•The genomes and proteomes of 12 Bifidobacterium and 46 Lactobacillus were reviewed and then compared for bacteriocin identification.•NCBI-Genome, UniProt-Proteome, Bactibase, and BAGL4 databases, as ...well as BLASTP, and Clustal Omega can be used for bacteriocin mining.•Lactobacillus species have more diversity and abundance of bacteriocin compared to Bifidobacterium species.•Notably, L. sakei, L. plamtarum, L. reuteri, L. fermentum, and L. casei had the highest pathogen inhibition (E. coli MG 1655); respectively.•A set of Lactobacillus bacteria including L. sakei, L. reuteri, L. fermentum, and L. casei can be proposed as a biosecure and safe solution to control gastrointestinal pathogens.
Bacteriocins are a large family of bacterial peptides or proteins, ribosomally synthesized with antimicrobial activity against other bacteria. We investigated and compared the genomes and proteomes of 12 Bifidobacterium and 46 Lactobacillus species for bacteriocins using NCBI-Genome, UniProt-Proteome, Bactibase, and BAGL4 databases. Selected Lactobacillus species were examined for bile salt resistance, acid and pH resistance, pepsin and trypsin enzyme resistance, and antibiotic resistance. Also, the antimicrobial activity of selected Lactobacillus species was evaluated against E. coli MG 1655. Results showed that Lactobacillus species have more diversity and abundance of bacteriocin compared to Bifidobacterium species. Notably, L. sakei, L. plamtarum, L. reuteri, L. fermentum, and L. casei had the highest pathogen inhibition; respectively. Therefore, a combination of these Lactobacillus species can be suggested as a biochemical and safe solution to control gastrointestinal pathogens and suitable alternatives to antibiotics and chemicals in food technology.
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To better apply the biocontrol agent Trichoderma spp. in Northeast China, collecting and screening more suitable native Trichoderma strains is necessary. In the present study, 10 isolates were ...obtained from Juglans mandshurica rhizosphere soils in Heilongjiang Province, and were identified as T. asperellum (four isolates), T. harzianum (four), T. hamatum (one), T. atroviride (one). The fastest-growing isolate per species on potato dextrose agar medium were further evaluated in stress tolerance tests (salt, alkali, nutritional stress, and low temperature) and confrontation assays (eight pathogens), which showed that T. asperellum TaspHu1 possessed the best adaptation and biological control ability. Then, Solanum lycopersicum (tomato) seeds were sown and treated with a series of concentrations of TaspHu1 spore suspension, as was unsown soil. Tomato seedlings treated by TaspHu1 had a significantly greater height, stem diameter, soluble protein content and soluble sugar content. Furthermore, their nitrate reductase activity and catalase activity were significantly increased, and these promoting effects depended on the concentration of the spore suspension. Meanwhile, a decrease in chlorophyll content was observed in the tomato seedlings treated with TaspHu1. In addition, strain TaspHu1 enhanced the tomato seedlings’ absorption of available nitrogen, but did not influence the soil available nitrogen content. Furthermore, the resistance of tomato seedlings against Alternaria alternata was enhanced by TaspHu1 (smaller, fewer leaf spots), the seedlings’ hormone signal transduction genes JAR1, MYC2, NPR1, PR1, and GH3.2 were highly expressed. Thus, TaspHu1 is a promising biocontrol candidate for use in agriculture and forestry.
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Kefir grains consist of complex symbiotic mixtures of bacteria and yeasts, and are reported to impart numerous health-boosting properties to milk and water kefir beverages. The objective of this work ...was to investigate the microbial communities in kefir grains, and explore the possibility of deriving useful probiotic strains from them. A total of 158 microbial strains, representing six fungal and 17 bacterial species, were isolated from milk and water kefir grains collected from a Singapore-based homebrewer. Based on 16S rRNA sequencing, isolated genera included
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
, and
. To characterize these isolates, a funnel approach, involving numerous phenotypic and genomic screening assays, was applied to identify kefir-derived microbial strains with the highest probiotic potential. Particular focus was placed on examining the pathogen inhibitory properties of kefir isolates toward enteric pathogens which pose a considerable global health burden. Enteric pathogens tested include species of
,
,
,
,
,
, and
. Well diffusion assays were conducted to determine the propensity of kefir isolates to inhibit growth of enteric pathogens, and a competitive adhesion/exclusion assay was used to determine the ability of kefir isolates to out-compete or exclude attachment of enteric pathogens to Caco-2 cells. Seven bacterial strains of
,
,
,
, and
, were ultimately identified as potential probiotics, and combined to form a "kefir probiotics blend." Desirable probiotic characteristics, including good survival in acid and bile environments, bile salt hydrolase activity, antioxidant activity, non-cytotoxicity and high adhesion to Caco-2 cells, and a lack of virulence or antimicrobial resistance genes. In addition, vitamin and γ-aminobutyric acid (GABA) synthesis genes, were identified in these kefir isolates. Overall, probiotic candidates derived in this study are well-characterized strains with a good safety profile which can serve as novel agents to combat enteric diseases. These kefir-derived probiotics also add diversity to the existing repertoire of probiotic strains, and may provide consumers with alternative product formats to attain the health benefits of kefir.
accounts for a significant number of foodborne illnesses around the world.
is microaerophilic and typically does not survive efficiently in oxygen-rich conditions. We recently reported that ...hyper-aerotolerant (HAT)
are highly prevalent in retail poultry meat. To assess the capabilities of HAT
in foodborne transmission and infection, in this study, we investigated the prevalence of virulence genes in HAT
and the survival in poultry meat in atmosphere at a refrigeration temperature. When we examined the prevalence of eight virulence genes in 70
strains from raw poultry meat, interestingly, the frequencies of detecting virulence genes were significantly higher in HAT
strains than aerosenstive
strains. This suggests that HAT
would potentially be more pathogenic than aerosensitive
. Under aerobic conditions, aerosensitive
survived at 4°C in raw poultry meat for 3 days, whereas HAT
survived in poultry meat for a substantially extended time; there was a five-log CFU reduction over 2 weeks. In addition, we measured the effect of other gas conditions, including N
and CO
, on the viability of HAT
in comparison with aerosensitive and aerotolerant strains. N
marginally affected the viability of
. However, CO
significantly reduced the viability of
both in culture media and poultry meat. Based on the results, modified atmosphere packaging using CO
may help us to control poultry contamination with HAT
.
Botrytis cinerea and Penicillium expansum produce deterioration in fruit quality, causing losses to the food industry. Thus, plant essential oils (EOs) have been proposed as a sustainable alternative ...for minimizing the application of synthetic fungicides due to their broad-spectrum antifungal properties. This study investigated the efficacy of five EOs in suppressing the growth of B. cinerea and P. expansum and their potential antifungal mechanisms. EOs of Mentha × piperita L., Origanum vulgare L., Thymus vulgaris L., Eucalyptus globules Labill., and Lavandula angustifolia Mill., were screened for both fungi. The results showed that the EO of T. vulgaris and O. vulgare were the most efficient in inhibiting the growth of B. cinerea and P. expansum. The concentration increase of all EO tested increased fungi growth inhibition. Exposure of fungi to EOs of T. vulgaris and O. vulgare increased the pH and the release of constituents absorbing 260 nm and soluble proteins, reflecting membrane permeability alterations. Fluorescence microscopic examination revealed that tested EOs produce structural alteration in cell wall component deposition, decreasing the hypha width. Moreover, propidium iodide and Calcein-AM stains evidenced the loss of membrane integrity and reduced cell viability of fungi treated with EOs. Fungi treated with EOs decreased the mitochondria activity and the respiratory process. Therefore, these EOs are effective antifungal agents against B. cinerea and P. expansum, which is attributed to changes in the cell wall structure, the breakdown of the cell membrane, and the alteration of the mitochondrial activity.
•Essential oils (EOs) have antifungal activity against B. cinérea and P. expansum.•EOs promote the release of fungal cell constituents of B. cinérea and P. expansum.•EO of O. vulgare and T. vulgaris altered fungal fluidity of cell membrane.•EO of O. vulgare and T. vulgaris altered the viability of spores and mycelia.•EO produce fungal physiological changes in mitochondria and cell wall of fungi.
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Microbial volatiles can promote plant growth and suppress diseases, nematodes and insects. Our knowledge of the effects of microbial volatiles on monocots such as rice and its pathogens and pests is ...still incomplete. As part of a screening initiative for beneficial bacterial species, we identified three strains (Bacillus sp., Paenibacillus sp. and Xanthomonas sp.) lethal to the rice root-knot nematode (Meloidogyne graminicola). Using both in vitro and in planta dual-chamber pot experiments, we found that volatiles from the beneficial bacteria were lethal to M. graminicola J2s and significantly reduced infection of susceptible rice. We conducted similar in vitro and in planta experiments against rice bacterial leaf blight Xanthomonas oryzae pv. oryzae. Exposure to bacterial volatiles inhibited the growth of X. oryzae pv. oryzae by 50–60% in vitro, but did not impact infection in planta. Finally, we found that bacterial volatiles from Bacillus sp. and Xanthomonas sp. inhibited rice germination and seedling development in vitro but did not affect plant growth in planta. These findings suggest that volatiles from beneficial bacteria have the potential to control M. graminicola, but that high volatile concentrations may inhibit plant growth.
•Bacterial volatiles were rapidly toxic to M. incognita in vitro.•Bacterial volatiles inhibited X. oryzae growth in vitro but not in planta.•Bacterial volatiles did not affect rice germination and seedling growth in planta.
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Potted poinsettia (Euphorbia pulcherrima) is one of the most important greenhouse ornamental crops in the United States, with an estimated wholesale value of $191 million in 15 top-producing states ...(USDA-NASS 2019). Because it is one of the most popular holiday flowers worldwide, limiting the losses of poinsettia plants from disease is critical to production (Lookabaugh et al. 2020). Pythium aphanidermatum is a recurrent disease and the predominant Pythium species causing poinsettia root rot disease, thereby significantly affecting poinsettia production in greenhouses across the United States (Lookabaugh et al. 2020; Múnera et al. 2019). Under favorable environmental conditions, P. aphanidermatum causes stunting, root rot, wilting, defoliation, chlorosis, and, in severe cases, plant death (Lookabaugh et al. 2017). Soilless substrate can be conducive to Pythium root rot because it has limited microbial activity (Stephens and Stebbins 1985); however, greenhouses may purchase plantlets or cuttings that are infected but asymptomatic from propagation greenhouses (Moorman 1986). When Pythium successfully intrudes into greenhouses, it can infect the whole greenhouse and become a source of primary inoculum (Krasnow and Hausbeck 2017). Because of the monocultural and humid Pythium-favorable environment of greenhouses, mycelium is easy to survive and reproduce, thus making Pythium an intractable problem (Krasnow and Hausbeck 2017). Replacing peatmoss, a commonly used soilless substrate, for poinsettia production with biochar provides several benefits, including mitigating climate change, increasing plant yield, and protecting wildlife habitats (Alexander et al. 2008). Biochar is a carbon-rich byproduct of pyrolysis (a main method for biofuel production), which is a process of thermochemical biomass decomposition under an oxygen-depleted or oxygen-limited environment with a specific period of time and temperature conditions (Demirbas and Arin 2002; Lehmann 2007). Several studies have shown that biochar can replace peatmoss-based substrate for greenhouse plant production such as tomato (Solanum lycopersicum), pepper (Capsicum annuum), mint (Mentha spp.), basil (Ocimum basilicum), Easter lily (Lilium longiflorum) and poinsettia (Guo et al. 2018a; Huang et al. 2019; Yan et al. 2020; Yu et al. 2020). Replacing peatmoss-based substrate with biochar has been proven to reduce the environmental concerns associated with peatmoss, such as rare wildlife habitat destruction, wetland ecosystem disturbance, and climate change interference (Alexander et al. 2008). Additionally, incorporating biochar in the substrate could reduce the initial investment for growers; because the price of peatmoss has been increasing, growers’ profits, especially when transportation costs are considered, have been hindered (Gu et al. 2013). Biochar can replace peatmoss for poinsettia plant production (Guo et al. 2018b) and has the potential to suppress plant diseases in different plant-pathogen systems. For instance, incubating sandy soil for 20 d and adding 1.33% (weight/weight) corn straw biochar (pH 9.73) in the container before transplanting suppressed pepper blight disease because of the improvement of soil chemical properties and increased beneficial microorganisms (Wang et al. 2019). Other studies with biochar-amended soil control disease caused by Pythium spp. were also reported with biochar at relatively low rates (≤3% weight/weight) (Jaiswal et al. 2019). In most cases, biochar provides synergistic effects with other components, and Trichoderma spp. has been reported as a reliable biological control agent for a wide range of pathogens, including P. aphanidermatum (Manoharachary and Nagaraju 2020). For instance, T. asperellum was proven to suppress tomato damping-off caused by P. aphanidermatum (Kipngeno et al. 2015). It has been shown that the efficacy of spent mushroom substrate against cucumber damping-off caused by P. aphanidermatum was related to the presence of Trichoderma spp. in the substrate (Al-Malikya et al. 2018). To date, there are not enough studies focusing on biochar suppressing plant disease development, and the biochar incorporation rate is relatively low (range, 0.5%–3%). The highest rate of biochar used in the phytopathogenic system was 50% (by volume) for testing its effects on Pythium ultimum with different crops (Gravel et al. 2013). The potential mechanisms of how biochar may influence plant disease include both direct and indirect influences on pathogens. For example, the chemical compounds of biochar affect pathogen growth; the physicochemical properties of biochar improve soil nutrients availability and abiotic conditions; the physical properties of biochar help absorb toxins and enzymes produced by pathogens, thus reducing virulence; the presence of biochar induces systemic resistance into host plants; and the physical properties of biochar enhance abundance and/or activities of beneficial microbes (Bonanomi et al. 2015; Graber et al. 2014). Because of the complexity of the biochar-plant-media-microorganisms system, it is difficult to decipher which mechanism is responsible for biochar impact disease development in any given phytopathogenic system (Graber et al. 2014). Except for the chemical compound mechanism, which can be identified and measured separately by removing the physical and chemical properties of biochar and their influences on pathogen and host plants, other mechanisms are difficult to identify and measure separately. We conducted an in vitro test and greenhouse trial to identify which mechanism is involved in the biochar-poinsettia-P. aphanidermatum system and test the effects of biochar on poinsettia root rot disease development.
Wolbachia
have been developed as a tool for protecting humans from mosquito populations and mosquito-borne diseases. The success of using
Wolbachia
relies on the facts that
Wolbachia
are maternally ...transmitted and that
Wolbachia
-induced cytoplasmic incompatibility provides a selective advantage to infected over uninfected females, ensuring that
Wolbachia
rapidly spread through the target pest population. Most transinfected
Wolbachia
exhibit a strong antiviral response in novel hosts, thus making it an extremely efficient technique. Although
Wolbachia
has only been used to control mosquitoes so far, great progress has been made in developing
Wolbachia
-based approaches to protect plants from rice pests and their associated diseases. Here, we synthesize the current knowledge about the important phenotypic effects of
Wolbachia
used to control mosquito populations and the literature on the interactions between
Wolbachia
and rice pest planthoppers. Our aim is to link findings from
Wolbachia
-mediated mosquito control programs to possible applications in planthoppers.
•First study on the fungal endophytic community isolated from feijoa fruit.•Two different cultivars host antagonistic fungi against Colletotrichum spp.•The most resistant cultivar hosted more ...biological control fungal agents.•T. harzianum, C. rosea and T. amestolkiae antagonized Colletotrichum spp.
Feijoa sellowiana (O. Berg) Burret is a tropical fruit from South America known as pineapple-guava or feijoa. Anthracnose is a fungal-caused disease that harms feijoa, and may completely reduce fruit production. The endophytic microbiota of feijoa fruits from native cultivars may provide new biocontrol agents against anthracnose. This work aimed to evaluate the diversity of endophytic cultivable fungi in feijoa fruits from two Brazilian native cultivars and verify potential agents against anthracnose pathogens: Colletotrichum nymphaeae and Colletotrichum siamense. The cultivable fungal diversity in feijoa fruits was assessed by fungi isolation, followed by fungal identification, through sequencing the ITS region of rDNA, and estimation of species abundance and frequency. Later, the antagonism of selected isolates was tested against Colletotrichum spp. by direct confrontation. Results demonstrated that isolated fungal communities slightly differed between the two cultivars. There was no difference in the Shannon index between the two cultivars. However, abundance and frequency of endophytes was respectively, 40% and 53% higher in the most resistant cultivar (Mattos), where Trichoderma harzianum, Trichoderma hamatum, Clonostachys rosea and Clonostachys rhizophaga were exclusively found. C. rosea and T. harzianum from cultivar 'Mattos', and Talaromices amestolkiae found in both cultivars ('Mattos' and 'Alcantara'), reduced mycelial growth and sporulation of Colletotrichum spp. Therefore, the endophytic cultivable community was slightly more abundant and rich in the most resistant cultivar of feijoa by encompassing more antagonistic species of fungi. This work also described for the first time the potential of endophytic fungi as biocontrol agents of feijoa pathogens.
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