The Influence of Water Activity and Temperature on Germination,Growth and Sporulation of <Emphasis Type="Italic">Stachybotrys chartarum</Emphasis> Strains

The objectives were to determine the influence of water activity (a_w, 0.997–0.92) and temperature (10–37°C) and their interactions on conidial germination, mycelial growth and sporulation of two strains of Stachybotrys chartarum in vitro on a potato dextrose medium. Studies were carried out by modifying the medium with glycerol and either spread plating with conidia to evaluate germination and germ tube extension or centrally inoculating treatment media for measuring mycelial growth rates and harvesting whole colonies for determining sporulation. Overall, germination of conidia was significantly influenced by a_w and temperature and was fastest at 0.997–0.98 a_w between 15 and 30°C with complete germination within 24 h. Germ tube extension was found to be most rapid at similar a_w levels and 25–30°C. Mycelial growth rates of both strains were optimal at 0.997 a_w between 25 and 30°C, with very little growth at 37°C. Sporulation was optimum at 30°C at 0.997 a_w. However, under drier conditions, this was optimum at 25°C. This shows that there are differences in the ranges of a_w x temperature for germination and growth and for sporulation. This may help in understanding the role of this fungal species in damp buildings and conditions under which immune-compromised patients may be at risk when exposed to such contaminants in the indoor air environment.     

Interactions of ancymidol with sucrose and α-naphthaleneacetic acid in promoting asparagus (Asparagus officinalis L.) somatic embryogenesis

Interactions of varying ancymidol concentrations with those of α-naphthaleneacetic acid (NAA) or sucrose in embryo induction medium were related to the production and development of asparagus (Asparagus officinalis L.) somatic embryos, and to the ability of these embryos to germinate. A significant sucrose×ancymidol interaction was observed only for the production of bipolar embryos; 4% sucrose with 0.75 mg l^–1 ancymidol gave the best result, 78 g^–1 callus. The frequency of globular embryos decreased as sucrose or ancymidol concentrations increased. Sucrose concentration affected embryo germination; 3% and 4% sucrose were optimal with approximately 60% and 40% of bipolar and globular embryos germinating, respectively. Significant ancymidol×NAA interactions were observed for the production of bipolar and globular embryos and their germination. Varying ancymidol concentrations affected embryo production and germination in combination with 0.1 mg l^–1 NAA, but not with 1.0 mg l^–1 NAA. The treatment combination of 0.1 mg l^–1 NAA with 0.75 mg l^–1 ancymidol produced the most bipolar embryos, 64 g^–1 callus, and the greatest percentages of bipolar and globular embryos germinated, 63% and 42%, respectively. Received: 19 August 1996 / Revision received: 24 April 1997 / Accepted: 22 May 1997     

Effects of UV-light andγ-rays on the survival,akinete formation and akinete germination inStigeoclonium pascheri

The damage produced by UV light to any of the three different stages of the life cycle of the parent generation of the green algaS. pascheri, i.e. akinetes, germinating akinetes and vegetative cells remained up to the stage of germination of akinetes of the first generation and no deleterious effect was reported thereafter. Lower doses of γ-rays (25–75 Gy) increased the percentage germination of akinetes and germinating akinetes of parent generation. The percentage germination of akinetes, germinating akinetes, survival of colonies originated from vegetative cells and sporulation of cells of the parent generation decreased with increasing doses from 100 to 300 Gy. The γ-induced effect to any of the three different stages was not transferred to the subsequent stage of algal generation.     

Environmental influences on akinete germination and development in Nodularia spumigena (Cyanobacteriaceae), isolated from the Gippsland Lakes, Victoria, Australia

This study was carried out to investigate the genesis of N. spumigena blooms by specifically studying the effects of environmental variables (salinity, nitrogen, phosphorus and light) on the germination of N. spumigena akinetes. Optimal conditions for maximum germination and germling growth were determined by exposing akinetes to a range of salinities and nutrient (nitrogen and phosphorus) concentrations under two different irradiances. At pre-determined time periods, treatments were sampled and the percent germination and length of germlings assessed. The results indicated that akinete germination and germling growth were optimal at salinities from 5 to 25 and significantly reduced outside this range. A positive correlation in germination was observed with increasing nutrient (phosphorus and nitrate) concentration. Similarly, germling growth increased with increasing concentrations of both nutrients. Irradiance significantly influenced both germination and growth during salinity experiments, whereas in nutrient addition experiments, irradiance had no effect on germination; however, growth was significantly influenced during phosphorus addition experiments. Consequently, salinity and light appeared to be most critical in the germination process for N. spumigena akinetes, with phosphorus most important for germling growth. The study showed that N. spumigena may be able to germinate under environmental conditions outside its optimal range, but the growth of the germling is significantly reduced, which in turn suggests that its ability to form a bloom outside its optimal environmental conditions would also be greatly reduced.     

Physiological and biochemical responses of <Emphasis Type="Italic">in vitro Fusarium oxysporum</Emphasis> f.sp. <Emphasis Type="Italic">niveum</Emphasis> to benzoic acid

The allelopathic potential of an artificially applied allelochemical, benzoic acid, on in vitro Fusarium oxysporum f.sp. niveum (a soil-borne pathogen causing watermelon wilt) was evaluated. Benzoic acid strongly inhibited its growth, sporulation and conidia germination, whereas it stimulated virulence factors of this pathogen. The biomass was reduced by 83–96 % and the conidia germinating rate and conidia production rate were decreased by 100 % at a concentration of >200 mg/L. However, phytopathogenic enzyme activities and mycotoxin production were stimulated with an increase of 10.2–1250 % for enzyme activities and 610–2630 % for mycotoxin yield.     

Effects of pH,NH<Subscript>4</Subscript>-N concentration,temperature, and storage period on basidiospore germination in an ectomycorrhizal ammonia fungus <Emphasis Type="Italic">Hebeloma vinosophyllum</Emphasis>

Basidiospore germination in an ectomycorrhizal ammonia fungus Hebeloma vinosophyllum was stimulated by 10–500 mM NH₄Cl aqueous solution at pH 4.5–9.0, but not by pure water. The basidiospores germinated at 10°–35°C with an optimum at 25°–30°C. The highest germination percentage (83.0%) was observed in 100 mM NH₄Cl aqueous solution adjusted to pH 8.0 by KOH, when the basidiospores were incubated at a density of 10⁶ spores/ml at 30°C for 14 days. The percent germination value decreased with the increased duration of storage under both dry and wet conditions. Humidity and temperature affected the longevity of H. vinosophyllum basidiospores. The basidiospores maintained their germination ability longer under a dry condition than under a wet condition. The greatest longevity was accomplished by storage at 15°C under a dry condition.     

Effect of actinomycin D on viability,sporulation and nucleotide pool ofBacillus megaterium

A transient 7-fold rise of ppGpp concentration, 2-3-fold increase of pppGpp concentration and 50 % drop of the concentration of GTP inBacillus megaterium cells immediately after their transfer to the sporulation medium were observed. Actinomycin D, in concentrations inhibiting RNA synthesis by 95%, blocked the rise of the (p)ppGpp pool and caused an instant several-fold increase of the GTP level. When the cells were exposed to actinomycin D in the sporulation medium for a 1-h period (time 0–1 h, 1–2 h or 2.20–3.20-h), they were able to form colonies on nutrient agar after being kept, in addition for 1–2 h in the sporulation medium free of the antibiotic. The ability of sporulation was, however, markedly limited. The share of cells that could sporulate increased when the irreversible sporulation phase was reached.     

Effect of onion (Allium cepa) root exudates on the hyphal growth of Gigaspora margarita

 The effect of root exudates from onions differing in P status on spore germination and hyphal growth of arbuscular mycorrhizal fungi was investigated. Onion (Allium cepa) was grown in solution culture at different phosphorus concentrations (0, 0.1, 1.0, 8.0 and 24.0 mg P l^–1) and root exudates were collected. When spores of the arbuscular mycorrhizal fungus, Gigaspora margarita were incubated with these root exudates, spore germination was only slightly affected but hyphal growth was greatly affected, particularly with exudates from P-deficient plants. This suggests that the P nutrition of host plants influences the composition of root exudates and thereby the hyphal growth of arbuscular mycorrhizal fungi. Accepted: 25 June 1995     

Germination and conversion of somatic embryos derived from mature Quercus robur trees: the effects of cold storage and thidiazuron

Somatic embryos of Quercus robur L. belonging to lines derived from mature trees were germinated in experiments designed to determine the effects of pregermination chilling and the temporary inclusion of thidiazuron (TDZ) in the germination medium. Germination response was evaluated in terms of the percentages of embryos exhibiting root-only elongation, shoot-only elongation, or both (conversion to plantlets). Conversion rates depended on genotype and were lower than those of oak zygotic embryonic axes germinated in vitro. Two months’ storage of somatic embryos at 4°C between maturation and germination treatments did not influence their conversion frequency, although root-only germination was promoted in the three embryogenic lines investigated. Addition of 0.01–5.0 μM TDZ to the germination medium for 7 or 18 days induced multiple shoot formation in the epicotyl region of germinating embryos, although the 18-day treatment was detrimental with TDZ concentrations of 0.5–5.0 μM. Exposure to 0.05–0.1 μM TDZ for 7 days increased the frequency of shoot-only elongation and decreased that of root-only elongation in embryogenic lines with both high and low conversion ability, but whereas the conversion rate of the hard-to-convert line Sainza was significantly increased, that of the readily converted line B-17 was negatively affected. As a result, with 0.1 μM TDZ the total potential plant recovery of Sainza (the conversion rate plus the percentage of embryos exhibiting shoot-only germination) was 64%, approximately the same as that of B-17. Shoots excised from shoot-only germinating embryos can be elongated and rooted by proven micropropagation procedures. An additional result was the finding that adventitious bud regeneration was induced on the cotyledons of TDZ treated embryos (69% with 0.5 μM TDZ), which may prove useful for genetic transformation. This study is the first to have shown that TDZ can increase the germination efficiency of oak somatic embryos.     

Foam control in biopesticide production from sewage sludge

Several antifoam agents were evaluated for the ability to control foam in the production of Bacillus thuringiensis-based biopesticides using sewage sludge as a raw material. Experiments were conducted in shake flasks as well as in 15 l fermentors with controlled parameters. Polypropylene glycol (PPG), the most commonly used antifoam agent in B. thuringiensis fermentation, inhibited cell growth, sporulation and decreased the entomotoxicity yield even at a concentration of 0.1% (v/v) in sewage sludge medium. About 40% reduction in entomotoxicity was observed when PPG was used at 0.3% (v/v). The impact of PPG on sporulation and toxin synthesis in tryptic soy yeast broth (TSYB) medium was also studied. The inhibitory effects were less severe in TSYB than in sludge medium. Another silicone-based antifoam agent, “Antifoam A”, showed less severe effect on growth and stendotoxin production. The problem of the inhibitory effect of chemical antifoam agents on growth and endotoxin production was minimised substantially with the use of vegetable oils such as canola, olive, and peanut oils. Canola and peanut oil stimulated both sporulation and δ-endotoxin synthesis. The stimulus effect varies with the monounsaturated fat contents of oils. Journal of Industrial Microbiology & Biotechnology (2000) 25, 86–92. Received 09 February 2000/ Accepted in revised form 06 June 2000     

Viability of dried vegetative cells and the formation and germination of reproductive structures inPithophora œdogonia, Cladophora glomerata andRhizoclonium hieroglyphicum under water stress

All dried vegetative cells ofPithophora œdogonia died within 1 h, while those ofCladophora glomerata andRhizoclonium hieroglyphicum retain viability to some extent for 1 and 8 d, respectively, under similar storage conditions. The viability of dried vegetative cells of eitherC. glomerata orR. hieroglyphicum decreased more or less equally when stored either at 20 °C. in light or dark or at 12 °C in dark, but was lost rapidly and drastically when stored at 0 °C in dark. Both dried and wet akinetes ofP. œdogonia were equally more viable when stored at 20 °C in dark than in light, but they lost germination ability when stored either at 12 or 0 °C in dark; this might be either due to loss of viability or dormancy induction at low temperatures. The water stress imposed by growing vegetative filaments either on highly agarized media, in NaCl-supplemented liquid media or in media undergoing progressive air-drying to complete dryness did not induce, but reduced akinete formation inP. œdogonia, decreased zoosporangium formation inC. glomerata andR. hieroglyphicum, decreased or totally suppressed akinete germination inP. œdogonia and zoospore germination inC. glomerata andR. hieroglyphicum. Akinetes ofP. œdogonia formed under water stress were equally viable, while zoosporangia ofC. glomerata andR. hieroglyphicum formed under water stress were comparatively less viable than those formed without any water stress. Akinete germination inP. œdogonia and zoospore germination inC. glomerata andR. hieroglyphicum were comparatively more sensitive to water stress than the formation of akinetes and zoosporangia. The akinete germination inP. œdogonia was more sensitive to water stress than zoospore germination inC. glomerata andR. hieroglyphicum and it might be either due to their large size, thick wall or dense content.     

Compatability of Metarhizium anisopliae var. anisopliae with chemical pesticides

The effects of various insecticides on the mycelial growth, sporulation and conidial germination of Metarhizium anisopliae var. anisopliae isolate E₉ were studied in the laboratory. Chlorpyrifos was the most toxic organophosphate to mycelial growth and sporulation at all concentrations. Temephos, malathion and leptophos were highly toxic to sporulation while malathion was the most inhibitory to germination. The carbamates, carbofuran, methomyl and oxamyl were moderately toxic to mycelial growth and sporulation while oxamyl had an adverse effect on germination. The pyrethroids (pyrethrin, permethrin and resmethrin) and the insect growth regulators (diflubenzuron and methoprene) were not inhibitory to the various developmental stages of isolate E₉. The chlorinated hydrocarbons (chlordane, lindane and toxaphene) were more deleterious than all other insecticide groups tested. Among the fungicides, benomyl and maneb produced the greatest inhibition.     

Germination and seedling growth of carrots under salinity and moisture stress

Poor crop stand is a common problem in saline areas. Germination and seedling emergence may be depressed as a result of impeded aeration, saline or dry conditions. In this study, we examined the effects of salinity and moisture stress and their interactions on seed germination and seedling growth of carrots. Variable soil matric and osmotic potentials were either obtained by equilibrating soil salinized to different degrees on a 0.5 MPa ceramic plate soil moisture extractor or by adding different amounts of salt solutions to the same mass of air-dried soil, based on a previously determined soil moisture release curve, and allowing to equilibrate for 1 week. Germination decreased significantly in the investigated silty soil (Aquic Ustifluvent) at soil moisture potentials higher than −0.01 MPa, whereas osmotic potentials as low as −0.5 MPa did not influence germination. Matric potentials of −0.3 and −0.4 MPa, respectively, resulted in a strong decrease (35–95%) of germination and delayed germination by 2 to 5 days in the silty soil to which different amounts (18 and 36%, respectively) and sizes (0.8–1.2 mm and 1.5–2.2 mm, respectively) of sand particles had been added. No effect of sand and grain diameter was detected. Germination was not affected by comparable osmotic potentials. Seedling growth showed a much higher sensitivity than germination to decreasing matric potentials, but was not affected by osmotic potentials ranging from −0.05 to −0.5 MPa. Optimum shoot growth occurred at matric potentials between −0.025 and −0.1 MPa. Shoot and root growth decreased markedly at matric potentials higher than −0.01 MPa. Fresh weight of shoots decreased gradually at matric potentials lower than −0.2 MPa. Root growth was significantly increased at matric potentials of −0.1 to −0.3 MPa, whereas comparable osmotic potentials did not have equivalent effects. It is concluded that germination and seedling growth are differently affected by comparable matric and osmotic stresses and that water stress exerts a more negative effect than salt stress.     

The effect of insecticides on growth,germination and cuticle-degrading enzyme production by Isaria fumosorosea

The influence of six chemical insecticides on growth, sporulation, conidial germination and cuticle-degrading enzyme production by Isaria fumosorosea were investigated under laboratory conditions. Maximum reduction in vegetative growth, sporulation and conidial germination in relation to the control treatment was observed for Chloranthraniliprole whereas Indoxacarb proved to be the safest insecticide causing lowest reduction in these parameters. Chloranthraniliprole, Chlorpyrifos and Chlorfenapyr caused higher reduction in enzyme activities (chitinase, Pr1, Pr2 and lipase) at all three concentrations whereas very low reduction in enzyme activities was caused by Hubendamide+ Avermectin and Indoxacarb when used at 10 µg/ml. The data presented can be used for future recommendations of these insecticides in IPM programmes where I. fumosorosea is an important control agent.     

Spores of microorganisms

Calcium-dipicolinate (Ca-DPA)-rich and Ca-DPA-deficientBacillus cereus spores were incubated in a synthetic medium with germination stimulants and in bactopeptone medium with a fairly high calcium ion concentration. In the complex medium the germination of Ca-DPA-rich spores was completely blocked at a concentration of 0.5m CaCl₂, whereas the complete blockage of germination in the synthetic medium required higher concentrations (0.6–0.8m) of calcium chloride. Ca-DPA-deficient spores germinated more slowly and less completely in the synthetic medium than in the bactopeptone medium. The germination of these spores took place, however, even at higher calcium ion concentrations (0.6–0.8m). On the contrary, lower calcium chloride concentrations (0.1–0.4m) accelerated the germination of these spores in the synthetic medium and the final percentage of phase-dark and stainable spores was higher. “H-forms” of the Ca-DPA-rich and Ca-DPA-deficient spores prepared by acid titration germinated in both media. The germination of the latter spores being slower and proceeding less completely. “H-forms” germinated completely or partially in media with a high concentration of calcium chloride. The percentage of germinated spores, however, was strongly influenced by the concentration of this cation, especially the “H-forms” of Ca-DPA-deficient spores. Moreover, the germination of Ca-DPA-deficient spores in this medium was affected by the length of previous storage and, in the case of “H-forms” by the pH at which they were titrated. It was assumed that the increased permeability of calcium into the calciumundersaturated spore periphery in Ca-DPA-deficient and in “H-forms” of spores of both types co-determines (in the presence of germinants) the germinability of bacterial spores.     

Effect ofAgrobacterium radiobacter and its polysaccharide on emergence and damping-off of tomato plants

Agrobacterium radiobacter B6 and agrobacteran (an exopolysaccharide of the succinoglycan group) stimulated seed germination and tomato plant emergence. The germination was most stimulated by dipping the seeds in 0.1 % agrobacteran for 30 min whereas plant emergence in garden soil was best with 0.4 % agrobacteran at 10–20°C. Treatment of the plants withA.radiobacter cells and agrobacteran solution at 30–35°C. had a lower effect.A.radiobacter cells applied on seed surface protected the plants against damping off in garden soil artificially inoculated with the fungiRhizoctonia solani andPythium ultimum; in soils contaminated withFusarium solani 0.1 to 0.2% agrobacteran had a higher protective effect than the bacterization. The difference can be attributed to the varying density ofA.radiobacter population in plant rhizosphere in the presence of different plantpathogenic fungi, different interactions of microorganisms in the rhizosphere and different mode of penetration of the pathogens into plant roots.     

Influence of culture conditions on production and freeze-drying tolerance of Paecilomyces fumosoroseus blastospores

With the goal of developing a defined medium for the production of desiccation-tolerant blastospores of the bioinsecticidal fungus Paecilomyces fumosoroseus, we evaluated the impact of various media components such as amino acids, carbohydrates, trace metals and vitamins on hyphal growth and sporulation of P. fumosoroseus cultures and on the freeze-drying tolerance of blastospores produced under these conditions. A comparison of 13 amino acids as sole nitrogen sources showed that glutamate, aspartate, glycine and arginine supported biomass accumulations (12–16 mg ml⁻¹) and blastospore yields (6–11 × 10⁸ blastospores ml⁻¹) comparable to our standard production medium which contains casamino acids as the nitrogen source. Using glutamate as the sole nitrogen source, tests with various carbohydrates showed that P. fumosoroseus grew best on glucose (18.8 mg biomass ml⁻¹) but produced similar blastospore concentrations (7.3–11.0 × 10⁸) when grown with glucose, glycerol, fructose or sucrose. P. fumosoroseus cultures grown in media with sodium citrate or galactose as the sole carbohydrate produced lower blastospore concentrations but more-desiccation-tolerant spores. Zinc was the only trace metal tested that was required for optimal growth and sporulation. In a defined medium with glutamate as the nitrogen source, vitamins were unnecessary for P. fumosoroseus growth or sporulation. When blastospores were freeze-dried in the absence of a suspension medium, residual glucose (>2.5% w/v) was required for enhanced spore survival. Thus, a defined medium containing basal salts, glucose, glutamate and zinc can be used to produce optimal concentrations of desiccation-tolerant blastospores of P. fumosoroseus. Received 27 October 1998/ Accepted in revised form 06 May 1999     

Seed germinating characteristics of 54 gramineous species in the alpine meadow on the eastern Qinghai-Tibet plateau

The germination experiment was started on March 3, 2004, and seeds were collected from July to October in 2003. We analyzed the percentage of germination, days to first germination, germination period and days to 50% germination. Among the 54 examined species, 26 species exceeded 80% germination, 11 species exceeded 60%–80% germination, 8 exceeded 40%–0%, 5 exceeded 20%–40%, and 4 showed less than 20%. A principal-component analysis revealed that the species were distributed along two statistically independent axes, the first primarily represented the germination rate and the second represented the time of germination process. Based on scores of germination characteristics, cluster analysis of the 54 gramineous species could be divided into 4 distinct groups: rapid, slow, intermediate germinating (germination percentage > 50%), and low germinating (germination percentage < 50%). The meaning of different groups to the vegetation regeneration was discussed. __________ Translated from Journal of Plant Ecology, 2006, 30(4): 624–632 [译自: 植物生态学报]     

Use of Beauveria bassiana in combination with commercial insecticides to manage Phauda flammans (Walker) (Lepidoptera: Phaudidae): Testing for compatibility and synergy

An entomopathogenic fungal strain, Beauveria bassiana PfBb, was identified from Phauda flammans (Lepidoptera: Phaudidae) larvae. The compatibility and synergy of B. bassiana PfBb employed in combination with three concentrations (i.e., recommended concentration, 20% and 10% of the recommended concentration) of five commercial insecticides were determined. Beta cypermethrin at 10% of recommended concentration had the lowest inhibitory effect on the mycelial growth of B. bassiana PfBb compared with other insecticides. Insecticides utilized at recommended concentration had no significant effect on the sporulation of B. bassiana PfBb, while the extent of their effect at 20% and 10% of recommended concentration differed among insecticides. Insecticides at 10% of recommended concentration had the lowest inhibition of sporulation and conidial germination compared with other concentrations. The conidial germination of B. bassiana PfBb was the highest after treatment with beta cypermethrin at 10% of recommended concentration. The cumulative mortality for 1 × 10⁷ spores/mL B. bassiana PfBb combined with each insecticide at 10% of recommended concentration was higher than that observed with the application of insecticides alone. The percent cadavers of Phauda flammans larvae observed after treatment with B. bassiana PfBb combined with beta cypermethrin at 10% of recommended concentration were not significantly different from those observed after infection with B. bassiana PfBb alone. Our findings demonstrate that B. bassiana PfBb combined with beta cypermethrin at 10% of recommended concentration could increase the efficiency of this insecticide.     

Propionyl-CoA carboxylase of Myxococcus xanthus: catalytic properties and function in developing cells

An acyl-coenzyme A carboxylase that carboxylates acetyl-CoA, butyryl-CoA, propionyl-CoA, and succinyl-CoA was purified from Myxococcus xanthus. Since the enzyme showed maximal rates of carboxylation with propionyl-CoA, the enzyme is thought to be propionyl-CoA carboxylase. The apparent K _m values for acetyl-CoA, butyryl-CoA, propionyl-CoA, and succinyl-CoA were found to be 0.2, 0.2, 0.03, and 1.0 mM, respectively. The native enzyme has a molecular mass of 605–615 kDa and is composed of nonidentical subunits (α and β) with molecular masses of 53 and 56 kDa, respectively. The enzyme showed maximal activity at pH 7.0–7.5 and at 25–30°C, and was affected by variation in concentrations of ATP and Mg²⁺. During development of M. xanthus, the propionyl-CoA carboxylase activity increased gradually, with maximum activity observed during the sporulation stage. Previous work has shown that a propionyl-CoA-carboxylase-deficient mutant of M. xanthus reduces levels of long-chain fatty acids. These results suggest that the propionyl-CoA carboxylase is also responsible for the carboxylation of acetyl-CoA to malonyl-CoA used for the synthesis of long-chain fatty acids during development. Received: 24 February 1998 / Accepted: 25 May 1998