Evaluating changes in growth and pigmentation of Cladosporium cladosporioides and Paecilomyces variotii in response to gamma and ultraviolet irradiation.

Melanin-containing fungi (black molds) have the capacity to thrive under extreme environmental conditions such as the elevated radiation levels inside the former Chernobyl reactors. These fungi have been hypothesized to grow toward and use gamma radiation as an energy source, but the literature does not clearly address which energies of the electromagnetic spectrum, if any, positively affect fungal growth. The goal of this work was to characterize the response of non-melanized and melanized fungi to two distinct electromagnetic wavelengths, i.e., ultraviolet (UV) and gamma ray, keeping absorption and other potentially confounding variables constant. Exposure to UV or gamma radiation induced significant changes in fungi pigmentation, but not growth rate of Cladosporium cladosporioides and Paecilomyces variotii. Specifically, increased pigmentation of both fungi was observed in samples exposed to UV, while decreased pigmentation was observed for gamma-irradiated samples. These results provide new insights into the role of electromagnetic energies on growth of fungi and provide an impetus to examine additional energies and types of radiation to develop a fundamental understanding of this phenomenon.

[THE INFLUENCE OF B-IRRADIATION ON MICROMYCETES ISOLATED FROM THE ZONE OF RADIONUCLIDE CONTAMINATION].

The resistance of the micromycetes to ß-irradiation had been studied. The study was conducted on two species: Cladosporium sphaerospermum Penz. and Alternaria alternata (Fr.) Keissl., each of them was represented by six strains. Half of strains were isolated from the inner locations of the "Shelter" object (SO), which were characterized by different levels of radionuclide contamination. For C. sphaerospermum strains maximum resistance to ß-radiation was observed among 20-day-old cultures. The greatest resistance to ß-radiation had been demonstrated by two strains: 5-1 (isolated from SO location with the highest level of contamination) and 852 (control). For A. alternata strains maximum resistance to ß-radiation was observed among 40-day-old cultures. As the most resistant were characterized 56 and 105 isolates from the SO inner location with a high level of the radionuclide contamination. Based on the obtained results we concluded about high resistance to irradiation of both studied species of anamorphic fungi, which achieved through different life strategies: C. sphaerospermum strains survive due to rapid and abundant formation of conidia, whereas conidia of A. alternata strains are formed slowly, but they have greater advantage under irradiation due to their multicellular structure and large sizes.

Characterization of a mutant strain of a filamentous fungus Cladosporium phlei for the mass production of the secondary metabolite phleichrome.

UV-mutagenesis was performed to obtain mutant strains that demonstrate altered production of phleichrome, a secondary metabolite of Cladosporium phlei. Among fifty mutants selected, based on the increased area and intensity of the purple pigment surrounding the colonies, the strain M0035 showed the highest production of phleichrome, more than seven fold over wild type. Plate cultures of the M0035 strain resulted in a total of 592 mg phleichrome consisting of 146 mg and 446 mg from the mycelia and agar media, respectively. The M0035 strain displayed a growth rate and a mycelial mass comparable to the parental strain but had significantly reduced asexual sporulation.

Treatment of fungal bioaerosols by a high-temperature, short-time process in a continuous-flow system.

Airborne fungi, termed fungal bioaerosols, have received attention due to the association with public health problems and the effects on living organisms in nature. There are growing concerns that fungal bioaerosols are relevant to the occurrence of allergies, opportunistic diseases in hospitals, and outbreaks of plant diseases. The search for ways of preventing and curing the harmful effects of fungal bioaerosols has created a high demand for the study and development of an efficient method of controlling bioaerosols. However, almost all modern microbiological studies and theories have focused on microorganisms in liquid and solid phases. We investigated the thermal heating effects on fungal bioaerosols in a continuous-flow environment. Although the thermal heating process has long been a traditional method of controlling microorganisms, the effect of a continuous high-temperature, short-time (HTST) process on airborne microorganisms has not been quantitatively investigated in terms of various aerosol properties. Our experimental results show that the geometric mean diameter of the tested fungal bioaerosols decreased when they were exposed to increases in the surrounding temperature. The HTST process produced a significant decline in the (1-->3)-beta-d-glucan concentration of fungal bioaerosols. More than 99% of the Aspergillus versicolor and Cladosporium cladosporioides bioaerosols lost their culturability in about 0.2 s when the surrounding temperature exceeded 350 degrees C and 400 degrees C, respectively. The instantaneous exposure to high temperature significantly changed the surface morphology of the fungal bioaerosols.

[Influence of low dozes of ionizing radiation on accumulation of melanin pigments and catalase and superoxidedismutase activities in Cladosporium cladosporioides].

Influence of low dozes of ionizing radiation on melanin pigments synthesis and activity of antioxidant enzymes catalase and superoxidedismutase of two strains of Cladosporium cladosporioides 4, (isolated from radioactive soil) and 396 (control) were investigated. It was shown, that in C. cladosporioides 4 under the exposure of ionizing radiation an increase of melanin synthesis in a stationary growth phase and increase of superoxidedismutase activity in a logarithmic phase were observed; in the control strain C. cladosporioides 396 activation of melanin synthesis and superoxide dismutase activity in both growth phases was revealed. It was established that in C. cladosporioides 4 the endocellular catalase activity in a logarithmic phase is 3.2 times higher, than in control strain. Under the action of ionizing radiation a 2-fold increase of this enzyme activity unlike the control strain in which the activity inhibition was revealed. The obtained results testify to the complex response of antioxidant systems and melanin to the action of low dozes of radiation which depends on the growth phase and presence of radioadaptation properties in the investigated fungi.

[Peculiarities of growth and development of strains Hormoconis resinae (Lindau) V. arx & De Vries F. Resinae and Cladosporium sphaerospermum penz].

The work deals with the effect of limitation of organic carbon (glucose) on the growth and morphology of two species of microscopic fungi Hormoconis resinae and Cladosporium sphaerospermum (11 strains), isolated from premises of the 4th unit of the Chernobyl NPP and isolation places which arc pure from radionuclides. The dissimilar reaction of each of the species to decreasing the amount of organic carbon in the culture medium has been established. Ontogenesis reduction was observed for both species under the conditions of limitations of organic carbon. In was manifested for H. resinae in reduction of the typical conidial sporulation and in transition to micelial way of existence, and only conidial sporulation and formation of "empty" micelium Were registered under such conditions for C. sphaerospermum. The studied strains were related to 3 ecologic groups by oligocarbotolerance criterion: typical saprotrophs, intermediate group, strains with a tendency to oligocarbotolerance.

EPR examination of Zn2+ and Cu2+ binding by pigmented soil fungi Cladosporium cladosporioides.

The purpose of this study was to examine the usefulness of electron paramagnetic resonance spectroscopy (EPR) to estimate zinc and copper ions biosorption from the environment by pigmented soil fungi Cladosporium cladosporioides. The existence of a low amount of pheomelanin, besides eumelanin, in C. cladosporioides samples was proved by the analysis of shape of their EPR spectra. Concentration of o-semiquinone free radicals in crude mycelium was 2.4x10(17) spin/g. Changes in free radicals system of C. cladosporioides cultured in the presence of Zn2+ and Cu2+ were analysed. Both magnetic and chemical interactions of zinc and copper ions with free radicals in C. cladosporioides melanin were found. Magnetically interacting diamagnetic Zn2+ ions increased the concentration of o-semiquinone free radicals in melanin existing in C. cladosporioides mycelium, whereas paramagnetic Cu2+ ions decreased this concentration. Chemical interactions of Zn2+ and Cu2+ ions decreased the free radical concentrations in C. cladosporioides melanin. Homogeneously distributed free radicals in C. cladosporioides melanin rise its activity in biosorption processes.

[Destruction of radioactive particles by strains of Cladosporium cladosporoides (FRES.) de Vries]. / Destruktsiia radioaktivnykh chastits shtammami Cladosporium cladosporoides (Fres.) de Vries.

Reactions on the ionizing radiation of 14 Cladosporium cladosporioides strains were studied. Only 5 of them displayed radiotropizm. The ability of C. cladosporioides strains 4 and 5 with positive radiotropizm and museum C. cladosporioides strain 396 and its alb-mutant SM without positive radiotropizm to destruct radioactive particles of Chernobyl and explosion origin was studied. Two ways of radioactive particles destruction by C. cladosporioides were established, one of them is a direct way by fungal overgrowth of hot particles and the second one an indirect way only by fungal metabolites. Mycelium of the studied C. cladosporioides strains sorbed radionuclides from radioactive particles during cultivation on the liquid and agarized media. No certain inclinations of the individual strains to accumulation of radionuclides 137Cs or 152Eu were ascertained.

[Peculiarities of linear growth of the melanin-containing fungi Cladosporium sphaerospermum Penz. and Alternaria alternata (Fr.) Keissler]. / Osobennosti lineinogo rosta melaninsoderzhashchikh gribov Cladosporium sphaerospermum Penz. i Alternaria alternata (Fr.) Keissler.

Results on determination of radial (linear) growth rate of melanin-containing fungi Cladosporium sphaerospermum Penz. and Alternaria alternata (Fr.) Keissler concerning place of their isolation and ecologic peculiarities are presented in the paper. Essential differences, as to all studied indices of the strains of C. sphaerospermum strains, isolated from premices of the ChNPP 4th unit from the control strains of this species have been established. Only strain 34 of C. sphaerospermum, isolated from the cable driving region of the "Shelter" object, which did not differ from the control strains as to all the studied indices, made the exception. The radial growth rate was 2-4 times as low and variability amplitude 10-30 times as high in strains 60 and 5-1 of C. sphaerospermum, (which suffered high radiation load), as in the control strains of this species. The radial growth rate of C. sphaerospermum studied strains was an order lower as a whole than that of A. alternata strains. All the above said evidence for implementation of K-type vital strategy by C. sphaerospermum species and in this connection one can suppose its active growth on the surface of walls and ferroconcrete structures of the ChNPP 4th unit. Absence of differences, as to the studied radial growth indices, between A. alternata strains isolated from the ChNPP 4th unit premices and control strains of the species can evidence for the existence of A. alternata species under the conditions of high radioactivity in the surviving state.

[The effect of gamma irradiation on the physiological-biochemical properties of strains of Cladosporium cladosporioides (Fres.) de Vries differing by the trait of radiotropism]. / Vliianie gamma-oblucheniia na fiziologo-biokhimicheskie svoistva shtammov Cladosporium cladosporioides (Fres.) de Vries, razlichaiushchikhsia po priznaku radiotropizma.

The influence of the low-intensity gamma-irradiation on the process of lipid peroxidation and the activities of the antioxidant glutathione-dependent system (catalase, glutathione-transferase) has been investigated in a number of Cladosporium cladosporioides (Fres.) de Vries strains. The dark-pigmented strains isolated from the habitats with different degree of radionuclide contamination, and the nonpigmented alb-mutant of the same species have been used in our work. The studied properties have been analyzed with the respect of the radiotropism property and of the presence of melanin pigment in the cell wall of these strains. The lipid perioxidation level under the effect of the low-intensity gamma-irradiation was greatly increased in Cladosporium cladosporioides 396 strain only. This strain was isolated from the radiation-pure soil. Catalase activity in a number of the studies strains correlated neither with their pigmentation, nor with the property of positive radiotropism. The correlation between the strain pigmentation and activity of glutathione transferase has been found.

[The protein-synthesizing activity of a number of strains of Cladosporium cladosporioides (Fres.) de Vries grown under conditions of continuous low-intensity gamma irradiation]. / Beloksinteziruiushchaia aktivnost' riada shtammov Cladosporium cladosporioides (Fres.) de Vries, vyrashchennykh v usloviiakh nepreryvnogo gamma-oblucheniia maloi intensivnosti.

Phenomena of melanization of radioactively polluted soils, due to prevalence of melanin-containing species and positive radiotropism of some micromycetes have been found during monitoring of mycobiota of the 30-km alienation zone of the Chernobyl NPP for 10 years. To elucidate the contribution of the melanin system to the cell protection against irradiation, the influence of gamma-irradiation on the activity of protein synthesis in four Cladosporium cladosporioides (Fres.) de Vries strains has been investigated. Two strains isolated from radioactively polluted substrates were characterised by the presence of positive radiotropism. Laboratory strain 396 and its alb-mutant (with blocked melanin synthesis), did not possess this feature. The protein synthesizing activity was assayed by incorporation of 14C-leucine in the protein fraction of mycelium, grown during 7 days under continuous gamma-irradiation of low intensity and without it. The protein synthesis was activated in the radioactively treated mycelium of dark-pigmented C. cladosporioides strains and it was suppressed in similarly treated mycelium of alb-mutant of C. cladosporioides. The rate of 14C-leucine incorporation into biomass of investigated strains correlated with positive radiotropism. The dependence between protein synthesis intensity and the availability of melanin protection system in micromycetes is assumed.

Resistance of some common fungi to gamma irradiation.

Ten species of fungi representing the genera Alternaria, Aspergillus, Caldosporium, Curvularia, Fusarium, and Penicillium were examined for their relative resistance to gamma irradiation from a 137Cs source. Inactivation doses for dematiaceous fungi in agar medium ranged from 0.6 to greater than 1.7 megarads, whereas those for moniliaceous fungi were less than 0.3 megarad. D10 values (the dose required to reduce the inoculum by 1 log) for Curvularia geniculata (greater than 0.29 megarad) exceeded those for control spores of Bacillus pumilus (0.15 megarad).