Revolutionizing nematode management to achieve global food security goals - An overview.

Nematodes are soil-dwelling organisms that inflict substantial damage to crops, resulting in significant declines in agricultural productivity. Consequently, they are recognized as one of the primary contributors to global crop damage, with profound implications for food security. Nematology research assumes a pivotal role in tackling this issue and safeguarding food security. The pursuit of nematology research focused on mitigating nematode-induced crop damage and promoting sustainable agriculture represents a fundamental strategy for enhancing food security. Investment in nematology research is crucial to advance food security objectives by identifying and managing nematode species, developing novel technologies, comprehending nematode ecology, and strengthening the capabilities of researchers and farmers. This endeavor constitutes an indispensable step toward addressing one of the most pressing challenges in achieving global food security and promoting sustainable agricultural practices. Primarily, research endeavors facilitate the identification of nematode species responsible for crop damage, leading to the development of effective management strategies. These strategies encompass the utilization of resistant crop varieties, implementation of cultural practices, biological control, and chemical interventions. Secondly, research efforts contribute to the development of innovative technologies aimed at managing nematode populations, such as gene editing techniques that confer resistance to nematode infestations in crops. Additionally, the exploration of beneficial microbes, such as certain fungi and bacteria, as potential biocontrol agents against nematodes, holds promise. The study of nematode ecology represents a foundational research domain that fosters a deeper comprehension of nematode biology and ecological interactions. This knowledge is instrumental in devising precise and efficacious management strategies.

Antifungal activity of green synthesized selenium nanoparticles and their effect on physiological, biochemical, and antioxidant defense system of mango under mango malformation disease.

Plant extract-based green synthesis of nanoparticles is an emerging class of nanotechnology that has revolutionized the entire field of biological sciences. Green synthesized nanoparticles are used as super-growth promoters and antifungal agents. In this study, selenium nanoparticles (SeNPs) were synthesized using Melia azedarach leaves extract as the main reducing and stabilizing agent and characterized by UV-visible spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and fourier transform infrared spectrometer (FTIR). The green synthesized SeNPs were exogenously applied on Mangifera indica infected with mango malformation disease. The SeNPs at a concentration of 30 µg/mL were found to be the best concentration which enhanced the physiological (chlorophyll and membrane stability index), and biochemical (proline and soluble sugar) parameters. The antioxidant defense system was also explored, and it was reported that green synthesized SeNPs significantly reduced the biotic stress by enhancing enzymatic and non-enzymatic activities. In vitro antifungal activity of SeNPs reported that 300 µg/mL concentration inhibited the Fusarium mangiferae the most. This study is considered the first biocompatible approach to evaluate the potential of green synthesized SeNPs to improve the health of mango malformation-infected plants and effective management strategy to inhibit the growth of F. mangifera.

Light and scanning electron microscopic characterization of aflatoxins producing Aspergillus flavus in the maize crop.

Maize (Zea mays L.) is considered as one of the main cereals, used as a source of food, forage, and processed products. The loss of maize productivity is reported due to effect on roots, stalks, ears, and kernels mainly caused by many fungi. Among these fungal pathogens of maize, Aspergillus flavus (A. flavus) are the most prevalent that produces highly toxigenic aflatoxins that are highly carcinogenic to the consumers. The present study is confined to isolate and characterize the A. flavus from maize seeds for accurate identification that can be helpful for determination and management of aflatoxins in maize crop. Eighty stored seed samples of maize were collected from warehouses where seeds are stored for food and feeding purposes. For the isolation of A. flavus, Potato Dextrose Agar was used. Isolated fungi were identified macro and microscopically using light microscope and scanning electron microscope. A total of 212 Aspergillus isolates were identified based on macro-morphological and micro-morphological characteristics. The results showed that A. flavus colonies were granular, flat with yellow-green to deep yellow-green colony color having a white border and compact, spherical spore heads. Rapid rate of growth was observed maturing in about 3-5 days. In microscopic features, A. flavus have apically swollen conidiophores with various conidia bearing cells in long and dry chains. Spherical conidial heads were split into several columns ranging 300-400 µm in diameter. This will be helpful for farmers, researchers and traders in future for correct identification of sources of aflatoxins. RESEARCH HIGHLIGHTS: Maize seed samples were collected from Pothohar region of Pakistan. The fungi were isolated on PDA. Aspergillus flavus was identified macro-morphologically by observing growth rate, colony color and texture. Furthermore, these fungi were identified micro-morphologically by using light and scanning electron microscope. The 212 Aspergillus flavus strains were isolated and identified.

Mycobiota Isolation and Aflatoxin B1 Contamination in Fresh and Stored Sesame Seeds from Rainfed and Irrigated Zones of Punjab, Pakistan.

ABSTRACT: This study was carried out to evaluate the prevalence of mycobiota and aflatoxin (AF) B1 contamination in sesame seeds from rainfed and irrigated zones of the Punjab, Pakistan. For this purpose, 100 sesame seed samples were collected directly from the fields of major sesame-producing areas in rainfed and irrigated zones. The agar plate method was used for isolation of mycobiota, and thin-layer chromatography was used to determine AFB1 concentrations. Seed samples were then stored for 12 months. After 12 months, the seeds were again analyzed for mycobiota and AFB1 for comparison. All samples were positive for fungal growth under fresh and stored conditions. Twenty-one fungal species of 10 genera were isolated. Aspergillus flavus was the most prevalent contaminant found in fresh and stored sesame seeds from rainfed and irrigated zones, followed by Aspergillus niger, Alternaria alternata, and Fusarium oxysporum. The least prevalent fungi were Aspergillus ochraceus and Cladosporium oxysporum. Analysis revealed that 92% of fresh and 99% of stored seed samples were contaminated with AFB1. In the rainfed zone, 88% of fresh and 100% of stored seed samples were contaminated with AFB1, with mean concentrations of 15.74 and 33.8 ppb, respectively. In the irrigated zone, 96% of fresh and 98% of stored seed samples were contaminated with AFB1, with mean concentrations of 20.5 and 27.56 ppb, respectively. AFB1 concentrations >20 ppb were found in 20% of fresh and 100% of stored seeds samples from the rainfed zone and in 28% of fresh and 60% of stored samples from the irrigated zone and thus were not fit for human consumption as per the maximum limit (20 ppb) assigned by the U.S. Food and Drug Administration and the Food and Agriculture Organization of the United Nations. This report is the first on the mycobiota and AFB1 contamination in sesame seeds from rainfed and irrigated zones of the Punjab, Pakistan. These baseline data are an initial step in the effort to deal with this significant food safety issue.

Consensus Recommendations for the Diagnosis and Management of Pancreatic Neuroendocrine Tumors: Guidelines from a Canadian National Expert Group.

Pancreatic neuroendocrine tumors (pNETs) are rare heterogeneous tumors that have been steadily increasing in both incidence and prevalence during the past few decades. Pancreatic NETs are categorized as functional (F) or nonfunctional (NF) based on their ability to secrete hormones that elicit clinically relevant symptoms. Specialized diagnostic tests are required for diagnosis. Treatment options are diverse and include surgical resection, intraarterial hepatic therapy, and peptide receptor radionuclide therapy (PRRT). Systemic therapy options include targeted agents as well as chemotherapy when indicated. Diagnosis and management should occur through a collaborative team of health care practitioners well-experienced in managing pNETs. Recent advances in pNET treatment options have led to the development of the Canadian consensus document described in this report. The discussion includes the epidemiology, classification, pathology, clinical presentation and prognosis, imaging and laboratory testing, medical and surgical management, and recommended treatment algorithms for pancreatic neuroendocrine cancers.

Morphological and pathogenic variability among Macrophomina phaseolina isolates associated with mungbean (Vigna radiata L.) Wilczek from Pakistan.

Macrophomina phaseolina is a serious pathogen of many crops. In the present studies, 65 isolates of Macrophomina phaseolina from different agroecological regions of Punjab and Khyber Pakhtunkhwa provinces of Pakistan were analyzed for morphological and pathogenic variability. Regardless of their geographic origins, significant differences were detected among 65 isolates in their radial growth, sclerotial size, and weight as well as in pathogenicity. Sixteen isolates were rated as fast growing, 11 as slow growing, and the rest of the isolates as medium growing. Nine isolates were classified as large sized, 26 as small sized, and the remaining 30 isolates as medium sized. Thirty five isolates were ranked as heavy weight, 12 as low weight, and the rest of isolates were grouped as medium weight. Ten fungal isolates appeared to be least virulent, whereas eight isolates of diverse origin proved to be highly virulent against mungbean cultivars. The remaining isolates were regarded as moderately virulent. No relationship was found among the morphological characters and pathogenicity of the isolates. These morphological and pathogenic variations in various isolates of M. phaseolina may be considered important in disease management systems and will be useful in breeding programmes of mungbean cultivars resistant to charcoal rot.

Exploring thermophilic cellulolytic enzyme production potential of Aspergillus fumigatus by the solid-state fermentation of wheat straw.

Cellulases can be used for biofuel production to decrease the fuel crises in the world. Microorganisms cultured on lignocellulosic wastes can be used for the production of cellulolytic enzymes at large scale. In the current study, cellulolytic enzyme production potential of Aspergillus fumigatus was explored and optimized by employing various cultural and nutritional parameters. Maximum endoglucanase production was observed after 72 h at 55 °C, pH 5.5, and 70 % moisture level. Addition of 0.3 % of fructose, peptone, and Tween-80 further enhanced the production of endoglucanase. Maximum purification was achieved with 40 % ammonium sulfate, and it was purified 2.63-fold by gel filtration chromatography. Endoglucanase has 55 °C optimum temperature, 4.8 optimum pH, 3.97 mM K m, and 8.53 µM/mL/min V max. Maximum exoglucanase production was observed at 55 °C after 72 h, at pH 5.5, and 70 % moisture level. Further addition of 0.3 % of each of fructose, peptone, and Tween-80 enhances the secretion of endoglucanase. It was purified 3.30-fold in the presence of 40 % ammonium sulfate followed by gel filtration chromatography. Its optimum temperature was 55 °C, optimum pH was 4.8, 4.34 mM K m, and 7.29 µM/mL/min V max. In the case of ß-glucosidase, maximum activity was observed after 72 h at 55 °C, pH 5.5, and 70 % moisture level. The presence of 0.3 % of fructose, peptone, and Tween-80 in media has beneficial impact on ß-glucosidase production. A 4.36-fold purification was achieved by 40 % ammonium sulfate precipitation and gel filtration chromatography. Optimum temperature of ß-glucosidase was 55 °C, optimum pH was 4.8, K m was 4.92 mM, and V max 6.75 µM/mL/min. It was also observed that fructose is better than glucose, and peptone is better than urea for the growth of A. fumigatus. The K m and V max values indicated that endoglucanase, exoglucanase, and ß-glucosidase have good affinity for their substrates.

Inactivation of the lipopeptide antibiotic daptomycin by hydrolytic mechanisms.

The lipopeptide daptomycin is a member of the newest FDA-approved antimicrobial class, exhibiting potency against a broad range of Gram-positive pathogens with only rare incidences of clinical resistance. Environmental bacteria harbor an abundance of resistance determinants orthologous to those in pathogens and thus may serve as an early-warning system for future clinical emergence. A collection of morphologically diverse environmental actinomycetes demonstrating unprecedented frequencies of daptomycin resistance and high levels of resistance by antibiotic inactivation was characterized to elucidate modes of drug inactivation. In vivo studies revealed that hydrolysis plays a key role, resulting in one or both of the following structural modifications: ring hydrolysis resulting in linearization (in 44% of inactivating isolates) or deacylation of the lipid tail (29%). Characterization of the mechanism in actinomycete WAC4713 (a Streptomyces sp. with an MIC of 512 µg/ml) demonstrated a constitutive resistance phenotype and established daptomycin's circularizing ester linkage to be the site of hydrolysis. Characterization of the hydrolase responsible revealed it to be likely a serine protease. These studies suggested that daptomycin is susceptible to general proteolytic hydrolysis, which was further supported by studies using proteases of diverse origin. These findings represent the first comprehensive characterization of daptomycin inactivation in any bacterial class and may not only presage a future mechanism of clinical resistance but also suggest strategies for the development of new lipopeptides.

Structural basis for streptogramin B resistance in Staphylococcus aureus by virginiamycin B lyase.

The streptogramin combination therapy of quinupristin-dalfopristin (Synercid) is used to treat infections caused by bacterial pathogens, such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium. However, the effectiveness of this therapy is being compromised because of an increased incidence of streptogramin resistance. One of the clinically observed mechanisms of resistance is enzymatic inactivation of the type B streptogramins, such as quinupristin, by a streptogramin B lyase, i.e., virginiamycin B lyase (Vgb). The enzyme catalyzes the linearization of the cyclic antibiotic via a cleavage that requires a divalent metal ion. Here, we present crystal structures of Vgb from S. aureus in its apoenzyme form and in complex with quinupristin and Mg2+ at 1.65- and 2.8-A resolution, respectively. The fold of the enzyme is that of a seven-bladed beta-propeller, although the sequence reveals no similarity to other known members of this structural family. Quinupristin binds to a large depression on the surface of the enzyme, where it predominantly forms van der Waals interactions. Validated by site-directed mutagenesis studies, a reaction mechanism is proposed in which the initial abstraction of a proton is facilitated by a Mg2+ -linked conjugated system. Analysis of the Vgb-quinupristin structure and comparison with the complex between quinupristin and its natural target, the 50S ribosomal subunit, reveals features that can be exploited for developing streptogramins that are impervious to Vgb-mediated resistance.

Chimeric streptogramin-tyrocidine antibiotics that overcome streptogramin resistance.

Streptogramin antibiotics are comprised of two distinct chemical components: the type A polyketides and the type B cyclic depsipeptides. Clinical resistance to the type B streptogramins can occur via enzymatic degradation catalyzed by the lyase Vgb or by target modification through the action of Erm ribosomal RNA methyltransferases. We have prepared through chemical and chemo-enzymatic approaches a series of chimeric antibiotics composed of elements of type B streptogramins and the membrane-active antibiotic tyrocidine that evade these resistance mechanisms. These new compounds show broad antibiotic activity against gram-positive bacteria including a number of important pathogens, and chimeras appear to function by a mechanism that is distinct from their parent antibiotics. These results allow for the development of a brand new class of antibiotics with the ability to evade type B streptogramin-resistance mechanisms.

Streptogramin antibiotics: mode of action and resistance.

The streptogramin antibiotics were discovered over 40 years ago but are only now emerging as important therapeutic agents for the treatment of infection caused by a variety of bacteria. The streptogramins consist of mixtures of two structurally distinct compounds, type A and type B, which are separately bacteriostatic, but bactericidal in appropriate ratios. These antibiotics act at the level of inhibition of translation through binding to the bacterial ribosome. Resistance to streptogramins occurs through a number of mechanisms including target modification, efflux, and enzyme catalyzed antibiotic modification. This review describes the current understanding of streptogramin function and resistance with emphasis on molecular mechanism and epidemiology.