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Ralf-udo Ehlers - One of the best experts on this subject based on the ideXlab platform.
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Life history trait analysis of the entomopathogenic nematode Steinernema feltiae provides the basis for prediction of dauer juvenile yields in monoxenic Liquid Culture
Applied Microbiology and Biotechnology, 2016Co-Authors: Temesgen Addis, Olaf Strauch, Asmamaw Teshome, Ralf-udo EhlersAbstract:Entomopathogenic nematodes ( Steinernema spp.) are used in integrated pest management to control insect pests in cryptic environments. The nematodes are mass produced in monoxenic Liquid Culture with their symbiotic bacteria Xenorhabdus spp. For a better understanding of nematode population dynamics, the life history traits (LHTs) of the entomopathogenic nematode Steinernema feltiae were assessed at 25 °C by observing single pairs of male and female nematodes using a hanging drop technique. To investigate the influence of different food supplies on nematode reproduction, the LHTs were assessed with a daily supply of 5 ×, 10 × and 20 × 10^9 cells ml^−1 of the nematode’s bacterial symbiont Xenorhabdus bovienii in semi-solid nematode growth gelrite (NGG) medium. Increasing bacterial density had a significant positive influence on the average number of offspring produced, which ranged from 359 to 813 per female. The intrinsic rate of natural increase r _m, which ranges from 1.10 to 1.19 day^−1, was neither influenced by the bacterial density, nor was the mean generation time T (5.12–5.25 days) and population doubling time (PDT) (0.64–0.59 days). The average lifespan of reproductive females, which ranged from 6.7 to 7.3 days, was positively correlated with bacterial density. A positive correlation between female body volume and bacterial density was recorded ( R = 0.67) as well as a significant positive correlation between female body size and offspring production ( R = 0.89) in hanging drops. Whether these data can be used to predict nematode yields in Liquid Culture was tested. The total female body volume calculated as the average female body volume × total number of parental females per millilitre 3 days after nematode inoculation was positively correlated ( R = 0.72) with nematode yields. The total female body volume on process day 3 is thus a good indicator for the estimation of nematode yield at the end of the process (12–15 days post dauer juvenile (DJ) inoculation) in both Erlenmeyer flasks and bioreactors. With a mean deviation of 9467 DJs ml^−1, the error resembles approximately 5 % of the final DJ yields.
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monoxenic Liquid Culture with escherichia coli of the free living nematode panagrolaimus sp strain nfs 24 5 a potential live food candidate for marine fish and shrimp larvae
Applied Microbiology and Biotechnology, 2013Co-Authors: Farhana Ayub, Laurent Seychelles, Olaf Strauch, Martina Wittke, Ralf-udo EhlersAbstract:The free-living, bacterial-feeding nematode Panagrolaimus sp. (strain NFS 24-5) has potential for use as live food for marine shrimp and fish larvae. Mass production in Liquid Culture is a prerequisite for its commercial exploitation. Panagrolaimus sp. was propagated in monoxenic Liquid Culture on Escherichia coli and parameters, like nematode density, population dynamics and biomass were recorded and compared with life history table data. A mean maximum nematode density of 174,278 mL−1 and a maximum of 251,000 mL−1 were recorded on day 17 after inoculation. Highest average biomass was 40 g L−1 at day 13. The comparison with life history table data indicated that the hypothetical potential of Liquid Culture is much higher than documented during this investigation. Nematode development is delayed in Liquid Culture and egg production per female is more than five times lower than reported from life history trait analysis. The latter assessed a nematode generation time of 7.1 days, whereas the process time at maximum nematode density in Liquid Culture was 16 days indicating that a reduction of the process time can be achieved by further investigating the influence of nematode inoculum density on population development. The results challenge future research to reduce process time and variability and improve population dynamics also during scale-up of the Liquid Culture process.
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Stabilisation of heat tolerance traits in Heterorhabditis bacteriophora through selective breeding and creation of inbred lines in Liquid Culture
BioControl, 2013Co-Authors: Samuel Anbesse, Nanette Hope Sumaya, Olaf Strauch, Anna Verena Dorfler, Ralf-udo EhlersAbstract:Entomopathogenic nematodes (EPNs) suffer from trait deterioration, a potential problem when these antagonists are transferred into artificial environments for mass production. In order to improve beneficial traits of EPN genetic selection and hybridization has been successfully carried out. Should these selected strains deteriorate during serial culturing the efforts would be in vain. Inbreeding might offer a possibility to stabilize traits but can also result in inbreeding depression. This study attempted to increase heat tolerance of Heterorhabditis bacteriophora by selective breeding for seven cycles either with nematodes propagated in vivo in Galleria mellonella or with in vitro propagated nematodes which were exposed to heat stress in monoxenic Liquid Culture. After release of the selection pressure, the tolerance was monitored over 15 additional reproductive cycles to compare the stability of the trait. Virulence of the selected strains was assessed to check for negative tradeoff effects. Heat tolerance was successfully increased in vivo (from 39.03 to 40.85 °C) and in vitro (from 39 to 40 °C) propagated H. bacteriophora , but could only be maintained in populations which were serially reared in Liquid Culture. When H. bacteriophora is Cultured in vivo, reproduction by cross fertilization is possible. In in vitro Culture male and female cannot mate and reproduction is solely by self-fertilizing hermaphrodite resulting in homozygous inbred lines. Trait deterioration seems to be restricted to in vivo propagated H. bacteriophora , whereas monoxenic Liquid Cultures handling large numbers of inbred lines provided genetically stable and virulent nematode populations. Selection using Liquid Culture technology is thus superior over in vivo propagation to sustain beneficial traits in H. bacteriophora not only for selective breeding but also for mass production.
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selective breeding for desiccation tolerance in Liquid Culture provides genetically stable inbred lines of the entomopathogenic nematode heterorhabditis bacteriophora
Applied Microbiology and Biotechnology, 2013Co-Authors: Samuel Anbesse, Nanette Hope Sumaya, Anna Verena Dorfler, Ralf-udo EhlersAbstract:The entomopathogenic nematode (EPN) Heterorhabditis bacteriophora is used in biological plant protection to control pest insects. In the past, several attempts targeted at an enhancement of the desiccation tolerance of EPN by genetic selection in order to improve their storage stability. The subsequent loss of improved beneficial traits after release of selection pressure has often been reported. In order to stabilize progress of selective breeding, selection during Liquid culturing was tested against propagation in host insects. After release of the selection pressure, the tolerance was monitored over additional reproductive cycles in vivo and in vitro to compare the stability of the trait. Furthermore, it was tested whether the virulence of the selected strains would be impaired. Exposure to desiccation stress prior to propagation, in vivo or in vitro, both resulted in increasing desiccation tolerance. When selection pressure was released, the gained tolerance was lost again during in vivo production, whereas the tolerance was maintained at a high level when EPNs were Cultured in Liquid Culture. In Heterorhabditis sp., Liquid Culture conditions produce highly homozygous, genetically stable inbred lines. The investigation provides easily applicable methods to improve and stabilize beneficial traits of heterorhabditid EPNs through selective breeding in Liquid Culture. Compared to nematodes from in vivo propagation, production in Liquid media yielded EPN of higher virulence.
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life cycle and population development of the entomopathogenic nematodes steinernema carpocapsae and s feltiae nematoda rhabditida in monoxenic Liquid Culture
Nematology, 2010Co-Authors: Ayako Hirao, Ralf-udo Ehlers, Olaf StrauchAbstract:The life cycle and population dynamics of the entomopathogenic nematodes Steinernema carpocapsae and S. feltiae were studied in monoxenic Liquid Culture with their symbiotic bacteria Xenorhabdus nematophila and X. bovienii . To distinguish between the different juvenile and adult stages, their size was recorded. No differences were observed between the species in the size of the juvenile stages but significant differences were recorded in the length of the F1 adults, pre-dauer (J2d) and dauer juvenile stages (DJ). On average, 90% of inoculated DJ of S. feltiae recovered and 77% of S. carpocapsae . In general, S. feltiae developed from the inoculum DJ to the adult approximately 1 day faster than S. carpocapsae . The sex ratio was female-biased (59.2 ± 2.2% in S. carpocapsae , 66.7 ± 2.6% in S. feltiae ) in the parental population but not in the F1 generations. Steinernematid adults, like heterorhaditids, respond to depleting food resources with the cessation of egg laying. Juveniles hatch inside the uterus and develop at cost of the maternal body content causing the death of the adult ( endotokia matricida ). In contrast to Heterorhabditis spp. and in vivo observations of steinernematids by other authors, who reported that readily developed DJ leave the carcass of the dead adult, in this study J2d emerged 12 h after cessation of egg laying. The density of both bacterial Cultures decreased due to the feeding of the parental juveniles. However, X. nematophila continued at very low density, whereas the density of X. bovienii increased again until 15 days post-inoculation. The vast majority of F1 S. carpocapsae offspring developed to DJ, whereas in S. feltiae a significant second and third generation of adults was observed, probably due to the increasing bacterial population. However, second and third generation adults in S. feltiae Cultures did not contribute significantly to the DJ yield. Mean yields of 158 × 10 3 DJ ml –1 were recorded for S. carpocapsae and 106 × 10 3 DJ ml –1 for S. feltiae . The results provide valuable information for future process improvement.
Gabriel Moura Mascarin - One of the best experts on this subject based on the ideXlab platform.
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Liquid Culture fermentation for rapid production of desiccation tolerant blastospores of beauveria bassiana and isaria fumosorosea strains
Journal of Invertebrate Pathology, 2015Co-Authors: Robert W Behle, Mark A Jackson, Nilce Naomi Kobori, Gabriel Moura Mascarin, Italo DelaliberaAbstract:Abstract A major constraint to the commercial use of fungal biocontrol agents is the availability of low-cost production media and processes. Previous attempts in producing Beauveria blastospores using Liquid Culture fermentation processes required long fermentation times (6–8 days) and produced cells that had poor survival after desiccation and storage. In this study, isolates of Beauveria bassiana and Isaria fumosorosea were evaluated for blastospore yield, desiccation tolerance, storage stability, and biocontrol efficacy using fermentation media containing acid hydrolyzed casein or cottonseed flour as the nitrogen source. Cultures of B. bassiana and I. fumosorosea grown in media containing cottonseed flour produced high blastospore concentrations (>1 × 109 mL−1) after 3 days which is comparatively less expensive nitrogen source than acid hydrolyzed casein. The resultant air-dried blastospores ( 14 months in contrast to 9.2–13.1 months for I. fumosorosea. Blastospores of B. bassiana and I. fumosorosea killed Bemisia tabaci whitefly nymphs faster and required lower concentrations compared with aerial conidia. Our findings support the use of Liquid Culture fermentation as a cost-effective process to rapidly produce high yields of stable and infective blastospores of either B. bassiana or I. fumosorosea. These results support further evaluation of blastospore sprayable formulations for the control of soft-bodied insects.
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Liquid Culture production of microsclerotia and submerged conidia by trichoderma harzianum active against damping off disease caused by rhizoctonia solani
Fungal Biology, 2015Co-Authors: Nilce Naomi Kobori, Mark A Jackson, Gabriel Moura Mascarin, David A SchislerAbstract:Abstract Media and culturing protocols were identified that supported the formation of submerged conidia and microsclerotia (MS) by Trichoderma harzianum Rifai strain T-22 using Liquid Culture fermentation. Liquid media with a higher carbon concentration (36 g L−1) promoted MS formation at all C:N ratios tested. Hyphae aggregated to form MS after 2 d growth and after 7 d MS were fully melanized. This is the first report of MS formation by T. harzianum or any species of Trichoderma. Furthermore, submerged conidia formation was induced by Liquid Culture media, but yields, desiccation tolerance, and storage stability varied with C:N ratio and carbon rate. Air-dried MS granules (
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Liquid Culture production of microsclerotia and submerged conidia by trichoderma harzianum active against damping off disease caused by rhizoctonia solani
Fungal Biology, 2015Co-Authors: Nilce Naomi Kobori, Mark A Jackson, Gabriel Moura Mascarin, David A SchislerAbstract:Media and culturing protocols were identified that supported the formation of submerged conidia and microsclerotia (MS) by Trichoderma harzianum Rifai strain T-22 using Liquid Culture fermentation. Liquid media with a higher carbon concentration (36 g L(-1)) promoted MS formation at all C:N ratios tested. Hyphae aggregated to form MS after 2 d growth and after 7 d MS were fully melanized. This is the first report of MS formation by T. harzianum or any species of Trichoderma. Furthermore, submerged conidia formation was induced by Liquid Culture media, but yields, desiccation tolerance, and storage stability varied with C:N ratio and carbon rate. Air-dried MS granules (<4% moisture) retained excellent shelf life under cool and unrefrigerated storage conditions with no loss in conidial production. A low-cost complex nitrogen source based on cottonseed flour effectively supported high MS yields. Amending potting mix with dried MS formulations reduced or eliminated damping-off of melon seedlings caused by Rhizoctonia solani. Together, the results provide insights into the Liquid Culture production, stabilization process, and bioefficacy of the hitherto unreported MS of T. harzianum as a potential biofungicide for use in integrated management programs against soilborne diseases.
Ayako Hirao - One of the best experts on this subject based on the ideXlab platform.
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life cycle and population development of the entomopathogenic nematodes steinernema carpocapsae and s feltiae nematoda rhabditida in monoxenic Liquid Culture
Nematology, 2010Co-Authors: Ayako Hirao, Ralf-udo Ehlers, Olaf StrauchAbstract:The life cycle and population dynamics of the entomopathogenic nematodes Steinernema carpocapsae and S. feltiae were studied in monoxenic Liquid Culture with their symbiotic bacteria Xenorhabdus nematophila and X. bovienii . To distinguish between the different juvenile and adult stages, their size was recorded. No differences were observed between the species in the size of the juvenile stages but significant differences were recorded in the length of the F1 adults, pre-dauer (J2d) and dauer juvenile stages (DJ). On average, 90% of inoculated DJ of S. feltiae recovered and 77% of S. carpocapsae . In general, S. feltiae developed from the inoculum DJ to the adult approximately 1 day faster than S. carpocapsae . The sex ratio was female-biased (59.2 ± 2.2% in S. carpocapsae , 66.7 ± 2.6% in S. feltiae ) in the parental population but not in the F1 generations. Steinernematid adults, like heterorhaditids, respond to depleting food resources with the cessation of egg laying. Juveniles hatch inside the uterus and develop at cost of the maternal body content causing the death of the adult ( endotokia matricida ). In contrast to Heterorhabditis spp. and in vivo observations of steinernematids by other authors, who reported that readily developed DJ leave the carcass of the dead adult, in this study J2d emerged 12 h after cessation of egg laying. The density of both bacterial Cultures decreased due to the feeding of the parental juveniles. However, X. nematophila continued at very low density, whereas the density of X. bovienii increased again until 15 days post-inoculation. The vast majority of F1 S. carpocapsae offspring developed to DJ, whereas in S. feltiae a significant second and third generation of adults was observed, probably due to the increasing bacterial population. However, second and third generation adults in S. feltiae Cultures did not contribute significantly to the DJ yield. Mean yields of 158 × 10 3 DJ ml –1 were recorded for S. carpocapsae and 106 × 10 3 DJ ml –1 for S. feltiae . The results provide valuable information for future process improvement.
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Influence of inoculum density on population dynamics and dauer juvenile yields in Liquid Culture of biocontrol nematodes Steinernema carpocapsae and S. feltiae (Nematoda: Rhabditida)
Applied Microbiology and Biotechnology, 2010Co-Authors: Ayako Hirao, Ralf-udo EhlersAbstract:For improvement of mass production of the rhabditid biocontrol nematodes Steinernema carpocapsae and Steinernema feltiae in monoxenic Liquid Culture with their bacterial symbionts Xenorhabdus nematophila and Xenorhabdus bovienii , respectively, the effect of the initial nematode inoculum density on population development and final concentration of dauer juveniles (DJs) was investigated. Symbiotic bacterial Cultures are pre-incubated for 1 day prior to inoculation of DJs. DJs are developmentally arrested and recover development as a reaction to food signals provided by their symbionts. After development to adults, the nematodes produce DJ offspring. Inoculum density ranged from 1 to 10 × 10^3 DJ per milliliter for S. carpocapsae and 1 to 8 × 10^3 DJs per milliliter for S. feltiae . No significant influence of the inoculum density on the final DJ yields in both nematode species was recorded, except for S. carpocapsae Cultures with a parental female density 300 for S. carpocapsae and almost 200 for S. feltiae . The compensative adaptation of fecundity to nematode population density is responsible for the lack of an inoculum (or parental female) density effect on DJ yields. At optimal inoculation density of S. carpocapsae , offspring were produced by the parental female population, whereas S. feltiae always developed a F1 female population, which contributed to the DJ yields and was the reason for a more scattered distribution of the yields. The F1 female generation was accompanied by a second peak in X. bovienii density. The optimal DJ inoculum density for S. carpocapsae is 3–6 × 10^3 DJs per milliliter in order to obtain >10^3 parental females per milliliter. Density-dependent effects were neither observed on the DJ recovery nor on the sex ratio in the parental adult generation. As recovery varied between different batches, assessment of the recovery of inoculum DJ batches is recommended. S. feltiae was less variable in DJ recovery usually reaching >90%. The recommended DJ inoculum density is >5 × 10^3 DJs per milliliter to reach >2 × 10^3 parental females per milliliter. The mean yield recorded for S. carpocapsae was 135 × 10^3 and 105 × 10^3 per mililiter for S. feltiae .
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life cycle and development of entomopathogenic nematodessteinernema carpocapsae and s feltiae in monoxenic Liquid Culture
2009Co-Authors: Ayako HiraoAbstract:Entomopathogenic nematodes (EPN) Steinernema carpocapsae and S. feltiae (Rhabditida:Nematoda) are symbiotically associated with the bacteria Xenorhabdus nematophila and X.bovienii, espectively. These bacto-helminthic complexes are widely used in biological control of economically important pest insects. One problem restricting a wider use of EPN in plant protection is high production costs. Although the mass production technology in Liquid Culture has been established for commercial purposes more than 15 years ago, process instability still causes variability in yields. In this thesis, the critical developmental steps of Steinernema carpocapsae and S. feltiae in monoxenic Liquid Culture were investigated.
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effect of temperature on the development of steinernema carpocapsae and steinernema feltiae nematoda rhabditida in Liquid Culture
Applied Microbiology and Biotechnology, 2009Co-Authors: Ayako Hirao, Ralf-udo EhlersAbstract:For commercial use of the entomopathogenic nematodes Steinernema carpocapsae and Steinernema feltiae in biological control of insect pests, they are produced in Liquid Culture on artificial media pre-incubated with their symbiotic bacteria Xenorhabdus nematophila and Xenorhabdus bovienii, respectively. After 1 day of the bacterial Culture, nematode dauer juveniles (DJs) are inoculated, which recover development. The adult nematodes produce DJ offspring, which are harvested and can be sprayed. This study determined optimal temperatures to obtain high DJ progeny within a short process time. Temperatures assessed were 23 degrees C, 25 degrees C, 27 degrees C, and 29 degrees C for S. carpocapsae and 20 degrees C, 23 degrees C, 25 degrees C, and 27 degrees C for S. feltiae. The recovery of inoculated DJs was hardly affected and was reduced only in S. carpocapsae at 29 degrees C. The fecundity (eggs in uterus) in S. carpocapsae reached a maximum at 27 degrees C; whereas, maximum yields were recorded at 25 degrees C. For both Steinernema spp., highest DJ densities were obtained after 15 days incubation at 25 degrees C. Optimal Culture temperature for both nematode species is 25 degrees C. S. carpocapsae was more sensible to suboptimal temperature than S. feltiae. Results on total DJ density and DJ proportion of the total nematode population were more variable at non-optimal temperature condition for S. carpocapsae than for S. feltiae. Suboptimal Culture temperature also reduced DJ infectivity.
Mark A Jackson - One of the best experts on this subject based on the ideXlab platform.
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Liquid Culture fermentation for rapid production of desiccation tolerant blastospores of beauveria bassiana and isaria fumosorosea strains
Journal of Invertebrate Pathology, 2015Co-Authors: Robert W Behle, Mark A Jackson, Nilce Naomi Kobori, Gabriel Moura Mascarin, Italo DelaliberaAbstract:Abstract A major constraint to the commercial use of fungal biocontrol agents is the availability of low-cost production media and processes. Previous attempts in producing Beauveria blastospores using Liquid Culture fermentation processes required long fermentation times (6–8 days) and produced cells that had poor survival after desiccation and storage. In this study, isolates of Beauveria bassiana and Isaria fumosorosea were evaluated for blastospore yield, desiccation tolerance, storage stability, and biocontrol efficacy using fermentation media containing acid hydrolyzed casein or cottonseed flour as the nitrogen source. Cultures of B. bassiana and I. fumosorosea grown in media containing cottonseed flour produced high blastospore concentrations (>1 × 109 mL−1) after 3 days which is comparatively less expensive nitrogen source than acid hydrolyzed casein. The resultant air-dried blastospores ( 14 months in contrast to 9.2–13.1 months for I. fumosorosea. Blastospores of B. bassiana and I. fumosorosea killed Bemisia tabaci whitefly nymphs faster and required lower concentrations compared with aerial conidia. Our findings support the use of Liquid Culture fermentation as a cost-effective process to rapidly produce high yields of stable and infective blastospores of either B. bassiana or I. fumosorosea. These results support further evaluation of blastospore sprayable formulations for the control of soft-bodied insects.
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Liquid Culture production of microsclerotia and submerged conidia by trichoderma harzianum active against damping off disease caused by rhizoctonia solani
Fungal Biology, 2015Co-Authors: Nilce Naomi Kobori, Mark A Jackson, Gabriel Moura Mascarin, David A SchislerAbstract:Abstract Media and culturing protocols were identified that supported the formation of submerged conidia and microsclerotia (MS) by Trichoderma harzianum Rifai strain T-22 using Liquid Culture fermentation. Liquid media with a higher carbon concentration (36 g L−1) promoted MS formation at all C:N ratios tested. Hyphae aggregated to form MS after 2 d growth and after 7 d MS were fully melanized. This is the first report of MS formation by T. harzianum or any species of Trichoderma. Furthermore, submerged conidia formation was induced by Liquid Culture media, but yields, desiccation tolerance, and storage stability varied with C:N ratio and carbon rate. Air-dried MS granules (
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Liquid Culture production of microsclerotia and submerged conidia by trichoderma harzianum active against damping off disease caused by rhizoctonia solani
Fungal Biology, 2015Co-Authors: Nilce Naomi Kobori, Mark A Jackson, Gabriel Moura Mascarin, David A SchislerAbstract:Media and culturing protocols were identified that supported the formation of submerged conidia and microsclerotia (MS) by Trichoderma harzianum Rifai strain T-22 using Liquid Culture fermentation. Liquid media with a higher carbon concentration (36 g L(-1)) promoted MS formation at all C:N ratios tested. Hyphae aggregated to form MS after 2 d growth and after 7 d MS were fully melanized. This is the first report of MS formation by T. harzianum or any species of Trichoderma. Furthermore, submerged conidia formation was induced by Liquid Culture media, but yields, desiccation tolerance, and storage stability varied with C:N ratio and carbon rate. Air-dried MS granules (<4% moisture) retained excellent shelf life under cool and unrefrigerated storage conditions with no loss in conidial production. A low-cost complex nitrogen source based on cottonseed flour effectively supported high MS yields. Amending potting mix with dried MS formulations reduced or eliminated damping-off of melon seedlings caused by Rhizoctonia solani. Together, the results provide insights into the Liquid Culture production, stabilization process, and bioefficacy of the hitherto unreported MS of T. harzianum as a potential biofungicide for use in integrated management programs against soilborne diseases.
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Comparison of air-drying methods for evaluating the desiccation tolerance of Liquid Culture-produced blastospores of Paecilomyces fumosoroseus
World Journal of Microbiology and Biotechnology, 1997Co-Authors: S Cliquet, Mark A JacksonAbstract:Various drying methods were tested to identify a standard procedure for evaluating the desiccation tolerance of Liquid Culture-produced blastospores of Paecilomyces fumosoroseus. Since our work is focused on optimizing fermentation conditions for the production of P. fumosoroseus, the criteria for selecting a drying method included ease of use, moderate spore survival after drying and limited variation in spore survival. Three air-drying methods were tested: P. fumosoroseus blastospores mixed with silica gel, with sand, or with diatomaceous earth. Humidity controlled drying was used in the diatomaceous earth drying method. Blastospore survivals after drying were 19% (C.V. range, 32 to 45%), 82% (C.V. range, 26 to 43%), and 2% (C.V. range 32 to 50%) for the silica gel, sand, and diatomaceous earth methods, respectively. Blastospores dried using the silica gel and sand methods had been rinsed in 0.7 m polyethylene glycol before drying and rehydrated in the same solution for determination of survival. The variation observed within each method was similar. The silica gel drying method was selected as most appropriate for our studies based on moderate blastospore survival (19%) and ease of use.
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Liquid Culture production of desiccation tolerant blastospores of the bioinsecticidal fungus paecilomyces fumosoroseus
Fungal Biology, 1997Co-Authors: Mark A Jackson, Michael R Mcguire, Lawrence A Lacey, Stephen P WraightAbstract:Liquid media with differing carbon concentrations and carbon-to-nitrogen ratios were tested for production of desiccation tolerant blastospores of Paecilomyces fumosoroseus. While all media tested supported sporulation in submerged Culture, high blastospore concentrations (5·8 × 108) spores ml−) were produced in media containing 80 g glucose l− and 13·2 g Casamino acids l− (MS medium) and a significantly higher percentage (79%) of these blastospores survived air drying. Media containing glucose concentrations greater than 20 g l − and Casamino acid concentrations between 13·2 and 40 g l− supported maximal production of desiccation tolerant blastospores. All 23 isolates of P. fumosoroseus grown in MS media produced high concentrations of desiccation tolerant blastospores. When stored at 4 °C, more than 60% of the lyophilized blastospores produced in MS medium were still viable after 7 months storage while less than 25% of the air-dried blastospores survived after 90 d storage. Standard whitefly bioassays were performed to compare air-dried blastospores of P. fumosoroseus ARSEF 4491 with solid substrate-produced conidia of Beauveria bassiana ARSEF 252. Air-dried blastospores of P. fumosoroseus gave LD50s of 60 and 113 blastospores mm− for the silverleaf whitefly (Bemisia argentifolii) in two separate bioassays with potency ratios (LD50 B. bassiana/LD50 P. fumosoroseus)of 3·9 and 3·8, respectively. These results have demonstrated that high concentrations of blastospores of P. fumosoroseus can be rapidly produced in Liquid Culture, remain viable following drying, and infect and kill silverleaf whitefly.
Olaf Strauch - One of the best experts on this subject based on the ideXlab platform.
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Life history trait analysis of the entomopathogenic nematode Steinernema feltiae provides the basis for prediction of dauer juvenile yields in monoxenic Liquid Culture
Applied Microbiology and Biotechnology, 2016Co-Authors: Temesgen Addis, Olaf Strauch, Asmamaw Teshome, Ralf-udo EhlersAbstract:Entomopathogenic nematodes ( Steinernema spp.) are used in integrated pest management to control insect pests in cryptic environments. The nematodes are mass produced in monoxenic Liquid Culture with their symbiotic bacteria Xenorhabdus spp. For a better understanding of nematode population dynamics, the life history traits (LHTs) of the entomopathogenic nematode Steinernema feltiae were assessed at 25 °C by observing single pairs of male and female nematodes using a hanging drop technique. To investigate the influence of different food supplies on nematode reproduction, the LHTs were assessed with a daily supply of 5 ×, 10 × and 20 × 10^9 cells ml^−1 of the nematode’s bacterial symbiont Xenorhabdus bovienii in semi-solid nematode growth gelrite (NGG) medium. Increasing bacterial density had a significant positive influence on the average number of offspring produced, which ranged from 359 to 813 per female. The intrinsic rate of natural increase r _m, which ranges from 1.10 to 1.19 day^−1, was neither influenced by the bacterial density, nor was the mean generation time T (5.12–5.25 days) and population doubling time (PDT) (0.64–0.59 days). The average lifespan of reproductive females, which ranged from 6.7 to 7.3 days, was positively correlated with bacterial density. A positive correlation between female body volume and bacterial density was recorded ( R = 0.67) as well as a significant positive correlation between female body size and offspring production ( R = 0.89) in hanging drops. Whether these data can be used to predict nematode yields in Liquid Culture was tested. The total female body volume calculated as the average female body volume × total number of parental females per millilitre 3 days after nematode inoculation was positively correlated ( R = 0.72) with nematode yields. The total female body volume on process day 3 is thus a good indicator for the estimation of nematode yield at the end of the process (12–15 days post dauer juvenile (DJ) inoculation) in both Erlenmeyer flasks and bioreactors. With a mean deviation of 9467 DJs ml^−1, the error resembles approximately 5 % of the final DJ yields.
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monoxenic Liquid Culture with escherichia coli of the free living nematode panagrolaimus sp strain nfs 24 5 a potential live food candidate for marine fish and shrimp larvae
Applied Microbiology and Biotechnology, 2013Co-Authors: Farhana Ayub, Laurent Seychelles, Olaf Strauch, Martina Wittke, Ralf-udo EhlersAbstract:The free-living, bacterial-feeding nematode Panagrolaimus sp. (strain NFS 24-5) has potential for use as live food for marine shrimp and fish larvae. Mass production in Liquid Culture is a prerequisite for its commercial exploitation. Panagrolaimus sp. was propagated in monoxenic Liquid Culture on Escherichia coli and parameters, like nematode density, population dynamics and biomass were recorded and compared with life history table data. A mean maximum nematode density of 174,278 mL−1 and a maximum of 251,000 mL−1 were recorded on day 17 after inoculation. Highest average biomass was 40 g L−1 at day 13. The comparison with life history table data indicated that the hypothetical potential of Liquid Culture is much higher than documented during this investigation. Nematode development is delayed in Liquid Culture and egg production per female is more than five times lower than reported from life history trait analysis. The latter assessed a nematode generation time of 7.1 days, whereas the process time at maximum nematode density in Liquid Culture was 16 days indicating that a reduction of the process time can be achieved by further investigating the influence of nematode inoculum density on population development. The results challenge future research to reduce process time and variability and improve population dynamics also during scale-up of the Liquid Culture process.
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Stabilisation of heat tolerance traits in Heterorhabditis bacteriophora through selective breeding and creation of inbred lines in Liquid Culture
BioControl, 2013Co-Authors: Samuel Anbesse, Nanette Hope Sumaya, Olaf Strauch, Anna Verena Dorfler, Ralf-udo EhlersAbstract:Entomopathogenic nematodes (EPNs) suffer from trait deterioration, a potential problem when these antagonists are transferred into artificial environments for mass production. In order to improve beneficial traits of EPN genetic selection and hybridization has been successfully carried out. Should these selected strains deteriorate during serial culturing the efforts would be in vain. Inbreeding might offer a possibility to stabilize traits but can also result in inbreeding depression. This study attempted to increase heat tolerance of Heterorhabditis bacteriophora by selective breeding for seven cycles either with nematodes propagated in vivo in Galleria mellonella or with in vitro propagated nematodes which were exposed to heat stress in monoxenic Liquid Culture. After release of the selection pressure, the tolerance was monitored over 15 additional reproductive cycles to compare the stability of the trait. Virulence of the selected strains was assessed to check for negative tradeoff effects. Heat tolerance was successfully increased in vivo (from 39.03 to 40.85 °C) and in vitro (from 39 to 40 °C) propagated H. bacteriophora , but could only be maintained in populations which were serially reared in Liquid Culture. When H. bacteriophora is Cultured in vivo, reproduction by cross fertilization is possible. In in vitro Culture male and female cannot mate and reproduction is solely by self-fertilizing hermaphrodite resulting in homozygous inbred lines. Trait deterioration seems to be restricted to in vivo propagated H. bacteriophora , whereas monoxenic Liquid Cultures handling large numbers of inbred lines provided genetically stable and virulent nematode populations. Selection using Liquid Culture technology is thus superior over in vivo propagation to sustain beneficial traits in H. bacteriophora not only for selective breeding but also for mass production.
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life cycle and population development of the entomopathogenic nematodes steinernema carpocapsae and s feltiae nematoda rhabditida in monoxenic Liquid Culture
Nematology, 2010Co-Authors: Ayako Hirao, Ralf-udo Ehlers, Olaf StrauchAbstract:The life cycle and population dynamics of the entomopathogenic nematodes Steinernema carpocapsae and S. feltiae were studied in monoxenic Liquid Culture with their symbiotic bacteria Xenorhabdus nematophila and X. bovienii . To distinguish between the different juvenile and adult stages, their size was recorded. No differences were observed between the species in the size of the juvenile stages but significant differences were recorded in the length of the F1 adults, pre-dauer (J2d) and dauer juvenile stages (DJ). On average, 90% of inoculated DJ of S. feltiae recovered and 77% of S. carpocapsae . In general, S. feltiae developed from the inoculum DJ to the adult approximately 1 day faster than S. carpocapsae . The sex ratio was female-biased (59.2 ± 2.2% in S. carpocapsae , 66.7 ± 2.6% in S. feltiae ) in the parental population but not in the F1 generations. Steinernematid adults, like heterorhaditids, respond to depleting food resources with the cessation of egg laying. Juveniles hatch inside the uterus and develop at cost of the maternal body content causing the death of the adult ( endotokia matricida ). In contrast to Heterorhabditis spp. and in vivo observations of steinernematids by other authors, who reported that readily developed DJ leave the carcass of the dead adult, in this study J2d emerged 12 h after cessation of egg laying. The density of both bacterial Cultures decreased due to the feeding of the parental juveniles. However, X. nematophila continued at very low density, whereas the density of X. bovienii increased again until 15 days post-inoculation. The vast majority of F1 S. carpocapsae offspring developed to DJ, whereas in S. feltiae a significant second and third generation of adults was observed, probably due to the increasing bacterial population. However, second and third generation adults in S. feltiae Cultures did not contribute significantly to the DJ yield. Mean yields of 158 × 10 3 DJ ml –1 were recorded for S. carpocapsae and 106 × 10 3 DJ ml –1 for S. feltiae . The results provide valuable information for future process improvement.
