isolation & purification virology MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
Lactobionic acid (LBA) is a newly identified natural polyhydroxy acid that is widely used in the food industry. In this study, the antibacterial effects and underlying mechanism of action of LBA against Staphylococcus aureus were investigated. LBA exhibited significant antibacterial activity against S. aureus with a determination of the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 15 mg/mL and 50 mg/mL, respectively. The Growth curves indicated that LBA directly inhibited the growth of S. aureus. Moreover, LBA induced the leakage of alkaline phosphatase and nucleotides in the culture medium, indicating damage to the integrity of the S. aureus cell wall membrane, which was confirmed by transmission electron microscopy observations. The relative electric conductivity measurements indicated that LBA changed the cell membrane permeability. The preservation effect of LBA was evaluated by quantifying the total number of colonies, total volatile base nitrogen (TVB-N), and thiobarbituric acid reactive substances (TBARS). Overall, these results revealed that LBA exerts its antibacterial activity by breaking down the structure of the bacterial cell wall and membrane, thereby releasing the cellular contents as well as inhibiting protein synthesis, which ultimately lead to cell death. The total number of colonies, the TVB-N value, and the TBARS of cold fresh meat treated with preservatives were significantly lower than those of the control group (P < 0.05). With these antibacterial characteristics, LBA has potential to be used as a safe food additive in the food industry.
- MeSH
- Anti-Bacterial Agents pharmacology MeSH
- Cell Membrane drug effects metabolism MeSH
- Cell Wall drug effects metabolism MeSH
- Disaccharides pharmacology MeSH
- Nitrogen analysis MeSH
- Food Preservation MeSH
- Thiobarbituric Acid Reactive Substances analysis MeSH
- Microbial Sensitivity Tests MeSH
- Microbial Viability drug effects MeSH
- Cell Membrane Permeability drug effects MeSH
- Colony Count, Microbial MeSH
- Staphylococcus aureus drug effects growth & development MeSH
- Publication type
- Journal Article MeSH
The surface conditions on the Moon are extremely harsh with high doses of ultraviolet (UV) irradiation (26.8 W · m-2 UVC/UVB), wide temperature extremes (-171°C to 140°C), low pressure (10-10 Pa), and high levels of ionizing radiation. External spacecraft surfaces on the Moon are generally >100°C during daylight hours and can reach as high as 140°C at local noon. A Lunar Microbial Survival (LMS) model was developed that estimated (1) the total viable bioburden of all spacecraft landed on the Moon as ∼4.57 × 1010 microbial cells/spores at contact, (2) the inactivation kinetics of Bacillus subtilis spores to vacuum as approaching -2 logs per 2107 days, (3) the inactivation of spores on external surfaces due to concomitant low-pressure and high-temperature conditions as -6 logs per 8 h for local noon conditions, and (4) the ionizing radiation by solar wind particles as approaching -3 logs per lunation on external surfaces only. When the biocidal factors of solar UV, vacuum, high-temperature, and ionizing radiation were combined into an integrated LMS model, a -231 log reduction in viable bioburden was predicted for external spacecraft surfaces per lunation at the equator. Results indicate that external surfaces of landed or crashed spacecraft are unlikely to harbor viable spores after only one lunation, that shallow internal surfaces will be sterilized due to the interactive effects of vacuum and thermal cycling from solar irradiation, and that deep internal surfaces would be affected only by vacuum with a degradation rate of -0.02 logs per lunation.
- MeSH
- Bacillus subtilis physiology radiation effects MeSH
- Models, Biological * MeSH
- Spacecraft MeSH
- Cosmic Radiation adverse effects MeSH
- Moon * MeSH
- Microbial Viability radiation effects MeSH
- Extraterrestrial Environment MeSH
- Space Simulation methods MeSH
- Spores, Bacterial physiology radiation effects MeSH
- Ultraviolet Rays adverse effects MeSH
- Vacuum MeSH
- Hot Temperature MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
This study describes a new method for fast identification of highly hydrophobic conidia of Aspergillus species from both simple and complex matrices. The method is based on recently developed preparative isoelectric focusing in a cellulose-based separation medium which had to be modified with respect to the highly hydrophobic surface of the conidia. Although Aspergillus conidia are colored, their zones in the cellulose bed were indicated by colored isoelectric point markers. The isoelectric point values of Aspergillus conidia were determined by capillary isoelectric focusing. Preparative isoelectric focusing was successfully used for preconcentration of individual conidia of cultivated strains of Aspergillus niger, Aspergillus fumigatus, Aspergillus flavus, and Aspergillus parasiticus, and also for separation of the conidia in a mixture. Subsequently, red pepper powder and peanuts spiked with Aspergillus niger and Aspergillus flavus conidia, respectively, were used as complex matrices. The detection limit for identification of the conidia in these complex matrices is 104 conidia mL-1 . The presence of conidia in the focused zones was confirmed by their subsequent analysis by capillary isoelectric focusing. Their viability was confirmed by a cultivation of the conidia extracted from the collected fractions after preparative isoelectric focusing.
The inactivation of four micromycete species by action of non-thermal plasma was followed. Two sources of plasma were compared, namely, positive corona discharge and dielectric barrier discharge. The corona discharge appeared as suitable for fungal spore inactivation in water suspension, whereas the barrier discharge inactivated spores on the surface of cultivation agar. Cladosporium sphaerospermum was the most sensitive, being inactivated within 10 min of exposure to plasma, whereas Aspergillus oryzae displayed decrease in viable cell count only, the complete inactivation was not achieved even after 40 min of exposure. Intermediate sensitivity was found for Alternaria sp. and Byssochlamys nivea. The significant delay of growth was observed for all fungi after exposure to sublethal dose of plasma, but we failed to express this effect quantitatively.
Disinfection aims at maximal inactivation of target organisms and the sustainable suppression of their regrowth. Whereas many disinfection efforts achieve efficient inactivation when the effect is measured directly after treatment, there are questions about the sustainability of this effect. One aspect is that the treated bacteria might recover and regain the ability to grow. In an environmental context, another question is how amenable surviving bacteria are to predation by omnipresent bacteriophages. Provisional data suggested that bacteria when subjected to sublethal heat stress might develop a phage-resistant phenotype. The result made us wonder about the susceptibility to phage-mediated lysis for bacteria exposed to a gradient of chlorine and UV-LED disinfection strengths. Whereas bacteria exposed to low sublethal chlorine doses still underwent phage-mediated lysis, the critical chlorine Ct of 0.5 mg min/L eliminated this susceptibility and induced phage resistance in the cells that survived treatment. In the case of UV, even the smallest tested dose of 2.8 mJ/cm2 abolished phage lysis leading to direct regrowth. Results suggest that bacteria surviving disinfection might have higher environmental survival chances directly after treatment compared to non-treated cells. A reason could possibly lie in their compromised metabolism that is essential for phage replication.
- MeSH
- Bacteriolysis drug effects radiation effects MeSH
- Chlorine physiology MeSH
- Disinfection MeSH
- Escherichia coli * drug effects radiation effects virology MeSH
- Stress, Physiological MeSH
- Coliphages isolation & purification physiology MeSH
- Microbial Viability drug effects radiation effects MeSH
- Colony Count, Microbial MeSH
- Flow Cytometry MeSH
- Ultraviolet Rays * MeSH
- Hot Temperature * MeSH
- Publication type
- Journal Article MeSH
The study evaluates the survivability and storage stability of seven Trichoderma strains belonging to the species: T. harzianum (1), T. atroviride (4), and T. virens (2) after the lyophilization of their solid state cultures on wheat straw. Biomass of Trichoderma strains was freeze-dried with and without the addition of maltodextrin. Furthermore, in order to determine the ability of tested Trichoderma strains to preserve selected technological features, the biosynthesis of extracellular hydrolases (cellulases, xylanases, and polygalacturonases) after a 3-month storage of lyophilizates was investigated. Strains of T. atroviride (except TRS40) and T. harzianum TRS85 showed the highest viability after lyophilization process (up to 100%). After 3 months of storage, T. atroviride TRS14 exhibited the highest stability (95.23%); however, the number of active conidia remained at high level of 106-107 cfu/g for all tested T. atroviride strains and T. harzianum TRS85. Interestingly, after a 3-month storage of lyophilized formulations, most of the tested Trichoderma strains exhibited higher cellulolytic and xylanolytic activities compared to the control, i.e., before freeze-drying process. The highest activities of these enzymes exhibited the following: T. atroviride TRS14-2.37 U/g and T. atroviride TRS25-21.47 U/g, respectively, whereas pectinolytic activity was weak for all tested strains, with the highest value of 0.64 U/g registered for T. virens TRS109.
- MeSH
- Biomass MeSH
- Time Factors MeSH
- Fermentation MeSH
- Hydrolases metabolism MeSH
- Freeze Drying * MeSH
- Microbial Viability * MeSH
- Triticum metabolism MeSH
- Drug Storage MeSH
- Spores, Fungal growth & development MeSH
- Trichoderma classification growth & development physiology MeSH
- Publication type
- Journal Article MeSH
