Inoculum Density Research Articles

Arbuscular mycorrhizal fungi trigger danger-associated peptide signaling and inhibit carbon-phosphorus exchange with nonhost plants.

In soil, arbuscular mycorrhizal fungi (AMF) meet the roots of both host and presumed nonhost plants, but the interactional mechanisms of AMF with and functional relevance for nonhost plants is little known. Here we show AMF can colonize an individually grown nonhost plant, Arabidopsis thaliana, and suppress the growth of Arabidopsis and two nonhost Brassica crops. This inhibitory effect increased with increasing AMF inoculum density, and was independent of AMF species or nutrient availability. 13 C isotope labeling and physiological analyses revealed no significant carbon-phosphorus exchange between Arabidopsis and AMF, indicating a lack of nutritional function in this interaction. AMF colonization activated the danger-associated peptide Pep-PEPR signaling pathway, and caused clear defense responses in Arabidopsis. The impairment of Pep-PEPR signaling in nonhost plants greatly compromised AMF-triggered defensive responses and photosynthesis suppression, leading to higher colonization rates and reduced growth suppression upon AMF inoculation. Pretreatment with Pep peptide decreased AMF colonization, and largely substituted for AMF-induced growth suppression in nonhosts, confirming that the Pep-PEPR pathway is a key participant in resistance to AMF colonization and in mediating growth suppression of nonhost plants. This work greatly increases our knowledge about the functional relevance of AMF and their mechanisms of interactions with nonhost plants.

Arnebia benthamii cell suspension cultures as a source of natural red pigments: optimization of shaking speed and inoculum density to maximize process productivity during sequential scaleup

Arnebia benthamii cell suspension cultures as a source of natural red pigments: optimization of shaking speed and inoculum density to maximize process productivity during sequential scaleup

Reduced Tomato Bacterial Wilt by Ferrous Chloride Application

Exogenous ferrous chloride (FeCl<sub>2</sub>) suppressed in vitro growth of Ralstonia pseudosolanacearum, causing bacteria for tomato bacterial wilt. More than 50 μM of FeCl<sub>2</sub> reduced the in vitro bacterial growth in dosedependent manners. Two to 200 μM of FeCl<sub>2</sub> did not affect the fresh weight of detached tomato leaves at 3 and 5 days after the petiole dipping without the bacterial inoculation. The bacterial wilt of the detached tomato leaves was evaluated by inoculating two different inoculum densities of R. pseudosolanacearum (10<sup>5</sup> and 10<sup>7</sup> cfu/ml) in the presence of FeCl<sub>2</sub>. Bacterial wilt in the detached leaves by 10<sup>5</sup> cfu/ml was efficiently attenuated by 10–200 μM of FeCl<sub>2</sub> at 3 and 5 days post-inoculation (dpi), but bacterial wilt by 10<sup>7</sup> cfu/ml was only reduced by 200 μM of FeCl<sub>2</sub> at 3 and 5 dpi. These results suggest that iron nutrients can be included in the integrated disease management of tomato bacterial wilt.

High-efficient removal of ammonium and co-production of protein-rich biomass from ultrahigh-NH4+ industrial wastewater by mixotrophic Galdieria sulphuraria

Microalgal cultivation system is regarded as an effective bioremediation system for NH4+-containing wastewater. However, ultrahigh NH4+ concentration in wastewater impeded the normal growth of most microalgal species leading to low NH4+ removal efficiency or even algal death, while indigenous bacteria and other biological contaminants in wastewater are negative for algal growth and eventually crash the microalgal-based wastewater treatment system. If maintaining sterile condition throughout the treatment process, the high consumption of energy must result in a high cost of operation with less valuable output. Aiming to achieve the goal of cost-effective NH4+ removal and protein-rich biomass co-production, a novel strategy of NH4+ reutilization from ultrahigh-NH4+ industrial wastewater was developed through photo-fermentation of the thermoacidophilic red alga Galdieria sulphuraria (G. sulphuraria) as cell factory. Results indicated that the highest protein content (71.66 % DW) was attained under optimal conditions with inoculum density of 1 × 108 cells mL−1, pH 3.5, 3380 mg NH4+ L−1 and light intensity of 230 μmol m−2 s−1 in shake flasks system for 4-day culture. Subsequently, repeated fed-batch culture under sterile and non-sterile mode was performed in ca. 5000 mg NH4+ L−1 wastewater medium in 5 L photo-fermenters, achieving a 98 % of NH4+ removal efficiency with a higher NH4+ removal rate (1705.67 mg L−1 d−1), biomass concentration (64.65 g L−1) and protein productivity (8.75 g L−1 d−1) under non-sterile culture mode. This work provided a new solution for high-efficient NH4+ removal coupled with protein-rich biomass production by a lower cost, high-value biomass output and environment-friendly way.

Effect of Inoculum Size and Age, and Sucrose Concentration on Cell Growth to Promote Metabolites Production in Cultured Taraxacum officinale (Weber) Cells.

Pentacyclic triterpenes, including lupeol, α- amyrin, and β-amyrin, present a large range of biological activities including anti-inflammatory, anti-cancer, and gastroprotective properties. The phytochemistry of dandelion (Taraxacum officinale) tissues has been widely described. Plant biotechnology offers an alternative for secondary metabolite production and several active plant ingredients are already synthesized through in vitro cultures. This study aimed to establish a suitable protocol for cell growth and to determine the accumulation of α-amyrin and lupeol in cell suspension cultures of T. officinale under different culture conditions. To this end, inoculum density (0.2% to 8% (w/v)), inoculum age (2- to 10-week-old), and carbon source concentration (1%, 2.3%, 3.2%, and 5.5% (w/v)) were investigated. Hypocotyl explants of T. officinale were used for callus induction. Age, size, and sucrose concentrations were statistically significant in cell growth (fresh and dry weight), cell quality (aggregation, differentiation, viability), and triterpenes yield. The best conditions for establishing a suspension culture were achieved by using a 6-week-old callus at 4% (w/v) and 1% (w/v) of sucrose concentration. Results indicate that 0.04 (±0.02) α-amyrin and 0.03 (±0.01) mg/g lupeol can be obtained in suspension culture under these starting conditions at the 8th week of culture. The results of the present study provide a backdrop for future studies in which an elicitor could be incorporated to increase the large-scale production of α-amyrin and lupeol from T. officinale.

The chickpea root rot complex in Saskatchewan, Canada- detection of emerging pathogens and their relative pathogenicity.

Chickpea fields in Saskatchewan, one of the three Canadian prairie provinces, have suffered from major health issues since 2019, but no definitive cause has been determined. Field surveys were conducted in Saskatchewan in 2020 and 2021 in order to develop a better understanding of root rot pathogens associated with chickpea. Root samples were analyzed for the presence of 11 potential chickpea root rot pathogens using end-point PCR. Fusarium redolens, F. solani and F. avenaceum were the most prevalent pathogen species detected in both survey years. The cause of Fusarium wilt in chickpea, F. oxysporum f. sp. ciceris, was not detected in either year, nor were Phytophthora spp. and Verticillium albo-atrum. Berkeleyomyces sp. was detected in one field in each year, and Verticillium dahliae was detected in several fields sampled in 2021. These two pathogens have not been reported previously on chickpea in Saskatchewan. The prevalence of Fusarium species obtained from 2021 root isolations was similar to that determined by molecular tests, with frequent isolation of F. redolens, F. oxysporum, F. avenaceum and F. solani. A series of indoor pathogenicity testing compared root disease severity caused by a selection of 16 isolates of six Fusarium species and single isolates of V. dahliae, Berkeleyomyces sp. and Macrophomina phaseolina. Results showed that select isolates of F. avenaceum were the most aggressive of the Fusarium isolates on chickpea. Despite relatively low inoculum density, a highly aggressive isolate of F. avenaceum caused severe stunting and more root rot symptoms than single isolates of V. dahliae, Berkeleyomyces sp. and M. phaseolina under the test conditions.

In vitro bioactive metabolite production and plant regeneration of medicinal plant Angelica sinensis

The root of Angelica sinensis (Oliv.) Diels is a traditional Chinese medicine (TCM) widely used for the cardio-cerebrovascular, anti-inflammatory, and anti-cancer agents, etc. Currently, the root yield is mainly limited by narrow geographical distribution, early bolting and flowering (EBF), continuous cropping obstacle, and germplasm degeneration. While two ancillary strategies to produce bioactive metabolites by bioreactor and innovate new germplasms by genome editing have not been conducted. Here is reported embryogenic callus induction, histomorphological structure identification, suspension cell culture, bioactive metabolite determination, shoot bud and root differentiation, and plantlet acclimatization at different treatments such as explants, hormones, and culture conditions. The embryogenic calli can be effectively induced (99.0%) from the root of aseptic seedlings by a combination of 2.0 mg/L IBA and 0.2 mg/L KT, and embryogenic cells including: three-cell, globular-, heart-, torpedo-, and cotyledon-shaped embryos were observed. The maximum growth rate, bioactive metabolites contents (i.e., ferulic acid, soluble sugar, flavonoids, and phenolic), and antioxidant capacities were observed at 9–12 d with inoculum density 40 g/L, 22 ℃ and 16/8 h light/dark. Robust plantlets can be obtained within 180 d after successive shoot bud and root differentiation as well as plantlet acclimation. Based on the strategies for the satisfaction of root demand, an effective and complete scheme is proposed for producing bioactive metabolites and regenerating plant of A. sinensis.

Assessment of Cultivation Parameters Influencing Polygalacturonase Production by Aspergillus sp. SO5 in Submerged Fermentation

Polygalacturonase represents an important enzyme of the pectinase consortium in the food and beverage industry. The present study aims to isolate, screen, and enhance physicochemical parameters for enzyme production under submerged fermentation. A total of 34 fungal strains were obtained from rotten fruits and 70.6 % of them are able to produce polygalacturonase by degrading pectin in pectin screening agar. The fungal isolate (SO5) that exhibited the greatest diameter of the hydrolysis zone (45.3 ± 0.04 mm) was selected for further study and later identified as Aspergillus sp. SO5, based on morphological characteristics using light microscopic observation. Several physicochemical parameters improved for pectinase production including incubation temperature, initial pH, agitation speed, inoculum density, and carbon and nitrogen sources. Under improved conditions, the polygalacturonase activity and fungal biomass increased up to 74.63 and 69.44 %, respectively. The finding also revealed that the improved physicochemical conditions enhance enzyme production and shorten the incubation period from 6 days to 5 days. HIGHLIGHTS This research paper highlighted the capability of indigenous fungus (Aspergillus) to produce polygalacturonase. The finding revealed that the improved physicochemical conditions including agitation speed, inoculum size, the concentration of pectin, and incorporation of yeast extract in the culture medium could enhance polygalacturonase production by up to 74.63 % (34.21 ± 0.49 U/mL). The improved physicochemical conditions not only enhance the polygalacturonase production but shorten the incubation period to obtain optimum enzyme production. GRAPHICAL ABSTRACT

Production and characterization of bioflocculant produced by Bacillus subtilis OL818309 and its flocculating effect on harmful algae

Bioflocculation is said to be a biological process where solid particles are separated from liquid suspension with the help of microorganisms. They are preferred to be an alternative to synthetic flocculants as they are non-toxic, eco-friendly and biodegradable compounds. The lower yield and efficacy limit industrial application of microbial flocculants. Hence, it is mandatory to determine a microbial source which had ability to produce bioflocculant at larger quantity with high efficiency. Therefore, it was intended in this study to isolate and identify a potential bioflocculant producing bacterium from Kurichi Lake and characterize the produced bioflocculant. The strain was identified as Bacillus subtilis through 16S rRNA sequencing deposited in the GenBank with accession number OL818309. Optimization of growth parameters for maximal bioflocculation was analyzed. It was found that pH of 7, growth temperature of 35 to 40°C at 48 hours of incubation with inoculum density of 3%, shaking speed of 165 rpm with guar gum as carbon source and yeast extract as nitrogen source aid in highest bioflocculant production. Moreover, batch fermentation was considered as suitable method for industrial scalability of bioflocculant production with a yield of 2.651 g/L. The bioflocculants are characterized by using FTIR, SEM, GC-MS and TGA. The purified bioflocculant was applied on algal polluted water. BOD, COD, TSS and TDS were evaluated. It was observed that 98.20% of flocculation occurred and clear supernatant was obtained. Overall results suggested that this strain has an ability to produce bioflocculants for industrial uses and also for environmental remediation.

Optimization of Submerged Culture Parameters of the Aphid Pathogenic Fungus Fusarium equiseti Based on Sporulation and Mycelial Biomass.

Fusarium equiseti (JMF-01), as an entomopathogenic fungus, can effectively control agricultural pests and has the potential to be a biocontrol agent. To promote mycelial growth and sporulation, we investigated the optimal submerged culture conditions for F. equiseti. In this study, we used the single-factor method and Box-Behnken design and determined the virulence of the submerged culture against Myzus persicae after optimization. As a result, the highly significant factors affecting the spore concentration of strain JMF-01 were the primary inoculum density and the initial pH, and the highly significant factor affecting the mycelial biomass was the medium-to-flask ratio. The highest mycelial biomass value was 0.35 g when the incubation time was 5.68 days, the initial pH was 5.11, the medium-to-flask ratio was 0.43, and 1 mL of the primary inoculum with spore density of 0.97 × 107 conidia/mL was added. When the incubation time was 6.32 days, the initial pH was 4.46, the medium-to-flask ratio was 0.35, the primary inoculum density was 1.32 × 107 conidia/mL of 1 mL, and the highest spore concentration of 6.49 × 108 blastospores/mL was obtained. Compared with the unoptimized medium conditions, the optimized submerged culture had the highest mycelial biomass and spore concentration, which were 3.46 and 2.06 times higher, respectively. The optimized submerged culture was highly pathogenic toward M. persicae, reaching a 95% mortality rate. Our results provide optimal submerged culture conditions for F. equiseti and lay the basis for later research to expand production for pest control.

Microcalorimetric growth behavior of E. coli ATCC 25922 in an MCDSC

Isothermal microcalorimetry can provide a general analytical tool for the characterization of bacterial growth. Methodologies and equipment have been studied to expand the application and disseminate the use of the technique. The MCDSC is a microcalorimeter capable of measuring in the range of 0.2 μW that can operate at a temperature range of −20 to 140 °C or under isothermal conditions. Here, we present the first investigation of MCDSC for E. coli growth with the Baranyi and Roberts modeling application. This study presented the calorimetric E. coli fingerprint at MCDSC and compares it with the plate count technique, giving the data more biological meaning. The calorimeter was able to accurately detect growth metabolism and discriminate E. coli at different inoculum densities. Additionally, the MCDSC can offer a new point of view for evaluating microbial growth, such as the significant reduction in error due to dispersed data by the viable counting method.

Letter to the Editor: In Vitro Activity of Oxazolidinone Against Nontuberculous Mycobacteria in China.

Letter to the Editor: In Vitro Activity of Oxazolidinone Against Nontuberculous Mycobacteria in China.

Improving bacoside yield of Bacopa monnieri (L.) Wettst. in temporary immersion system by increasing immersion time and lowering the intervals

Bacopa monnieri (L.) Wettst. or Brahmi has been used in Ayurvedic medicine and currently use as an alternative medicinal herb for several therapeutic healing. Therefore, in vitro mass propagation of B. monnieri for high quality plant production using temporary immersion system (TIS) was necessarily examined. Explants of B. monnieri as regenerated shoots from leaf segments were used to determine the effects of culture system, immersion time and inoculum explant density on growth and bacoside production of B. monnieri. Statistically significant differences in growth and biomass accumulation were observed in the TIS compared with continuous immersion and semi-solid systems. Production of bacoside A, bacopaside II, bacopasaponin C, and total bacoside in B. monnieri obtained from microcontainer cultivation was significantly higher than TIS, whereas total yield of bacosides obtained from different culture systems showed no significant differences. Three immersions per day for 10 min duration promoted growth and biomass accumulation of B. monnieri, while cultivation with 20 explants per container offered optimal inoculum density for large-scale production. Various concentrations and yields of bacoside were obtained from different immersion interval conditions. Reducing immersion duration improved bacoside production. Five explants per container provided the highest bacoside content but yield per container was the lowest.

Pectinase Production by Aspergillus Niger Ar-2 Using Orange Peels As Substrate

Pectinases are the group of enzymes that catalyzes the degradation of pectic substances. Pectinase are enzymes that are remarkably employed in most industries because they have a large variety of applications, such as increasing juice extraction by decreasing the viscosity of concentrates in cellulose fibre preparation, coffee/tea fermentation and also for the clarification of juices and wines. This research was carried out for pectinase production by Aspergillus niger AR2 using local orange peel as substrate. Aspergillus niger was isolated from spoiled orange fruit and identified using phenotypic and molecular techniques. The isolate was screened for pectinase production on pectin agar. Fermentation was carried out by Aspergillus niger AR2 at fermentation days 3, 4 and 5; the amount of substrate (15g), pH (5), temperature (300C) and inoculum density of 106 (spore/mL). After fermentation, crude pectinase was extracted for enzyme assay. Enzyme activity was measured based on the amount of D-galacturonic acid released by the crude enzyme. Pectinase produced was used for orange juice extraction from mashed oranges and compared with juice with no enzymes. The results have shown that maximum pectinase production by A. nigerAR2 was found to be at a temperature of 300C, inoculum density of 106 (spore/mL), pH 5 at day 5 using orange peels as substrate with an activity of 3.04±0.024 (U/ml). The result shows that the pectinase produced was effective in orange juice extraction from mashed oranges due to the increase in the volume of orange juice.

Antimicrobial Susceptibility of Clinical Isolates of Candida Species to Ethanolic Extracts of Ziziphus Abyssinica Leaves

Pectinases are the group of enzymes that catalyzes the degradation of pectic substances. Pectinase are enzymes that are remarkably employed in most industries because they have a large variety of applications, such as increasing juice extraction by decreasing the viscosity of concentrates in cellulose fibre preparation, coffee/tea fermentation and also for the clarification of juices and wines. This research was carried out for pectinase production by Aspergillus niger AR2 using local orange peel as substrate. Aspergillus niger was isolated from spoiled orange fruit and identified using phenotypic and molecular techniques. The isolate was screened for pectinase production on pectin agar. Fermentation was carried out by Aspergillus niger AR2 at fermentation days 3, 4 and 5; the amount of substrate (15g), pH (5), temperature (300C) and inoculum density of 106 (spore/mL). After fermentation, crude pectinase was extracted for enzyme assay. Enzyme activity was measured based on the amount of D-galacturonic acid released by the crude enzyme. Pectinase produced was used for orange juice extraction from mashed oranges and compared with juice with no enzymes. The results have shown that maximum pectinase production by A. nigerAR2 was found to be at a temperature of 300C, inoculum density of 106 (spore/mL), pH 5 at day 5 using orange peels as substrate with an activity of 3.04±0.024 (U/ml). The result shows that the pectinase produced was effective in orange juice extraction from mashed oranges due to the increase in the volume of orange juice.

Volumetric Spore Traps Are a Viable Alternative Tool for Estimating Heterobasidion Infection Risk

Prophylactic stump treatments against the conifer root rot fungus Heterobasidion annosum s.l. should take into account the airborne inoculum density of the pathogen, in order to be economically feasible. Our objective was to test if an automatic volumetric spore trap (AVST) could be used as a sensitive alternative of passive traps for quantifying Heterobasidion airspora in forest stands. The routinely used wood disc exposure method (WDE) was implemented simultaneously with AVST in five coniferous monocultures and three near-natural stands without silvicultural management in Czechia. Air sampling took place for 24-h intervals in five months of the main sporulation period. The atmospheric concentration of H. annosum s.l. spores (cHa) was determined by qPCR with generic and species-specific primers. AVST detected more target species than WDE on 77% of sampling occasions. When comparing the relative abundance of the three European H. annosum s.l. species detected by AVST and WDE, H. parviporum and H. abietinum were found to be overrepresented on wood discs. cHa in November was significantly higher than in May and June, confirming the seasonal pattern typical for temperate Europe. For an accurate and rapid estimation of Heterobasidion primary infection risk, the usage of AVST is highly recommended.

Adapting to the projected epidemics of Fusarium head blight of wheat in Korea under climate change scenarios.

Fusarium head blight (FHB) of wheat, mainly caused by Fusarium graminearum Schwabe, is an emerging threat to wheat production in Korea under a changing climate. The disease occurrence and accumulation of associated trichothecene mycotoxins in wheat kernels strongly coincide with warm and wet environments during flowering. Recently, the International Panel for Climate Change released the 6th Coupled Model Intercomparison Project (CMIP6) climate change scenarios with shared socioeconomic pathways (SSPs). In this study, we adopted GIBSIM, an existing mechanistic model developed in Brazil to estimate the risk infection index of wheat FHB, to simulate the potential FHB epidemics in Korea using the SSP245 and SSP585 scenarios of CMIP6. The GIBSIM model simulates FHB infection risk from airborne inoculum density and infection frequency using temperature, precipitation, and relative humidity during the flowering period. First, wheat heading dates, during which GIBSIM runs, were predicted over suitable areas of winter wheat cultivation using a crop development rate model for wheat phenology and downscaled SSP scenarios. Second, an integrated model combining all results of wheat suitability, heading dates, and FHB infection risks from the SSP scenarios showed a gradual increase in FHB epidemics towards 2100, with different temporal and spatial patterns of varying magnitudes depending on the scenarios. These results indicate that proactive management strategies need to be seriously considered in the near future to minimize the potential impacts of the FHB epidemic under climate change in Korea. Therefore, available wheat cultivars with early or late heading dates were used in the model simulations as a realistic adaptation measure. As a result, wheat cultivars with early heading dates showed significant decreases in FHB epidemics in future periods, emphasizing the importance of effective adaptation measures against the projected increase in FHB epidemics in Korea under climate change.

Optimized conversion of wheat straw into single cell oils by Yarrowia lipolytica and Lipomyces tetrasporus and synthesis of advanced biofuels

This paper deals with the optimized conversion of undetoxified wheat straw hydrolysates into microbial lipids by two oleaginous yeasts, Yarrowia lipolytica and Lipomyces tetrasporus. Wheat straw were pretreated by steam explosion at 203 °C for 300 s and hydrolysed at 20% solid-to-liquid ratio by using an enzymatic loading of 15 FPU/g substrate. The mixed wheat straw hydrolysates (WHS) contained 86 gL-1 glucose and 22 gL-1 xylose, 2.3 gL-1 acetic acid, 0.9 gL-1 furanic compounds. The fermentation process was optimized in terms of the inoculum age and density, medium composition, and bioreactor feeding strategy. In particular, the different capacity of the two yeasts to overcome the toxic effect of the biomass degradation by-products, in different inoculum ages, was deeply investigated. Two hydrolysates concentration were tested: WSH containing 86 gL-1 glucose and 22 gL-1 xylose and the diluted medium containing 40 gL-1 glucose and 22 gL-1 xylose. The results indicated that both yeasts were able to detoxify WSH and grow on undetoxified hydrolysates as effect of the intrinsic capacity to metabolize the furan derivatives. Y. lipolytica was able to detoxify the medium in all the investigated set-ups, while L. tetrasporus was able to detoxify the medium only if inoculated in the stationary phase of growth. After the process optimization in shaken flasks, the production of Single Cell Oils (SCOs) by L. tetrasporus was carried out in a medium-scale bioreactor of 10L obtaining lipid yield and cell content of 21% and 62%, respectively. The extracted SCOs, with high oleic and palmitic acid content, were converted into biodiesel displaying overall features in accordance with international biodiesel standards, namely ASTM and EN 14214.

Evaluation of Dilution Susceptibility Testing Methods for Aztreonam in Combination with Avibactam against Enterobacterales.

As multidrug and pan-resistance among Enterobacterales continue to increase, there is an urgent need for more therapeutic options to treat these infections. New β-lactam and β-lactam inhibitor (BLI) combinations have a broad spectrum of activity, but those currently approved do not provide coverage against isolates harboring metallo-β-lactamases (MBL). Aztreonam (ATM) and avibactam (AVI) in combination (ATM/AVI; AVI at 4 μg/mL fixed concentration) provides a similarly broad range of activity while maintaining activity against MBL-producing isolates. The in vitro susceptibility testing of ATM/AVI by standard methods was evaluated during development. This study investigated the impact of nonstandard testing conditions on the activity of ATM/AVI as observed during broth microdilution testing as well as the equivalency between agar dilution and broth microdilution MIC values when testing a diverse panel of Enterobacterales (N = 201). Nonstandard test conditions evaluated included inoculum density, atmosphere of incubation, media pH, varied medium cation concentrations, incubation time, varied serum concentrations, testing in pooled urine instead of media, addition of blood to the media, and the presence of surfactant. Generally, apart from low pH and high inoculum density, nonstandard testing parameters did not affect ATM/AVI broth microdilution MIC values. Correlation of MIC values obtained by agar dilution and broth microdilution resulted in an essential agreement of 97.0% for all tested Enterobacterales. Variation of standard testing conditions had little impact on broth microdilution MIC values for ATM/AVI. The correlation between broth microdilution and agar dilution MICs suggests both methods are reliable for determination of ATM/AVI MIC values. IMPORTANCE Increasing antibiotic resistance and emergence of pan-resistant isolates threaten the ability to control infections and to provide many other medical interventions such as surgery and chemotherapy, among others. New therapies are required to control emerging resistance mechanisms, including the increase in metallo-β-lactamases. Some new antibiotic combinations provide coverage against highly resistant isolates but are unable to target organisms that produce metallo-β-lactamases. Aztreonam in combination with avibactam provides a broad spectrum of activity against highly resistant isolates that also targets metallo-β-lactamase-producing organisms. An important part of drug development is the ability for clinical labs to determine the susceptibility of isolates to the antimicrobial. This manuscript investigates the in vitro susceptibility testing of aztreonam/avibactam with nonstandard testing conditions and a correlation study between broth microdilution and agar dilution against clinical isolates encoding a variety of resistance mechanisms. Overall, aztreonam/avibactam was generally unaffected by changes in testing conditions and showed strong agar/broth correlation.

Can Beauveria bassiana reduce the root lesion nematode, Pratylenchus thornei, infection on wheat?

BackgroundLimited number of control methods against root-lesion nematodes has increased the search for alternative management strategies. Due to secondary metabolites such as toxins and enzymes secreted by the entomopathogenic fungus, Beauveria bassiana, the number of studies on nematicidal potentials on many plant parasitic nematodes has increased. Almost no work was done on the nematicidal activity of B. bassiana, which is widely used as a bio-insecticide, on the root lesion nematode, Pratylenchus thornei, commonly found on wheat in Turkey. In the present study, it was aimed to determine the pathogenicity of two native B. bassiana isolates (BIM-001 and BY2) obtained from Turkey against P. thornei on wheat under controlled conditions.ResultsSpore suspension of B. bassiana isolates affected P. thornei soil, root, final nematode density and reproduction rate at different degrees according to spore concentration. The soil, root, total nematode density, and reproduction rate in the control on İkizce cv. were 1234.0 adult + larvae/500 g soil, 1105.0 adult + larvae/per pot, 2341.0 (soil + root density) and 5.8 (PF(final nematode density/PI (initial inoculum density)), respectively. It was determined that these parameter values were at the lowest at 108 spore/ml than other concentrations in both isolates of B. bassiana. In 108 spore/ml concentrations of BIM-001 isolate, while P. thornei soil, root, total nematode density, and reproduction rate on İkizce were 641.7 adult + larvae/500 g soil, 930.9 adult + larvae/per pot, 1572.6 (soil + root density) and 3.9 (PF/PI), respectively, these parameter values were found to be 645.2 adult + larvae/500 g soil, 849.0 adult + larvae/per pot, 1492.2 (soil + root density) and 3.6 (PF/PI) at 108 spore/ml concentrations of BY2 isolate. It was observed that the reproduction rate of P. thornei decreased at 108 spore/ml concentration of BIM-001 and BY2 isolates compared to the control.ConclusionNative B. bassiana isolates of BIM-001 and BY2 reduced P. thornei on wheat and the concentration was important for the pathogenicity of B. bassiana. While the reproduction rate of P. thornei at 108 and 107 spores/ml concentrations in both isolates decreased than the control. At 106 spore/ml concentration it was found similar to the control. Even though B. bassiana is known as an effective biocontrol agent against insects and some plant-parasitic nematodes, more detailed studies should be done on its effect on P. thornei.