Biopriming of Durum Wheat Seeds with Endophytic Diazotrophic Bacteria Enhances Tolerance to Fusarium Head Blight and Salinity

There is growing interest in the use of bio inoculants based on plant growth-promoting bacteria (PGPB) to promote plant growth under biotic and abiotic stresses. Here, we provided a detailed account of the effectiveness of a number of endophytic PGPB strains, isolated from the roots of the halophyte Salicornia brachiata in promoting durum wheat growth and enhancing its tolerance to salinity and fusarium head blight (FHB) disease. Bacillus spp. strains MA9, MA14, MA17, and MA19 were found to have PGPB characteristics as they produced indole-3-acetic acid, siderophores, and lytic enzymes, fixed free atmospheric nitrogen, and solubilized inorganic phosphate in vitro. Additionally, the in vivo study that involved in planta inoculation assays under control and stress conditions indicated that all PGPB strains significantly (p < 0.05) increased the total plant length, dry weight, root area, seed weight, and nitrogen, protein, and mineral contents. Particularly, the MA17 strain showed a superior performance since it was the most efficient in reducing disease incidence in wheat explants by 64.5%, in addition to having the strongest plant growth promotion activity under salt stress. Both in vitro and in vivo assays showed that MA9, MA14, MA17, and MA19 strains were able to play significant PGPB roles. However, biopriming with Bacillus subtilis MA17 offered the highest plant growth promotion and salinity tolerance, and bioprotection against FHB. Hence, it would be worth testing the MA17 strain under field conditions as a step towards its commercial production. Moreover, the strain could be further assessed for its plausible role in bioprotection and growth promotion in other crop plants. Thus, it was believed that the strain has the potential to significantly contribute to wheat production in arid and semi-arid regions, especially the salt-affected Middle Eastern Region, in addition to its potential role in improving wheat production under biotic and abiotic stresses in other parts of the world.

Mining of two novel aldehyde dehydrogenases (DHY-SC-VUT5 and DHY-G-VUT7) from metagenome of hydrocarbon contaminated soils

Background

Aldehyde dehydrogenases are vital for aerobic hydrocarbon degradation and is involved in the last step of catalysing the oxidation of aldehydes to carboxylic acids. With the global increase in hydrocarbon pollution of different environments, these enzymes have the potential to be used in enzymatic bioremediation applications.

Results

Fifteen fosmid clones with hydrocarbon degrading potential were functionally screened to identify dehydrogenase enzymes. Accordingly, the fosmid insert of the positive clones were sequenced using PacBio next generation sequencing platform and de novo assembled using CLC Genomic Work Bench. The 1233 bp long open reading frame (ORF) for DHY-SC-VUT5 was found to share a protein sequence similarity of 97.7% to short-chain dehydrogenase from E. coli. The 1470 bp long ORF for DHY-G-VUT7 was found to share a protein sequence similarity of 23.9% to glycine dehydrogenase (decarboxylating) (EC 1.4.4.2) from Caulobacter vibrioides (strain NA1000 / CB15N) (Caulobacter crescentus). The in silico analyses and blast against UNIPROT protein database with the stated similarity show that the two dehydrogenases are novel. Biochemical characterization revealed, that the highest relative activity was observed at substrate concentrations of 150 mM and 50 mM for DHY-SC-VUT5 and DHY-G-VUT7, respectively. The K_m values were found to be 13.77 mM with a V_max of 0.009135 μmol.min^− 1 and 2.832 mM with a V_max of 0.005886 μmol.min^− 1 for DHY-SC-VUT5 and DHY-G-VUT7, respectively. Thus, a potent and efficient enzyme for alkyl aldehyde conversion to carboxylic acid.

Conclusion

The microorganisms overexpressing the novel aldehyde dehydrogenases could be used to make up microbial cocktails for biodegradation of alkanes. Moreover, since the discovered enzymes are novel it would be interesting to solve their structures by crystallography and explore the downstream applications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12896-021-00677-8.

Development and validation of TOF/Q-TOF MS/MS, HPLC method and in vitro bio-strategy for aflatoxin mitigation

Some secondary metabolites produced by fungi are carcinogenic, hepatotoxic, and/or cause birth defects in humans and animals. We developed and optimised bio-analytical tools for detection of metabolites, aflatoxins and evaluated the effectiveness of the methods in co-infected maize tissues. Isolate KSM012 (atoxigenic) demonstrated no peaks and no blue fluorescence on HPLC and TLC plates respectively confirming non-toxicity. AFB1 and AFB2 were produced by Isolate KSM015 in addition to AFG1 and AFG2, which is an indication of possible S_BG morphotype. The limits of quantification and detection ranged from 0.02 to 35.81 µg/mL and 0.01-6.8 µg/mL, respectively. The best mass spectrum with lowest noise was obtained at 100% ACN and sterile water spiked with 0.1% formic acid at a flow rate of 0.3 mL/min. The positive ion mode with electrospray ionisation application exhibited better fragmentation for mycotoxins. In total 17 metabolites were detected by targeted and formula mass. KDVI maize line exhibited high fungal colonisation in comparison to GAF4 at equal co-infection ratio 50:50. AFB1 and AFG2 were remarkably higher in GAF4 in comparison to sensitive KDV1 (p ˂ 0.05). The detection limits, linearity and sensitivity showed the method developed was suitable for the determination of mycotoxin in comparisons to the guidelines of European Commission 657/EC 2002.

Breakthroughs in the discovery and use of different peroxidase isoforms of microbial origin

Peroxidases are classified as oxidoreductases and are the second largest class of enzymes applied in biotechnological processes. These enzymes are used to catalyze various oxidative reactions using hydrogen peroxide and other substrates as electron donors. They are isolated from various sources such as plants, animals and microbes. Peroxidase enzymes have versatile applications in bioenergy, bioremediation, dye decolorization, humic acid degradation, paper and pulp, and textile industries. Besides, peroxidases from different sources have unique abilities to degrade a broad range of environmental pollutants such as petroleum hydrocarbons, dioxins, industrial dye effluents, herbicides and pesticides. Ironically, unlike most biological catalysts, the function of peroxidases varies according to their source. For instance, manganese peroxidase (MnP) of fungal origin is widely used for depolymerization and demethylation of lignin and bleaching of pulp. While, horseradish peroxidase of plant origin is used for removal of phenols and aromatic amines from waste waters. Microbial enzymes are believed to be more stable than enzymes of plant or animal origin. Thus, making microbially-derived peroxidases a well-sought-after biocatalysts for versatile industrial and environmental applications. Therefore, the current review article highlights on the recent breakthroughs in the discovery and use of peroxidase isoforms of microbial origin at a possible depth.

Molecular and Vegetative Compatibility Groups Characterization of Aspergillus flavus Isolates from Kenya

The genus Aspergillus contains diverse species and the identification is complicated. Vegetative compatibility groups (VCGs) and molecular mechanisms were deployed to study the species. The study was randomly conducted in four counties in Kenya based on the history of aflatoxicosis and maize cultivation. Thirty-seven Aspergillus flavus isolates from Nandi, Kisumu, Homa Bay and Makueni were characterized to determine their taxonomic status based on their VCGs and genotypes. A phylogenetic analysis of ITS1 and ITS2 sequences of the isolates investigated revealed ITS primers discriminating some of the A. flavus isolates as 100% sequence identity to the RefSeq. Nit mutants' complementation test revealed strong heterokaryon incompatibility between isolates of Nandi region (67%) and Makueni (33%). The trend based on VCGs and molecular findings showed high incidence of toxigenic A. flavus in Makueni, which could be the reason why the region frequently experiences chronic aflatoxicosis incidences over the last few decades as compared to other regions. Interestingly, we have discovered all S and L-morphotypes including the rare S/L-morphotypes, which implies that Kenya is home to all morphotypes of A. flavus. Thus, the analysis provides a deeper understanding of the taxonomic relationship between the A. flavus isolates and could help contextualise the data obtained for each isolate with respect to VCG genetic diversity and genotypes. Determining the primary causal agents of aflatoxin contamination is critical for predicting risk of contamination events and designing and implementing effective management strategies.

Translation initiation factor IF2 contributes to ribosome assembly and maturation during cold adaptation

Cold-stress in Escherichia coli induces de novo synthesis of translation initiation factors IF1, IF2 and IF3 while ribosome synthesis and assembly slow down. Consequently, the IFs/ribosome stoichiometric ratio increases about 3-fold during the first hours of cold adaptation. The IF1 and IF3 increase plays a role in translation regulation at low temperature (cold-shock-induced translational bias) but so far no specific role could be attributed to the extra copies of IF2. In this work, we show that the extra-copies of IF2 made after cold stress are associated with immature ribosomal subunits together with at least another nine proteins involved in assembly and/or maturation of ribosomal subunits. This finding, coupled with evidence that IF2 is endowed with GTPase-associated chaperone activity that promotes refolding of denatured GFP, and the finding that two cold-sensitive IF2 mutations cause the accumulation of immature ribosomal particles, indicate that IF2 is yet another GTPase protein that participates in ribosome assembly/maturation, especially at low temperatures. Overall, these findings are instrumental in redefining the functional role of IF2, which cannot be regarded as being restricted to its well documented functions in translation initiation of bacterial mRNA.

Global invasive Cochliobolus species: cohort of destroyers with implications in food losses and insecurity in the twenty-first century

Matching the global food demand by 2050 and to ensure the stability of food security in over than 99 countries, it is necessary to scale up the production of food such as sorghum, wheat, rice, maize and sugarcane which are however natural hosts of Cochliobolus species. Cochliobolus species major epidemics such as the Great Bengal famine, Southern corn leaf blight, and Northern leaf spot blight were associated with substantial economic losses in the past decades. Thus, there is an urgent need to establish a specific coordinated global surveillance program for the migration of invasive Cochliobolus species, planning contextual control programs engaging all agricultural stakeholders and information sharing in real time for prevention of disastrous Cochliobolus disease outbreak effects. We discuss pertinent outcome of interactions of cash crops with Cochliobolus species having devastating impact on the livelihood of farmers and food security. While post-genomic era elucidated prominent differences among Cochliobolus heterostrophus, C. carbonum, C. victoriae, C. lunatus and C. miyabeanus, their destructive potentials and implications in food losses remained unearthed. Intriguingly, the annual colossal losses caused by Cochliobolus species in the production perspective of sorghum, wheat, rice, maize, cassava and soybean is estimated over 10 billion USD worldwide. This paper provides a comprehensive analysis of the invasive Cochliobolus species distribution and diversity, evolving pathogenicity, persistent diseases, threats and epidemics, consequences on food crops production and increasing global food insecurity issues.