Viable fungi in corn dust

Numbers of viable fungal propagules in corn dusts in southern Georgia were estimated during various farm and grain elevator operations in 1979, 1980, and 1982. A six-stage Andersen sampler for viable microbial particles was used to sample the dusts with various agar media. The most abundant fungi in corn dusts were species of yeasts: Aspergillus, Penicillium, Cladosporium, Alternaria. Helminthosporium, and Fusarium. However, the relative abundance of these fungi differed between years. There was a greater incidence of the Aspergillus flavus group in the hot, dry year of 1980 compared with the cooler, wetter years of 1979 and 1982. Fungi in the corn dusts sampled numbered between 10(4) and 10(9) viable propagules per m3 of air. By contrast, outdoor air often contained fewer than 10(4) viable fungal propagules per m3. Most A. flavus propagules were deposited at stages three and four of the Andersen sampler, with correspond to the trachea, primary bronchi, and secondary bronchi in the human respiratory system. In an assessment of the air spores by exposing sterile petri dishes, more large-spored fungi, like Alternaria tenuis, and fewer small-spored fungi, such as A. flavus, were detected when compared with colony counts from petri dishes exposed to air in the Anderson sampler.     

Viable airborne fungi in Riyadh, Saudi Arabia

An aerobiological study to identify and quantify allergenic fungi and their seasonal fluctuations was conducted at two different sites, (Al-Batha, a more developed area in the south and Al-Ulia, a less developed area in the north) in Riyadh city, using portable Personal Volumetric Air Sampler (Burkard Manufacturing Co., England). Sampling was conducted twice a week in both the morning and in the afternoon at both sites, for a period of 12 months. Airborne fungi were grouped into major and minor components depending upon their frequency of appearance and catch percentage in the air. Cladosporium spp., Penicillium spp., Aspergillus spp., Alternaria spp. and Ulocladium spp. were included as major components. Minor components included Drechslera spp., Rhizopus spp., Fusarium spp. and Stachybotryis spp. In general, higher concentrations of fungi were found at the developed (Al-Batha) site than at the less developed (Al-Ulia) site, both in the morning and in the afternoon.     

Secalonic acid D: natural contaminant of corn dust.

The mycotoxin secalonic acid D was detected for the first time as a natural contaminant of corn dust obtained from grain storage elevators. Secalonic acid D amounts ranged from 0.3 to 4.5 ppm (0.3 to 4.5 micrograms/g), as determined by reversed-phase high-performance liquid chromatography.     

Toxigenic fungi associated with stored corn

A total of 246 fungal isolates were obtained from 25 moldy corn samples collected in central Iowa. Either water or ether extracts of all corn samples except one exhibited some degree of toxicity in mice and/or ducklings. At least one toxigenic isolate was obtained from each corn sample. Extracts of cultures of 99 of the fungal isolates, involving 13 genera, produced death in one or more of the assay animals. The majority of the toxigenic isolates belonged to the generaAspergillus andPenicillium. Three isolates ofTrichothecium roseum were highly toxic to ducklings and mice. The ducklings exhibited a flaccid paralysis shortly after receiving an oral dose of extracts of these three isolates. Death frequently occurred following a second oral dose given 24 hr later. Mice given intraperitoneal injections of extracts ofT. roseum first exhibited lethargy and intermittent tremors, then hyperemotivity, roughening of the hair coat, abdominal respirations, incoordination, dyspnea and clonic convulsions with death occurring usually within 10 to 20 min.

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Zusammenfassung Insgesamt sind 246 Pilzisolierungen von 25 verschimmelten Getreideproben, die in Zentral-Iowa gesammelt worden sind, erhalten worden. Sowohol Wasser- wie Aether-Extrakte von allen Getreideproben zeigten eine gewisse Toxizität in Mäusen als auch in Entchen außer einer einzigen Probe. Kulturextrakte von 99 der Pilzisolierungen, die 13 Gattungen umfaßten, verursachten den Tod in einem oder in mehreren Versuchstieren. Die Mehrheit der toxischen Isolierungen gehörte den GattungenAspergillus undPenicillium an. Drei Isolierungen vonTrichothecium roseum waren hoch toxisch für Entchen und Mäuse. Die Entchen zeigten eine schlaffe Paralyse kurz nachdem sie eine orale Dosis der Auszüge dieser drei Isolierungen erhalten hatten. Tod erfolgte häufig nach der zweiten oralen Dosis innerhalb 24 Stunden. Mäuse, die eine intraperitoneale Injektion der Auszüge vonT. roseum erhielten, zeigten erst eine Lethargie und einen intermittierenden Tremor, dann eine Hyperemotivität, aufgerauhte Haarbedeckung, abdominale Atmung, Inkoordination, Dyspnoe, klonische Zuckungen und Tod gewöhnlich innerhalb 10 bis 20 Minuten.

     

Levels of bacteria, fungi, and endotoxin in bulk and aerosolized corn silage.

Three samples of silage taken from the surface of a silo and from depths of 20 and 45 cm in the silo were studied for identification of the potential agents causing symptoms of organic dust toxic syndrome. The samples were examined by dilution plating before and after aerosolization in an acoustical dust generator. Aerosol samples were collected by liquid impinger and filter cassettes. The samples were examined for total aerobic bacteria, anaerobic bacteria, gram-negative bacteria, lactobacilli, listeriae, thermophilic actinomycetes, fungi, and endotoxin. Very high levels of total aerobic bacteria and fungi were found in the surface sample (up to 10(9) CFU/g in the bulk sample and up to 10(9) CFU/m3 after aerosolization), whereas the corresponding values from the deepest site were 100 to 50,000 times lower. Aspergillus fumigatus predominated among the fungi, whereas Bacillus and gram-negative organisms (Pseudomonas, Alcaligenes, Citrobacter, and Klebsiella species) prevailed among bacteria. Thermophilic actinomycetes occurred in numbers up to 10(7) CFU/g in the bulk samples, whereas anaerobic bacteria, lactobacilli, and listeriae were only few or absent. The concentration of endotoxin was high in the surface sample (up to 211.4 Endotoxin Units/mg) and about 200-fold lower in the sample from the deepest site. The results show that contact with dust from the surface of silage carries the risk of exposure to high concentrations of microorganisms, of which A. fumigatus and endotoxin-producing bacteria are the most probable disease agents.     

丛枝菌根真菌侵染Bt玉米及对其生长的影响

以2个不同转化事件的Bt玉米5422Bt1(Bt11)和5422CBCL(Mon810)及其同源常规玉米5422为对象,研究接种摩西球囊霉(Glomus mosseae)对Bt玉米与常规玉米生长的影响.结果表明:3个品系玉米接菌处理的菌根侵染率明显不同,菌根侵染各参数值总体呈现5422Bt1>5422CBCL>5422趋势;接种处理均促进了玉米的生长,其效应随玉米品系和生育期的不同而呈现差异,喇叭口期5422的地上部干重和总干重显著增加,拔节期5422Bt1的叶片数、茎粗以及喇叭口期的叶片数、茎粗、地上部干重、总干重显著高于对照,5422CBCL拔节期的叶片数和喇叭口期地下部干重增加显著;3个玉米品系菌根真菌依赖性与接菌效应为5422Bt1>5422CBCL>5422,2个Bt玉米品系与Glomus mosseae间的兼容性更好,接种处理对Bt玉米的生长促进作用强于常规玉米.     

Thermogravimetric kinetics of corn stalk pretreated by oleaginous fungi Cunninghamella echinulata

The thermogravimetric and composition of corn stalk pretreated by oleaginous fungi Cunninghamella echinulata had been studied in this paper. Results indicated that pretreatment by oleaginous fungi C. echinulata could decrease the activation energy and make the pyrolysis more efficient and energy-saving. By bio-pretreatment, the contents of elements agreed with the weight loss, sugar content, and oil contents, especially the sulfur content was greatly decreased, greatly eliminating the inventory of gas contamination such as the emission of SOx and making the pyrolysis more environmentally friendly. Therefor, corn stalk with sugar pretreated by oleaginous fungi C. echinulata should be a good pyrolysis material to obtain high quality bio-oil.     

Occurrence of fungi and mycotoxins in corn silage, Jalisco State, Mexico

The aim of this study was to evaluate the chemical composition, mold count and mycotoxin contamination of corn silage collected during a six month-period. The results indicated that the chemical composition and the physicochemical parameters evaluated did not show significant variation during the sampling time. Fungal count on RBC ranged from 1.7 x 10(3) to 9 x 10e8 CFU/g. Mucor, Penicillium and Aspergillus spp. were the most frequent fungal species in the corn silage. Fusarium count ranged from 1.6 x 10(3) to 1.6 x 10e8 CFU/g in Nash Snyder culture media. Aflatoxin B, fumonisins, ochratoxin A, ochratoxin B, deoxynivalenol, and zearalenone were detected throughout the period of corn silage maintenance (100% positive samples). However, only deoxynivalenol levels were higher than the maximum limit recommended by the FDA.     

Controlling fungi that colonize eggs of the western corn rootworm in the laboratory

Females of the polyphagous, ectoparasitoid, Exeristes roborator (F.) (Hymenoptera: Ichneumonidae), learned an olfactory stimulus associated with an artificial host microhabitat in the laboratory. In a two-choice olfactometer, females previously given hosts only in association with one stimulus showed a greater tendency to visit exclusively, and spend time in, chambers containing a source of that stimulus, than control females. Learning of olfactory cues could act in conjunction with learning of visual cues to allow the parasitoid to identify accurately microhabitats that experience has taught it contain hosts. It could also allow the parasitoid to identify these resources when visual cues are not available.

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Résumé Nous avons supposé que les femelles polyphages de l'ichneumonide ectoparasite, E. roborator (F.), pourraient apprendre les stimuli olfactifs liés au microhabitat artificiel dans lequel elles avaient attaqué leur hôte. 4 lots de femelles ont été placés dans des conditions différentes: le microhabitat des hôtes du premier lot était du Parafilm imprégné d'odeur de pomme; celui des hôtes du second était un Parafilm non traité. Les hôtes des lots témoins 3 et 4 étaient présentés respectivement avec les deux microhabitats et sans aucun microhabitat. Placées dans un olfactomètre statique contenant du Parafilm traité à la pomme et du Parafilm vierge, des femelles du lot 1 ont eu tendance à ne visiter que l'enceinte contenant du Parafilm traité à la pomme, elles ont passé environ 75% de leur temps dans cette enceinte. A l'opposé, les femelles des 3 autres lots ont eu tendance à ne visiter que l'enceinte sans odeur de pomme, et elles n'ont passé que 34 à 46% de leur temps dans l'enceinte traitée à la pomme. Les différences entre les réactions du lot 1 et des autres lots sont significatives, mais entre les lots 2, 3 et 4, elles ne le sont pas. Une expérience témoin confirme que les préférences des femelles du lot 1 ne sont pas innées; E. roborator a donc appris à reconnaitre les stimuli olfactifs du microhabitat sentant la pomme. L'apprentissage des signaux olfactifs liés au microhabitat de l'hôte pourrait s'effectuer seul ou en relation avec l'apprentissage de signaux visuels permettant au parasitoïde d'identifier avec précision les microhabitats d'un hôte convenable.

     

Use of molecular markers for monitoring fungi involved in stalk rot of corn

Summary Separate genes conferring antibiotic drag resistance have been inserted into Fusarium graminearum and Fusarium moniliforme. These organisms are associated with stalk rot of corn, a disease of uncertain cause. Antibiotic resistant fungi were obtained by developing a gene transfer system using whole cells as recipients for DNA. Hygromycin B and benomyl-resistant colonies were isolated by treating fungal tissue with lithium acetate and adding plasmid vectors containing the respective genes which give drug resistance. The DNA was stably integrated into the fungal chromosome. Following plant inoculation, disease symptoms developed and the isolates were recovered on selective medium. In each case, these fungi retained the transformed phenotype, although extensive rearrangements and/or deletions occurred. Specific molecular tagging allows detailed studies of this interaction and should be of general use in situations involving complex multiple pathogen diseases.     

Viable but nonculturable bacteria in drinking water.

Klebsiella pneumoniae, Enterobacter aerogenes, Agrobacterium tumefaciens, Streptococcus faecalis, Micrococcus flavus, Bacillus subtilis, and Pseudomonas strains L2 and 719 were tested for the ability to grow and maintain viability in drinking water. Microcosms were employed in the study to monitor growth and survival by plate counts, acridine orange direct counts (AODC), and direct viable counts (DVC). Plate counts dropped below the detection limit within 7 days for all strains except those of Bacillus and Pseudomonas. In all cases, the AODC did not change. The DVC also did not change except that the DVC, on average, were ca. 10-fold lower than the AODC.     

Airborne dust,bacteria, actinomycetes and fungi at a flourmill

A study was carried out on suspended dust, bacterial and fungal aerosols in a four-storey flourmill building located in Giza, Egypt. Airborne microorganisms were quantitatively isolated using liquid impinger and gravimetric samplers during the period from March 2004 to February 2005. Suspended dust varied from 1.96 to 16.3 mg m⁻³ and 0.69 to 1.8 mg m⁻³ in the indoor and outdoor environments, respectively. Suspended dust was significantly greater (P < 0.05) at bran package, double roller, purifiers and flour storage units in comparison to the outdoor reference site. The dust levels exceed the occupational exposure limit (OEL) of 0.5 mg m⁻³ for flour dust. Airborne microbial counts were found at median values, between sampling locations, ranged from 0 to >10⁴ CFU m⁻³. Gram-negative bacteria were found in small numbers (0–10² CFU m⁻³). The highest concentration of actinomycetes (>10³ CFU m⁻³) was detected in the storage unit. Airborne fungal counts were found at the median values, between sampling locations, varied from 10³ to 10⁴ CFU m⁻³. The counts of airborne bacteria and fungi were significantly greater (P < 0.05) at the purifiers and double roller mill units in comparison to the outdoor reference site using the liquid impinger sampler. Microbial levels associated with bulk deposited dust averaged between 10⁵ and 10⁶ CFU g⁻¹. Alcaligenes (5.4%) Pseudomonas (3.87%) and Enterobacter (3.1%) were the predominant Gram-negative species while Bacillus (29.4%) and Micrococci (13.9%) were the major components of Gram-positive bacteria. Aspergillus and Penicillium were the predominant fungal types indoor whereas Cladosporium (35.2%) and Aspergillus species (22.2%) were the predominant fungal types outdoor. A number of allergenic and toxigenic bioaerosols were found in the flourmill workplace.     

Inhibition of plant-pathogenic fungi by a corn trypsin inhibitor overexpressed in Escherichia coli

The cDNA of a 14-kDa trypsin inhibitor (TI) from corn was subcloned into an Escherichia coli overexpression vector. The overexpressed TI was purified based on its insolubility in urea and then refolded into the active form in vitro. This recombinant TI inhibited both conidium germination and hyphal growth of all nine plant pathogenic fungi studied, including Aspergillus flavus, Aspergillus parasiticus, and Fusarium moniliforme. The calculated 50% inhibitory concentration of TI for conidium germination ranged from 70 to more than 300 microgram/ml, and that for fungal growth ranged from 33 to 124 microgram/ml depending on the fungal species. It also inhibited A. flavus and F. moniliforme simultaneously when they were tested together. The results suggest that the corn 14-kDa TI may function in host resistance against a variety of fungal pathogens of crops.     

Viable fungi in the air of indoor environments of the National Archive of the Republic of Cuba

The aim of this study was to analyze the viable fungi in the air of indoor environments of the National Archive of the Republic of Cuba (NARC). The samples were taken in fifteen areas (five points for the three floors) at 2 days (rainy and dry seasons) using a biocolector SAS in 3 h: 10:00 a.m., 1:00 p.m. and 4:00 p.m. The fungal concentration was indicated as colony forming units per cubic meter of air (cfu/m³ of air). It was concluded that indoor air of the NARC was not polluted due to the average fungal concentration that was obtained (59 and 327 cfu/m³ of air in rainy and dry seasons, respectively). In front of the electric transformers, the fungal concentration was significantly higher than those obtained along the corridors of the lower-ground floor. A trend to the increasing of fungal concentration was observed: when the floors were increased, in dry season was higher than rainy season, where also there was biggest fungal diversity. Among the fungal genera isolated, Aspergillus had the highest relative frequency of appearance, and in dry season, it was isolated Actinobacillus sp. (Actinomycetes). Six fungal species were isolated in both samplings: Aspergillus alliaceus, Aspergillus niger, Cladosporium cladosporioides, Fusarium oxysporum, Penicillium chrysogenum and Mucor racemosus. All of fungal species isolated have high biodeteriogenic capacity, and the 61 % showed pathogenic attributes.     

Characterization of fungi transferred by dust storms in Kuwait and their plant pathogenicity

Dust storms carry large amounts of plant detritus and microorganisms that may cause diseases in humans, animals or plants. These storms are frequent in Kuwait throughout the year. This research was conducted to identify the fungal species carried by the dust storms in Kuwait, originating from the northwesterly direction, with emphasis on plant pathogens. Fungi were isolated from settled dust samples and identified using established microbiological and molecular approaches. Fungal isolates identified as Fusarium oxysporum from settled dust were examined for pathogenicity using a number of crop plants. In total, 17 genera of fungi were identified in the dust samples. These fungi included plant pathogens or facultative plant parasites that were transported in the dust storms as viable propagules. The most common dust-carried fungi belonged to the genera Fusarium, Alternaria, Ulocladium, Phoma, Aspergillus, Acremonium and Penicillium. The F. oxysporum isolates that had been characterized by partial 18S rRNA gene sequencing were pathogenic, causing root and stem rot in tomato, bean and cucumber, but not squash.     

Viable Septoria spp. in celery seed samples

In a simple, routine test developed to detect viable Septoria spp. in samples of celery seed, seed washings are inoculated on to celery seedlings. Viable infection was detected in fifty-four samples between 1960 and 1966. The method can be used to detect viable infection on one seed in several thousand. Spore exudation during ‘blotter’ tests was shown to be associated with lesion production both in the seedling inoculation test and in growing-on tests. A high incidence of saprophytic fungi indicates that seed has not been treated but a low incidence does not mean that the sample is healthy.     

Levels of bacteria, fungi, and endotoxin in bulk and aerosolized corn silage

Three samples of silage taken from the surface of a silo and from depths of 20 and 45 cm in the silo were studied for identification of the potential agents causing symptoms of organic dust toxic syndrome. The samples were examined by dilution plating before and after aerosolization in an acoustical dust generator. Aerosol samples were collected by liquid impinger and filter cassettes. The samples were examined for total aerobic bacteria, anaerobic bacteria, gram-negative bacteria, lactobacilli, listeriae, thermophilic actinomycetes, fungi, and endotoxin. Very high levels of total aerobic bacteria and fungi were found in the surface sample (up to 10(9) CFU/g in the bulk sample and up to 10(9) CFU/m3 after aerosolization), whereas the corresponding values from the deepest site were 100 to 50,000 times lower. Aspergillus fumigatus predominated among the fungi, whereas Bacillus and gram-negative organisms (Pseudomonas, Alcaligenes, Citrobacter, and Klebsiella species) prevailed among bacteria. Thermophilic actinomycetes occurred in numbers up to 10(7) CFU/g in the bulk samples, whereas anaerobic bacteria, lactobacilli, and listeriae were only few or absent. The concentration of endotoxin was high in the surface sample (up to 211.4 Endotoxin Units/mg) and about 200-fold lower in the sample from the deepest site. The results show that contact with dust from the surface of silage carries the risk of exposure to high concentrations of microorganisms, of which A. fumigatus and endotoxin-producing bacteria are the most probable disease agents.