Electron Microscopy of Young Candida albicans Chlamydospores

One- to three-day-old cultures of Candida albicans bearing chlamydospores were grown and harvested by a special technique, free of agar, and prepared for ultramicrotomy and electron microscopy. These young chlamydospores exhibited a subcellular structure similar to that of the yeast phase, e.g., cytoplasmic membrane, ribosomes, and mitochondria. Other structural characteristics unique to chlamydospores were a very thick, layered cell wall, the outer layer of which was continuous with the outer layer of the suspensor cell wall and was covered by hair-like projections; membrane bound organelles; and large lipoid inclusions. Only young chlamydospores less than 3 to 4 days old exhibited these ultrastructural characteristics.     

Interactions of Phytophthora cinnamomi and Trichoderma spp. in relation to propagule production in soil cultures at 26 degrees C1

Effects of Trichoderma harzianum and T. polysporum on chlamydospore production by two isolates of Phytophthora cinamomi were determined over a 21-day period in nonsterile, sterilized, and sterilized amended soil. Trichoderma was either coinoculated with P. cinnamomi or added to the cultures on day 3 of the incubation period. In nonsterile soil, conversion of mycelial fragments in the P. cinnamomi inoculum to chlamydospores resulted in an initial slight increase in chlamydospore numbers. In cultures where either of the Trichoderma isolates was added on day 3, a significiant reduction in chlamydospore numbers was observed on day 4; however, neither of the Trichoderma isolates at either inoculation time significantly affected clamydospore numbers by day 21. Results from studies with sterilized amended soil indicated that a reduction in P. cinnamomi chlamydospore numbers by either of the Trichoderma isolates was dependent upon availability of simple carbohydrates. In sterilized nonamended soil, the number of chlamydospores was increased in cultures containing either Trichoderma isolate; in sterilized amended soil chlamydospore numbers were initially reduced, followed by a general increase as the nutrients were depleted. Neither of the Trichoderma isolates exhibited significant antagonistic qualities toward P. cinnamomi.     

Absence of Obvious Short Term Impact of the Nematode-Trapping Fungus Duddingtonia Flagrans on Survival and Growth of the Earthworm Aporrectodea Longa

The nematode-trapping fungus Duddingtonia flagrans may be used in biological control of parasitic nematode larvae in faeces of domestic host animals after feeding the hosts with fungal chlamydospores. In this experiment a possible undesirable fungal impact on earthworms, of the species Aporrectodea longa, was investigated. As earthworms eat animal faeces, D. flagrans may come into contact with earthworms both in their alimentary tract and on their body surface. However during the experimental period of 20 days, when earthworms were living in soil and eating cattle faeces that were heavily infested with viable chlamydospores of D. flagrans there were no indications of internal or external mycosis among the earthworms.     

Ammonium excretion by a mutant of the nitrogen-fixing cyanobacterium Anabaena siamensis

Anabaena siamensis isolated from rice fields in Thailand is a fast growing cyanobacterium with a high nitrogen-fixing activity. Mutant strains resistant to the l-glutamate analogue, l-methionine sulfoximine (MSX) were isolated by ethyl methanesulfonate mutagenesis. A stable mutant named A. siamensis SS1, which released ammonium to the medium, was studied further. In batch cultures the rate of ammonium production peaked at the early log phase and gradually decreased until the 4th day of growth when the cultures reached a density of 90 μg chl ml⁻¹. To obtain constant release of ammonium by SS1, continuous culture experiments were performed at a cell density of 5 μg chl ml⁻¹ and the following results were obtained: (1) growth rate as the parent (μ:0·123 h⁻¹) in the presence and absence of 500 μm MSX; (2) 48% GS transferase activity when compared with the parent; (3) ammonium excretion at a rate of 8 μmol (mg chl)⁻¹ h⁻¹ as measured up to 20 generations (120 h); (4) depressed nitrogenase activity; and (5) 30% higher nitrogenase activity than that of the parent. SS1 immobilized in alginate beads (5 μg chl ml⁻¹) exhibited values of glutamine synthetase and nitrogenase activity similar to those of free cells. However, ammonium excretion at the rate of 11·61 μmol (mg chl)⁻¹ h⁻¹ was obtained only up to 20 h after loading in bioreactors, due to the fast growth of SS1 as also occurred in batch cultures.     

Evaluating the effectiveness of a Mexican strain of Duddingtonia flagrans as a biological control agent against gastrointestinal nematodes in goat faeces

The use of Duddingtonia flagrans in the control of goat nematodes was investigated. Initially, the time of passage of chlamydospores through the digestive tract of goats was evaluated. Two groups of seven parasite-free kids were formed. Group A received a single dose of 3.5x10(6) D. flagrans chlamydospores (FTHO-8 strain) per kg of live weight. Group B did not receive any chlamydospores. Faeces were obtained from each kid daily from day 4 prior to inoculation until day 5 post-inoculation (PI) and were placed in Petri dishes containing water agar. Gastrointestinal nematode infective larvae were added to each Petri dish and incubated at 25 degrees C for 7 days. Petri dishes were examined to detect the fungus and trapped nematodes. A second trial evaluated the effect of D. flagrans on the number of gastrointestinal nematode larvae harvested from goat faecal cultures in naturally infected goats. Two groups of seven goats were formed. The treated group received a single dose of 3.5x10(6) D. flagrans chlamydospores per kg of liveweight. The control group did not receive any chlamydospores. Faeces were obtained twice daily from each kid. Two faecal cultures were made for each kid. One was incubated for 7 days and the other for 14 days. Gastrointestinal nematode larvae were recovered from each culture and counted. Percentage of larval development reduction was determined using a ratio of larvae/eggs deposited in the control and treated groups. Duddingtonia flagrans survived the digestive process of goats, and maintained its predatory activity, being observed from 21 to 81 h PI (3 to 4 days). A reduction in the infective larvae population in the treated group compared to the non-treated group was observed in both incubation periods (7 days: 5.3-36.0%; 14 days: 0-52.8%, P>0.05). Although a single inoculation of D. flagrans can induce a reduction of infective larvae collected from faeces, a different scheme of dosing may be needed to enhance the efficacy of D. flagrans in goats.     

Production of Chlamydospores and Conidia in Submerged Culture by Rhynchosporium alismatis, a Mycoherbicide of Alismataceae in Rice Crops

The objective of this work was to evaluate the production of chlamydospores and conidia of Rhynchosporium alismatis in a liquid Czapex-Dox based medium supplemented with increasing concentrations of sodium nitrate and malt extract. In addition, the germination of chlamydospores was evaluated. A high concentration of malt extract (4.4 g L^-1) as the sole carbon source and a high level of sodium nitrate as the sole nitrogen source (3.3 g L^-1) were shown to increase chlamydospore production while agitation (150 rpm) enhanced conidial yields. Maximum chlamydospore production (2.03×10⁵±0.7 total chlamydospores mg DW^-1) was achieved in cultures grown in a medium supplemented with 8.8 g L^-1 malt extract and 5.74 g L^-1 sodium nitrate. Two days growth was required for maximum chlamydospore and conidial production, while 6 days was necessary to obtain maximum dry weight accumulation (350 mg per flask). Germination of chlamydospores (90%) was significantly higher than germination of conidia (47%) after 2 days growth.     

Susceptibility of elk to lungworms from cattle

Two studies were conducted to determine the infectivity of the lungworm, (Dictyocaulus viviparus) of cattle origin, in Rocky Mountain elk (Cervus elaphus nelsoni) or wapiti. In the first study, each of three 9-mo-old elk was administered 3,000 D. viviparus larvae from cattle using a nasogastric tube. In the second study, four 16-mo-old elk were each inoculated with 2,000 D. viviparus from cattle using a nasogastric tube. Elk were observed daily for signs of respiratory disease, and fecal samples were collected during the studies and evaluated for lungworm larvae using a modified Baermann technique. One elk was euthanatized during the patent period for recovery of adult lungworms, and three elk were euthanatized after larvae were no longer detected in feces. Lungworm larvae were not detected before inoculation in any of the 16-mo-old elk, but were detected 22 days after inoculation in one elk, 23 days after inoculation in two elk and 24 days after inoculation in all four elk. The prepatent period of this cattle isolate of D. viviparus in elk is therefore 22 to 24 days. The precise prepatent period was not determined in the three 9-mo-old elk, but larvae were detected in all three elk 25 days after inoculation. Numbers of larvae ranged from 1/ to 101/g feces with peak larval detection occurring 32 to 50 days after inoculation. Elk shed larvae from 22 to 83 days after inoculation, and patent periods of the parasite ranged from 24 to 62 days. Clinical signs of respiratory disease, with the exception of mild coughing after exercise, were not observed during the infections. Results from this experiment indicated that D. viviparus larvae of cattle origin can mature in elk and larvae can be passed in large numbers in feces, but this cattle isolate of D. viviparus was not highly pathogenic in elk.     

Administration of the nematophagous fungus Duddingtonia flagrans to goats: an evaluation of the impact of this fungus on the degradation of faeces and on free-living soil nematodes

The environmental impact of Duddingtonia flagrans, a potential biological control agent for nematode parasites, was tested in a 2-year-plot study using goat faeces. The trial assessed the impact of fungal presence on the disintegration of faeces and on non-target, free-living soil nematode populations. Three groups of goats experimentally infected by Trichostrongylus colubriformis received three different doses of D. flagrans chlamydospores (0 chlamydospores/kg body weight (BW), 0.5 × 10(6) chlamydospores/kg BW or 5 × 10(6) chlamydospores/kg BW). One hundred grams of faeces containing T. colubriformis eggs and D. flagrans chlamydospores at three different concentrations were deposited on pasture plots on four different occasions: May 2003, September 2003, June 2004 and September 2004. Faeces were weighed 2, 4, 6, 8, 10, 12, 14, 16, 18 and 20 weeks after deposit and immediately afterwards replaced to their initial positions. In addition, soil samples were taken just below faecal deposits to evaluate the impact of fungal presence on non-target free-living nematodes. Results showed that there was no treatment effect on the pellet degradation rate. Analysis of soil nematode fauna failed to demonstrate any effect of the dose rate of 0.5 × 10(6) chlamydospores/kg BW, while a reduction of the number of free-living nematodes was seen for the maximal chlamydospore concentration at autumn sets.     

The predatory capability of three nematophagous fungi in the control of Haemonchus contortus infective larvae in ovine faeces

The effect of oral administration of three different nematode-trapping fungi, in aqueous suspension containing either Dactylaria sp. or Arthrobotrys oligospora conidia or Duddingtonia flagrans chlamydospores, on the number of Haemonchus contortus infective larvae in sheep faeces, was evaluated. The three selected species of fungi produce three-dimensional adhesive nets in the presence of nematodes. Sixteen Creole sheep were divided into four groups of four animals each. Groups 1 and 2 were orally drenched with a suspension containing 2x10(7) conidia of either A. oligospora or Dactylaria sp. Group 3, received a similar treatment, with D. flagrans chlamydospores, instead of conidia, being administered, at the same dose. Group 4 acted as control, without any fungi. Faecal samples were collected directly from the rectum of each sheep and faecal cultures were prepared and incubated at 15 and 21 days. Larvae were recovered from faecal cultures and counted. The highest reduction of the nematode population occurred in the D. flagrans group, reaching reductions of 96.3% and 91.4% in individual samplings in plates incubated for 15 and 21 days, respectively. Arthrobotrys oligospora showed moderate reductions in the faecal larval population, ranging between 25-64% at 15 days incubation. In general, Dactylaria sp., was less efficient in its trapping ability. Despite the inconsistent results with Dactylaria sp., reduction percentages of 73.4% and 80.7% were recorded in individual samplings during the first and second days, in plates incubated for 15 days. Duddingtonia flagrans, was shown to be a potential biological control agent of H. contortus infective larvae.     

ITS2 sequences of Dictyocaulus species from cattle, roe deer and moose in Sweden: molecular evidence for a new species.

Total DNA was isolated from adult lungworms of the genus Dictyocaulus, collected from cattle, moose (Alces alces) and roe deer (Capreolus capreolus) in Sweden. The second ribosomal internal transcribed spacer was amplified with PCR, and DNA sequences were determined from nine individual worms that all came from different hosts in order to avoid analysis of siblings. The sequence data obtained were aligned and compared with similar data derived from German lungworm isolates from cattle and fallow deer (Cervus dama). These analyses clearly showed that specimens of the cattle lungworm, Dictyocaulus viviparus, were almost identical irrespective of their geographical origin. However, when the second internal transcribed spacer sequence of D. viviparus was compared with that of lungworms from moose and roe deer, major differences were noticed. Although lungworms collected from these cervids had identical second internal transcribed spacer sequences, they proved to be genetically different from Dictyocaulus eckerti of German fallow deer, displaying a 66.5% similarity. In an evolutionary tree, inferred by maximum likelihood analysis, the Dictyocaulus species from cattle and wild cervids clustered as compared with Dictyocaulus filaria from sheep. The study has thus demonstrated that A. alces and C. capreolus in Sweden are parasitised with a Dictyocaulus species that is different from D. viviparus and D. eckerti, indicating that we are dealing with a new species in moose and roe deer.     

Culture age impacts Plectosporium alismatis propagule yields and subsequent desiccation and UV-radiation tolerance

The effect of culture age on yields, desiccation tolerance and resistance to ultraviolet radiation of Plectosporium alismatis, a potential mycoherbistat of aquatic weeds in Australian rice fields, was studied. P. alismatis was grown in a liquid basal medium supplemented with malt extract and sodium nitrate and harvested after 7, 14 or 21 days incubation. Although chlamydospore yields harvested from 14-day-old liquid cultures were significantly higher (29.2×10⁵ chlamydospores mL^?1) than chlamydospore yields harvested from 7-day-old liquid cultures (1.07×10⁵ chlamydospores mL^?1) or from 21-day-old liquid cultures, the germination of freshly-harvested chlamydospores from 7-day-old cultures (72.7%) was significantly reduced when propagules were grown for 14 days (55.3%). When exposed to UV-radiation, conidia and chlamydospores harvested from 14-day-old cultures germinated at a lower rate (<20%) than conidia and chlamydospores harvested from 7-day-old cultures (>40%). When conidia and chlamydospores were dried and subsequently exposed to UV, less than 30% of propagules harvested from 7-day-old cultures germinated, whereas less than 10% of propagules harvested from 14-day-old cultures germinated. A three-way analysis of variance including culture age, UV exposure and type of propagules confirmed that the culture age had more impact on the germination of fresh or dry propagules (P=0.00001 and P=0.0004, respectively) than the type of propagules considered (P=0.5). These results demonstrate that the culture age impacts significantly propagule yields and germination of P. alismatis conidia and chlamydospores, particularly after stress caused by dehydration and/or exposure to UV-B radiation.     

Interspecific competition between the nematode-trapping fungus, Duddingtonia flagrans, and selected microorganisms and the effect of spore concentration on the efficacy of nematode trapping

The fungus, Duddingtonia flagrans, is able to trap and kill free-living nematode larvae of the cattle parasite Cooperia oncophora when chlamydospores are mixed in cattle faeces. Isolates of Bacillus subtilis (two isolates), Pseudomonas spp. (three isolates) and single isolates of the fungal genera Alternaria, Cladosporium, Fusarium, Trichoderma and Verticillium were isolated from cattle faeces and shown to reduce D. flagrans growth on agar plates. When these isolates were added to cattle faeces containing D. flagrans and nematode larvae of C. oncophora, developing from eggs, none of the isolates reduced nematode mortality attributed to D. flagrans. Similarly, the coprophilic fungus Pilobolus kleinii, which cannot be cultivated on agar, also failed to suppress the ability of D. flagrans to trap and kill developing larvae of C. oncophora. Increasing chlamydospore doses of D. flagrans in faecal cultures resulted in higher nematode mortality. Thus, no evidence of interspecific or intraspecific competition was observed. The consequences of these findings are discussed.     

Chlamydospore Production,Inoculation Methods and Pathogenicity of Fusarium oxysporum M12-4A,a Biocontrol for Striga hermonthica

Fusarium oxysporum isolate M12-4A is currently being evaluated for the biological control of Striga hermonthica . Inoculum production, inoculum delivery to the target, chlamydospore germination, and weed growth suppression of this weed-pathogen system were investigated. Liquid fermentation systems using organic material were evaluated for the production of large numbers of chlamydospores. A 1% sorghum straw powder (< 1 mm) substrate, exposed to black light at 21°C for 21 days, yielded 3.23 X 10 8 colony forming units (CFU) l -1 medium. A two-stage fermentation system using 5% w/v straw substrate under black light at 30°C for 14 days yielded 3.5 X 10 8 CFU l -1 medium. In vitro variations in chlamydospore germination were governed by the presence of exogenous carbon, nitrogen, and sorghum root exudates. Ammonium-nitrogen compounds and urea, in combination with glucose had a stronger stimulatory effect on chlamydospore germ tube growth than did potassium nitrate. Maximal germ tube elongation occurred when chlamydospores were exposed to urea at a C/N ratio of 10. Some mineral solutions and sorghum root exudates inhibited chlamydospore germ tube elongation; however, arabic gum, a complex polysaccharide, stimulated chlamydospore germ tube elongation and the production of secondary chlamydospores. In field trials, chlamydospore powder harvested from small-scale fermenters reduced S. hermonthica emergence by 92%. Complete inhibition of S. hermonthica emergence occurred when the chlamydospore powder was added to the soil at sowing and when sorghum seeds coated with chlamydospores were sown. Effective biological control of S. hermonthica was achieved using a simple fermentation system with sorghum straw as the inoculum growth substrate. For inoculum delivery to the farmers' fields, sorghum seeds were coated with the inoculum using arabic gum as the adhesive. This simple delivery system permits a uniform inoculation of the field as well as the proper positioning of the inoculum in the immediate environment of sorghum roots, where S. hermonthica attaches to its host. To facilitate a broad usage of F. oxysporum M12-4A for the biocontrol of S. hermonthica , we propose an inoculum production strategy based on a cottage industry model that utilizes a liquid fermentation process and inexpensive locally-available substrates including sorghum straw and arabic gum.     

Dictyocaulus viviparus: re-emerging or never been away?

For over 40 years a highly effective vaccine against the bovine lungworm has been commercially available. The use of it successfully reduced the number of outbreaks in calves. However, the past decade has seen a dramatic increase in lungworm outbreaks in adult cows in the UK. This might indicate that Dictyocaulus viviparus is re-emerging as a significant parasite in the dairy cattle industry. Much is still unknown, and here the most important aspects requiring urgent attention are put into perspective.     

THE RESPONSE OF GROWTH AND BIOCHEMICAL COMPOSITION TO VARIATIONS IN DAYLENGTH, TEMPERATURE, AND IRRADIANCE IN THE MARINE DIATOM THALASSIOSIRA PSEUDONANA (BACILLARIOPHYCEAE)

The relationships between the growth rate of the marine diatom Thalassiosira pseudonana (Hustedt) and irradiance, daylength, and temperature were determined in nutrient-sufficient semicontinuous cultures. The initial slopes of the growth versus total daily irradiance curves were not affected by temperature or daylength. Growth versus irradiance was best modeled as a hyperbolic function at short daylengths and better modeled as an exponential function at longer daylengths. The maximum or light-saturated growth rates at each daylength were modeled as a hyperbolic function of daylength. This model was extended in a novel manner to include temperature dependence providing a framework that can be used to interpret other experimental data on growth rate versus daylength. The resulting model should be useful in global models of phytoplankton growth. Carbon, nitrogen, and chl a quotas were influenced by daylength, irradiance, and temperature. Both C and N quotas were positive exponential functions of irradiance, whereas N and chl a quotas were significantly greater for cells grown at the lower temperature. The ratio chl a :C quota (chl a :Q_c) was a strong negative exponential function of total daily irradiance. Cells grown at 10° C had significantly greater chl a :Q_c ratios than those grown at 18° C, and daylength also had a significant positive influence on chl a :Q_c. The apparent effect of daylength on chl a :Q_c was removed by standardizing chl a :Q_c to growth rate (μ), resulting in a temperature-dependent relationship between chl a :Q_c·μ⁻¹ and irradiance that accounted for 95% of the variation in the data.     

EFFECTS OF ULTRAVIOLET‐A RADIATION AND NUTRIENT AVAILABILITY ON THE CELLULAR COMPOSITION OF PHOTOPROTECTIVE COMPOUNDS IN GLENODINIUM FOLIACEUM (DINOPHYCEAE)1

The photoprotective response in the dinoflagellate Glenodinium foliaceum F. Stein exposed to ultraviolet‐A (UVA) radiation (320–400 nm; 1.7 W · m²) and the effect of nitrate and phosphate availability on that response have been studied. Parameters measured over a 14 d growth period in control (PAR) and experimental (PAR + UVA) cultures included cellular mycosporine‐like amino acids (MAAs), chls, carotenoids, and culture growth rates. Although there were no significant effects of UVA on growth rate, there was significant induction of MAA compounds (28 ± 2 pg · cell^?1) and a reduction in chl a (9.6 ± 0.1 pg · cell^?1) and fucoxanthin (4.4 ± 0.1 pg · cell^?1) compared to the control cultures (3 ± 1 pg · cell^?1, 13.3 ± 3.2 pg · cell^?1, and 7.4 ± 0.3 pg · cell^?1, respectively). In a second investigation, MAA concentrations in UVA‐exposed cultures were lower when nitrate was limited (P < 0.05) but were higher when phosphate was limiting. Nitrate limitation led to significant decreases (P < 0.05) in cellular concentration of chls (chl c₁, chl c₂, and chl a), but other pigments were not affected. Phosphate availability had no effect on final pigment concentrations. Results suggest that nutrient availability significantly affects cellular accumulation of photoprotective compounds in G. foliaceum exposed to UVA.     

ALKALINE PHOSPHATASE ACTIVITIES AMONG POPULATIONS OF THE COLONY-FORMING DIAZOTROPHIC CYANOBACTERIUM TRICHODESMIUM SPP. (CYANOBACTERIA) IN THE RED SEA

Alkaline phosphatase activities of the diazotrophic marine cyanobacterium Trichodesmium were studied among natural populations in the northern Red Sea and in laboratory cultures of Trichodesmium sp. strain WH9601. Open-water tuft-shaped colonies of Trichodesmium showed high alkaline phosphatase activities with 2.4–11.7 μmol p-nitrophenylphosphate (PNPP) hydrolyzed·μg chl a ^{− 1}·h ^{− 1}, irrespective of date or origin of the sample. Coastal populations of the Trichodesmium tuft colonies had low alkaline phosphatase activities with 0.2–0.5 μmol PNPP·μg chl a ^{− 1}·h ^{− 1}. An exception was the Trichodesmium fall maximum, when both tuft colonies and the plankton community (<100 μm) had alkaline phosphatase activities of 0.6–7.4 μmol PNPP·μg chl a ^{− 1}·h ^{− 1}. Likewise, the more rare puff and bow-tie colonies of Trichodesmium spp. in coastal waters had elevated alkaline phosphatase activities (0.8–1.6 μmol PNPP·μg chl a ^{− 1}·h ^{− 1}) as compared with tuft colonies coinhabiting the same waters. Intact filaments of tuft-forming Trichodesmium sp. strain WH9601 from phosphate-replete cultures had a base alkaline phosphatase activity of 0.5 μmol PNPP·μg chl a ^{− 1}·h ^{− 1}. This activity underwent a 10-fold increase in phosphate-deplete cultures and in cultures supplied with glycerophosphate as the sole P source. The elevated level of alkaline phosphatase activity was sustained in P-deplete cultures, but it declined in cultures with glycerophosphate. The decline is suggested to result from feedback repression of alkaline phosphatase synthesis by the phosphate generated in the glycerophosphate hydrolysis. The enhanced alkaline phosphatase activities of Trichodesmium spp. populations provide evidence that P stress is an important factor in the ecology of Trichodesmium in the northern Red Sea.     

Growth of the Fungus Duddingtonia flagrans in Soil Surrounding Feces Deposited by Cattle or Sheep Fed the Fungus to Control Nematode Parasites

The results reported in this paper represent work from two separate experiments, namely a plot trial using cattle feces conducted at Kungsãngen in Uppsala, Sweden and a plot trial using sheep feces undertaken at Tåstrup in Copenhagen, Denmark. In both trials, a technique was used to monitor the level of Duddingtonia flagrans propagules in soil surrounding feces. The feces were from animals fed or not fed D. flagrans fungal chlamydospores. Also presented are the numbers of soil nematodes in soil surrounding sheep feces. The results indicate that D. flagrans has little growth beyond the fecal environment into surrounding soil when chlamydospores are fed to either sheep or cattle. This is substantiated by the soil nematode data. No statistical differences in the number of nematode taxa identified, Shannon Weiner H′, proportion of various feeding groups, and B/B + F (B and F are the proportions of bacterial and fungal-feeding nematodes) were found when soil surrounding sheep feces containing chlamydospores and parasitic nematode eggs was compared to soil surrounding feces containing parasitic nematode eggs alone. It is unlikely that the application of D. flagrans as a biological control agent against the free-living stages of nematode parasites of these livestock will negatively affect populations of nontarget soil nematodes.     

Microcycle speculation in theClaviceps purpurea 244

The mutant strainClaviceps purpurea 244 forming hyphae composed mainly from sclerotiumlike cells was found to sporulate both in liquid and solid media, particularly in the form of terminal chlamydospores (4.0 × 6.5 μm). Chlamydospores produced during submerged cultivation germinated, new chlamydospores being formed directly from germ tubes, or, occasionally, conidia (the so-called microcycle) or new vegetative mycelium were formed. The ultrastructures of the chlamydospores and vegetative cells was identical. The cytoplasm was filled with ribosomes and contained lipid inclusions and vacuoles with membrane invaginations. Strain 244 cultivated under submerged conditions produced 150 μg/ml clavins, with elymoclavin predominating (82 %). The parent strainClaviceps purpurea 129 only produced chlamydospores on the vegetative mycelium, whereas no microcycle was detected; under submerged conditions it produced mainly agroclavin (85 %) at a concentration of 4 mg/ml.     

Changes in the Levels of Ribulose-l,5-bisphosphate Carboxylase/Oxygenase (Rubisco) in Tetraedron minimum (Chlorophyta) during Light and Shade Adaptation

Exponentially growing cultures of the chlorophyta Tetraedronminimum were allowed to photoadapt to low (50µmole quantam^–2s^–1) and high (500µmole quanta m^–2–1)irradiance levels. In these cultures, various aspects of theorganization of the photosynthetic apparatus and related differencesin its performance were studied. In this organism, the observed five-fold increase in pigmentationof low-light adapted cells was due to increases in the numbersof PSU's, while their sizes remained constant. Using radioimmunoassay technique, we found that high-light adaptedalgae had over five times more Rubisco per PSU than their low-lightadapted counterparts. The high-light adapted algae also exhibited far higher (x2.3)light saturated photosynthetic rates per chl a. This increasewas the result of a reduction of tau, , the turnover time ofPS II reaction centers. We propose that the increase in Rubisco per PSU in high-lightadapted algae explains the reduction in , which results in thehigher P_max rates per chl a in these algae. The relationship is non linear, since the increase in Rubiscoper PSU was x5.3 whereas that in P_mM per chl a was only x2.3. (Received July 30, 1988; Accepted December 2, 1988)