Chrysosporium species, potential spoilage organisms of chocolate

Standard methods of analysing foods for the presence of moulds are inadequate for thedetection of genera such as Chrysosporium which do not grow at the high wateractivities of most mycological media. The use of malt, yeast, 50% glucose agar (MY50G) insealed containers as an enrichment medium allowed time for germination and growth ofheat-stressed spores. Three Chrysosporium spp., C. xerophilum Pitt, C. inops (Carmichael) and C. farinicola (Burnside) Skou, were isolated fromcommercial chocolate bars with a water activity (a _w ) of approximately0·28. Chrysosporium inops was isolated from commercial milk crumb and anew Chrysosporium sp. was isolated from Ghanaian cocoa beans. In chocolates madeby coating MY50G agar (a_w = 0·89) with chocolate (a_w = 0·27) containing C. inops arthroconidia, two types of deterioration were seenafter storage. The first was fat bloom due to recrystallization of the cocoa butter on the outer andinner chocolate surface. The second was growth of C. inops which occurred on theinside chocolate surface adjacent to the MY50G agar filling and on the outside surface afterholding at 92% equilibrium relative humidity (erh) for 12 d. There was some evidence that C. inops could grow on the outside of chocolates held at 5·7% erh after 4months' storage at 25 °C. The appearance of the white fungal growth was not unlikefat bloom to the naked eye but was clearly different with the electron microscope.     

Ethanol production in table jelly by two species of Chrysosporium

Different commercial brands of tablet jelly were stored in sealed containers for 12 weeks at an initial water activity of 0·90. The surface of those containing real fruit juice became covered with a dense white mould identified as Chrysosporium inops. That of those without fruit juice did not. This type of spoilage has been observed in commercially stored samples. When spores of this fungus and the closely related species, C. xerophilum , were added to commercial tablet jelly, the fungi grew only on samples containing real fruit juice. It is suggested that the fruit juice may provide some essential nutrient required for growth of these nutritionally fastidious species as well as the fungal spores themselves. Ethanol was detected in the headspace gas of stored samples of mouldy jelly. The production of ethanol by the two Chrysosporium species was confirmed by fermentation of glucose in liquid batch culture: approximately 2% ethanol was formed in 14 d. The ability of C. xerophilum and C. inops to utilize the Embden-Meyerhof-Parnas pathway may explain why these slow-growing xerophilic moulds become dominant after storage at low oxygen tension.     

Comparison of Atmospheric Conditions for Culture of Clinical Specimens of Neisseria gonorrhoeae

We cultured 55 clinical specimens of Neisseria gonorrhoeae in the following atmospheric conditions: (i) 10% carbon dioxide in a CO(2) incubator; (ii) a candle extinction jar; (iii) an air convection incubator; and (iv) an anaerobic jar without added CO(2). The number and size of colonies growing on modified Thayer-Martin medium were evaluated after incubation of cultures for 24 and 48 h at 36 C. After 24 h, the specimens from the candle extinction jar had the greatest number and size of colonies, but after 48 h growth was approximately equal for specimens from the candle jar and the CO(2) incubator. Only 19 of 55 specimens grew in the air convention incubator. None of 55 clinical specimens or of 10 laboratory strains grew anaerobically. Development of colonial morphology for colony types 1, 2, 3, and 4 was studied at 24 h on a base medium that contained no hemoglobin. The relative numbers of the four colony types in specimens were comparable after 24 h of incubation in any of the three atmospheric conditions under which growth occurred, but the different types were distinguished most readily when grown in the candle extinction jar.     

Temperature and water activity minima for growth of spoilage moulds from meat

L owry , P.D. & G ill , C.O. 1984. Temperature and water activity minima for growth of spoilage moulds from meat. Journal of Applied Bacteriology 56 , 193–199.
Five species of fungi were isolated from mould spoilage on meat other than black spot. 'White spot' colonies yielded Chrysosporium pannorum or an Acremonium sp .; 'whiskers' colonies yielded Thamnidium elegans or Mucor racemosus , and blue-green colonies yielded Penicillium corylophilum. Chrysosporium pannorum was moderately xerotolerant with a minimum growth temperature of — 5C. The Acremonium sp. and P. corylophilum showed a similar level of xerotolerance but had a minimum growth temperature of — 2C. Mucor racemosus was no more xerotolerant than many spoilage bacteria and did not grow below - 1C, but grew rapidly at 3C and above. Thamnidium elegans grew at — 7C on supercooled medium and an intrinsic minimum growth temperature of — 10C was indicated. However, the low xerotolerance of this species precluded growth on frozen media below — 5C. It seems therefore that — 5C is the practical limiting temperature for mould growth on meat, and mould spoilage usually indicates that surfaces of freezer stored meats have approached and possibly exceeded 0C.     

Influence of water activity and temperature on survival of and colony formation by heat-stressed Chrysosporium farinicola aleuriospores.

The ability of sublethally heat-stressed aleuriospores of Chrysosporium farinicola to form colonies on yeast extract-glucose agar (YGA) supplemented with sufficient glucose, sorbitol, glycerol, and NaCl to achieve reduced water activity (aw) in the range of 0.88 to 0.95 was determined. The effects of the aw of diluent and incubation temperature during recovery and colony formation were also investigated. Aleuriospores harvested from 14-day-old cultures grown at 25 degrees C were less resistant to heat inactivation compared with aleuriospores from 20-day-cultures. Increased populations of heat-stressed aleuriospores were recovered as the aw of YGA was decreased from 0.95 (glucose and glycerol) and 0.94 (sorbitol) to 0.89 and 0.88, respectively. In NaCl-supplemented YGA, populations recovered at an aw of 0.94 were greatly reduced compared with populations detected at an aw of 0.92; no colonies were formed on NaCl-supplemented YGA at an aw of 0.88. Tolerance to aw values above 0.88 to 0.89 as influenced by solute type was in the order of glucose greater than sorbitol greater than glycerol greater than NaCl. Incubation at 20 degrees generally resulted in an increase in recoverable aleuriospores compared with incubation at 25 degrees C or at 30 degrees C for 14 days followed by 20 degrees C for 10 days. The lethal effect of NaCl on heat-stressed aleuriospores was enhanced at 30 degrees C. The retention of viability of aleuriospores held in sucrose-peptone water diluent (aw, 0.936) for 20 min was essentially the same as that observed when aleuriospores were held in peptone water (aw, 0.997).(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of water activity and temperature on survival of and colony formation by heat-stressed Chrysosporium farinicola aleuriospores

The ability of sublethally heat-stressed aleuriospores of Chrysosporium farinicola to form colonies on yeast extract-glucose agar (YGA) supplemented with sufficient glucose, sorbitol, glycerol, and NaCl to achieve reduced water activity (aw) in the range of 0.88 to 0.95 was determined. The effects of the aw of diluent and incubation temperature during recovery and colony formation were also investigated. Aleuriospores harvested from 14-day-old cultures grown at 25 degrees C were less resistant to heat inactivation compared with aleuriospores from 20-day-cultures. Increased populations of heat-stressed aleuriospores were recovered as the aw of YGA was decreased from 0.95 (glucose and glycerol) and 0.94 (sorbitol) to 0.89 and 0.88, respectively. In NaCl-supplemented YGA, populations recovered at an aw of 0.94 were greatly reduced compared with populations detected at an aw of 0.92; no colonies were formed on NaCl-supplemented YGA at an aw of 0.88. Tolerance to aw values above 0.88 to 0.89 as influenced by solute type was in the order of glucose greater than sorbitol greater than glycerol greater than NaCl. Incubation at 20 degrees generally resulted in an increase in recoverable aleuriospores compared with incubation at 25 degrees C or at 30 degrees C for 14 days followed by 20 degrees C for 10 days. The lethal effect of NaCl on heat-stressed aleuriospores was enhanced at 30 degrees C. The retention of viability of aleuriospores held in sucrose-peptone water diluent (aw, 0.936) for 20 min was essentially the same as that observed when aleuriospores were held in peptone water (aw, 0.997).(ABSTRACT TRUNCATED AT 250 WORDS)     

几种虫生真菌菌株的培养性状及其对褐飞虱的毒力

从褐飞虱Nilaparvata lugens (St(a)l)罹病虫体上新分离出的一种黄绿绿僵菌菌株Metarhizium flavoviride (Mf82),与实验室保存的黄绿绿僵菌、金龟于绿僵菌和白僵菌3种菌种5个菌株作为对比,研究了在SDAY和PDA培养基上的培养性状,并测定了它们对褐飞虱成虫的毒力.结果表明:...     

Clockwise and counterclockwise pinwheel colony morphologies of Bacillus subtilis are correlated with the helix hand of the strain

Helical macrofiber-producing strains of Bacillus subtilis grown on fresh complex medium semisolid surfaces formed "pinwheel"-shaped colonies. Clockwise pinwheel projections arose from colonies of strains that produce right-handed helical macrofibers in fluid cultures. Most strains able to make left-handed helical macrofibers in fluid grew as disorganized wavy colonies without directed projections. A phage-resistant left-handed mutant was found that produces very tight colonies with pinwheel projections that lie counterclockwise relative to the colony. The pinwheel colony morphology is interpreted therefore in terms of the cell surface organization and helical growth.     

A Technique for Predicting the Solvent-Producing Ability of Clostridium acetobutylicum

Changes in colony morphology were associated with the degeneration of solvent-producing strains of Clostridium acetobutylicum. The most efficient solvent-producing strains gave rise exclusively to colonies with dense centers containing large numbers of spores. Many outgrowths of various morphologies developed from the perimeter of such colonies after several days of incubation. The most degenerate cultures did not produce solvents and gave rise to large diffuse colonies that did not contain spores. These diffuse colonies did not produce outgrowths. Intermediate colony types were also observed. These could be derived from liquid cultures that were relatively poor solvent producers or from the outgrowths of colonies of efficient solvent-producing strains. Some of these intermediate types produced spores but did so less frequently than the high-solvent-producing strains. The spores of the intermediate types could not be distinguished from those of the most efficient solvent producers on the basis of heat sensitivity. The relationship observed between colony morphology and solvent production provides a method for predicting the solvent-producing potential of C. acetobutylicum cultures.     

Glucose and penicillin concentrations in agar medium below fungal colonies

The growth of colonies of Rhizoctonia cerealis and Penicillium chrysogenum on solid media in plate cultures was studied. When grown on defined media containing 10-50 mM-glucose, R. cerealis did not cause a significant reduction in the glucose concentration of the medium in advance of colonization, but did cause the formation of a steep glucose concentration gradient in the substrate below the colony; the medium directly below the centre of a 7 cm diameter colony of R. cerealis was exhausted of glucose even when the fungus was grown on medium containing 50 mM-glucose. Penicillin produced by colonies of P. chrysogenum accumulated in the medium in advance of fungal colonization. For a period up to about 18 d after inoculation, the concentration of penicillin in the medium throughout the plate increased with colony development and thereafter, except at the margins of the plate, decreased.     

大兴安岭地区土壤中的暗色丝孢菌Ⅰ

A total of 50 isolates of soil dematiaceous hyphomycetes belonging to 39 species in 18 genera were found from the area of Dahingganling Mountain Range. Among them, Monodictys arxanensis is a new species. Chrysosporium fastidium, Exserohilum pedicellatum, Monodictys asperospora, Papulaspora brachiata, Scolecobasidium anelli, Scolecobasidium verruculosum and Ulocladium tuberculatum are new to China. The other 31 taxa which have been previously reported from China are also listed. Specimens (dried cultures) and living cultures of all fungi studied have been deposited in the Herbarium of Shandong Agricultural University: Plant Pathology (HSAUP).     

Change in medium components and colony morphology due to mycelial growth of ectomycorrhizal fungusTricholoma bakamatsutake

Mycelia ofTricholoma bakamatsutake isolate No. 4 grew at temperatures ranging from 10 to 30°C, and the optimum was around 25°C. In well-buffered media of initial pH 5.0 and 6.0, No. 4 mycelia secreted gluconic acid and lowered medium pH. Mycelial growth then accelerated slightly; and with the exhaustion of glucose, growth and secretion of gluconic acid stopped. In 10 different media of initial pH 4.0–7.0, No. 4 mycelia showed higher gluconic acid secretion with higher initial pH. No. 4 mycelial grew best in pH 5.0 media, in which gluconic acid secretion was low. Mycelia of 29 isolates including No. 4 grew better in the media in which less glucose, total carbon and total nitrogen remained, and almost all isolates secreted gluconic acid. Most of the 29 isolates showed irregular colony shapes with rough mycelial fronts, brown pigmentation and aerial hypha on colony surfaces, and brown pigmentation of media under colonies. Dissimilarities were calculated with coded morphological characters on colonies, and similarity between isolates was found not to correlate with proximity of origin. Chlamydospores were observed on every colony of the 29 isolates. Chlamydospores were present on colonies of No. 4, reaching to 2 mm from the mycelial front, where brown pigmentation had not yet developed, and the numbers of chlamydospores incresed with mycelial aging.     

Conjugative Plasmid in Corynebacterium flaccumfaciens subsp. oortii That Confers Resistance to Arsenite, Arsenate, and Antimony(III)

The membrane filter (MF) method for detection and enumeration of coliform bacteria in drinking water requires that the coliforms both grow and produce a green metallic sheen when the filter is incubated on modified Endo medium at 35 degrees C for 22 h. Large numbers of noncoliform bacteria, which are enumerated by the standard plate count (SPC) technique, can interfere with the detection of coliforms on MF. This paper presents quantitative evidence from laboratory experiments on the interference of specific SPC bacteria on coliform colony sheen production on MF. Pseudomonas aeruginosa and Aeromonas hydrophila caused significant reductions in Escherichia coli sheen colony counts when present at 3,000 and 220 per filter, respectively. The Flavobacterium sp. and Bacillus sp. selected for this study from SPC did not interfere with coliform colony sheen production. Excessive crowding of E. coli and Enterobacter cloacae colonies on MF also caused a reduction in the number of colonies that produced sheen. Even when there was no crowding (14 colonies per filter), only a fraction of the E. cloacae colonies produced sheen colonies on modified Endo medium.     

Landscape mulches and termite nutritional ecology: growth and survival of incipient colonies of Coptotermes formosanus (Isoptera: Rhinotermitidae)

Alate swarms are one of the major visible signs of the expansion of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), in an area. Successful establishment of an incipient colony is thought to mainly rely on available food resources and moisture. The large-scale use of tree-based mulches in landscapes may inadvertently contribute to local establishment and growth of C. formosanus colonies. This research investigated the nutritional ecology of incipient colonies of C. formosanus feeding on seven tree-based, weathered, and nonweathered landscape mulches: pine straw, pine bark, cedar wood, water oak, eucalyptus, cypress, and melaleuca. Incipient colonies of C. formosanus feeding on pine straw, either weathered or nonweathered, produced significantly more progeny over the course of 1-yr feeding than colonies feeding on the other mulches tested. Regardless of weathered or not, the incipient colonies feeding on pine straw, eucalyptus, bald cypress, and water oak mulches had significantly greater survival rates after 360 d (53-77%) than colonies feeding on the other mulches tested (0-13%), but colonies feeding on nonweathered water oak had significantly lower survival (8%) than those kept on weathered water oak (58%). Colony fitness values were significantly different between the weathering treatment groups and among the different types of mulches. With regard to colony growth characteristics, three distinct growth patterns were identified: a high number of progeny (>100) with high colony survival rate (>50%), a medium number of progeny (12-50) with high colony survival rate (>50%), and a small number of progeny (0-10) with low colony survival rate (<5%). These findings suggest that different types of mulch substrates could significantly impact the nutritional ecology of the founding pairs and the successful establishment of incipient colonies during the swarming season.     

Mutants of Rhodospirillum rubrum Obtained After Long-Term Anaerobic, Dark Growth

Rhodospirillum rubrum S(1) cells were grown for more than 100 generations under strict anaerobic, dark conditions in liquid medium with sodium pyruvate. During this time, growth became nonpigmented. When cells were streaked onto the surface of solid growth medium in anaerobic bottles and placed in the dark, a few light-red colonies developed, but the majority was nonpigmented. Mutants were obtained from colonies selected on the basis of pigmentation and bacteriochlorophyll a content. The growth, ultrastructure, and light reactivity of two mutants were examined. Mutant C synthesized bacteriochlorophyll a (7.2 mumoles per mg of protein), altered membrane structures, and chromatophores during dark growth. Examination of light-induced changes of the absorption spectrum of this mutant suggested that only an electron transport pathway, which included the low potential cytochrome-like pigment C428, could be detected. Mutant C grew anaerobically in the light, whereas mutant G1 was light sensitive and produced only trace amounts of bacteriochlorophyll a (0.6 mumole per ml of protein). Poorly pigmented G1 cells contained unusual membrane structures. When dark-grown G1 colonies were placed in the light, deep-red colored papillae developed in the nonpigmented colonies. During anaerobic, dark growth with sodium pyruvate, both C and G1 synthesized poly-beta-hydroxybutyrate and produced acetate, carbon dioxide, and hydrogen gas.     

Variation of colony morphology and chromosomal rearrangement in Candida tropicalis pK233

UV irradiation treatment of the asexual yeast Candida tropicalis gave rise to morphological mutants exhibiting at least four different types of abnormal colonies on glucose-containing solid medium. These mutants were named according to their colony morphologies: 'doughnut', 'frilly', 'echinoid' and 'walnut' mutants. The doughnut mutant produced a wrinkled colony with a hollow in its central region that was rich in filamentous pseudohyphal cells. With increased incubation time, the colony gradually changed to a reticulate shape. The parent strain, which normally produced smooth colonies, gave similar colonies to those of the doughnut mutant when grown in medium containing oleic acid as carbon source. Both the frilly and the walnut mutants produced pseudohyphal cells in a similar fashion to the doughnut mutant. The echinoid mutant produced an echinulate colony morphology with aerial hyphae and contained true hyphal cells as well as pseudohyphal ones. Pulsed-field gel electrophoresis showed that the echinoid and frilly mutants had different karyotypes from that of their parent strain, suggesting the occurrence of chromosomal rearrangements associated with these morphological mutations.     

Agar underlay method for recovery of sublethally heat-injured bacteria

A method of recovering sublethally heat-injured bacteria was developed. The procedure (termed the agar underlay method) uses a nonselective agar underlaid with a selective medium. In a two-chambered petri dish, the Lutri plate (LP), a nonselective agar is inoculated with a population of sublethally heat-injured bacteria. After a 2-h repair incubation period, selective agar is added to the bottom chamber of the LP and incubated. By diffusing through the nonselective top agar, selective agents from the underlay medium impart selectivity to the system. By the agar underlay method, recovery rates of the heat-injured food-borne pathogens Escherichia coli O157:H7 and Salmonella typhimurium were not different (P > 0. 05) from recovery rates determined with nonselective media. Sublethally heat-injured cells (60 degrees C for 1.5 min in buffer or 80 degrees C for 30 s on meat surfaces) grew and produced a typical colony morphology and color reaction when the agar underlay procedure was used with the appropriate respective selective agars. Unlike agar overlay methods for injury repair, the agar underlay procedure allows the typical selective-medium colony morphology to develop and allows colonies to be more easily picked for further characterization. Higher recovery rates of heat-injured fecal enterococci from bovine fecal samples and total coliforms from animal waste lagoons were obtained by the agar underlay method with selective agars than by direct plating on the respective selective media.     

Isolation ofThiobacillus ferrooxidans from various habitats and their growth pattern on solid medium

Different strains of iron-oxidizingThiobacillus ferrooxidans were grown and purified on solid medium containing Bapco agar, agarose, and carrageenan (Type 1). These strains produced easily countable isolated colonies that could be transferred after 7 days of incubation at 30°C. Increase in viable cell number in relation to growth and iron oxidation was studied by both microscopic count and direct plating method. Colony morphology of different strains growing on solid medium helped in differentiating the colony types.     

Mycoflora of camel and goat hairs from Al-Arish,Egypt

The frequency of occurrence of fungi in 120 hair samples of camel and goat from four different localities of Al-Arish governorate was determined.Twenty-six genera and 54 species were collected from the two substrates and the most common genera were Chrysosporium and Aspergillus, followed by Cladosporium. From the preceding genera Chrysosporium keratinophilum, C. tropicum, C. indicum, Aspergillus flavus, A. niger and Cladosporium cladosporioides. Also, other keratinophilic fungi were isolated such as C. luteum, C. pannorum, C. parvum, C. dermatitidis, C. inops, Arthroderma tuberculatum, Histoplasma capsulatum and Myceliophthora vellerea.     

Rhizobium japonicum derivatives differing in nitrogen-fixing efficiency and carbohydrate utilization.

Four derivatives of Rhizobium japonicum 110 were isolated on the basis of morphologically different colonies formed on yeast extract-mannitol-HM salts medium. All are able to nodulate Lee soybeans. The bacteria-plant associations formed by each clone have measurable acetylene-reducing activity, but those formed by two of these clones (designated L1-110 and L2-110) are 5- to 10-fold less efficient than those formed by the others (designated I-110 and S-110). These derivatives were not detectable with ordinary culture techniques since, because of cell adherence, genetically mixed colonies result. When a detergent (Tween 40 at 0.01%, vol/vol) was added to the dilution medium, separate clones resulted. The metabolic basis for the gross differences in colony morphology on yeast extract-mannitol-HM salts medium was found to be that L1-110 and L2-110 utilized p-mannitol for growth, whereas I-110 and S-110 did not. These clones differ analogously in ability to utilize D-arabitol. Clones I-110 and L1-110 were chosen for studies of growth rates on various carbohydrates. Although clone I-110 and clone L1-110 did not differ in growth rates on a number of sugars, such as gluconate, arabinose, glycerol, and mannose, they differed in growth rates on glucose and fructose. Although clone I-110 grew faster on glucose than did clone L1-110, clone L1-110 grew faster on fructose than did clone I-110. Clones I-110 and L1-110 showed identical responses to several antibiotics and deoxyribonucleic acid (DNA) synthesis inhibitors and identical susceptibility to some highly specific bacteriophages. Identical buoyant densities of their DNAs in isopycnic CsCl density gradients and identical thermal denaturation temperatures of their DNAs suggest that clones I-110 and L1-110 have the same DNA base composition. Preliminary DNA/DNA hybridization experiments show that strain I-110 DNA and strain L1-110 DNA have a high degree of common polynucleotide sequences.