Spore Concentration Research Articles

A simple and effective aerosol pathogen disinfection test for a flowing air disinfector

Aerosol transmission is an important disease transmission route and has been especially pertinent to hospital and biosafety laboratories during the SARS-CoV-2 pandemic. The thermal resistance of airborne SARS-CoV-2 is lower than that of Bacillus subtilis spores, which are often used to test the effectiveness of SARS-CoV-2 and other pathogen disinfection methods. Herein, we propose a new method to test the disinfection ability of a flowing air disinfector (a digital electromagnetic induction air heater) using B. subtilis spores. The study provides an alternative air disinfection test method. The new test system combined an aerosol generator and a respiratory filter designed in-house and could effectively recover spores on the filter membrane at the air outlet after passing through the flowing air disinfector. The total number of bacterial spores used in the test was within the range of 5 × 105–5 × 106 colony-forming units (CFUs) specified in the technical standard for disinfection. The calculation was based on the calculation method in Air Disinfection Effect Appraisal Test in Technical Standard for Disinfection (2002 Edition). At an air speed of 3.5 m/s, we used a digital electromagnetic induction air heater to disinfect flowing air containing 4.100 × 106 CFUs of B. subtilis spores and determined that the minimum disinfection temperature was 350 °C for a killing rate of 99.99%. At 400 °C, additional experiments using higher spore concentrations (4.700 × 106 ± 1.871 × 105 CFU) and a higher airspeed (4 m/s) showed that the killing rate remained>99.99%. B. subtilis spores, as a biological indicator for testing the efficiency of dry-heat sterilization, were killed by the high temperatures used in this system. The proposed method used to test the flowing air disinfector is simple, stable, and effective. This study provides a reference for the development of test systems that can assess the disinfection ability of flowing air disinfectors.

Features of the seasonal dynamics of airborne fungal spore concentrations in Ukraine

Fungi represent a distinct kingdom of ubiquitous living beings. Most other organisms are constantly in contact with elements of the fungal body. In particular, the widespread vegetation of fungi in the environment, their sporulation and the further spread of spores and mycelia by air currents make the contact of fungal particles with human respiratory organs inevitable. This can lead to the development of sensitization and allergies. Therefore, the aim of the presented study was to determine the taxonomy of airborne fungal spores, the qualitative and quantitative changes in this composition at different times of the year compared with previous sporulation seasons, as well as the prevention of allergic diseases. The study of fungal sporulation was carried out from 2011 to 2021 by volumetric method using Burkard trap of a Hirst type in a 24-hour mode (from February to November). The device was installed on the roof of the chemical building of the National Pirogov Memorial Medical University, Vinnytsya. Reading of the microscopic slides obtained from air samples was carried out using light microscopes with a magnification of 400 and 1000 by the method of 12 vertical transects. It was found that spores of various taxonomic groups of fungi, namely, of Asco- and Basidiomycetes were observed throughout the growing season from March to October with the highest concentrations in mid and late summer. Thus, in June, July and August, peak concentrations of spores of the fungi Ganoderma, Coprinus, Cladosporium were observed; in July, September and October – of Ustilaginales; from July to November – of Alternaria, Epicoccum; in October – of different Basidiospores, and also Periconia, Stemphylium and Uredinales; in September – of Agrocybe. Among all studied micromycetes, concentrations of Cladosporium spores were the highest. However, significant sporulation persisted even in the autumn period, which made fungal spores a specific causative agent of airborne respiratory diseases at this time, especially against the background of low pollen concentrations. Climate change can lead to modification in the length of the fungal growing season. This information should be taken into account when predicting the symptoms of seasonal allergies in the population.

Fungal Contamination of Building Materials and the Aerosolization of Particles and Toxins in Indoor Air and Their Associated Risks to Health: A Review.

It is now well established that biological pollution is a major cause of the degradation of indoor air quality. It has been shown that microbial communities from the outdoors may significantly impact the communities detected indoors. One can reasonably assume that the fungal contamination of the surfaces of building materials and their release into indoor air may also significantly impact indoor air quality. Fungi are well known as common contaminants of the indoor environment with the ability to grow on many types of building materials and to subsequently release biological particles into the indoor air. The aerosolization of allergenic compounds or mycotoxins borne by fungal particles or vehiculated by dust may have a direct impact on the occupant's health. However, to date, very few studies have investigated such an impact. The present paper reviewed the available data on indoor fungal contamination in different types of buildings with the aim of highlighting the direct connections between the growth on indoor building materials and the degradation of indoor air quality through the aerosolization of mycotoxins. Some studies showed that average airborne fungal spore concentrations were higher in buildings where mould was a contaminant than in normal buildings and that there was a strong association between fungal contamination and health problems for occupants. In addition, the most frequent fungal species on surfaces are also those most commonly identified in indoor air, regardless the geographical location in Europe or the USA. Some fungal species contaminating the indoors may be dangerous for human health as they produce mycotoxins. These contaminants, when aerosolized with fungal particles, can be inhaled and may endanger human health. However, it appears that more work is needed to characterize the direct impact of surface contamination on the airborne fungal particle concentration. In addition, fungal species growing in buildings and their known mycotoxins are different from those contaminating foods. This is why further in situ studies to identify fungal contaminants at the species level and to quantify their average concentration on both surfaces and in the air are needed to be better predict health risks due to mycotoxin aerosolization.

Investigation of spatial and temporal variations of airborne Poaceae, Myrtaceae and Cupressaceae pollen and Alternaria spores in Sydney, Australia, 2017–2020

There is a need for information on pollen exposure to assess allergy risk. Monitoring of aeroallergens in a city is usually limited to the use of a single trap for the whole area. While a single trap provides enough information on background pollen concentration for the area, varying pollen exposure across different urban environments, however, is not considered. In this study, we analysed aerobiological data of three pollen seasons (2017–2020) recorded with a volumetric pollen trap in Sydney, Australia. In order to assess spatial differences in pollen exposure across the city, we installed ten gravimetric traps recording pollen deposition for eight weeks during the summer of 2019/2020. We considered the influence of meteorological variables, land use, urbanisation and distance to the sea. Our results showed differences in pollen season characteristics across the three analysed seasons and correlations with meteorological parameters. Considering all years, we found for Poaceae and Alternaria the strongest positive correlation with mean temperature and for Myrtaceae and Cupressaceae with maximum temperature. Likewise, there were negative correlations with humidity (Myrtaceae, Cupressaceae, Alternaria) and precipitation (Myrtaceae, Cupressaceae). Days with medically relevant pollen and spore concentrations varied between years and we recorded the highest amount in 2017/2018 for Poaceae and Alternaria and in 2019/2020 for Myrtaceae. In addition, we found spatial and temporal variations of pollen deposition. However, we did not detect significant correlations between pollen deposition and land use, which can be attributable to drought conditions prior to the sampling campaign and the temporal setting in the pollen season. This study highlights the importance of continuous volumetric aerobiological monitoring as well as the assessment of pollen exposure at several locations across a large urban area.

Optimization of Single-step Pravastatin Production by Penicillium brefeldianum ESF21P through Response Surface Methodology

The aim of the present study was to optimize the fermentation process for enhanced production of pravastatin by a wild-type Penicillium brefeldianum ESF21P strain using statistical approaches. Initial screening of significant variables influencing pravastatin production was carried out using 27-3 fractional factorial design. The seven variables involved in this study were slant age, spore concentration, inoculum volume, fermentation time, temperature, initial pH of the medium and agitation rate. Amongst these, slant age, fermentation time, initial pH of the medium and agitation rate had significant influences on pravastatin accumulation. These four variables were further optimized using the central composite rotatable design of response surface methodology. The analysis revealed that the optimal values of the selected variables were a slant age of 5.95 days, fermentation time of 11.87 days, initial pH of the medium of 6.13 and agitation rate of 211.31 rpm (rounded to 210 rpm). These optimized conditions resulted in a maximum level of pravastatin accumulation (234.36 mg/L), approaching the value predicted by the model of 251.19 mg/L. This study confirmed that statistical approaches can be successfully applied as practical tools in improving single-step production of pravastatin by Penicillium brefeldianum ESF21P.

Spore dispersal patterns of the ascomycete fungus Ramulariacollo-cygni and their influence on disease epidemics

Ramularia leaf spot is a major economic disease of barley caused by the dothidiomycete fungus Ramulariacollo-cygni. The fungus has a complex life cycle which includes extensive late season spore release events and a seed-borne phase. Predicting disease epidemics during the growing season remains a difficult challenge. To better understand the interaction between spore movement and disease epidemics, spore samplers were set up in Germany (two sites over 4 years), Poland (seven sites over 2 years) and the UK (two sites over 9 years), where the disease has been observed. Spore concentrations were determined using a real time PCR assay, and meteorological data were obtained from co-located automatic stations. Spore release events were seen to peak in June on mainland Europe and July in the UK. The pattern of spore release was broadly similar across countries with earlier peaks in mainland Europe. A relationship was observed in the UK between July spore levels and disease in following winter barley crops. Rainfall and temperature were proposed as significant drivers of spore release in these months. The major environmental parameter associated with spore release across the two UK sites was crop surface wetness, although some site-specific interactions were noted for rainfall and wind movement. Regression analysis of spore patterns and disease epidemics indicates a relationship between spore levels 75–105 days pre harvest and final disease levels in UK winter barley crops. This relationship was not observed in spring barley. The implications on risk forecasts are discussed.

Entomopathogenic Fungi as a Potential Management Tool for the Control of Urban Malaria Vector, Anopheles stephensi (Diptera: Culicidae).

Anopheles stephensi (Diptera: Culicidae) is the vector of urban malaria in India and has a significant impact in transmitting infection in cities and towns. Further, WHO has also alarmed its invasive nature as a threat to African countries. Entomopathogenic fungi such as Beauveria bassiana and Metarhizium anisopliae have been found to be highly effective in controlling vector mosquito populations and therefore could be used in integrated vector control programs. Before employing the entomopathogenic fungi into the control programs, an effective isolate must be selected. Two separate experiments were conducted to evaluate the efficacy of Beauveria bassiana (Bb5a and Bb-NBAIR) and Metarhizium anisopliae (Ma4 and Ma-NBAIR) isolates against An. stephensi. Cement and mud panels were treated with fungal conidia with the concentration of 1 × 107 conidia/mL and adult An. stephensi mosquitoes were exposed to the treated panels (24 h after conidia were applied) by conducting WHO cone bioassay tests. The survival of the mosquitoes was monitored daily until the 10th day. In the second experiment, second instar larvae of An. stephensi were treated with fungal (Bb5a, Bb-NBAIR, Ma4 and Ma-NBAIR) conidia and blastospores with the spore concentration of 1 × 107 spores/mL. The survival of larvae was monitored until pupation. All the fungal isolates tested caused mortality in the adult mosquitoes, with varying median survival times. The Bb5a isolate reported lesser median survival times on both cement and mud panels (6 days). The treated mosquitoes showed similar survival rates for each fungal isolate irrespective of the panel type. There was no mortality in the treated larvae; however, a delay in larval development to pupae was observed compared with the untreated control larvae. Ma4-treated larvae took 11 days (95% CI = 10.7-11.2) to become pupae when compared with the untreated control larvae (6 days [95% CI = 5.6-6.3]). The findings of this study will be useful to consider EPF as a tool for the management of vector mosquitoes.

Examination of Different Sporidium Numbers of Ustilago maydis Infection on Two Hungarian Sweet Corn Hybrids' Characteristics at Vegetative and Generative Stages.

Corn smut is one of the major diseases in corn production. The cob infection causes high economic and quality loss. This research investigated the effects of three different concentrations of corn smut infection (2500, 5000, and 10,000 sporidia/mL) on two Hungarian sweet corn hybrids (Desszert 73 and Noa). Plants were infected at the vegetative (V4-V5) and the generative (V7) stages. The effects of the corn smut infection were evaluated at 7 and 14 days after the pathogen infection (DAPI) at vegetative and at 21 DAPI at generative stages. The photosynthetic pigments (relative chlorophyll, chlorophyll-a and b, and carotenoids), malondialdehyde (MDA), and proline concentration, activities of the antioxidant enzymes [ascorbate peroxidase (APX), guaiacol peroxidase (POX), and superoxide dismutase (SOD)], morphological characteristics (plant height, stem and cob diameter, cob length, cob and kernel weights), mineral contents (Al, B, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, P, Pb, S, Sr, and Zn), and quality parameters (dry matter, fiber, fat, ash, nitrogen, and protein) were measured. At both sampling times (7 and 14 DAPI) in both hybrids, the corn smut infection reduced the photosynthetic pigments (relative chlorophyll, chlorophylls-a, and b, and carotenoids) irrespective of the spore concentration. Under the same conditions, the MDA and proline contents, as well as the activities of APX, POX, and SOD increased at both sampling times. The negative effects of the corn smut infection were also observed at the generative stage. Only the 10,000 sporidia/mL of corn smut caused symptoms (tumor growth) on the cobs of both hybrids at 21 DAPI. Similarly, this treatment impacted adversely the cob characteristics (reduced cob length, kernel weight, and 100 grains fresh and dry weight) for both hybrids. In addition, crude fat and protein content, Mg, and Mn concentration of grains also decreased in both hybrids while the concentration of Al and Ca increased. Based on these results, the sweet corn hybrids were more susceptible to corn smut at the vegetative stage than at the generative stage.

Rainfall effects on vertical profiles of airborne fungi over a mixed land-use context at the Brazilian Atlantic Forest biodiversity hotspot

Whilst fungi are a large fraction of primary biological aerosol particles (PBAPs) and their impact on global climate has been widely recognised, few studies have empirically assessed fungal vertical profiles and diversity relating those with rainfall. Here, we show the results of fungal PBAPs before and after a rainfall event during a fieldwork campaign using a hot-air balloon over a mixed land-use context at the Brazilian Atlantic Forest biodiversity hotspot. Four flights of c. 1 hour each were performed in the early morning from 8th until 11th of March 2022, and data were collected at three sampling heights (0, 150 and 300 m). Rainfall estimation using IMERG data indicated the precipitation event was of 15–20 mm and ERA5/ECMWF data highlighted that most of the airborne samples were taken above the boundary layer height. After the rainfall, the concentration of fungal spores at the ground level remained unchanged, whereas it was reduced to between 2- and 2.5-fold for the 150 and the 300 m heights, respectively. This was also accompanied by a reduction in the number of Pink-CFU, indicating a major drop in fungal PBAPs at higher altitudes associated with the rain. In addition, total spore concentration indicated Cladosporium sp. as dominant at all sampling heights, accounting for more than 80% of all spores, whereas Aspergillus/Penicillium-like represented less than 20%. Our results show the effects of rainfall and altitude on the concentration of fungal PBAPs, indicating how wet removal impacts fungi vertical profiles which has knock-on-effects on cloud and precipitation formation.

Corrigendum: Uncertainty in coprophilous fungal spore concentration estimates

Corrigendum: Uncertainty in coprophilous fungal spore concentration estimates

Effect of prevailing winds and land use on Alternaria airborne spore load

Alternaria spores are a common component of the bioaerosol. Many Alternaria species are plant pathogens, and their conidia are catalogued as important aeroallergens. Several aerobiological studies showing a strong relationship between concentrations of airborne spore and meteorological parameters have consequently been developed. However, the Alternaria airborne load variation has not been thoroughly investigated because it is difficult to assess their sources, as they are a very common and widely established phytopathogen. The objective of this study is to estimate the impact of vegetation and land uses as potential sources on airborne spore load and to know their influence, particularly, in cases of long-medium distance transport. The daily airborne spore concentration was studied over a 5-year period in León and Valladolid, two localities of Castilla y León (Spain), with differences in their bioclimatic and land use aspects. Moreover, the land use analysis carried out within a 30 km radius of each monitoring station was combined with air mass data in order to search for potential emission sources. The results showed a great spatial variation between the two areas, which are relatively close to each other. The fact that the spore concentrations recorded in Valladolid were higher than those in León was owing to prevailing winds originating from large areas covered by cereal crops, especially during the harvest period. However, the prevailing winds in León came from areas dominated by forest and shrubland, which explains the low airborne spore load, since the main Alternaria sources were the grasslands located next to the trap. Furthermore, the risk days in this location presented an unusual wind direction. This study reveals the importance of land cover and wind speed and direction data for establishing potential airborne routes of spore transport in order to improve the Alternaria forecasting models. The importance of conducting Alternaria aerobiological studies at a local level is also highlighted.

The persistence of time: the lifespan of Bacillus anthracis spores in environmental reservoirs

Anthrax is a lethal bacterial zoonosis primarily affecting herbivorous wildlife and livestock. Upon host death Bacillus anthracis vegetative cells form spores capable of surviving for years in soil. Anthrax transmission requires host exposure to large spore doses. Thus, conditions that facilitate higher spore concentrations or promote spore survival will increase the probability that a pathogen reservoir infects future hosts. We investigated abiotic and pathogen genomic variation in relation to spore concentrations in surface soils (0–1 cm depth) at 40 plains zebra (Equus quagga) anthrax carcass sites in Namibia. Specifically, how initial spore concentrations and spore survival were affected by seasonality associated with the timing of host mortality, local soil characteristics, and pathogen genomic variation. Zebras dying of anthrax in wet seasons—the peak season for anthrax in Etosha National Park—had soil spore concentrations 1.36 orders of magnitude higher than those that died in dry seasons. No other variables considered affected spore concentrations, and spore survival rates did not differ among sites. Surface soils at these pathogen reservoirs remained culture positive for a range of 3.8–10.4 years after host death. Future research could evaluate if seasonal patterns in spore concentrations are driven by differences in sporulation success or levels of terminal bacteremia.

Modeling on the Effects of Deliberate Release of Aerosolized Inhalational Bacillus anthracis (Anthrax) on an Australian Population.

This study aimed to determine optimal mitigation strategies in the event of an aerosolized attack with Bacillus anthracis, a category A bioterrorism agent with a case fatality rate of nearly 100% if inhaled and untreated. To simulate the effect of an anthrax attack, we used a plume dispersion model for Sydney, Australia, accounting for weather conditions. We determined the radius of exposure in different sizes of attack scenarios by spore quantity released per second. Estimations of different spore concentrations were then used to calculate the exposed population to inform a Susceptible-Exposed-Infected-Recovered (SEIR) deterministic mathematical model. Results are shown as estimates of the total number of exposed and infected people, along with the burden of disease, to quantify the amount of vaccination and antibiotics doses needed for stockpiles. For the worst-case scenario, over 500,000 people could be exposed and over 300,000 infected. The number of deaths depends closely on timing to start postexposure prophylaxis. Vaccination used as a postexposure prophylaxis in conjunction with antibiotics is the most effective mitigation strategy to reduce deaths after an aerosolized attack and is more effective when the response starts early (2 days after release) and has high adherence, while it makes only a small difference when started late (after 10 days).

Glycerol ginger extract addition to edible coating formulation for preventing oxidation and fungal spoilage of stored walnuts

During storage, walnuts can undergo oxidation processes that lead to a decay of product quality and the development of rancidity and off-flavor. The present study investigated how the application of a chitosan coating, containing a glycerol ginger extract (GGE) rich in bioactive compounds, can preserve walnut quality during storage. Glycerol can be considered a green extraction solvent, which allows to obtain extract rich in polyphenols and with high radical scavenging activity. GGE employed in the formulation of a chitosan-based coating determined significantly lower (p < 0.05) lipid oxidation and peroxides values in walnuts stored under stressing temperature conditions (45 °C), in comparison to Control (uncoated sample) and even in comparison to the walnuts coated with sole chitosan. Moreover, when artificially inoculated with Aspergillus flavus spore suspension, walnuts treated with GGE-enriched coating evidenced the lowest disease incidence and the lowest spore concentration. Results obtained encourage the application of coating containing GGE even in other rich lipid matrices that can easily undergo oxidation process or spoilage caused by phytopathogenic fungi.

High-resolution palynology signals in surface sediments of coastal Hainan Island of China

Studies on pollen in marine surface sediments are important for understanding the distribution mechanisms of pollen and spores into the ocean, and they are also useful in micro-paleontological studies. In this study, high-resolution palynological analysis of marine surface sediment samples from the south and southeastern inner-shelf regions of Hainan Island was performed to understand the distribution mechanism of marine surface pollen and its relationship with terrestrial vegetation. The results indicated that fern spores are the most common type, followed by tree pollen and herbaceous pollen. A majority of total pollen and spore concentrations are dominated by fern spores because the sample sites are highly concentrated with Microlepia and Polypodiaceae spores, mainly due to anthropogenic activities. The variation in tree pollen concentrations (especially for Pinus, Quercus, and Castanopsis) suggested that these pollen grains were transported mainly by wind patterns and rivers from Hainan Island. The pollen concentrations and percentage analysis in the study area showed that the inner-shelf sites have higher values than far offshore sites, reflecting a relationship between modern pollen distribution patterns and nearby landmass vegetation. Based on the principal component analysis of the resulting pollen and spore percentages, there are two main factors affecting the pollen distribution around the study area: possible human activities that have modified Hainan Island and wind–river transport toward the study area. This is the first study to discover that the presence of fern spores across the shelf is unusual, implying widespread lateral mixing in the south and southeastern Hainan Island inner-shelf region.

PATHOGENICITY OF ISOLATES OF ENTOMOPATHOGENIC FUNGI TO WORKERS OF Acromyrmex heyeri (Forel, 1899) (HYMENOPTERA: FORMICIDAE)

Leaf-cutting ants stand out among the main pests of agricultural and forestry crops. Chemical control is the most used method to control these insect pests, requiring the development of techniques that are less harmful to the environment. The present study aimed at verifying the action of Beauveria bassiana (Bals.) Vuill, Cordyceps fumosorosea (Wize), and Metarhizium anisopliae (Metsch.) Sorokin isolates on the in vitro mortality of Acromyrmex heyeri (Forel). Seven isolates of entomopathogenic fungi were used: three isolates of Beauveria bassiana (IBCB 66, IBCB 170, and IBCB 632), one isolate of Cordyceps fumosorosea (IBCB 130), and three isolates of Metarhizium anisopliae (IBCB 348, IBCB 383, and IBCB 425), and five concentrations of spores (1.0×104, 1.0×105, 1.0×106, 1.0×107, and 1.0×108 spores mL-1) for each fungal isolate. The control treatment consisted of autoclaved distilled water and 0.01% Tween 40, without fungal pathogens. The experiments were carried out in a completely randomized design with five replications. Estimation of lethal concentrations of LC50 and LC90 was performed using Probit analysis. The isolates of B. bassiana, C. fumosorosea, and M. anisopliae were pathogenic to leaf-cutting ants with the five tested concentrations of spores. Higher mortality of the specimens was reached with increasing concentration. The entomopathogenic fungi evaluated in this study proved to be efficient agents for the biological control of Acromyrmex heyeri.

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.

Mutual effects on mycotoxin production during co-culture of ochratoxigenic and aflatoxigenic Aspergillus strains.

Mycotoxin co-occurrence compromises the safety of food crops worldwide. Environmental factors, as well as fungal interaction, can substantially influence the infectivity of mycotoxigenic fungi and their subsequent production of multi-mycotoxin. Here, we investigated the mutual effects of the co-culture of ochratoxigenic and aflatoxigenic Aspergillus strains on the co-production of ochratoxin A (OTA) and aflatoxin B1 (AFB1). Single cultures of ochratoxigenic A. carbonarius and A. alliaceus grew optimally at 25°C, whereas aflatoxigenic A. flavus grew optimally at 35°C. The maximum levels of OTA and AFB1 were achieved at 25°C, whereas mycotoxin production decreased at 35°C. During competitive growth of the ochratoxigenic and aflatoxigenic isolates, inhibition or stimulation of mycotoxin production was dependent on the fungal strain, temperature, and the ratio of the spore concentration. Aspergillus carbonarius and A. alliaceus generally produced OTA, with similar patterns of relative OTA levels at all temperatures. AFB1 production by A. flavus in the presence of ochratoxigenic Aspergillus species was inhibited at 25°C and stimulated at 35°C. These results indicated that the temperature, presence of other mycotoxigenic Aspergillus species, and ratio of the initial spore concentration significantly contributed to the co-production of OTA and AFB1.

Impact of the immobilized Bacillus cereus MG708176 on the characteristics of the bio-based self-healing concrete

Novel carrier units were evaluated for their bio-healing benefits in our study to increase the efficacy of concrete healing. Bacillus cereus MG708176, an alkali-tolerant, calcite precipitating, endospore-forming strain was added as a bio-healing agent after its immobilization on wood ash units. A spore concentration of [1.3 × 107 spore/cm3] combined with 2.5% w/w urea was added to cement. Beams of 40 × 40 × 160 mm were used and tested for completely damaged mortar specimens after 7, 14, and 28 days of water treatment. Using wood ash bacterial mortars, totally destructed specimens were fully healed in all time intervals. Positive changes in concrete mechanical properties in bacterial wood ash treatment that were 24.7, 18.9, and 28.6% force for compressive, flexural, and tensile strengths more than control. The micro-images of the Scanning Electron Microscope (SEM) showed the dense concrete structure via calcite, Bacillafilla, and ettringite formation. Our results have shown improvements in the concrete healing efficiency and the mechanical concrete properties by filling the concrete cracks using a calcite-producing bacterium that is immobilized on wood ash units.

Lethal and sub-lethal effects of Cordyceps fumosorosea on the demography and biochemistry of Phenacoccus solenopsis

ABSTRACT The cotton mealybug, Phenacoccus solenopsis Tinsley, is a highly invasive pest of cotton. The use of entomopathogenic fungi as a bio-pesticide could provide an alternative to current chemical control measures that preserve the environment and biodiversity, and ensures good quality of crops. Lethal, sub-lethal and trans-generational studies are needed to assess the effects of myco-insecticides on such pests. The pathogenicity of different spore concentrations of Cordyceps fumosorosea Wize was assessed against second-instar nymphs by immersion while focusing on lethal (LC50) and sub-lethal (LC30) spore concentration treatments of C. fumosorosea on filial (F0) and first filial (F1) generations. After treatment at LC50 and LC30 spore concentrations of C. fumosorosea, the progeny of P. solenopsis showed reduced nymphal duration, adult longevity and fecundity as compared with controls. Also, total pre-oviposition period (TPOP), adult pre-oviposition period (APOP) and oviposition days (Od) were reduced with the increasing spore concentration of C. fumosorosea. In addition, population growth parameters such as net reproductive rates (Ro) and mean generation time (T) were dramatically reduced. The level of expression of acetylcholinesterase (AChE), esterases (EST), acid and alkaline phosphatases (ACP, ALP) and glutathione S-transferases (GST) were also examined. Significant expression of EST, GST, ALP, ACP and AChE (7.15, 4.51, 4.54, 2.80 and 8.32 μmol/min of mg/ml protein), respectively were observed at 8 × 107 conidia/mL of C. fumosorosea. Pathogenicity even at sub-lethal doses as well as the production of detoxifying enzymes indicates that C. fumosorosea is the most effective fungus against P. solenopsis.