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1.
Arch Microbiol ; 202(2): 391-398, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31680188

RESUMO

Bacterial surface molecules have an important role in the rhizobia-legume symbiosis. Ensifer meliloti (previously, Sinorhizobium meliloti), a symbiotic Gram-negative rhizobacterium, produces two different exopolysaccharides (EPSs), termed EPS I (succinoglycan) and EPS II (galactoglucan), with different functions in the symbiotic process. Accordingly, we undertook a study comparing the potential differences in alfalfa nodulation by E. meliloti strains with differences in their EPSs production. Strains recommended for inoculation as well as laboratory strains and native strains isolated from alfalfa fields were investigated. This study concentrated on EPS-II production, which results in mucoid colonies that are dependent on the presence of an intact expR gene. The results revealed that although the studied strains exhibited different phenotypes, the differences did not affect alfalfa nodulation itself. However, subtle changes in timing and efficacy to the effects of inoculation with the different strains may result because of other as-yet unknown factors. Thus, additional research is needed to determine the most effective inoculant strains and the best conditions for improving alfalfa production under agricultural conditions.


Assuntos
Galactanos/metabolismo , Glucanos/metabolismo , Medicago sativa/metabolismo , Medicago sativa/microbiologia , Polissacarídeos Bacterianos/metabolismo , Sinorhizobium meliloti/metabolismo , Proteínas de Bactérias/genética , Fertilizantes/microbiologia , Regulação Bacteriana da Expressão Gênica , Nodulação/fisiologia , Simbiose/fisiologia
2.
J Anim Sci ; 98(1)2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31850497

RESUMO

Fescue toxicosis is problematic for growing steers, causing lower DMI and productivity when fed endophyte-infected (E+) tall fescue. A complete understanding of underlying mechanisms of how fescue toxicosis affects growing steers is lacking. Therefore, the overall objective of this multiexperiment study was to determine whether ruminally dosed ergovaline (ERV) affects rumen motility, rumen contents, and eating patterns. In Exp. 1, an 8-h period to assess ruminal motility began 4 h after feeding by monitoring pressure changes using a wireless system for 21 d. Eight ruminally cannulated steers (283 kg BW) were pair fed with alfalfa cubes (1.5 × NEm) and assigned to endophyte free (E-; 0 µg ERV/kg BW/d) or E+ treatment (20 µg ERV/kg BW/d). Overall, E+ steers had more frequent rumen contractions (Seed P = 0.05 and day of feeding P = 0.02). On days 7 to 9, both treatments showed lower frequencies and E- steers had greater amplitude of contractions (P < 0.001) that corresponded with decreased DMI. In Exp. 2, steers remained in pairs assigned in Exp. 1 (322 kg BW), but reversed seed treatments while increasing ERV levels (titrated 0, 5, 10, 15, and 20 µg ERV/kg BW/d over 57 d). There were no differences between E- and E+ for frequency (P = 0.137) or amplitude of contractions (P = 0.951), but increasing ERV dosage, decreased frequency (P = 0.018) and amplitude (P = 0.005), coinciding with lower DMI. In Exp. 3, 8 steers (589 kg) were pair fed and ruminally dosed 15 µg ERV/kg BW/d, and rumen motility data were collected for 21 d. E- steers showed higher amplitude and lower frequency of contractions than E+ steers with seed (P < 0.001), day (P < 0.001), and seed × day (P < 0.04) effects, but rumen fill was not different between E- and E+ (P > 0.29). Serum prolactin concentrations were lower in E+ steers in Exp. 1 to 3. Eating patterns of pair-fed E- and E+ steers were relatively slower in E+ than E- (Exp. 4) by measuring every 2 h across 24 h. Number of meals were higher in E+ than E- steers, but meal duration and meal size were not different between treatments. Rumen content (DM%) tended to be higher in E+ than in E- when steers were fed once a day (P = 0.07), but there was no difference for rumen content (DM%) when E- and E+ steers were fed 12 times a day (P = 0.13). These results suggest the changes in rumen fill associated with fescue toxicosis may be driven more by changes in feeding behavior and eating pattern rather than by changes in motility.


Assuntos
Ergotaminas/efeitos adversos , Comportamento Alimentar/efeitos dos fármacos , Festuca/química , Intoxicação por Plantas/veterinária , Ração Animal/análise , Animais , Bovinos , Digestão , Ingestão de Alimentos , Endófitos , Masculino , Medicago sativa/microbiologia , Prolactina , Distribuição Aleatória , Sementes/microbiologia
3.
Int J Food Microbiol ; 312: 108374, 2020 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-31669765

RESUMO

Salmonella enterica outbreaks in sprouts originate from contaminated seeds; conventional prevention technologies have been reported from many research institutes. In this study, we applied a biological control approach to inhibit S. enterica growth using the seed-dwelling non-antagonistic bacteria. We isolated non-antibacterial seed-dwelling bacteria from vegetable sprouts. A total of 206 bacteria exhibiting non-antibacterial activity against S. enterica were subjected to alfalfa sprout development tests. Eight isolates exhibiting no deleterious effect on the growth of alfalfa sprouts were tested for S. enterica growth inhibition on alfalfa seeds and sprouts, and an isolate EUS78 was finally selected for further investigation. Based on 16S rRNA, gyrB, and rpoB gene sequence analyses, strain EUS78 was identified as Erwinia persicina. In population competition, the S. enterica population increased by >3 log CFU/g after 6 days of alfalfa sprout growth, whereas S. enterica growth was significantly inhibited by treatment with EUS78 (P < .05). This effect of S. enterica growth inhibition by EUS78 was sustained until the end of the alfalfa sprout harvest. Overall, bacterial strain EUS78 significantly reduced S. enterica growth on alfalfa sprouts in a manner consistent with competitive exclusion. These findings led us to monitor EUS78 behavior on seeds during early sprout development using fluorescence and scanning electron microscopy. Strain EUS78 initially colonized alfalfa sprout seed coat edges, cotyledons, and finally root surfaces during early sprout germination. As alfalfa sprouts grew, EUS78 bacterial cells established colonies on newly emerged plant tissues such as root tips. The results of this study suggest that strain EUS78 has potential as a biological control agent to inhibit S. enterica contamination in the sprout food industry.


Assuntos
Antibiose/fisiologia , Agentes de Controle Biológico , Erwinia/fisiologia , Medicago sativa/microbiologia , Salmonella enterica/crescimento & desenvolvimento , Sementes/microbiologia , DNA Girase/genética , RNA Polimerases Dirigidas por DNA/genética , Erwinia/genética , Microbiologia de Alimentos , Indústria de Processamento de Alimentos , Germinação/fisiologia , Medicago sativa/química , RNA Ribossômico 16S/genética , Verduras/microbiologia
4.
Plant Dis ; 103(12): 3199-3208, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31642735

RESUMO

In this study, we provide a polyphasic characterization of 18 Pseudomonas spp. strains associated with alfalfa leaf spot symptoms in Iran. All of the strains were pathogenic on alfalfa, although the aggressiveness and symptomology varied among the strains. All strains but one were pathogenic on broad bean, cucumber, honeydew, and zucchini, whereas only a fraction of the strains were pathogenic on sugar beet, tomato, and wheat. Syringomycin biosynthesis genes (syrB1 and syrP) were detected using the corresponding PCR primers in all of the strains isolated from alfalfa. Phylogenetic analyses using the sequences of four housekeeping genes (gapA, gltA, gyrB, and rpoD) revealed that all of the strains except one (Als34) belong to phylogroup 2b of P. syringae sensu lato, whereas strain Als34 placed within phylogroup 1 close to the type strain of P. syringae pv. apii. Among the phylogroup 2b strains, nine strains were phylogenetically close to the P. syringae pv. aptata clade, whereas the remainder were scattered among P. syringae pv. atrofaciens and P. syringae pv. syringae strains. Pathogenicity and host range assays of the bacterial strains evaluated in this study on a set of taxonomically diverse plant species did not allow us to assign a "pathovar" status to the alfalfa strains. However, these results provide novel insight into the host range and phylogenetic position of the alfalfa-pathogenic members of P. syringae sensu lato, and they reveal that phenotypically and genotypically heterogeneous strains of the pathogen cause bacterial leaf spot of alfalfa.


Assuntos
Medicago sativa , Pseudomonas syringae , Genes Bacterianos/genética , Genótipo , Irã (Geográfico) , Medicago sativa/microbiologia , Filogenia , Doenças das Plantas/microbiologia , Pseudomonas syringae/genética
5.
Artigo em Inglês | MEDLINE | ID: mdl-31610770

RESUMO

An epidemiological investigation and a retrospective case-control study were conducted into an outbreak of Salmonella Havana in alfalfa sprouts, in Adelaide, Australia. In total, 31 cases of S. Havana were notified during June and July 2018 and linked to the outbreak. Eighteen cases and 54 unmatched controls were included in a case-control study. Results from the case-control study indicated an increased risk of illness linked to the consumption of alfalfa sprouts; this was supported by trace-back, sampling and environmental investigations. This outbreak of S. Havana was caused by consumption of alfalfa sprouts from one local sprouts producer. It is unclear as to when in the production of alfalfa sprouts the contamination occurred. However, contaminated seeds and poor pest control are the most likely causes. This investigation highlights the importance of ensuring that producers take appropriate action to minimise the likelihood of contamination and to comply with legislation and standards for primary production and food safety.


Assuntos
Contaminação de Alimentos , Microbiologia de Alimentos , Medicago sativa/microbiologia , Infecções por Salmonella/epidemiologia , Salmonella enterica , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos de Casos e Controles , Surtos de Doenças , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Sementes/microbiologia , Austrália do Sul/epidemiologia , Adulto Jovem
6.
J Environ Sci Health B ; 54(12): 964-971, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31429367

RESUMO

Sensitivity of 24 isolates of Colletotrichum destructivum O'Gara, collected from alfalfa plants in Serbia, to eight selected fungicides, was investigated in this study. Molecular identification and pathogenicity test of isolates tested were also performed. Fungicide sensitivity was evaluated in vitro, using mycelial growth assay method. All isolates exhibited significant pathogenicity, causing necrosis at the alfalfa seedling root tips two days after inoculation. Using the primer pair GSF1-SR1 and by comparing the amplified fragments of the tested isolates with the marker (M), the presence of the amplicon of the expected size of about 900 bp was determined for all isolates. The isolates tested in this study showed different sensitivity towards fungicides in vitro. Mycelial growth was highly inhibited by QoI (quinone outside inhibitors) fungicide pyraclostrobin (mean EC50=0.39 µg mL-1) and by DMI (demethylation-inhibiting) fungicide tebuconazole (mean EC50=0.61 µg mL-1), followed by azoxystrobin (mean EC50=2.83 µg mL-1) and flutriafol (mean EC50=2.11 µg mL-1). Multi-site fungicide chlorothalonil and MBC (methyl benzimidazole carbamate) fungicide thiophanate-methyl evinced moderate inhibition with mean EC50=35.31 and 62.83 µg mL-1, respectively. Thirteen isolates were sensitive to SDHI (succinate dehydrogenase inhibitors) fungicide boscalid and fluxapyroxad, (mean EC50=0.49 and 0.19 µg mL-1, respectively), while the rest of isolates were highly resistant.


Assuntos
Colletotrichum/efeitos dos fármacos , Fungicidas Industriais/toxicidade , Medicago sativa/microbiologia , Estrobilurinas/toxicidade , Colletotrichum/enzimologia , Colletotrichum/crescimento & desenvolvimento , Proteínas Fúngicas/antagonistas & inibidores , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Doenças das Plantas/microbiologia , Pirimidinas/toxicidade , Sérvia , Succinato Desidrogenase/antagonistas & inibidores , Succinato Desidrogenase/genética , Succinato Desidrogenase/metabolismo , Triazóis/toxicidade
7.
Lett Appl Microbiol ; 69(4): 252-257, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31429475

RESUMO

Alfalfa sprouts have been implicated in multiple foodborne disease outbreaks. This study evaluated the growth of Listeria monocytogenes during sprouting of alfalfa seeds and the effectiveness of daily chlorine dioxide & ozone rinsing in controlling the growth. Alfalfa seeds inoculated with L. monocytogenes were sprouted for 5 days (25°C) with a daily aqueous ClO2 (3 ppm, 10 min) or ozone water (2 ppm, 5 min) rinse. Neither treatment significantly reduced the growth of L. monocytogenes on sprouting alfalfa seeds. The initial level of L. monocytogenes was 3·44 ± 0·27, which increased to c. 7·0 log CFU per g following 3 days of sprouting. There was no significant difference in the bacterial population between the treatment schemes. Bacterial distribution in roots (7·63 ± 0·511 log CFU per g), stems (7·51 ± 0·511 log CFU per g) and leaves (7·41 ± 0·511 log CFU per g) were similar after 5 days. Spent sanitizers had significantly lower levels of bacterial populations compared to the spent distilled water control. The results indicated that sprouting process provides a favourable condition for the growth of L. monocytogenes and the sanitizer treatment alone may not be able to reduce food safety risks. SIGNIFICANCE AND IMPACT OF THE STUDY: Sprouts are high-risk foods. Consumption of raw sprouts is frequently associated with foodborne disease outbreaks. Optimum sprouting procedure involves soaking seeds in water followed by daily water rinsing to maintain a moist environment that is also favourable for the growth of pathogenic micro-organisms. The present study emphasized the potential food safety risks during sprouting and the effect of applying daily sanitizer rinsing in the place of water rinsing to reduce those risks. The finding of this study may be useful in the development of pre-harvest and post-harvest risk management strategies.


Assuntos
Compostos Clorados/farmacologia , Doenças Transmitidas por Alimentos/prevenção & controle , Listeria monocytogenes/crescimento & desenvolvimento , Medicago sativa/microbiologia , Óxidos/farmacologia , Água/farmacologia , Contagem de Colônia Microbiana , Microbiologia de Alimentos/métodos , Inocuidade dos Alimentos/métodos , Ozônio/farmacologia , Raízes de Plantas/microbiologia , Sementes/microbiologia , Verduras/microbiologia , Água/química
8.
Environ Microbiol Rep ; 11(5): 727-735, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31430046

RESUMO

The nitrogen (N) fertilizer required to supply a bioenergy industry with sufficient feedstocks is associated with adverse environmental impacts, including loss of oxidized reactive nitrogen through leaching and the production of the greenhouse gas nitrous oxide (N2 O). We examined effects on crop yield, N fate and the response of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) to conventional fertilizer application or intercropping with N-fixing alfalfa, for N delivery to switchgrass (Panicum virgatum), a potential bioenergy crop. Replicated field plots in Prosser, WA, were sampled over two seasons for reactive nitrogen, N2 O gas emissions, and bacterial and archaeal ammonia monooxygenase gene (amoA) counts. Intercropping with alfalfa (70:30, switchgrass:alfalfa) resulted in reduced dry matter yields compared to fertilized plots, but three times lower N2 O fluxes (≤ 4 g N2 O-N ha-1 d-1 ) than fertilized plots (12.5 g N2 O-N ha-1 d-1 ). In the fertilized switchgrass plots, AOA abundance was greater than AOB abundance, but only AOB abundance was positively correlated with N2 O emissions, implicating AOB as the major producer of N2 O emissions. A life cycle analysis of N2 O emissions suggested the greenhouse gas emissions from cellulosic ethanol produced from switchgrass intercropped with alfalfa cultivation would be 94% lower than emissions from equivalent gasoline usage.


Assuntos
Amônia/metabolismo , Fertilizantes , Medicago sativa/microbiologia , Óxido Nitroso/análise , Panicum/microbiologia , Microbiologia do Solo , Agricultura , Medicago sativa/crescimento & desenvolvimento , Oxirredução , Washington
9.
Food Microbiol ; 84: 103261, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31421775

RESUMO

Sprouts are considered a healthy ready-to-eat food and has gained popularity in recent years. The objective of the present study was to determine the dynamics of sprouts' microbiome during cold storage to the end of their shelf-life at home. The microbiological quality of fresh alfalfa (Medicago sativa) and mung bean (Vigna radiata) sprouts from two commercial brands was tested and the number of APC ranges from 5.0 to 8.7 log CFU/g in alfalfa and 6.7 to 9.3 log CFU/g in mung bean sprouts. In the case of alfalfa, but not mung beans, there were differences in the mean numbers of APC between the two brands. The number of coliform bacteria ranges from 4.3 to 7.7 log CFU/g in alfalfa and 4.1 to 8.1 log CFU/g in mung bean sprouts. Four independent batches of sprouts were used for DNA preparation and were sampled immediately after purchase and once a week during subsequent storage in refrigerator until the end of their shelf-life. Microbial population of the sprouts was determined using next generation sequencing of 16S rRNA amplicons. Alfalfa sprouts were dominated by Pseudomonas throughout the storage time with relative abundance of >60% at 3 weeks. Fresh mung bean sprouts were dominated by both Pseudomonas and Pantoea, but Pantoea became the dominant taxa after 2 weeks of storage, with >46% of relative abundance. The bacterial communities associated with sprouts were largely dependent on the sprout type, and less dependent on the brand. The species richness and diversity declined during storage and the development of spoilage. Among the 160 genera identified on sprouts, 23 were reported to contain known spoilage-associated species and 30 genera comprise potential human pathogenic species. This study provides new insight into the microbiome dynamics of alfalfa and mung bean sprouts during cold storage.


Assuntos
Microbiologia de Alimentos , Medicago sativa/microbiologia , Microbiota , Refrigeração , Sementes/microbiologia , Vigna/microbiologia , Bactérias/genética , Bactérias/crescimento & desenvolvimento , Contagem de Colônia Microbiana , Armazenamento de Alimentos , Germinação , RNA Ribossômico 16S , Sementes/crescimento & desenvolvimento , Vigna/crescimento & desenvolvimento
10.
J Appl Microbiol ; 127(4): 985-995, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31287933

RESUMO

AIMS: Ferulic acid esterase (FAE)-producing Lactobacillus species isolated from ensiled Elymus nutans growing on the Qinghai-Tibetan plateau were characterized, and effects of their application to the alfalfa ensiling process and the evidence to synergic effect between cellulase and FAE were investigated. METHODS AND RESULTS: The results of 16S rRNA gene sequence and species-specific polymerase chain reaction amplification showed that two screened strains with high FAE activity were Lactobacillus plantarum A1 (LP) and L. brevis A3 (LBr). The optimum temperature and pH for the LP and LBr was 37°C and 6·4 respectively. The FAE exhibited a good stability at temperatures between 25 and 50°C and at pH values of 5·0-7·0. The two strains and a commercial cellulase (CE) were applied as additives to alfalfa silage. After 60 days of ensiling, the lactic acid in the control and CE groups were significantly lower than those of the other treatment groups. The neutral detergent fibre and acid detergent fibre contents in the LP group were significantly lower than those observed in the other groups. At the same time, the combination of CE and FAE-producing lactic acid bacteria synergistically improved the fermentation quality of the silage. CONCLUSIONS: The addition of the FAE-producing strain of L. plantarum A1 to alfalfa silage improved its fermentation quality, and reduced the fibre content of the silage. SIGNIFICANCE AND IMPACT OF THE STUDY: The screened homo-fermentative and FAE-producing strain of L. plantarum A1 could be a candidate strain in improving fermentation quality and fibre digestibility of ensiled forages.


Assuntos
Hidrolases de Éster Carboxílico/metabolismo , Elymus/microbiologia , Lactobacillus/metabolismo , Medicago sativa , Silagem/microbiologia , Celulase/metabolismo , Fibras na Dieta/análise , Fermentação , Ácido Láctico/análise , Ácido Láctico/metabolismo , Lactobacillus/enzimologia , Lactobacillus/genética , Medicago sativa/química , Medicago sativa/microbiologia , RNA Ribossômico 16S/genética , Silagem/análise
11.
Mycorrhiza ; 29(4): 389-395, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31218402

RESUMO

Arbuscular mycorrhizal fungi (AMF) are considered a potential biotechnological tool for mitigating heavy metal (HM) toxicity. A greenhouse experiment was conducted to evaluate the impacts of the AM fungus Rhizophagus irregularis on cadmium (Cd) uptake, mycorrhizal colonization, and some plant growth parameters of Medicago sativa (alfalfa) in Cd-polluted soils. In addition, expression of two metal chelators (MsPCS1 (phytochelatin synthase) and MsMT2 (metallothionein)) and two metal transporter genes (MsIRT1 and MsNramp1) was analyzed using quantitative real-time PCR (qRT-PCR). Cd addition had a significant negative effect on mycorrhizal colonization. However, AMF symbiosis promoted the accumulation of biomass under both stressed and unstressed conditions compared with non-mycorrhizal (NM) plants. Results also showed that inoculation with R. irregularis significantly reduced shoot Cd concentration in polluted soils. Transcripts abundance of MsPCS1, MsMT2, MsIRT1, and MsNRAMP1 genes were downregulated compared with NM plants indicating that metal sequestration within hyphal fungi probably made Cd concentration insufficient in root cells for induction of these genes. These results suggest that reduction of shoot Cd concentration in M. sativa colonized by R. irregularis could be a promising strategy for safe production of this plant in Cd-polluted soils.


Assuntos
Aminoaciltransferases/genética , Cádmio/metabolismo , Glomeromycota/fisiologia , Medicago sativa/metabolismo , Metalotioneína/genética , Micorrizas/fisiologia , Proteínas de Plantas/genética , Poluentes do Solo/metabolismo , Aminoaciltransferases/metabolismo , Transporte Biológico , Medicago sativa/genética , Medicago sativa/microbiologia , Metalotioneína/metabolismo , Proteínas de Plantas/metabolismo , Simbiose
12.
FEMS Microbiol Lett ; 366(7)2019 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-31062028

RESUMO

Polyamines are ubiquitous molecules containing two or more amino groups that fulfill varied and often essential physiological and regulatory roles in all organisms. In the symbiotic nitrogen-fixing bacteria known as rhizobia, putrescine and homospermidine are invariably produced while spermidine and norspermidine synthesis appears to be restricted to the alfalfa microsymbiont Sinorhizobium meliloti. Studies with rhizobial mutants deficient in the synthesis of one or more polyamines have shown that these compounds are important for growth, stress resistance, motility, exopolysaccharide production and biofilm formation. In this review, we describe these studies and examine how polyamines are synthesized and regulated in rhizobia.


Assuntos
Poliaminas/metabolismo , Sinorhizobium meliloti/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica , Medicago sativa/microbiologia , Sinorhizobium meliloti/genética , Sinorhizobium meliloti/crescimento & desenvolvimento
13.
Ecotoxicology ; 28(6): 599-611, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31140046

RESUMO

Copper-based fungicides have been used for a long time in viticulture and have accumulated in many vineyard soils. In this study, incrementing Cu(OH)2-based fungicide application from 0.05 to 5 g Cu kg-1 on two agricultural soils (an acidic sandy loam (L, pH 4.95) and an alkaline silt loam (D, pH 7.45)) resulted in 5 times more mobile Cu in the acidic soil. The most sensitive parameters of alfalfa (Medicago sativa) growing in these soils were the root nodule number, decreasing to 34% and 15% of the control at 0.1 g Cu kg-1 in soil L and at 1.5 g Cu kg-1 in soil D, respectively, as well as the nodule biomass, decreasing to 25% and 27% at 0.5 g Cu kg-1 in soil L and at 1.5 g Cu kg-1 in soil D, respectively. However, the enzymatic N2-fixation was not directly affected by Cu in spite of the presence of Cu in the meristem and the zone of effective N2-fixation, as illustrated by chemical imaging. The strongly different responses observed in the two tested soils reflect the higher buffering capacity of the alkaline silt loam and showed that Cu mitigation and remediation strategies should especially target vineyards with acidic, sandy soils.


Assuntos
Cobre/metabolismo , Fungicidas Industriais/efeitos adversos , Medicago sativa/efeitos dos fármacos , Fixação de Nitrogênio/efeitos dos fármacos , Nodulação/efeitos dos fármacos , Disponibilidade Biológica , Hidróxidos/metabolismo , Medicago sativa/crescimento & desenvolvimento , Medicago sativa/microbiologia
14.
Ecotoxicol Environ Saf ; 179: 241-248, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31051397

RESUMO

Using of arbuscular mycorrhizal fungi (AMF) has emerged as a new technique to alleviate the toxic metals stress through changing their chemical behavior. The present work was conducted as a factorial arrangement based on a completely randomized design to study the inoculation effects of Glomus intraradices, Glomus mosseae and Glomus etunicatum, on Pb and Zn fractions in the rhizosphere of alfalfa by using rhizobox technique in two agricultural soils with different Zn and Pb concentrations [with low (LH) and high (HH) concentration levels]. The results showed that AMF colonization promoted plant growth and lowered the shoot and root Pb and shoot Zn concentrations in the studied soils compared to uninoculated treatments. Mycorrhizal colonization significantly increased the Ca(NO3)2- extractable Zn and ORG-Zn (respectively 500 and 59.6% more than the uninoculated treatment) and decreased the OXI-Zn (20.32% less than the none inoculated treatment) in the HH soil. By contrast, mycorrhizae slightly increased the CARB, OXI and ORG-Zn forms in the LH soil compared to the uninoculation condition. In the AMF- treated HH soil, an increase was recorded in the Ca(NO3)2- extractable Pb, EXCH-Pb and CARB-Pb (respectively, 17.65, 3.09 and 14.22% compared to the none inoculated treatment) and a decrease in the OXI and ORG-Pb forms (respectively, 28.79 and 13.51% compared to the uninoculated treatment). A reverse status was observed for Pb changes in the LH soil. Depending on the contamination level, the mycorrhizal inoculation differentially affected the Pb and Zn fractions at different distances from the root surface. In the LH soil, at <5 mm distance (i.e. rhizospheric soil), the mycorrhizal inoculation decreased the CARB (about 17.99%) and OXI -Zn (about 29.63%) forms compared to bulk soil (i.e. > 5 mm distance) while ORG-Zn was increased up to 48.63%. However, Ca(NO3)2- extractable, CARB and ORG-Pb was increased in rhizosphere soil (respectively, 89.33, 3.84 and 6.14%) and OXI-Pb was decreased up to 10.36% compared to the bulk soil. In the HH soil, mycorrhizal inoculation increased the CARB and OXI-Zn (respectively, 1.76 and 5.71%) and OXI-Pb fractions (11.56%) compared to the <5 mm distances. Whereas, it reduced the Ca(NO3)2- extractable, EXCH, and ORG-Zn (Respectively, 52.70, 19.19 and 30.16%) and Ca(NO3)2- extractable, CARB and ORG-Pb (respectively, 47.18, 3.70 and 5.79%). These results revealed that depending on the soil contamination level and nature of the element, AMF colonization affects biogeochemical fractions of the metals and their accumulation in the plant tissues.


Assuntos
Glomeromycota/efeitos dos fármacos , Chumbo/análise , Medicago sativa/microbiologia , Micorrizas/efeitos dos fármacos , Rizosfera , Poluentes do Solo/análise , Zinco/análise , Biodegradação Ambiental , Glomeromycota/genética , Irã (Geográfico) , Medicago sativa/crescimento & desenvolvimento , Micorrizas/química , Distribuição Aleatória , Projetos de Pesquisa , Solo/química , Simbiose
15.
Plant Dis ; 103(7): 1565-1576, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31033401

RESUMO

Verticillium wilt caused by Verticillium alfalfae results in severe production losses in alfalfa crops and is a Class A quarantined disease in China. During 2015 to 2017, 365 alfalfa fields from 21 locations in six provinces were surveyed, and 45 fields from three closely located sites in Gansu, China were found to have alfalfa plants with symptoms typical of Verticillium wilt, with disease incidence of 12.6 to 53.6%. Isolates were identified to species using morphological characteristics and a maximum likelihood phylogeny of the concatenated partial sequences of actin, elongation factor, glyceraldehyde-3-phosphate dehydrogenase, and tryptophan synthase gene regions of Verticillium isolates. Isolation incidence was 93.9% from roots, 71.7% from stems, 66.1% from petioles, and 32.2% from leaves of field-infected plants, indicative of systemic disease and sporadic distribution of this pathogen. In greenhouse tests, the pathogen infected seedlings and colonized vascular tissues when inoculated on seeds, on root tips, in soil, or in injured, but not uninjured, aerial tissues, causing systemic symptoms like those in the field and significant losses. Pathogenicity testing also revealed that five locally grown perennial legumes (stylo, milkvetch, sainfoin, white clover, and red clover) could host V. alfalfae, with a high virulence to milkvetch, sainfoin, and stylo. This study confirmed that V. alfalfae has become established in some regions of Gansu, China and that is a risk to the alfalfa industry in China.


Assuntos
Medicago sativa , Verticillium , Virulência , China , Genes Fúngicos/genética , Especificidade de Hospedeiro , Medicago sativa/microbiologia , Doenças das Plantas/microbiologia , Verticillium/classificação , Verticillium/crescimento & desenvolvimento , Verticillium/patogenicidade , Verticillium/fisiologia , Virulência/genética
16.
Appl Environ Microbiol ; 85(11)2019 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-30902860

RESUMO

Contamination of fresh produce with pathogenic Escherichia coli, including Shiga-toxigenic E. coli (STEC), represents a serious risk to human health. Colonization is governed by multiple bacterial and plant factors that can impact the probability and suitability of bacterial growth. Thus, we aimed to determine whether the growth potential of STEC for plants associated with foodborne outbreaks (two leafy vegetables and two sprouted seed species) is predictive of the colonization of living plants, as assessed from growth kinetics and biofilm formation in plant extracts. The fitness of STEC isolates was compared to that of environmental E. coli isolates at temperatures relevant to plant growth. Growth kinetics in plant extracts varied in a plant-dependent and isolate-dependent manner for all isolates, with spinach leaf lysates supporting the highest rates of growth. Spinach extracts also supported the highest levels of biofilm formation. Saccharides were identified to be the major driver of bacterial growth, although no single metabolite could be correlated with growth kinetics. The highest level of in planta colonization occurred on alfalfa sprouts, though internalization was 10 times more prevalent in the leafy vegetables than in sprouted seeds. Marked differences in in planta growth meant that the growth potential of STEC could be inferred only for sprouted seeds. In contrast, biofilm formation in extracts related to spinach colonization. Overall, the capacity of E. coli to colonize, grow, and be internalized within plants or plant-derived matrices was influenced by the isolate type, plant species, plant tissue type, and temperature, complicating any straightforward relationship between in vitro and in planta behaviors.IMPORTANCE Fresh produce is an important vehicle for STEC transmission, and experimental evidence shows that STEC can colonize plants as secondary hosts, but differences in the capacity to colonize occur between different plant species and tissues. Therefore, an understanding of the impact that these plant factors have on the ability of STEC to grow and establish is required for food safety considerations and risk assessment. Here, we determined whether growth and the ability of STEC to form biofilms in plant extracts could be related to specific plant metabolites or could predict the ability of the bacteria to colonize living plants. Growth rates for sprouted seeds (alfalfa and fenugreek) but not those for leafy vegetables (lettuce and spinach) exhibited a positive relationship between plant extracts and living plants. Therefore, the detailed variations at the level of the bacterial isolate, plant species, and tissue type all need to be considered in risk assessment.


Assuntos
Meios de Cultura/química , Extratos Vegetais/química , Plantas/microbiologia , Escherichia coli Shiga Toxigênica/crescimento & desenvolvimento , Temperatura , Biofilmes/crescimento & desenvolvimento , Contagem de Colônia Microbiana , Contaminação de Alimentos/análise , Microbiologia de Alimentos , Inocuidade dos Alimentos , Especificidade de Hospedeiro , Cinética , Alface/microbiologia , Medicago sativa/microbiologia , Folhas de Planta/microbiologia , Plântula/microbiologia , Escherichia coli Shiga Toxigênica/isolamento & purificação , Spinacia oleracea/microbiologia , Trigonella/microbiologia , Verduras/microbiologia
17.
Int. microbiol ; 22(1): 111-120, mar. 2019. graf, tab
Artigo em Inglês | IBECS | ID: ibc-184819

RESUMO

Plant-microbe interactions such as rhizobacteria legumes are interesting in organic farming that has undergone significant expansion in the world. The organic agriculture is as an environment-friendly technique and a sustainable alternative to intensive agricultural system. Three types of soil were chosen, organic (ORG), conventional (CON), and fallow land (NA) to isolate soil bacteria-nodulating Medicago sativa, in order to develop microbial inoculants for use in agricultural sustainable system. Soil analysis revealed significant higher amounts of total nitrogen, organic carbon, total phosphorus, and matter detected in ORG. As for heavy metals, ORG showed high Cu content due to the authorized chemical use in organic farming. A sample of 130 bacteria was isolated from Medicago sativa nodule, genetically characterized by PCR/RFLP of ribosomal 16S RNAs, and a great dominance of Sinorhizobium meliloti (88.4%, 73.8%, and 55.5%) is obtained among NA-, CON-, and ORG-managed soils, respectively. The ORG showed the high bacterial diversity with 13.3% of non-identified strains. The resistance against five pesticides (Prosper, Cuivox, Fungastop, Nimbecidine, and Maneb) revealed a maximum of inhibitory concentration about 10 mg l−1 of Prosper, 12 mg l−1 of Cuivox, 6 ml l−1 of Fungastop, 7.5 ml l−1of Nimbecidine, and 25 ml l−1 of Maneb. The analysis of the symbiotic properties and plant growth-promoting potential revealed two efficient strains significantly increased alfalfa dry weight through producing siderophores, phosphorus, and indole acetic acid (13.6 mg ml−1 and 19.9 mg ml−1 respectively). Hence, we identify two tolerant and efficient strains, Achromobacter spanium and Serratia plymuthica, isolated from Medicago sativa nodule with valuable potential able to phytostabilize pesticide-contaminated soils


No disponible


Assuntos
Medicago sativa/microbiologia , Bactérias/isolamento & purificação , Nódulos Radiculares de Plantas/microbiologia , Antibacterianos/metabolismo , Carbono/análise , Praguicidas/metabolismo , Bactérias/classificação , Bactérias/genética , Análise por Conglomerados , DNA Bacteriano , DNA Ribossômico , Testes de Sensibilidade Microbiana , Nitrogênio/análise , Fósforo/análise , Polimorfismo de Fragmento de Restrição , RNA Ribossômico 16S , Análise de Sequência de DNA , Simbiose
18.
Int J Food Microbiol ; 295: 19-24, 2019 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-30784855

RESUMO

Seeds are usual source of contamination and their sprouts are commonly associated foodborne illness. Therefore, the aim of this study was to evaluate the antibacterial vapor phase efficiency of allspice, thyme and rosemary essential oils on two foodborne pathogens in in vitro and on alfalfa seeds, including the chemical profile of the tested EOs and their effect on the sensory characteristics of the sprouts. Antibacterial activity was determined through the minimal inhibitory concentration (MIC) of EOs in vapor phase to inhibit the growth of Listeria monocytogenes and Salmonella Typhimurium in culture media and on alfalfa seeds. Also, the germination and the effect on sensory characteristics of the sprouts were determined. Thyme EO was the most effective of the tested EOs on culture media and on alfalfa seeds, against both bacteria. When rosemary EO was tested against L. monocytogenes in alfalfa seeds, the MIC (4.0 mL/Lair) was higher, compared to the one obtained in culture media (2.7 mL/Lair). But when this EO was tested against S. Typhimurium, the MIC in alfalfa seeds was lower than in culture media (11.7 vs 13.3 mL/Lair). Allspice EO resulted more effective against both bacteria in alfalfa seeds (6.0 mL/Lair for L. monocytogenes and 6.7 mL/Lair for S. Typhimurium), compared to culture media (12.0 mL/Lair for L. monocytogenes and 13.3 mL/Lair for S. Typhimurium). Vapor phase EOs MICs resulted in significant (p ≤ 0.05) decreases of L. monocytogenes and S. Typhimurium counts compared to the control. There also was a significant (p ≤ 0.05) difference between systems (in vitro or on alfalfa seeds) despite the microorganism or the evaluated EO. Treatment alfalfa seed with vapor phase EOs, did not affect the seed germination. Sensory acceptability of the sprouts, obtained of treated seeds, did not were significant (p ≥ 0.05) different of the sprouts obtained from the non-treated seeds.


Assuntos
Microbiologia de Alimentos/métodos , Medicago sativa/microbiologia , Óleos Voláteis/farmacologia , Antibacterianos/farmacologia , Listeria monocytogenes , Medicago sativa/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Pimenta/química , Rosmarinus/química , Plântula/efeitos dos fármacos , Sementes/efeitos dos fármacos , Thymus (Planta)/química
19.
J Food Prot ; 82(3): 522-527, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30810377

RESUMO

The germination conditions of sprouted vegetables consisting of relatively high temperatures and humidity, low light, and abundance of nutrients are ideal for pathogen survival and growth. The continual occurrence of outbreaks and recalls associated with sprout vegetables indicate additional measures are needed to improve product safety. The objective of this study was to evaluate the efficacy of a mixture of Lactobacillus plantarum, Pediococcus acidilactici, and Pediococcus pentosaceus (LPP) against Listeria monocytogenes and Salmonella on alfalfa sprouts during 5 days of sprouting at 20°C and its influence on sprout quality. Alfalfa seeds were inoculated with L. monocytogenes or Salmonella (each at 1 and 3 log CFU/g) and LPP (7 log CFU/g). Populations of LPP were maintained at 7.5 to 8.0 log CFU/g throughout sprouting. LPP had a significant effect on the growth of L. monocytogenes and Salmonella ( P < 0.05). After 5 days of sprouting, populations of L. monocytogenes at an initial concentration of 1 and 3 log CFU/g of seeds treated with LPP were approximately 4.5 and 1.0 log CFU/g less than the untreated seeds, respectively. Populations of Salmonella at an initial concentration of 1 and 3 log CFU/g were 1.0 log CFU/g less than the control. LPP did not compromise the yield, seedling length, or pH of the sprouts.


Assuntos
Lactobacillus plantarum , Listeria monocytogenes , Medicago sativa/microbiologia , Pediococcus acidilactici , Pediococcus pentosaceus , Salmonella/crescimento & desenvolvimento , Antibiose , Contagem de Colônia Microbiana , Contaminação de Alimentos , Microbiologia de Alimentos , Lactobacillus plantarum/fisiologia , Listeria monocytogenes/crescimento & desenvolvimento , Pediococcus acidilactici/fisiologia , Pediococcus pentosaceus/fisiologia , Sementes , Verduras
20.
Int Microbiol ; 22(1): 111-120, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30810937

RESUMO

Plant-microbe interactions such as rhizobacteria legumes are interesting in organic farming that has undergone significant expansion in the world. The organic agriculture is as an environment-friendly technique and a sustainable alternative to intensive agricultural system. Three types of soil were chosen, organic (ORG), conventional (CON), and fallow land (NA) to isolate soil bacteria-nodulating Medicago sativa, in order to develop microbial inoculants for use in agricultural sustainable system. Soil analysis revealed significant higher amounts of total nitrogen, organic carbon, total phosphorus, and matter detected in ORG. As for heavy metals, ORG showed high Cu content due to the authorized chemical use in organic farming. A sample of 130 bacteria was isolated from Medicago sativa nodule, genetically characterized by PCR/RFLP of ribosomal 16S RNAs, and a great dominance of Sinorhizobium meliloti (88.4%, 73.8%, and 55.5%) is obtained among NA-, CON-, and ORG-managed soils, respectively. The ORG showed the high bacterial diversity with 13.3% of non-identified strains. The resistance against five pesticides (Prosper, Cuivox, Fungastop, Nimbecidine, and Maneb) revealed a maximum of inhibitory concentration about 10 mg l-1 of Prosper, 12 mg l-1 of Cuivox, 6 ml l-1 of Fungastop, 7.5 ml l-1of Nimbecidine, and 25 ml l-1 of Maneb. The analysis of the symbiotic properties and plant growth-promoting potential revealed two efficient strains significantly increased alfalfa dry weight through producing siderophores, phosphorus, and indole acetic acid (13.6 mg ml-1 and 19.9 mg ml-1 respectively). Hence, we identify two tolerant and efficient strains, Achromobacter spanium and Serratia plymuthica, isolated from Medicago sativa nodule with valuable potential able to phytostabilize pesticide-contaminated soils.


Assuntos
Bactérias/classificação , Bactérias/isolamento & purificação , Medicago sativa/microbiologia , Nódulos Radiculares de Plantas/microbiologia , Antibacterianos/metabolismo , Bactérias/genética , Bactérias/metabolismo , Carbono/análise , Análise por Conglomerados , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Testes de Sensibilidade Microbiana , Nitrogênio/análise , Praguicidas/metabolismo , Fósforo/análise , Filogenia , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Solo/química , Simbiose
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