[Ligninolytic enzyme production by white rot fungi during paraquat (herbicide) degradation]

Bioaugmentation: a strategy for enhanced degradation of pesticides in biobed

Biopurification system (BPS) or biobeds are low-cost system for decontamination of on-farm generated pesticide waste. A biobed contains a mixture of soil, lignocellulosic biomass and organic matter source (compost/peat) and works on the principal of retention of pesticide in high organic matter matrix and its subsequent degradation by microbes. Bioaugmentation, a green technology, is defined as the improvement of the degradative capacity of biobeds by augmenting specific microorganisms. During last 20 years, several studies have evaluated pesticide degradation in biobeds augmented with bacterial and fungal species and prominent microorganism include genus Pseudomonas, Sphingomonas, Arthrobacter, Phanerochaete, Stereum, Delftia, Trametes, Streptomyces etc. Degradation of pesticides belonging to major classes have been studied in the bioaugmented biobeds. Studies suggested that some pesticides were degraded faster in the bioaugmented biobeds subject to survival and proliferation of degrading microbe. However, no effect of bioaugmentation was observed on degradation of some pesticides and no clear reason for the same was evident. Bioaugmentation with pesticide degrading microorganisms/consortium in combination with rhizosphere-assisted biodegradation could be an optimal strategy for accelerating the degradation of pesticides in biobeds.

The role of Phanerochaete australis in enhancing defense activity against Magnaporthe oryzae in upland rice

The inclusion of biological control in the integrated management of rice blast (Magnaporthe oryzae [Mo]) reduces pesticide application. Phanerochaete australis (Pha) has been shown to be a potential inducer of resistance to rice blast. Pha was isolated saprophytically from the rice phylloplane and studied for its interaction with Mo in the defense process of upland rice plants against the pathogen attack. Investigating the Pha × Mo interaction in a completely randomized design, the suppression of leaf blast and the epidemiological components of disease development were quantified in vivo, whereas the physiological and biochemical aspects, as defense enzymes and oxidative complex components, were evaluated in vitro during the induction of resistance. In the Pha × Mo interaction, it was found that seed treatment can significantly reduce disease severity by up to 93%, increase the photosynthetic apparatus, mobilize photoassimilates to the defense system, intensify defense enzyme and oxidant complex activities (chitinase [CHI], β-1,3-glucanase [GLU], lipoxygenase [LOX], phenylalanine ammonia-lyase [PAL], poliphenoloxidase [PPO], peroxidase [POX], catalase [CAT], cuperoxide dismutase [SOD]), decrease phenolic compounds (TPCs), and increase photosynthetic pigment levels compared with the negative control (Mo). When treating the seed, we are referring to an induction process where there is no physical contact between the pathogens. The enzymes produced by the interaction between the microorganisms validate this process; thus, Pha acts as an inducer of resistance to upland rice plants challenged with Mo.

Enzymatic Bioprospecting of Fungi Isolated from a Tropical Rainforest in Mexico

The humid tropical environment provides an ideal place for developing a high diversity of plants; this is why it is an interesting site for the enzymatic bioprospecting of fungi that are responsible for the recycling of organic matter in an efficient and accelerated way and whose enzymes could have multiple biotechnological applications. For this study, 1250 isolates of macroscopic and microscopic fungal morphotypes were collected from soil, leaf litter, and wood. One hundred and fifty strains (50 from each source) were selected for the enzymatic screening. From the first phase, 51 strains with positive activity for laccase, protease, amylase, xylanase, and lipase enzymes were evaluated, of which 20 were isolated from leaf litter, 18 from the soil, and 13 from wood. The 10 best strains were selected for the enzymatic quantification, considering the potency index and the production of at least two enzymes. High laccase activity was detected for Trametes villosa FE35 and Marasmius sp. CE25 (1179 and 710.66 U/mg, respectively), while Daedalea flavida PE47 showed laccase (521.85 U/mg) and protease activities (80.66 U/mg). Fusarium spp. PH79 and FS400 strains had amylase (14.0 U/mg, 49.23 U/mg) and xylanase activities (40.05 U/mg, 36.03 U/mg) respectively. These results confirm the enzymatic potential of fungi that inhabit little-explored tropical rainforests with applications in industry.

Biorremediación de carbamazepina por hongos y bacterias en aguas residuales

La carbamazepina (CBZ), un fármaco psiquiátrico, antiepiléptico; mayormente utilizado en la actualidad para tratar enfermedades como la epilepsia y neuralgia del trigémino; es un contaminante emergente, considerado como una fuente importante de contaminación de fuentes hídricas, al no ser totalmente metabolizado por el organismo y ser excretado por vía urinaria y fecal, sin cambios o en forma de metabolitos conjugados. Estos contaminantes pasan por tratamientos de aguas residuales, sin embargo, los tratamientos convencionales no son capaces de degradarlo, produciendo daños a los seres vivos que habitan y necesitan de este recurso natural para poder sobrevivir. Frente a este problema, el objetivo de esta revisión fue identificar tratamientos biológicos con la utilización de microorganismos (bacterias y hongos) para la degradación de este compuesto recalcitrante. Los microorganismos identificados con mayor porcentaje de degradación de carbamazepina fueron Labrys portucalensis F11 y Trametes versicolor; la primera una bacteria que se adapta a diferentes fuentes de carbono; y el segundo un hongo denominado de pudrición de la madera, que presenta enzimas oxidativas que le permiten degradar una amplia gama de contaminantes emergentes. Trametes versicolor, es el microorganismo mayormente estudiado para los procesos de degradación de carbamazepina, con porcentajes de degradación de hasta el 94% a una temperatura de 25°C y un pH de 4.5.

A Path Forward: Promoting Microbial-Based Methods in the Control of Invasive Plant Species

In this review, we discuss the unrealized potential of incorporating plant-microbe and microbe-microbe interactions into invasive plant management strategies. While the development of this as a viable strategy is in its infancy, we argue that incorporation of microbial components into management plans should be a priority and has great potential for diversifying sustainable control options. We advocate for increased research into microbial-mediated phytochemical production, microbial controls to reduce the competitiveness of invasive plants, microbial-mediated increases of herbicidal tolerance of native plants, and to facilitate increased pathogenicity of plant pathogens of invasive plants.

TOXICIDAD AGUDA DEL HERBICIDA PARAQUAT EN Oreochromis niloticus (CICHLIDAE) Y Macrobrachium olfersii (PALAEMONIDAE)

El Paraquat es un herbicida utilizado en la actividad agropecuaria para controlar hierbas, su modo de acción es por medio de contacto y no selectivo. Debido a su alta solubilidad en agua y baja volatilidad representa un riesgo potencial para organismos acuáticos, principalmente los que son cultivados con aguas superficiales que reciben impacto de la actividad agrícola. La tilapia Oreochromis niloticusy el langostino Macrobrachium olfersiison organismos de importancia comercial para la industria acuícola del estado de Veracruz, México.El objetivo de este estudio fue determinar la Concentración Letal Media (CL50) del herbicida Dasurquat® (ingrediente activo Paraquat) a través de un bioensayo de toxicidad aguda (96 horas). Se utilizaron como especímenes de prueba a juveniles de tilapia O. niloticus(peso promedio = 10 mg, longitud total= 8,75 mm) y otro el ensayo fue con poslarvas de langostino M. olfersii(peso promedio = 5 mg, longitud total= 5,72 mm). Se emplearon cinco concentraciones (5, 10, 20, 40 y 80 µl L-1para el bioensayo con juveniles de tilapia; para el bioensayo con poslarvas de langostino las concentraciones fueron  0,1, 0,2, 0,5, 0,7 y 1 µl L-1). El diseño experimental consideró un control negativo, con dos repeticiones y dos réplicas por cada tratamiento. El análisis de datos se realizó con el método Probit para determinar la CL50a 96 horas, se obtuvo un valor para juveniles de O. niloticusde 17,49 µl L-1con intervalo de confianza (95 %) con límite inferior de 13,75 µl L-1y límite superior 22,25 µl L-1, para las larvas de M. olfersiise obtuvo un valor de 0,31 µl L-1con intervalo de confianza (95 %) con límite inferior de 0,26 µl L-1y límite superior 0,35 µl L-1. El análisis de varianza demostró que no existió diferencia estadística significativa (p > 0.05) entre las réplicas de los tratamientos. Se concluye que es necesario continuar con estudios para evaluar su toxicidad en organismos acuáticos debido al amplio uso de este herbicida en la actividad agropecuaria, y determinar su riesgo para otras actividades productivas además de la acuicola.

Paraquat Degradation From Contaminated Environments: Current Achievements and Perspectives

Paraquat herbicide has served over five decades to control annual and perennial weeds. Despite agricultural benefits, its toxicity to terrestrial and aquatic environments raises serious concerns. Paraquat cannot rapidly degrade in the environment and is adsorbed in clay lattices that require urgent environmental remediation. Advanced oxidation processes (AOPs) and bioaugmentation techniques have been developed for this purpose. Among various techniques, bioremediation is a cost-effective and eco-friendly approach for pesticide-polluted soils. Though several paraquat-degrading microorganisms have been isolated and characterized, studies about degradation pathways, related functional enzymes and genes are indispensable. This review encircles paraquat removal from contaminated environments through adsorption, photocatalyst degradation, AOPs and microbial degradation. To provide in-depth knowledge, the potential role of paraquat degrading microorganisms in contaminated environments is described as well.

Influence of Paraquat on Four Rhizobacteria Strains: Pantoea agglomerans, Rhizobium nepotum, Rhizobium radiobacter and Rhizobium tibeticum

Background:

Soil microorganisms are exposed to herbicides after treatment, which leads to their interaction. The result of this interaction may be the degradation of the herbicides by the microorganisms and by the way, they use the degradation products as an energy source for their own physiological processes, or herbicides have a toxic effect on these microorganisms. Herbicide toxicity becomes severe instantly after application when its concentration in soil is the highest. Paraquat is one of the most widely used herbicides in agriculture; inappropriate use of this herbicide represents an immense pollution problem for soil, therefore on microorganisms. However, the knowledge about the effect of paraquat on soil microorganisms has been limited.

Objectives:

The purpose of the current study was to determine the effect of paraquat application on four nitrogen-fixing bacteria:Pantoea agglomerans, Rhizobium nepotum, Rhizobium tibeticumandRhizobium radiobacter.

Methods:

Paraquat was applied as the sole source of carbon at a rate (0 g/L, 0.5 g/L, 1 g/L, 3 g/L, 6 g/L and 12 g/L). The effect of paraquat treatments was determined by agar diffusion method and the rate of the growth of bacterial colonies in each treatment.

Results:

In the agar diffusion method, the bacterial strains were inhibited by paraquat, in which the inhibition zone was wider with the increase of paraquat concentration; also, analysis of the Colony Forming Units (CFUs) mostly showed a declining in bacterial growth. In comparison with the control, the growth of the four strains was decreased by increasing the paraquat concentration. Comparing strains with each other,Pantoea agglomeransis the most resistant strain to paraquat.

Conclusion:

Our study has shown the impact of the irrational use of pesticide upon the beneficial bacteria in question. For that, the results of this research have a positive impact on the natural environment, which will have tangible social and economic impacts.