Biodegradation of the cyanobacterial toxin anatoxin-a by a Bacillus subtilis strain isolated from a eutrophic lake in Saudi Arabia.

Anatoxin-a (ATX-a) is a neurotoxin produced by some species of cyanobacteria. Due to its water solubility and stability in natural water, it could pose health risks to human, animals, and plants. Conventional water treatment techniques are not only insufficient for the removal of ATX-a, but they also result in cell lysis and toxin release. The elimination of this toxin through biodegradation may be a promising strategy. This study examines for the first time the biodegradation of ATX-a to a non-toxic metabolite (Epoxy-ATX-a) by a strain of Bacillus that has a history of dealing with toxic cyanobacteria in a eutrophic lake. The Bacillus strain AMRI-03 thrived without lag phase in a lake water containing ATX-a. The strain displayed fast degradation of ATX-a, depending on initial toxin concentration. At the highest initial concentrations (50 & 100 µg L- 1), total ATX-a degradation took place in 4 days, but it took 6 & 7 days at lower concentrations (20, 10, and 1 µg L- 1, respectively). The ATX-a biodegradation rate was also influenced by the initial toxin concentration, reaching its maximum value (12.5 µg L- 1 day- 1) at the highest initial toxin concentrations (50 & 100 µg L- 1). Temperature and pH also had an impact on the rate of ATX-a biodegradation, with the highest rates occurring at 25 and 30 ºC and pH 7 and 8. This nontoxic bacterial strain could be immobilized within a biofilm on sand filters and/or sludge for the degradation and removal of ATX-a and other cyanotoxins during water treatment processes, following the establishment of mesocosm experiments to assess the potential effects of this bacterium on water quality.

Analysis of rhizosphere fungal diversity in lavender at different planting years based on high-throughput sequencing technology.

Continuous cropping is a common cultivation practice in lavender cultivation, and the structure of the soil microbial community is one of the main reasons affecting the continuous cropping disorder in lavender; however, the relationship between the number of years of cultivation and inter-root microbial composition has not yet been investigated; using Illumina high-throughput sequencing we detected fungal community structure of rhizosphere soil under 1 (L1), 3 (L3), 5 (L5) and 0 (L0) years' of lavender cultivation in Yili, Xinjiang China. The results showed that with the extension of planting years, the physical-chemical characteristics of the soil shifted, and the diversity of the fungal communities shrank, the abundance and richness of species decreased and then increased, and the phylogenetic diversity increased, The structure of the soil fungal communities varied greatly. At phylum level, dominant fungal phyla were Ascomycetes, Basidiomycetes, etc. At genus level, dominant genera were Gibberella, Mortierella, etc, whose absolute abundance all increased with increasing planting years (P < 0.05); redundancy analysis showed that thesoil physicochemical characteristics significantly correlated with dominant bacterial genera. The FUN Guild prediction showed that six groups of plant pathogens and plant saprotrophs changed significantly (P < 0.05), the amount of harmful bacteria in the soil increased while the amount of arbuscular mycorrhizal fungui (AMF) decreased, leading to a continuous cropping obstacle of lavender. The findings of this study provida theoretical foundation for the management of continuous cropping and the prevention fungus-related diseases in lavender.

Presence of the neurotoxin ß-N-methylamino-L-alanine in irrigation water and accumulation in cereal grains with human exposure risk.

The present study demonstrates the presence of the neurotoxin ß-N-methylamino-L-alanine and its cyanobacterial producers in irrigation water and grains of some cereal plants from farmlands irrigated with Nile River water in Egypt. BMAA detected by LC-MS/MS in phytoplankton samples was found at higher concentrations of free form (0.84-11.4 µg L-1) than of protein-bound form (0.16-1.6 µg L-1), in association with the dominance of cyanobacteria in irrigation water canals. Dominant cyanobacterial species isolated from these irrigation waters including Aphanocapsa planctonica, Chroococcus minutus, Dolichospermum lemmermanni, Nostoc commune, and Oscillatoria tenuis were found to produce different concentrations of free (4.8-71.1 µg g-1 dry weight) and protein-bound (0.1-11.4 µg g-1 dry weight) BMAA. In the meantime, BMAA was also detected in a protein-bound form only in grains of corn (3.87-4.51 µg g-1 fresh weight) and sorghum (5.1-7.1 µg g-1 fresh weight) plants, but not in wheat grains. The amounts of BMAA accumulated in these grains correlated with BMAA concentrations detected in relevant irrigation water canals. The presence of BMAA in cereal grains would constitute a risk to human and animal health upon consumption of contaminated grains. The study, therefore, suggests continuous monitoring of BMAA and other cyanotoxins in irrigation waters and edible plants to protect the public against exposure to such potent toxins.

How Does Zinc Improve Salinity Tolerance? Mechanisms and Future Prospects.

Salinity stress (SS) is a serious abiotic stress and a major constraint to agricultural productivity across the globe. High SS negatively affects plant growth and yield by altering soil physio-chemical properties and plant physiological, biochemical, and molecular processes. The application of micronutrients is considered an important practice to mitigate the adverse effects of SS. Zinc (Zn) is an important nutrient that plays an imperative role in plant growth, and it could also help alleviate the effects of salt stress. Zn application improves seed germination, seedling growth, water uptake, plant water relations, nutrient uptake, and nutrient homeostasis, therefore improving plant performance and saline conditions. Zn application also protects the photosynthetic apparatus from salinity-induced oxidative stress and improves stomata movement, chlorophyll synthesis, carbon fixation, and osmolytes and hormone accumulation. Moreover, Zn application also increases the synthesis of secondary metabolites and the expression of stress responsive genes and stimulates antioxidant activities to counter the toxic effects of salt stress. Therefore, to better understand the role of Zn in plants under SS, we have discussed the various mechanisms by which Zn induces salinity tolerance in plants. We have also identified diverse research gaps that must be filled in future research programs. The present review article will fill the knowledge gaps on the role of Zn in mitigating salinity stress. This review will also help readers to learn more about the role of Zn and will provide new suggestions on how this knowledge can be used to develop salt tolerance in plants by using Zn.