Preliminary report on a catalyst derived from induced cells of Rhodococcus rhodochrous strain DAP 96253 that delays the ripening of selected climacteric fruit: bananas, avocados, and peaches.

Despite the use of refrigeration, improved packaging, adsorbents, and ethylene receptor blockers, on average, nearly 40% of all fruits and vegetables harvested in the US are not consumed. Many plant products, especially fruit, continue to ripen after harvesting, and as they do so, become increasingly susceptible to mechanical injury, resulting in increased rot. Other plant products during transportation and storage are susceptible to chill injury (CI). There is a real need for products that can delay ripening or mitigate the effects of CI, yet still permit full ripeness and quality to be achieved. Preliminary results are discussed where catalyst derived from cells of Rhodococcus rhodochrous DAP 96253, grown under conditions that induced high levels of nitrile hydratase, were able to extend the ripening and thus the shelf-life of selected climacteric fruits (banana, avocado, and peach). A catalyst, when placed in proximity to, but not touching, the test fruit delayed the ripening but did not alter the final ripeness of the fruit tested. Organoleptic evaluations conducted with control peaches and with peaches exposed to, but not in contact with, the catalyst showed that the catalyst-treated peaches achieved full, natural levels of ripeness with respect to aroma, flavor, sweetness, and juice content. Furthermore, the results of delayed ripening were achieved at ambient temperatures (without the need for refrigeration).

Microcycle conidiation and medusa head conidiophores of aspergilli on indoor construction materials and air filters from hospitals.

Microcycle conidiation and microniche colonization by aspergilli was observed in-situ on various indoor construction and finishing materials. Microcycle conidiation, direct conidiogenesis from a conidium or spore with minimal intervening hyphal development, for several decades has been considered a survival mechanism during stress for a variety of moulds. Adhesive transparent tape mounts and bulk materials from various indoor materials, including air filters from hospitals and healthcare institutions, were transported to the laboratory for light microscopic and scanning electron microscopic observations. Additional materials were held in moist chambers over nonsterile soils and examined periodically for fungal development. Microcycle conidiation was observed usually in areas of sparse fungal development, mostly in association with isolations of members of the Aspergillus flavus-, A. versicolor-, A. niger groups. Branched conidiophores and medusa heads, more often associated with colonization by Eurotium spp., were observed on some preserved woods. These conidiogenesis processes might be factors in the survival and blooms of indoor aspergilli.

Effects of anti-odor automobile air-conditioning system products on adherence of Serratia marcescens to aluminum.

Sixteen commercial products for use in automobile air-conditioning systems (ACS), most designated for abatement of malodors presumably of microbial origin, were examined for their potential to inhibit attachment and to detach cells of the Gram-negative bacterium Serratia marcescens on aluminum sections. Numbers of attached cells were appreciably reduced (>60%) following immersion in three alcohol-type and two acrylic-coating-type products. Several products had essentially no effect on the attached cells. Most of the products indicated for alleviation of associated microbial odors from ACS provided only short-term effects. When products were coated onto aluminum prior to exposure to the cells, water-insoluble coatings appeared to provide more consistent inhibition of primary adherence of S. marcescens. The differences in degrees of primary adherence of a selected strain of S. marcescens to variously treated aluminum provided a rapid and reproducible assessment of potential antimicrobial efficacy of ACS products.

Toxic effects of Ag(I) and Hg(II) on Candida albicans and C. maltosa: a flow cytometric evaluation.

The effects of Ag(I) and Hg(II) on membrane potential and integrity of cells of Candida albicans and C. maltosa were determined with a flow cytometric procedure that employed an anionic membrane potential-sensitive dye, bis-(1,3-dibutylbarbituric acid) trimethine oxonol, and a membrane integrity indicator, propidium iodide. The membrane potentials of cells of both species were reduced rapidly within 15 min of exposure to Ag(I). No threshold dose for Hg(II) existed, and cells of both species lost membrane potential gradually in Hg(II) solutions. Cells of both species lost membrane integrity more rapidly in Ag(I) solutions than in Hg(II) solutions. In Ag(I) solutions, the decrease in the numbers of cells recoverable in culture occurred at a rate similar to the rate of cell depolarization and membrane permeabilization. In Hg(II) solutions, loss of cell recoverability preceded the loss of membrane potential and membrane integrity. C. albicans, in contrast to C. maltosa, showed no loss of membrane integrity after exposure to Hg(II) solutions for 1 h. Different rates of binding of Ag(I) and Hg(II) between the two species suggest that the two ions target different primary sites.

Volatile organic compounds associated with microbial growth in automobile air conditioning systems.

Volatile organic compounds from Penicillium viridicatum and Methylobacterium mesophilicum growing on laboratory media and on component materials of automobile air conditioners were analyzed with gas chromatography and mass spectrometry. P. viridicatum produced compounds such as 4-methyl thiazole, terpenes and alcohols, whereas M. mesophilicum produced dimethyl disulfide, dimethyl trisulfide, and chlorophenol with growth on laboratory media. In comparison with laboratory media, fewer volatiles were detected from colonized foam insulation materials. Biofilms of M. mesophilicum on aluminum evaporator components produced mainly dimethyl disulfide. These biofilms, after inoculation with P. viridicatum, produced offensive smelling alcohols and esters such as 2-methyl propanol, 3-penten-2-ol, and the ethyl ester of butanoic acid. The moisture and substrates innate to the automobile air conditioning systems provided an environment suitable for microbial biofilm development and odor production. Reduction of retained moisture in the air conditioning system coupled with use of less susceptible or antimicrobial substrates are advised for remediation of the noxious odors.

The occurrence and persistence of mixed biofilms in automobile air conditioning systems.

Twelve automobile air conditioner systems from six manufacturers and three countries, selected mostly because of complaints of unpleasant odors in the passenger compartment, were examined for microbial growth by direct microscopy and enrichment culture. Mixed populations of fungi and bacteria (with occasional protozoa) were observed in biofilms in at least some of the components from all used units. The aluminum heat exchanger fins from ten evaporators demonstrated bacterial biofilms that yielded Methylobacterium mesophilicum. Penicillium viridicatum colonized components from four units. These bacteria and fungi were recoverable repeatedly from these units during 'dry' storage of up to 27 months. This report associates a bacterial-fungal community with disagreeable air quality in some automobiles.

Mycotoxins of Alternaria alternata produced on ceiling tiles.

The production of mycotoxins by Alternaria alternata in cellulosic ceiling tiles was examined with thin-layer chromatography and high-performance liquid chromatography procedures. Alternariol and alternariol monomethyl ether were found in ceiling tile extracts, whereas extracts of control rice cultures of all three isolates produced these mycotoxins plus altenuene and altertoxin I. Extensive fungal growth and mycotoxin production occurred in the ceiling tiles at relative humidities of 84-89% and 97%.

Transformation of chlororesorcinol by the hydrocarbonoclastic yeasts Candida maltosa, Candida tropicalis, and Trichosporon oivide.

The inhibitory effects of chlorinated monoaromatic compounds on three hydrocarbonoclastic yeasts grown on glucose or resorcinol were examined. At concentrations of 1.0 M, all of the monoaromatic compounds were inhibitory. When the concentration of chlororesorcinol was significantly reduced (0.0005 M), the inhibition to each yeast was minimized. Extracts of the cultures of yeasts growing on resorcinol plus chlororesorcinol were analyzed for residual resorcinol and chlororesorcinol with high pressure liquid chromatography. Neither compound was detected in the culture broth of Candida maltosa, but several unidentified compounds were present. Only chlororesorcinol was detected in the culture broth of Trichosporon oivide, and both resorcinol and chlororesorcinol were present in extract from cultures of C. tropicalis. Cultures of C. maltosa grown on resorcinol-yeast nitrogen base, washed and suspended in phosphate buffer and subsequently incubated with chlororesorcinol, turned the culture broth a distinct pink color. The data indicate that C. maltosa has the potential to co-metabolize chlororesorcinol.

Fungal colonization of air filters and insulation in a multi-story office building: production of volatile organics.

Secondary air filters in the air-handling units on four floors of a multi-story office building with a history of fungal colonization of insulation within the air distribution system were examined for the presence of growing fungi and production of volatile organic compounds. Fungal mycelium and conidia of Cladosporium and Penicillium spp. were observed on insulation from all floors and both sides of the air filters from one floor. Lower concentrations of volatile organics were released from air filter medium colonized with fungi as compared with noncolonized filter medium. However, the volatiles from the colonized filter medium included fungal metabolites such as acetone and a carbonyl sulfide-like compound that were not released from noncolonized filter medium. The growth of fungi in air distribution systems may affect the content of volatile organics in indoor air.

Allergic fungal sinusitis in the southeastern USA: involvement of a new agent Epicoccum nigrum Ehrenb. ex Schlecht. 1824.

Alternaria alternata, Aspergillus spp., Bipolaris spicifera, Curvularia lunata, Epicoccum nigrum and Fusarium solani were isolated repeatedly from groups of patients among 96 diagnosed with allergic fungal sinusitis (AFS). Epicoccum nigrum was obtained consistently from four patients, one of whom yielded mycelial masses consistent in morphology with E. nigrum. Fifteen of the predominant fungi recovered from air samples from selected patients' residences included the same species isolated from the mucin of its inhabitants. Air samples from other buildings, whose occupants (non-AFS individuals) complained of poor indoor air quality or of symptoms of the sick building syndrome (SBS), yielded some of the same species involved in AFS. An association of SBS with AFS was not established. Eight of the species implicated in AFS were found to colonize the surfaces of indoor construction and finishing materials at sites other than the residence of the patient. To our knowledge, this is the first report that E. nigrum can colonize nasal sinuses and cause AFS.

Fungal colonization of air filters from hospitals.

Air filters of various types, selected on the basis of discoloration, were collected from the primary and secondary filter banks of the heating, ventilating, and air-conditioning systems in seven hospitals in the eastern United States and examined with direct microscopy for fungal colonization. Microscopic observations and culture results showed that filters from five of the hospitals were colonized with fungi including species of Acremonium, Alternaria, Aspergillus, Cladosporium, Epicoccum, Penicillium, and Rhinocladiella, and a Beauveria-like fungus. Several of these commonly airborne species, e.g., Epicoccum purpurescens (syn. E. nigrum) and Rhinocladiella sp., had not been previously reported to colonize (with conidiogenesis) air filters.

Fungal colonization of fiberglass insulation in the air distribution system of a multi-story office building: VOC production and possible relationship to a sick building syndrome.

Complaints characteristic of those for sick building syndrome prompted mycological investigations of a modern multi-story office building on the Gulf coast in the Southeastern United States (Houston-Galveston area). The air handling units and fiberglass duct liner of the heating, ventilating and air conditioning system of the building, without a history of catastrophic or chronic water damage, demonstrated extensive colonization with Penicillium spp and Cladosporium herbarum. Although dense fungal growth was observed on surfaces within the heating-cooling system, most air samples yielded fewer than 200 CFU m-3. Several volatile compounds found in the building air were released also from colonized fiberglass. Removal of colonized insulation from the floor receiving the majority of complaints of mouldy air and continuous operation of the units supplying this floor resulted in a reduction in the number of complaints.

Initial oxidative and subsequent conjugative metabolites produced during the metabolism of phenanthrene by fungi.

Three filamentous fungi were examined for the ability to biotransform phenanthrene to oxidative (phase I) and conjugative (phase II) metabolites. Phenanthrene metabolites were purified by high-performance liquid chromatography (HPLC) and identified by UV/visible absorption, mass, and 1H NMR spectra. Aspergillus niger ATCC 6275, Syncephalastrum racemosum UT-70, and Cunninghamella elegans ATCC 9245 initially transformed [9-(14)C]phenanthrene to produce metabolites at the 9,10-, 1,2-, and 3,4-positions. Subsequently, sulfate conjugates of phase I metabolites were formed by A. niger, S. racemosum, and C. elegans. Minor glucuronide conjugates of 9-phenanthrol and phenanthrene trans-9, 10-dihydrodiol were formed by S. racemosum and A. niger, respectively. In addition, C. elegans produced the glucose conjugates 1-phenanthryl beta-D-glucopyranoside and 2-hydroxy-1-phenanthryl beta-D-glucopyranoside, a novel metabolite. [9-(14)C]Phenanthrene metabolites were not detected in organic extracts from biotransformation experiments with the yeasts, Candida lipolytica 37-1, Candida tropicalis ATCC 32113, and Candida maltosa R-42.

Effects of extracts of fiberglass insulations on the growth of Aspergillus fumigatus and A. versicolor.

Water extracts of thermal and acoustic fiberglass insulations used in the duct work of heating, ventilation and air conditioning (HVAC) systems supported germination of conidia and growth of Aspergillus versicolor (Vuillemin) Tiraboschi 1908-9 and Aspergillus fumigatus Fresenius 1863. Urea, formaldehyde and unidentified organics were detected in the extracts. Formaldehyde in concentrations similar to those found in the extracts restricted the growth of both species in enriched media. A. versicolor, the more common species associated with fiberglass insulations, was more resistant to formaldehyde than A. fumigatus.

Fungal colonization of synthetic substrates for use in space craft.

Materials being used or considered for use in space flights were examined for their susceptibility to fungal colonization. The materials included soft goods (clothing) and insulation and fabrication products such as Velcro attachments and elastic cord binders. Materials were exposed for at least 28 days in a high-humidity chamber colonized with over 50 species of fungi, including those species recommended for determining recalcitrance of materials to fungal biodegradation. At least nine of 25 products demonstrated extensive microscopic colonization by fungi, mostly by Acremonium obclavatum. Challenge procedures that rely on observations with the unaided eye, or 40 x magnification of growth by a restricted number of fungal species with a cellulosic substrate as a positive control, are insufficient for determining the resistance of synthetic substrates to fungal colonization.

Fungal colonization of air filters for use in heating, ventilating, and air conditioning (HVAC) systems.

New and used cellulosic air filters for HVAC systems including those treated with antimicrobials were suspended in vessels with a range of relative humidities (55-99%) and containing non-sterile potting soil which stimulates fungal growth. Most filters yielded fungi prior to suspension in the chambers but only two of 14 nontreated filters demonstrated fungal colonization following use in HVAC systems. Filters treated with antimicrobials, particularly a phosphated amine complex, demonstrated markedly less fungal colonization than nontreated filters. In comparison with nontreated cellulosic filters, fungal colonization of antimicrobial-treated cellulosic filters was selective and delayed.

Fungal production of volatiles during growth on fiberglass.

Acoustic and thermal fiberglass insulation materials used in heating, ventilation, and air-conditioning systems were colonized with fungi in laboratory chambers. The mixed fungal population, principally Aspergillus versicolor, Acremonium obclavatum, and Cladosporium herbarum, produced odoriferous volatiles, including 2-ethyl hexanol, cyclohexane, and benzene. These volatiles may be related to poor indoor air quality and the sick building syndrome.

Effect of relative humidity on fungal colonization of fiberglass insulation.

Fiberglass duct liners and fiberglass duct boards from eight buildings whose occupants complained of unacceptable or moldy odors in the air were found to be heavily colonized by fungi, particularly by Aspergillus versicolor. Unused fiberglass was found to be susceptible to fungal colonization in environmental chambers dependent upon relative humidity. No colonization was observed at relative humidities below 50%.

Enantiomeric Composition of the trans-Dihydrodiols Produced from Phenanthrene by Fungi.

The trans-dihydrodiols produced during the metabolism of phenanthrene by Cunninghamella elegans, Syncephalastrum racemosum, and Phanerochaete chrysosporium were purified by high-performance liquid chromatography (HPLC). The enantiomeric compositions and optical purities of the trans-dihydrodiols were determined to compare interspecific differences in the regio- and stereoselectivity of the fungal enzymes. Circular dichroism spectra of the trans-dihydrodiols were obtained, and the enantiomeric composition of each preparation was analyzed by HPLC with a chiral stationary-phase column. The phenanthrene trans-1,2-dihydrodiol produced by C. elegans was a mixture of the 1R,2R and 1S,2S enantiomers in variable proportions. The phenanthrene trans-3,4-dihydrodiol produced by P. chrysosporium was the optically pure 3R,4R enantiomer, but that produced by S. racemosum was a 68:32 mixture of the 3R,4R and 3S,4S enantiomers. The phenanthrene trans-9,10-dihydrodiol produced by P. chrysosporium was predominantly the 9S,10S enantiomer, but those produced by C. elegans and S. racemosum were predominantly the 9R,10R enantiomer. The results indicate that although different fungi may exhibit similar regioselectivity, there still may be differences in stereoselectivity that depend on the species and the cultural conditions.