Extracellular antimutagenic activities of selected probiotic Bifidobacterium and Lactobacillus spp. as a function of growth phase

The capabilities of selected strains from genera Lactobacillus and Bifidobacterium to produce extracellular bioactive compounds with antimutagenic properties against benzo[a]pyrene (BaP) and sodium azide (SA) were tested as a function of growth phase. The bacterial supernatants from exponential and stationary phases were characterized with different patterns of antimutagenic activity against the two mutagens. All lactobacilli exhibited either no effect or low antimutagenicity against BaP during exponential growth. Higher antimutagenic activities of lactobacilli supernatants were observed in the stationary phase against SA as well. An exception was Lactobacillus sakei 23K which expressed a relatively low percent of inhibition of mutagenesis (PI = 28.14 +/- 7.41) in the exponential phase and no antimutagenic activity in the stationary phase. Of the bifidobacteria, only Bifidobacterium adoleascentis ATCC 15703 exhibited higher antimutagenecity against BaP in the exponential phase. The same bacterial supernatants however, did not possess any antimutagenicity against SA in either the exponential or stationary phases. B. bifidum ATCC 11863 did not express any significant differences in its activity against either BaP or SA in the exponential or stationary phases. Only B. breve ATCC 15700 expressed a high antimutagenic effect against SA in the stationary phase but exhibited no effect during exponential growth. Overall, bacterial antimutagenic responses were associated with growth phase and type of mutagen.     

Effect of culture conditions on the formation of struvite by Myxococcus xanthus

The amount of struvite (MgNH₄PO₄·6H₂O) produced by Myxococcus xanthus as well as the culture parameter values (pH, total phosphorus, total Kjeldahl nitrogen) were dependent on the culture medium used. Struvite formation started during the exponential phase and the maximum concentration was observed at the beginning of stationary growth phase. The addition of each medium component to the liquid culture influenced the amount of crystal produced. This amount did not depend on the pH increase during the culture period. The moment of the bacterial growth phase, at which each medium component was added, influenced the struvite formation.     

Presence of bacteria in aqueous solution influences virus adsorption on nanoparticles

Virus contamination in wastewater is usually accompanied by the existence of various bacteria. Nanoparticles (NPs) have been shown to efficiently remove virus. In this study, bacterial cells, supernatants, and cultures were harvested separately from three strains at the culture ages of 6 and 24 h, corresponding to the log and stationary phases, respectively. The aim is to investigate how their presence affects virus adsorption on the three Fe and Al oxide NPs (α-Fe₂O₃, γ-Fe₂O₃-B, and Al₂O₃) and how these effects change with bacterial growth phase. Bacteriophage phiX174 was used as a virus model. Results showed that bacterial cells, supernatants, and cultures harvested at 6 h generally reduced virus adsorption by an average of 0.75?±?0.84, 7.7?±?9.0, and 10.3?±?8.6 %, respectively, while those harvested at 24 h reduced virus adsorption by an average of 2.1?±?0.93, 21.5?±?6.6, and 24.6?±?6.9 %, respectively. Among the NPs, α-Fe₂O₃ showed more sensitivity to bacteria than the other two, probably because of its relatively higher value of point of zero charge. It was found that cell-induced and supernatant-induced reductions were combined to achieve added results, in which the supernatants contributed much more than the cells, implying that the bacterial exudates might be more crucial in the reduced virus adsorption than the bacterial cells. These results strongly demonstrated that the bacteria-induced reduction in virus adsorption became more significant with culture age. It is suggested that studies conducted in the absence of bacteria may not accurately evaluate the potential of virus removal efficiency of the NPs in bacteria-containing environments.     

Cross-reactivity of anti-Salmonella egg-yolk antibodies to Salmonella serovars

The cross-reactivity of egg yolk antibodies specific to antigens of Salmonella Enteritidis and Salmonella Typhimurium to killed bacterial cells of common Salmonella serovars were tested using an indirect Enzyme Linked Immunosorbent Assay (ELISA). Egg yolk antibodies were produced against purified fimbriae, flagella and lipopolysaccharide (LPS) of S. Enteritidis strain ATCC13076 and flagella, LPS and outer membrane proteins (OMP) of S. Typhimurium strain ATCC13311. For immunological specificity of egg yolk antibodies against killed bacterial cells, we found that the titers of the anti-S. Enteritidis egg yolk antibodies were higher than those of the anti-S. Typhimurium antibodies. In the evaluation of cross-reactivity of these egg yolk antibodies to various Salmonella serovars, we observed that the anti-S. Enteritidis antibodies exhibited more specific affinity than those of the anti-S. Typhimurium antibodies. All S. Enteritidis strains reacted specifically with the anti-S. Enteritidis fimbrial and flagellar egg yolk antibody whereas anti-S. Enteritidis LPS and anti-S. Typhimurium LPS, OMP and flagellar antibodies displayed non–specific reactivity to all Salmonella serovars used in this study. This finding suggests that it may be possible to design a anti-fimbrial egg yolk antibody of S. Enteritidis as a diagnostic tool and a cocktail of OMP and LPS antigens of S. Enteritidis and S. Typhimurium could be used for administering broad spectrum passive immunity to protect against the colonization of pathogenic Salmonella strains in food animals.     

Fungicidal Activity of Artemisia herba alba Asso (Asteraceae)

The antifungal activity of Artemisia herba alba was found to be associated with two major volatile compounds isolated from the fresh leaves of the plant. Carvone and piperitone were isolated and identified by GC/MS, GC/IR, and NMR spectroscopy. Antifungal activity was measured against Penicillium citrinum (ATCC 10499) and Mucora rouxii (ATCC 24905). The antifungal activity (IC₅₀) of the purified compounds was estimated to be 5 μ g/ml, 2 μ g/ml against Penicillium citrinum and 7 μ g/ml, 1.5 μ g/ml against Mucora rouxii carvone and piperitone, respectively.     

Identification of lactic acid bacteria isolated from wine using real-time PCR

Different lactic acid bacteria strains have been shown to cause wine spoilage, including the generation of substances undesirable for the health of wine consumers. The aim of this study was to investigate the occurrence of selected species of heterofermentative lactobacilli, specifically Lactobacillus brevis, Lactobacillus hilgardii, and Lactobacillus plantarum in six different Slovak red wines following the fermentation process. In order to identify the dominant Lactobacillus strain using quantitative (real time) polymerized chain reaction (qPCR) method, pure lyophilized bacterial cultures from the Czech Collection of Microorganisms were used. Six different red wine samples following malolactic fermentation were obtained from selected wineries. After collection, the samples were subjected to a classic plate dilution method for enumeration of lactobacilli cells. Real-time PCR was performed after DNA extraction from pure bacterial strains and wine samples. We used SYBR® Green master mix reagents for measuring the fluorescence in qPCR. The number of lactobacilli ranged from 3.60 to 5.02 log CFU mL^?1. Specific lactobacilli strains were confirmed by qPCR in all wine samples. The number of lactobacilli ranged from 10³ to 10⁶ CFU mL^?1. A melting curve with different melting temperatures (T_m) of DNA amplicons was obtained after PCR for the comparison of T_m of control and experimental portions, revealing that the most common species in wine samples was Lactobacillus plantarum with a T_m of 84.64°C.     

Cytogenotoxic activity of herbicidal and fungicidal pesticides on Triticum aestivum root meristem

Phytotoxicity, cytotoxicity and genotoxicity of pesticides with various mechanisms of targeted activity were studied in a hydroponic culture of 2-day-old seedlings of Triticum aestivum. All studied pesticides (with the exception of metribuzin) exhibited dose-dependent phytotoxicity (inhibited the growth of the main root and reduced the yield of root biomass). All studied pesticides did not affect mitotic index in the root apex meristem but did affect the duration of some phases of mitosis. Herbicides increased, while fungicides, on the contrary, decreased the duration of the cytokinesis phase. All pesticides (1 μg/mL) exhibited genotoxic activity: in the root apex meristem the number of cells with mitotic abnormalities was significantly higher than in the control variant (7–14 times). The genotoxic activity of metribuzin and tebuconazole was 2 times lower than for tribenuron-methyl, fenoxaprop-P-ethyl, epoxiconazole and azoxystrobin. The genotoxicity of the studied pesticides was combined: depending on the class of the pesticide, clastogenic or aneugenous effects dominated.

     

Metabolism of nC11 fatty acid fed to Trichoderma koningii and Penicillium janthinellum II: Production of intracellular and extracellular lipids

Abstract

Little is known about the fungal metabolism of nC₁₀ and nC₁₁ fatty acids and their conversion into lipids. A mixed batch culture of soil fungi, T. koningii and P. janthinellum, was grown on undecanoic acid (UDA), a mixture of UDA and potato dextrose broth (UDA+PDB), and PDB alone to examine their metabolic conversion during growth. We quantified seven intracellular and extracellular lipid classes using Iatroscan thin-layer chromatography with flame ionization detection (TLC-FID). Gas chromatography with flame ionization detection (GC-FID) was used to quantify 42 individual fatty acids. Per 150 mL culture, the mixed fungal culture grown on UDA+PDB produced the highest amount of intracellular (531 mg) and extracellular (14.7 mg) lipids during the exponential phase. The content of total intracellular lipids represented 25% of the total biomass-carbon, or 10% of the total biomass dry weight produced. Fatty acids made up the largest class of intracellular lipids (457 mg/150 mL culture) and they were synthesized at a rate of 2.4 mg/h during the exponential phase, and decomposed at a rate of 1.8 mg/h during the stationary phase, when UDA+PDB was the carbon source. Palmitic acid (C_16:0), stearic acid (C_18:0), oleic acid (C_18:1), linoleic acid (C_18:2) and vaccenic acid (C_18:1) accounted for >80% of the total intracellular fatty acids. During exponential growth on UDA+PDB, hydrocarbons were the largest pool of all extracellular lipids (6.5 mg), and intracellularly they were synthesized at a rate of 64 μg/h. The mixed fungal species culture of T. koningii and P. janthinellum produced many lipids for potential use as industrial feedstocks or bioproducts in biorefineries.     

Effect of culture conditions on the formation of struvite by Myxococcus xanthus

The amount of struvite (MgNH₄PO₄·6H₂O) produced by Myxococcus xanthus as well as the culture parameter values (pH, total phosphorus, total Kjeldahl nitrogen) were dependent on the culture medium used. Struvite formation started during the exponential phase and the maximum concentration was observed at the beginning of stationary growth phase. The addition of each medium component to the liquid culture influenced the amount of crystal produced. This amount did not depend on the pH increase during the culture period. The moment of the bacterial growth phase, at which each medium component was added, influenced the struvite formation.     

Inhibitory properties of Enterococcus spp. isolated from faeces of healthy dogs

The aim of the present study was to evaluate the inhibitory effect by the cross-streak method of nine Enterococcus faecium strains isolated from faeces of healthy dogs and their treated and non-treated cell-free supernatant (CFS) by the well-diffusion test on the growth of potentially pathogenic bacteria isolated from clinical cases and aflatoxigenic Aspergillus section Flavi and the consequent aflatoxin B₁ (AFB₁) production. Results obtained from the cross-strake assay showed that E. faecium MF1, GJ18 and GJ40 presented the major inhibitory activity against all pathogenic strains assayed; E. faecium GJ40 produced the larger inhibitory zones (26–27 mm). Well-diffusion test results showed that the majority of the enterococci strains CFS had antimicrobial activity against the pathogenic microorganisms, especially on Gram negative indicators. Cell-free supernatant of E. faecium GJ40 was the one that produced the largest inhibition zones (14 to 21 mm) in the majority of the indicator microorganisms assayed. All supernatants treated with 10 N NaOH (pH6) showed no inhibitory effect on the indicator strain assayed. With respect to fungal inhibition, any of the CFS assayed significantly inhibited the Aspergillus strains growth. But, in general, all CFS reduced AFB₁ production from 8 to 87%. The results demonstrate that enterococci isolated from healthy dog feaces produce substances with the capacity to inhibit some potential pathogenic bacteria growth and the capacity of inhibiting or reducing the AFB₁ production in vitro.     

Listeria monocytogenes batch culture growth response to metabolic inhibitors

In certain environments nutrient and energy sources available to microorganisms can be limited. Foodborne pathogens must efficiently adapt in order to be successfully transmitted through the food chain to their hosts. For the intracellular foodborne pathogen Listeria monocytogenes, little is known regarding its response to nutrient/energy-limiting conditions. The alternative stress responsive sigma factor σ^B has been reported to contribute to survival under specific stresses. Therefore, the effects of several metabolic inhibitors on growth of L. monocytogenes wild-type and a ΔsigB mutant were examined. In the absence of inhibitors, both strains reached stationary phase after 18 h at 23°C and 10 h at 37°C. All of the metabolic inhibitors slowed growth of either strain, with few differences observed among the different inhibitors.     

纯二氧化碳条件下小球藻固定CO2

微藻固碳已经成为消减温室气体排放的新的研究热点。利用静态吸收方法,考查了通人纯CO2对普通小球藻生长特点、固定CO2效率以及藻液pH值变异的影响。结果表明：通入纯CO2使小球藻生长延滞期显著延长,比普通培养延长10～12d,对其他生长阶段的影响不大;小球藻固定CO2速率可分为2个过程,即物理固碳过程和生物固碳过程,前者在藻细胞延滞期发生,峰值由CO。溶解于培养液造成,后者在藻细胞生长的指数期、稳定期和衰退期发生,峰值由藻细胞指数生长造成,2个过程中,固定CO2速率的变化趋势都是先增大后降低;纯CO2条件下,藻液pH值变化速率高,4d内,藻液即被酸化,随后藻液pH值变化速率逐渐降低,且pH值稳定在适宜水平。因此,采用小球藻固定高浓度CO2时,建议提高接种量并加强培养前期的pH值监测和调控,以保证藻液保持适宜的pH值,并缩短培养时间,提高生物固碳效率。     

Toxicity of twenty-two plant essential oils against pathogenic bacteria of vegetables and mushrooms

Toxicity of twenty-two essential oils to three bacterial pathogens in different horticultural systems: Xanthomonas campestris pv. phaseoli (causing blight of bean), Clavibacter michiganensis subsp. michiganensis (bacterial wilt and canker of tomato), and Pseudomonas tolaasii (causal agent of bacterial brown blotch on cultivated mushrooms) was tested. Control of bacterial diseases is very difficult due to antibiotic resistance and ineffectiveness of chemical products, to that essential oils offer a promising alternative. Minimal inhibitory and bactericidal concentrations are determined by applying a single drop of oil onto the inner side of each plate cover in macrodilution assays. Among all tested substances, the strongest and broadest activity was shown by the oils of wintergreen (Gaultheria procumbens), oregano (Origanum vulgare), and lemongrass (Cymbopogon flexuosus. Carvacrol (64.0–75.8%) was the dominant component of oregano oils, while geranial (40.7%) and neral (26.7%) were the major constituents of lemongrass oil. Xanthomonas campestris pv. phaseoli was the most sensitive to plant essential oils, being susceptible to 19 oils, while 11 oils were bactericidal to the pathogen. Sixteen oils inhibited the growth of Clavibacter michiganensis subsp. michiganensis and seven oils showed bactericidal effects to the pathogen. The least sensitive species was Pseudomonas tolaasii as five oils inhibited bacterial growth and two oils were bactericidal. Wintergreen, oregano, and lemongrass oils should be formulated as potential biochemical bactericides against different horticultural pathogens.     

间歇运行式生物滴滤池处理油漆废气中试研究

为研究间歇运行式生物滴滤池对油漆生产厂废气净化能力,建立一座中试规模生物滴滤池（BTF）,接种降解菌群,采用8 h/d运行方式净化某油漆厂包装车间废气,并用PCR-DGGE技术揭示BTF细菌群落结构与工艺运行条件间的联系。油漆厂包装车间废气中挥发性有机物（VOCs）主要为甲苯、乙苯、混合二甲苯（间、对和邻二甲苯）,BTF对甲苯、乙苯、混合二甲苯最大去除率分别为88.8%、83.7%和86.3%。DGGE分析显示,BTF稳定运行时,主要优势菌相对丰度较为稳定（F,P>0.05）,其细菌多样性显著低于启动期（F,P>0.05）;同时,下层填料细菌多样性高于上层填料,其细菌结构变化也较上层明显;另外,提升培养液浓度至2倍和4倍对菌群结构亦无显著影响。     

Exploring micromycetes biodiversity for screening benzo[a]pyrene degrading potential

Twenty-five strains of filamentous fungi, encompassing 14 different species and belonging mainly to Ascomycetes, were tested for their ability to degrade benzo[a]pyrene (BaP) in mineral liquid medium. The most performing isolates for BaP degradation (200 mg?l^?1) in mineral medium were Cladosporium sphaerospermum with 29 % BaP degradation, i.e., 82.8 μg BaP degraded per day (day^?1), Paecilomyces lilacinus with 20.5 % BaP degradation, i.e., 58.5 μg BaP day^?1, and Verticillium insectorum with 22.3 % BaP degradation, i.e., 64.3 μg BaP day^?1, after only 7 days of incubation. Four variables, e.g., biomass growth on hexadecane and glucose, BaP solubilization, activities of extracellular- and mycelium-associated peroxidase, and polyethylene glycol degradation, were also studied as selective criteria presumed to be involved in BaP degradation. Among these variables, the tests based on polyethylene glycol degradation and on fungal growth on hexadecane and glucose seemed to be the both pertinent criteria for setting apart isolates competent in BaP degradation, suggesting the occurrence of different mechanisms presumed to be involved in pollutant degradation among the studied micromycetes.     

Identification and methionine analog tolerance of environmental bacterial isolates selected on methionine analog containing medium

Methionine is the first limiting amino acid in poultry feed. Currently, methionine supplement is synthesized from an expensive chemical process requiring hazardous chemicals. Therefore, the objectives of this study were isolation of methionine producing bacteria from environmental samples and quantification of methionine production in these isolated bacteria. MCGC medium was selected as the isolation medium for methionine-producing bacteria by using Corynebacterium glutamicum ATCC13032 and Escherichia coli ATCC23798 as the positive and negative controls, respectively. Thirty-nine bacterial strains were obtained from environmental samples. Only strains A121, A122, A151 and A181 were able to tolerate up to 0.1% (w/v) of ethionine or norleucine. These isolated strains were identified by sequencing small subunit rRNA genes. The results revealed that bacterial strains A121, A122, A151and A181 were Klebsiella species, Acinetobacter baumannii, A. baumannii and Pseudomonas aeruginosa, respectively. When methionine production in strains A121 and A181 was quantitated, strains A121 and A181 generated methionine up to 31.1 and 124.6 μg/ml, respectively.     

The in vitro effect of selected essential oils on the growth and mycotoxin production of Aspergillus species

The aim of the present study was to assess the antifungal and anti-toxinogenic activity of 15 essential oils (EOs) against three fungi of the genus Aspergillus (A. parasiticus KMi-227-LR, A. parasiticus KMi-220-LR and A. flavus KMi-202-LR). The minimum inhibitory doses (MIDs) of the tested essential oils and their antifungal activity were determined using the micro-atmosphere method. The original commercial essential oil samples of Jasminum officinale L., Thymus vulgaris L., Syzygium aromaticum (L.) Merrill &; Perry, Rosmarinus officinalis L., Ocimum basilicum L., Eucalyptus globulus Labill., Salvia officinalis L., Citrus limon (L.) Burm, Origanum vulgare L., Lavandula angustifolia Mill., Carum carvi L., Citrus sinensis (L.) Osbeck., Zingiber officinalis Rosc., Mentha piperita L. and Cinnamomum zeylanicum Nees. (C. verum J.S.Presl.) were produced in Slovakia (Calendula a.s., Nová ?ubovňa, Slovakia). All essential oils exhibited activity against all tested strains of fungi. After 14 days of incubation, A. flavus (KMi-202-LR) showed the highest susceptibility with a growth inhibition percentage (GIP) of 18.70% to C. limon and 5.92% to C. sinensis, while A. parasiticus (KMi-220-LR) exhibited a GIP of 20.56% to J. officinale. The minimum inhibitory doses (MIDs) of EOs with the most significant activity were recorded. The best antifungal activity, using the micro-atmosphere method was found in S. aromaticum with an MID of 62.5 μL L^?1 air, T. vulgaris (MID of 62.5 μL L^?1 air) and O. vulgare (MID of 31.5 μL L^?1 air) against all tested strains. Mycotoxin production of the tested strains was evaluated by the thin layer chromatography (TLC) method. Mycotoxin production of AFB₁ and AFG₁ was inhibited following all treatments with C. carvi, R. officinale and S. officinale, Eucalyptus globulus L. and O. basilicum L. Essential oils exhibited a potential inhibition activity against toxic fungi, although, these affected only the production of AFB₁.     

Toxicity and bioaccumulation of copper in three green microalgal species

The effective concentrations of copper on the inhibition of the growth of Scenedesmus obliquus, Chlorella pyrenoidosa and Closterium lunula at 96 h (96 h EC50) were determined to be 50, 68 and 200 microg/l, respectively. The low initial bioaccumulation of Cu by C. lunula was found to be responsible for its tolerance to Cu. The amount of Cu accumulated by all three microalgae reached the maximum value and decreased quickly after the peak followed by a slow decrease over the next 6 d. Bioaccumulation of Cu by C. lunula was directly proportional to the initial Cu concentration. After reaching the first peak after 1 d, the bioconcentration factor of Cu by microalgae declined to its minimum value during the exponential growth phase but increased in the stationary growth phase again. This indicates that desorption of Cu from microalgae was higher during the exponential growth phase but lower in the stationary growth phase. Smaller microalgae with low 96 h EC50 values are more efficient in removing Cu from wastewater.