Phototropic fluence-response curves for Pilobolus crystallinus sporangiophore

Fluence-response relationships were examined for positive and negative phototropism induced by blue (450 nm) and ultraviolet-B (UV-B, 280 nm) light, respectively, in the Pilobolus crystallinus sporangiophore. Fluence-response curves for both blue and UV-B light obtained by changing the fluence by varying exposure time only showed the classical first and second positive bending. However, fluence-response curves obtained by varying the fluence rate were bell-shaped irrespective of the length of the exposure time. With increasing exposure time the peak became higher along the ascendant arm and the descendant arm was shifted toward the higher fluence. The Bunsen-Roscoe reciprocity law was valid only when the fluence was less than approx. 400 pmol·m^-2 for both blue and UV-B light. Because the shapes of the fluence-response curves for blue and UV-B light were nearly the same, the photoreceptor systems for both blue and UV-B light are considered to be the same.Abbreviation UV-B ultraviolet-B     

布雷费尔德对真菌的进化观点在真菌分类中所起的影响*

布雷费尔德(O. Brefeld)虽对真菌纯培养方法的改进和真菌发育与生理知识作出了不少贡献,但他的主要贡献还是对真菌系统发育的观点。按照他的这种观点,卵菌不是真正的真菌,它应与粘菌一起排除在真菌之外,而真正的真菌应从接合菌开始。他并将子囊菌和担子菌分别分为半子囊菌和真子囊菌,半担子菌和真担子菌。     

Major sterols of Achlya bisexualis

Fucosterol, 24-methylene cholesterol, and cholesterol have been identified as major sterols in Achlya bisexualis. 7-Dehydrofucosterol has also been tentatively identified.     

Blue-light-induced shift of the phototropic fluence-response curve in Pilobolus sporangiophores

The effects of preirradiation with blue light on the shift of the fluence-response curve for the first and the second positive curvatures were examined in Pilobolus crystallinus (Wiggers) Tode sporangiophores. A 1-min preirradiation with blue light at 47 or 960 nmol·m^-2 lowered the fluence-response curve for the first positive curvature and shifted the peak to a higher fluence. The fluence-response curve was shifted back to a lower fluence when a dark period was inserted between the preirradiation and the curvature-inducing light. This shift back to lower fluence was biphasic when the fluence was high (960 nmol · m^-2), indicating the participation of two components in the phototropic reaction for the first positive curvature.The fluence-response curve for the second positive curvature did not seem to be shifted to a higher fluence region when fluence was varied by varying exposure time. However, the fluence-response curve obtained by varying the fluence rate of a 20-min irradiation period indicated that the second positive curvature was also shifted to a higher-fluence region by preirradiation with blue light. A small shoulder appeared on the fluence-response curve when preirradiation at a high fluence rate was given.Abbreviations BL blue light - CIL curvature-inducing light     

Phycomycetes parasitizing the ovaries of blackflies (simuliidae)

The developmental stages of the fungus in the ovary and freshwater are discussed. Based on the evidence to date the simuliid host is infected in the early larval instars. Parasitism results in a destruction of the ovarian tissues with no or few eggs produced. The fungus replaces the ovarian tissue and produces massive numbers of spores which are released by the female fly at the time of oviposition. After oviposition, infected flies do not seek a blood meal. Longevity of the host does not appear to be affected by the presence of the fungus. The spores released by the fly during oviposition did not withstand desiccation and did not develop on the artificial media tested; development occurs only in water. Development of sporangia takes 5 to 7 days at 4°C, and 2 to 3 days at temperatures above 10°C. The developmental process in spores from S. verecundum was followed from the formation of sporangia to the opening of discharge tubes which zoospores were presumed to be released but not observed.     

In vitro carotenogenesis by wild type and mutants of Phycomyces blakesleeanus

Cell extracts from shake cultures of the wild type and six mutant strains of Phycomyces converted [2-¹⁴C] MVA into carotenes, squalene and prenyl phosphates. Oxygen was required for the desaturation of phytoene. When compared with the wild type, cells extracts of carB and carR mutants are much less effective in phytoene dehydrogenation and lycopene cyclization, respectively. This confirms previous conclusions about the biochemical functions of the carB and carR genes, which were based on genetic and in vivo studies. CarA strain mutants accumulate, in vivo, much less β-carotene than the wild type. This correlates with a 10-fold decrease in carotenogenesis in vitro. The addition of retinol to incubations of cell extracts of the wild type and C2 strains stimulated β-carotene formation. Both carB and carR mutants show enhanced total carotenogenic activities in vitro and the carS mutant shows a higher β-carotene-synthesizing activity than the wild type. It is suggested that the feed-back regulatory mechanism known to control this pathway operates at the level of enzyme synthesis.     

The effect of diphenylamine on carotenogenesis in Phycomyces blakesleeanus

The presence of diphenylamine (DPA) during growth of mutant strains of Phycomyces blakesleeanus caused the expected inhibition of the formation of unsaturated carotenes, and the accumulation of phytoene in all cases. Cell extracts from DPA-grown cultures incubated with [2-¹⁴C]mevalonic acid, also exhibited these effects. Inhibition of in vitro carotenogenesis was similarly shown by extracts from normally-grown mycelia, incubated with DPA. Removal of DPA from mycelia or from cell extracts, resulted in the formation of unsaturated carotenes. The ratio of 15-cis-all-trans-phytoenes from mycelia grown ± DPA was only marginally altered, but, in vitro, the presence of DPA caused a significant increase in the formation of the all-trans isomer in the C5 strain. These results indicate that DPA acts by post-translational regulation of enzymic activities.     

Species-strain dependence of stereoselectivity in microbial oxidation of thioethers

The stereoselectivity in the aerobic, microbial oxidation of thioethers and sulphoxides is shown to be dependent on species and strain. A strain of Aspergillus niger was used to obtain an optically active dialkyl sulphoxide.     

布雷费尔德对真菌的进化观点在真菌分类中所起的影响

布雷费尔德(O. Brefeld)虽对真菌纯培养方法的改进和真菌发育与生理知识作出了不少贡献,但他的主要贡献还是对真菌系统发育的观点。按照他的这种观点,卵菌不是真正的真菌,它应与粘菌一起排除在真菌之外,而真正的真菌应从接合菌开始。他并将子囊菌和担子菌分别分为半子囊菌和真子囊菌,半担子菌和真担子菌。     

Quiesone: An inhibitor of the germination of Peronospora tabacina conidia

A potent germination inhibitor of Peronospora tabacina conidia has been isolated from tobacco leaves infected with this pathogen. From consideration of its spectral properties, it is suggested that the structure of this inhibitor is 5-isobutyroxy-β-ionone. The effects of this inhibitor on the germination of P. tabacina conidia have been investigated.