RESUMEN
AIMS: This study evaluated the effects of exogenous lactic acid bacteria (LAB) on silage fermentation and bacterial community of reed canary grass (RCG) straw. METHODS AND RESULTS: The leaf, stem and whole crop of RCG straw were separately ensiled in small bag silos, without (control) or with inoculation of two exogenous LAB (LP, Lactobacillus plantarum; LB, Lactobacillus buchneri), and stored at ambient temperature of <20°C. Inoculation of exogenous LAB decreased (P < 0·05) bacterial alpha diversity and shifted (P < 0·05) bacterial community compositions, but did not change (P> 0·05) the relative abundance of Lactobacillus. Particularly, inoculation of LB increased (P < 0·05) acetic acid and propionic acid contents, decreased (P < 0·05) butyric acid (BA) and ammonia-N contents, separated (P < 0·05) the bacterial community in silage. However, the exogenous LAB inoculated silages were characterized by main distribution of yeasts, presence of undesirable bacterial genera such as Clostridium and high levels of BA and ammonia-N. CONCLUSION: Inoculation of exogenous LAB exerted a limited influence on the silage fermentation and bacterial community compositions of RCG straw on the Qinghai-Tibetan Plateau. SIGNIFICANCE AND IMPACT OF THE STUDY: Commercial LAB inoculants are not always efficient on enhancing silage quality and stability. Thus, an alternative additive for inhibiting undesirable microbes during storage is important to improve RCG silage quality on the Qinghai-Tibetan Plateau.
Asunto(s)
Lactobacillales/fisiología , Microbiota , Phalaris/microbiología , Ensilaje/microbiología , Amoníaco/análisis , Amoníaco/metabolismo , Bacterias/clasificación , Bacterias/crecimiento & desarrollo , Bacterias/metabolismo , Ácidos Grasos Volátiles/análisis , Ácidos Grasos Volátiles/metabolismo , Fermentación , Lactobacillales/metabolismo , Phalaris/química , Ensilaje/análisis , Tibet , Levaduras/clasificación , Levaduras/crecimiento & desarrollo , Levaduras/metabolismoRESUMEN
Conventional weed control methods often have environmental impact. The present study was conducted to screen selected accessions of Pseudomonas for both potential biocontrol of Phalaris minor and Avena fatua and potential concurrent growth promotion of wheat. The four Pseudomonas strains (B11, T19, T24, and T75) were found positive for cyanide production, siderophore production, phosphorus solubilization, oxidase activity, catalase activity, and ACC deaminase activity in vitro. These strains were phytotoxic, causing up to 73.3% mortality in the lettuce seedling bioassay. Consortia of compatible Pseudomonas strains increased A. fatua and P. minor seedling mortality up to 50.0% and 56.7%, respectively, and reduced root length up to 73.8% and 53.9%, respectively, as compared with the uninoculated control. Consortia of compatible Pseudomonas strains increased wheat shoot length, root length, fresh biomass, dry biomass, and leaf greenness up to 41.6%, 100%, 79.9%, 81.5%, and 21.1%, respectively, over the uninoculated control. Four of the 11 Pseudomonas consortia tested expressed good weed suppression and wheat growth promotion capacity and deserve further experimentation. The findings from this study may lead to the formulation of bioherbicides that will improve human and environmental health.
Asunto(s)
Avena/microbiología , Phalaris/microbiología , Pseudomonas/fisiología , Triticum/crecimiento & desarrollo , Control de Malezas/métodos , Humanos , Plantones/microbiología , Semillas/microbiologíaRESUMEN
The impact of contrasting water quality treatments on wetland plant-associated microbial communities was investigated in this study using 12 lab-scale wetland mesocosms (subsurface flow design) planted with reed canary grass (Phalaris arundinacea) or water speedwell (Veronica anagallis-aquatica) over a 13-week period. Mesocosms received water collected from two sites along the Grand River (Ontario, Canada) designated as having either high or poor water quality according to Grand River Conservation Authority classifications. All mesocosms were established using sediment collected from the high water quality site and received water from this source pre-treatment. Resulting changes to microbial community structure were assessed using PCR-denaturing gel gradient electrophoresis (DGGE) on microbial 16S rDNA sequences extracted from rhizoplane, rhizosphere, and water samples before and after exposure to water quality treatments. Functional community changes were determined using Biolog™ EcoPlates which assess community-level carbon source utilization profiles. Wetland mesocosm removal of inorganic nutrients (N, P) and fecal coliforms was also determined, and compared among treatments. Treatment-specific effects were assessed using a repeated measures restricted maximum likelihood (REML) analysis. Structural and functional characteristics of rhizoplane microbial communities were significantly influenced by the interaction between plant species and water treatment (P = 0.04, P = 0.01). Plant species-specific effects were observed for rhizosphere structural diversity (P = 0.01) and wetland water community metabolic diversity (P = 0.03). The effect of water treatment alone was significant for structural diversity measurements in wetland water communities (P = 0.03). The effect of plant species, water quality treatment, and the interaction between the two is dependent on the microhabitat type (rhizoplane, rhizosphere, or water). Rhizoplane communities appear to be more sensitive to water quality-specific environmental changes and may be a good candidate for microbial community-based monitoring of wetland ecosystems.
Asunto(s)
Bacterias/aislamiento & purificación , Microbiota , Phalaris/microbiología , Ríos/química , Ríos/microbiología , Veronica/microbiología , Bacterias/clasificación , Bacterias/genética , Bacterias/metabolismo , Ontario , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/metabolismo , Purificación del Agua , Calidad del Agua , HumedalesRESUMEN
Extended soil contamination by polychlorinated biphenyls (PCBs) represents a global environmental issue that can hardly be addressed with the conventional remediation treatments. Rhizoremediation is a sustainable alternative, exploiting plants to stimulate in situ the degradative bacterial communities naturally occurring in historically polluted areas. This approach can be enhanced by the use of bacterial strains that combine PCB degradation potential with the ability to promote plant and root development. With this aim, we established a collection of aerobic bacteria isolated from the soil of the highly PCB-polluted site "SIN Brescia-Caffaro" (Italy) biostimulated by the plant Phalaris arundinacea. The strains, selected on biphenyl and plant secondary metabolites provided as unique carbon source, were largely dominated by Actinobacteria and a significant number showed traits of interest for remediation, harbouring genes homologous to bphA, involved in the PCB oxidation pathway, and displaying 2,3-catechol dioxygenase activity and emulsification properties. Several strains also showed the potential to alleviate plant stress through 1-aminocyclopropane-1-carboxylate deaminase activity. In particular, we identified three Rhodococcus strains able to degrade in vitro several PCB congeners and to promote lateral root emergence in the model plant Arabidopsis thaliana in vivo. In addition, these strains showed the capacity to colonize the root system and to increase the plant biomass in PCB contaminated soil, making them ideal candidates to sustain microbial-assisted PCB rhizoremediation through a bioaugmentation approach.
Asunto(s)
Proteínas Bacterianas/genética , Phalaris/microbiología , Raíces de Plantas/microbiología , Bifenilos Policlorados/metabolismo , Rhodococcus/genética , Contaminantes del Suelo/metabolismo , Arabidopsis/crecimiento & desarrollo , Arabidopsis/microbiología , Proteínas Bacterianas/metabolismo , Biodegradación Ambiental , Liasas de Carbono-Carbono/genética , Liasas de Carbono-Carbono/metabolismo , Catecol 2,3-Dioxigenasa/genética , Catecol 2,3-Dioxigenasa/metabolismo , Expresión Génica , Oxidación-Reducción , Phalaris/crecimiento & desarrollo , Raíces de Plantas/crecimiento & desarrollo , Rhodococcus/enzimología , Metabolismo Secundario/genética , Suelo/química , Microbiología del SueloRESUMEN
Diclofenac (DCF), a non-steroidal anti-inflammatory drug (NSAID) and sulfamethoxazole (SMX), an antimicrobial agent, are in common use and can be often detected in the environment. The constructed wetland systems (CWs) are one of the technologies to remove them from the aquatic environment. The final effect of the treatment processes depends on many factors, including the interaction between plants and the plant-associated microorganisms present in the system. Bacteria living inside the plant as endophytes are exposed to secondary metabolites in the tissues. Therefore, they can possess the potential to degrade aromatic structures, including residues of pharmaceuticals. The endophytic strain MG7 identified as Microbacterium sp., obtained from root tissues of Phalaris arundinacea exposed to DCF and SMX was tested for the ability to remove 2 mg/l of SMX and DCF in monosubstrate cultures and in the presence of phenol as an additional carbon source. The MG7 strain was able to remove approximately 15% of DCF and 9% of SMX after 20 days of monosubstrate culture. However, a decrease in the optical density of the MG7 strain cultures was observed, caused by an insufficient carbon source for bacterial growth and proliferation. The adsorption of pharmaceuticals onto autoclaved cells was negligible, which confirmed that the tested strain was directly involved in the removal of DCF and SMX. In the presence of phenol as the additional carbon source, the MG7 strain was able to remove approximately 35% of DCF and 61% of SMX, while an increase in the optical density of the cultures was noted. The higher removal efficiency can be explained by adaptive mechanisms in microorganisms exposed to phenol (i.e. changes in the composition of membrane lipids) and by a co-metabolic mechanism, where non-growth substrates can be transformed by non-specific enzymes. The presence of both DCF and SMX and the influence of the supply frequency of CWs with the contaminated wastewater on the diversity of whole endophytic bacterial communities were demonstrated. The results of this study suggest the capability of the MG7 strain to degrade DCF and SMX. This finding deserves further investigations to improve wastewater treatment in CWs with the possible use of pharmaceuticals-degrading endophytes.
Asunto(s)
Bacterias/metabolismo , Diclofenaco/metabolismo , Endófitos/metabolismo , Phalaris/microbiología , Sulfametoxazol/metabolismo , Antibacterianos/metabolismo , Antiinflamatorios no Esteroideos/metabolismo , Bacterias/aislamiento & purificación , Biodegradación Ambiental , Carbono/metabolismo , Endófitos/aislamiento & purificación , Fenol/farmacología , Aguas Residuales/microbiología , Contaminantes Químicos del Agua/metabolismo , HumedalesRESUMEN
RATIONALE: The biological activities most commonly associated with indole-diterpenoids are tremorgenicity in mammals and toxicity in insects through modulation of ion channels. The neurotoxic effects of some analogues are the cause of syndromes such as 'ryegrass staggers' and 'Paspalum staggers' in cattle and sheep. Our purpose was to obtain and interpret mass spectra of some pure Claviceps-related indole-diterpenoids (paspaline, paspalinine, paxilline, paspalitrems A and B) to facilitate identification of related compounds for which standards were not available. METHODS: C. paspali-infected Paspalum dilatatum as well as C. purpurea sclerotia obtained from infected Phalaris arundinacea were extracted and the extracts separated via liquid chromatography. Low- and high-resolution mass spectra were then obtained of known and potentially unknown indole-diterpenoids. RESULTS: At least 20 different indole-diterpenoids were detected in the C. paspali extract with molecular masses ranging from 405 Da (C28H40NO) to 517 Da (C32H40NO5). The C. purpurea sclerotia were shown to contain several indole-diterpenoids with molecular masses ranging from 405 Da (C28H40NO) to 419 Da (C28H38NO2). CONCLUSIONS: This study demonstrates for the first time that C. purpurea may also produce indole-diterpenoids. This might explain why grazing of Phalaris spp. is occasionally connected with a tremorgenic syndrome in cattle, called 'phalaris staggers'.
Asunto(s)
Claviceps/química , Diterpenos/química , Indoles/química , Espectrometría de Masas/métodos , Diterpenos/análisis , Análisis de Fourier , Indoles/análisis , Phalaris/microbiologíaRESUMEN
During the last decade, the application of arbuscular mycorrhizal fungi (AMF) as bioenhancers has increased significantly. However, until now, it has been difficult to verify the inoculation success in terms of fungal symbiont establishment in roots of inoculated plants because specific fungal strains could not be detected within colonized roots. Using mitochondrial large subunit ribosomal DNA, we show that Rhizophagus irregularis (formerly known as Glomus intraradices) isolate BEG140 consists of two different haplotypes. We developed nested PCR assays to specifically trace each of the two haplotypes in the roots of Phalaris arundinacea from a field experiment in a spoil bank of a former coal mine, where BEG140 was used as inoculant. We revealed that despite the relatively high diversity of native R. irregularis strains, R. irregularis BEG140 survived and proliferated successfully in the field experiment and was found significantly more often in the inoculated than control plots. This work is the first one to show tracing of an inoculated AMF isolate in the roots of target plants and to verify its survival and propagation in the field. These results will have implications for basic research on the ecology of AMF at the intraspecific level as well as for commercial users of mycorrhizal inoculation.
Asunto(s)
ADN Ribosómico/genética , Glomeromycota/genética , Mitocondrias/genética , Micorrizas/aislamiento & purificación , Phalaris/microbiología , Secuencia de Bases , Minas de Carbón , República Checa , ADN de Hongos/genética , ADN Mitocondrial/genética , Marcadores Genéticos , Glomeromycota/aislamiento & purificación , Glomeromycota/fisiología , Haplotipos , Datos de Secuencia Molecular , Micorrizas/genética , Micorrizas/fisiología , Phalaris/fisiología , Filogenia , Raíces de Plantas/microbiología , Reacción en Cadena de la Polimerasa/métodos , Alineación de Secuencia , Análisis de Secuencia de ADN , Microbiología del Suelo , SimbiosisRESUMEN
BACKGROUND: We hypothesized that alfalfa (ALF) or birdsfoot trefoil (BFT) eaten prior to a meal of endophyte-infected tall fescue (TF) or reed canarygrass (RCG) would provide benefits not possible when TF or RCG are eaten alone. In trial 1, four groups of five lambs were first offered ALF for 30 min followed by either TF or RCG for 3.5 h in a 2 × 2 factorial arrangement of a completely randomized design that included grass (TF or RCG) with or without ALF. Trial 2 was similar to trial 1 except we used a new group of lambs fed BFT. Forage, fecal and urine samples were collected and analyzed for dry matter intake and apparent digestibility of dry matter, energy (in Kcal), nitrogen and neutral detergent fiber. RESULTS: A meal of either ALF or BFT prior to eating TF or RCG caused lambs to eat more total dry matter and nitrogen (both in g d⻹) and energy (in MJ d⻹) than lambs fed only TF or RCG (P < 0.05). Lambs fed ALF slightly reduced intake of TF and RCG relative to unsupplemented animals. Lambs fed BFT ate slightly less RCG, but much more TF than unsupplemented animals (P < 0.10). Lambs ate much less BFT than ALF, but they were stimulated to eat TF to a greater degree by BFT than by ALF. CONCLUSIONS: The enhanced intake of TF by lambs provided BFT, as well as the greater nutrient intake by lambs fed legumes and grasses was likely due in part to complementary profiles of alkaloids, saponins, and tannins.
Asunto(s)
Alimentación Animal/microbiología , Digestión , Endófitos/crecimiento & desarrollo , Festuca/microbiología , Lotus/química , Medicago sativa/química , Phalaris/microbiología , Alcaloides/administración & dosificación , Alcaloides/efectos adversos , Alcaloides/antagonistas & inhibidores , Alimentación Animal/análisis , Animales , Regulación del Apetito , Cruzamientos Genéticos , Fibras de la Dieta/administración & dosificación , Fibras de la Dieta/análisis , Endófitos/aislamiento & purificación , Ingestión de Energía , Festuca/efectos adversos , Festuca/química , Phalaris/efectos adversos , Phalaris/química , Saponinas/administración & dosificación , Oveja Doméstica , Taninos/administración & dosificación , UtahRESUMEN
Several methods of molecular analysis of microbial diversity, including terminal restriction fragment length polymorphism (T-RFLP) analysis are based on measurement of the DNA fragment length. Significant variation between sequence-determined and measured length of restriction fragments (drift) has been observed, which can affect the efficiency of the identification of microorganisms in the analyzed communities. In the past, this variation has been attributed to varying fragment length and purine content. In this study, principal component analysis and multiple regression analysis were applied to find the contributions of those and several other fragment characteristics. We conclude that secondary structure melting point and G+C nucleotide content, besides the fragment length, contribute to the variation observed, whereas the contribution of purine content is less important. Incomplete denaturation of the sample at the start of electrophoretic separation of fragments has been excluded as a major cause of the variation observed. Our regression model explains the observed drift variation by approximately 56%, with standard deviation of the prediction equal to approximately 1.3 bp.