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91.
Agents known to influence Ca2+ homeostasis affected significantly the vegetative growth and starvation-induced conidiation ofTrichoderma viride. Ca2+ in millimolar concentrations stimulated both growth and conidiation; a Ca2+ deprivation of the fungus by the chelation of extracellular Ca2+ (not Mg2+ or divalent trace metals) with EGTA (ethyleneglycolbis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid) restricted both the
vegetative growth rate and starvation-induced conidiation. Both processes were affected by either Ca2+ or EGTA with different efficiencies. Divalent cations (Sr2+, Ba2+, Co2+, Ni2+, Mg2+, Cd2+, Cu2+, Mn2+) and La3+ (inorganic Ca2+ blockers) in millimolar concentrations exerted complex (stimulatory, inhibitory, or biphasic) effects on growth and conidiation.
In general, their effects on the two processes were mutually different either qualitatively, or quantitatively, or both. Organic
Ca2+ antagonists (verapamil and dihydropyridines) inhibited the vegetative growth. The results show that Ca2+ is required for vegetative growth and conidiation, and that different Ca2+-dependent mechanisms may be involved in the two processes. Divalent cations could serve as a tool for investigating the relationship
between growth and conidiation. 相似文献
92.
Vanadate (NaVO3) in concentrations between 0.1–3.0 mmol/L inhibited the production of secondary metabolites (SMs) of strains of the following
species:Trichoderma viride, Penicillium purpurogenum, Penicillium citrinum, Talaromyces avellaneus, andVerticillium psalliotœ. Growth was either not affected by NaVO3, or the inhibition of the SM production occurred at lower NaVO3, concentrations than that of the growth. Thus, at some NaVO3 concentration the SM production was inhibited but the growth remained unaffected. The results suggest that NaVO3 exerts a specific action either on the SM biosynthetic pathway(s) or on the export of SMs from cells. 相似文献
93.
Seven streptomycete strains were tested for biotransformation of salicylate. The products were identified by nuclear magnetic resonance spectroscopy and three types of conversion were found. Streptomyces cinnamonensis and Streptomyces spectabilis formed gentisate and salicylamide concurrently. Streptomyces rimosus transformed salicylate to salicylamide. Streptomyces lividans, Streptomyces coelicolor, Streptomyces griseus and Streptomyces avermitilis produced only gentisate. Time course studies of salicylate conversion by thin-layer chromatography and high pressure liquid chromatography showed that salicylamide was accumulated in the culture broth, whereas gentisate was further metabolized.Key words: salicylate, gentisate, salicylamide, biotransformation, Streptomyces spp. 相似文献
94.
Growth and fecundity of Daphnia after diapause and their impact on the development of a population 总被引:1,自引:1,他引:0
Laboratory and field investigations revealed that the life history traits of exephippial and parthenogenetic generations of Daphnia differ substantially. Daphniids hatching from resting eggs grow faster and their definitive body sizes are bigger than of hatchlings from subitaneous eggs. Size at maturity for exephippial animals is significantly larger. In spite of this, they mature a few days earlier than parthenogenetic females. In this study, the difference was 3–4 days for the laboratory experiments and 1–3 days for the field. Fecundity of the exephippial generation is markedly higher. Here, the clutch size for this generation was up to 3.5–4.0 times as large as for the parthenogenetic generation. Moreover, obtained results suggest that the relationship between clutch size and body length for both generations differ significantly.Estimates of the intrinsic rate of increase for field Daphnia populations demonstrated that life history traits of exephippial animals lead to a two or threefold higher rate of increase in the conditions of invertebrate predation pressure. Under moderate fish pressure, obtained r values for the daphniids hatching from resting eggs were larger than those from subitaneous. High growth rate of exephippial females is disadvantageous only under the conditions of severe pressure by fish. Obtained results suggest that hatchlings from diapausing eggs an acceleration of population increase by several times during the beginning of the development of a population with periodical re-establishment from resting eggs. 相似文献
95.
M. J. Martínez C. Muñoz F. Guillen A. T. Martínez 《Applied microbiology and biotechnology》1994,41(5):500-504
Homoveratric acid (HVA) degradation was observed in cultures of Pleurotus eryngii lacking lignin peroxidase (LiP) activity. Extracellular enzymes seemed responsible for this transformation, and the lack of activity after ultrafiltration of the culture liquid suggests that the presence of some low-molecular-size compounds is required. This hypothesis is supported by rapid HVA transformation after addition of the synthetic laccase substrate 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) to the ultrafiltered liquid. HVA transformation by the extracellular enzymes from P. eryngii takes place via C-C breakdown and formation of veratryl alcohol, which is further transformed into veratraldehyde. The same major compounds were found during HVA transformation by LiP from Phanerochaete chrysosporium, but this reaction was not stimulated by ABTS. Although the involvement of other enzymes cannot be ruled out, purified laccase from Pleurotus eryngii caused the same HVA transformation pattern in presence of ABTS. Moreover, veratryl alcohol oxidation by P. eryngii laccase was demonstrated in the presence of ABTS. These results suggest that enzymatic systems lacking LiP could be responsible for natural degradation of lignin. 相似文献
96.
Jan Nešvera Jitka Hochmannová Miroslav Pátek Alena Šroglová Věra Bečvářová 《Applied microbiology and biotechnology》1994,40(6):864-866
Gram-positive facultative methylotrophic coryneform bacterium Brevibacterium methylicum was efficiently transformed with various plasmids using electroporation of intact cells. In addition to the plasmid vectors pEC71 and pZ6-1 constructed on the basis of cryptic plasmids from coryneform bacteria, broad-host-range plasmids pLS5 (derivative of plasmid pMV158 from Streptococcus agalactiae) and RSF1010 belonging to the incompatibility group IncQ from Gram-negative bacteria were found to be present as autonomous structurally unchanged DNA molecules in B. methylicum transformants. With the exception of pZ6-1, all these plasmids were stably maintained in B. methylicum cells grown under non-selective conditions. When plasmid DNAs isolated from B. methylicum were used, the highest efficiency of transformation (105 transformants/g DNA) was achieved.
Correspondence to: J. Nevera 相似文献
97.
The correlation between pollen/ovule (P/O) ratio and breeding system has generally been accounted for either on the basis that P/O reflects pollination efficiency, or in terms of the sex allocation theory. The following were assessed for taxa belonging to genus Astragalus subgenus Epiglottis: 1) Degree of correlation between P/O and the breeding system, measured by means of autofertility; 2) The absence or existence of correlation between P/O and pollen grain size; and 3) The ability of various theories to account for the results obtained. Results showed a minimal correlation between P/O and autofertility, and between P/O and pollen grain size in the taxa studied. Analysis of these results in terms of the sex allocation theory enabled this correlation to be explained as a function of the variation existing between taxa with respect to the resources invested in each pollen grain and in each ovule. The predictive capacity of this theory, which has moreover proven valuable in explaining the structural peculiarities of the androecium in these taxa, was also highlighted. The type of self-pollination applicable was also discussed, as was the phenotypic model of selection of self-fertilization considered most plausible for these taxa. 相似文献
98.
G. Sekaninová M. Hofer I. Rychlík J. Pillich M. Kolářová V. Zajícová D. Kubíčková 《Folia microbiologica》1994,39(5):381-386
A new bacteriophage typing set, composed of 22 phages, was established as a tool for differentiation ofProteus strains. All the phages were tailed and included 4 morphological types (A1, A2, B1 and C1). They were classified into the
familiesMyoviridae, Siphoviridae andPodoviridae. From the set, 19 phages had double-stranded DNA and 3 were single-stranded DNA phages. 相似文献
99.
Cells ofBacillus megaterium contain 35–45% of poly(3-hydroxybutyrate) (PHB) at the beginning of the stationary phase. This amount is only slightly affected
by the medium composition. The PHB granules are spherical with the mean diameter of 1.15 μm. 相似文献
100.
Manganese peroxidase as an extracellular enzyme is produced by the white rot fungusPhanerochœte chrysosporium under nutrient nitrogen or carbon limitation. The effect of nitrogen concentration on the activity of manganese peroxidase
was studied using ammonium nitrate andl-asparagine as nitrogen sources. The highest activity of the enzyme was observed in cultures grown in a medium containing
75 mg/L ammonium nitrate and 0.15 g/Ll-asparagine. Manganese peroxidase was not detectable in cultures grown in the presence 0.5 g/L ammonium nitrate and 1 g/Ll-asparagine. 相似文献