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1.
Tetranychus evansi Baker and Pritchard and Tetranychus urticae Koch (Acari: Tetranychidae) are important pests of Solanaceae in many countries. Several studies have demonstrated that T. urticae is an acceptable prey to many predatory mites, although the suitability of this prey depends on the host plant. T. evansi, has been shown to be an unfavorable prey to most predatory mites that have been tested against it. The predator Phytoseiulus fragariae Denmark and Schicha (Acari: Phytoseiidae) has been found in association with the two species in Brazil. The objective of
this work was to compare biological parameters of P. fragariae on T. evansi and on T. urticae as prey. The study was conducted under laboratory conditions at 10, 15, 20, 25 and 30°C. At all temperatures, survivorship
was lower on T. evansi than on T. urticae. No predator reached adulthood at 10°C on the former species; even on the latter species, only about 36% of the predators
reached adulthood at 10°C. For both prey, in general, duration of each life stage was shorter, total fecundity was lower and
intrinsic rate of population increase (r
m
) was higher with increasing temperatures. The slower rate of development of P. fragariae on T. evansi resulted in a slightly higher thermal requirement (103.9 degree-days) on that prey than on T. urticae (97.1 degree-days). The values of net reproduction rate (R
0), intrinsic rate of increase (r
m
) and finite rate of increase (λ) were significantly higher on T. urticae, indicating faster population increase of the predator on this prey species. The highest value of r
m
of the predator was 0.154 and 0.337 female per female per day on T. evansi and on T. urticae, respectively. The results suggested that P. fragariae cannot be considered a good predator of T. evansi. 相似文献
2.
Erika P. J. Britto Manoel G. C. GondimJr. Jorge B. Torres Komi K. M. Fiaboe Gilberto J. Moraes Markus Knapp 《BioControl》2009,54(3):363-368
Predatory behaviour and reproductive output of the ladybird beetle Stethorus tridens Gordon as function of the tomato red spider mite (TRSM), Tetranychus evansi Baker & Pritchard, densities was investigated in the laboratory. Adult female of S. tridens were isolated in cylindrical plastic arenas, containing a leaf disc of Solanum americanum Mill. with 5, 20, 40, 60, 80 or 100 T. evansi nymphs. The number of prey consumed and eggs laid were evaluated daily for ten consecutive days, starting at the oviposition.
Oviposition of S. tridens was positively correlated with prey consumption and lower threshold prey consumption for S. tridens laying eggs was 16.3 mites per day. The instantaneous rate of attack (ca. discovery area) and the handling time were 0.0062 h−1 and 0.83 h, and 0.00254 h−1 and 0.78 h, respectively, for predators at the 1st- and 10th-oviposition day. The predator exhibited a type II functional
response at 1st- and 10th-oviposition day with a maximum consumption per predator of 33 T. evansi nymphs per day at the highest prey density. The ladybird beetle S. tridens is often collected associated with red spider mite colonies on solanaceous wild plants and the results suggest the potential
of this ladybird beetle to control T. evansi in tomatoes crops.
Handling editor: Eric Lucas. 相似文献
3.
The two-spotted spider mite, Tetranychus urticae Koch, is an important pest of tomato in different parts of the world. Biological control of this pest on this crop has not
been very successful. Phytoseiulus
macropilis (Banks) has been used commercially for the control of T. urticae on different crops, but no information has been published on its potential to control T. urticae on tomato. The objective of this work was to compare the performance of a Brazilian population of P. macropilis on tomato with its performance on other plant species, relating the observed variation to the respective types and densities
of trichomes. It has been hypothesized that the presence of the webbing produced by T. urticae could help the predator to avoid contact with trichomes and consequently to improve its performance on tomato plants. This
hypothesis was also evaluated. Phytoseiulus
longipes Evans was included in the work as a control, given that it has been reported to be a promising predator of Tetranychus species on tomato. The study was conducted under laboratory conditions. It was found that the performance of P. macropilis was similar to that of P. longipes and that trichomes hampered the locomotion as well as prey consumption and oviposition rate of both predators; that the presence
of webbing resulted in higher levels of prey consumption and of predator oviposition; and that the presence of webbing eliminated
the negative effect of trichomes of eggplants and partially eliminated the negative effect of trichomes of the ‘cerasiforme’
tomato variety. The observed density of trichomes in ‘Carmem’ one of the most common tomato varieties grown in Brazil, seems
not to have interfered significantly with the prey consumption and the oviposition rate of P. macropilis. The results suggest that the latter is a promising predator of T. urticae on tomato. Complementary studies are warranted, to further evaluate the potential of P. macropilis for use as a biological control agent of this pest. 相似文献
4.
Nico Varo Andy J. Green Marta I. Sánchez Cristina Ramo Jesús Gómez Juan A. Amat 《Hydrobiologia》2011,664(1):163-171
Chemical communication may inform about the location of prey, predators, co-specifics, and mate partners in zooplankton. In
this study, we evaluated several life-history traits of the rotifer, Brachionus calyciflorus, exposed to conditioned media by a rotifer predator (Asplanchna brightwelli) and a cladocera competitor (Daphnia similis), quantifying population growth and life-table demography at two algal food levels (2.0 and 0.5 × 106 cells ml−1 of Chlorella pyrenoidosa). At both food levels, B. calyciflorus grown in predator-conditioned media had lower population abundance and slower population growth rate than controls. Conversely,
the competitor-conditioned media treatments produced both higher rotifer population abundance and faster population growth
rate than controls. Life-history parameters varied significantly depending on the presence of predator and competitor-conditioned
media. The Asplanchna-conditioned media significantly decreased gross reproductive rate (GRR): 8–9 offsprings per female; net reproductive rate
(R
0): 6–7 offsprings per female; population growth rate (r): 0.34–0.37 day−1; and increased generation time (T): 5.5–5.6 days. On the other hand, The Daphnia-conditioned media significantly increased the GRR (13–14 offsprings per female); net reproductive rate (8–9 offsprings per
female); population growth rate (0.42–0.43 day−1); and decreased generation time (4.9–5.0 days). However, the effects of food level on the life-history characteristic were
not significant in both treatments. Maximum values of the population abundance and the population growth rate are significantly
influenced by the predator densities and pre-culture time. This study suggests that rotifers use variable life-history strategies
(low reproduction and high survivorship versus high reproduction and low survivorship) based on the presence of predators
and competitors. 相似文献
5.
The growth and survival of larvae can be significantly enhanced through close association with patches of high prey concentration.
However, the taxis and kinesis responses used by larvae to locate and maintain residence in micro-patches remains poorly understood.
In this study, the behavioral responses of Pacific cod (Gadus macrocephalus) and walleye pollock (Theragra chalcogramma) larvae (45–100 dph) to light, prey scent, and prey were examined. Both species displayed an ontogenetic shift in response
to a horizontal light gradient, with small larvae (11–13 mm SL) exhibiting a positive phototaxis and large larvae (23–32 mm
SL) exhibiting a negative phototaxis. Whether this reversal is related to ontogenetically appropriate foraging cues or some
other aspect of the environment remains to be determined. Neither species displayed significant behavioral responsiveness
to the introduction of olfactory prey cues at either size. The aggregating (taxis) response of large larvae to introduction
of live prey was stronger than that of small larvae, possibly due to increased reaction distances and encounter rates. In
addition, both species exhibited a kinesis response of reducing the frequency of swimming bouts in response to introduction
of live prey. These results suggest that the scale of prey patchiness and the physical factors that determine patch encounter
rates are a significant determinant of larval growth and survival in the early feeding stages of marine fishes. 相似文献
6.
Yingen Xue Alan Meats G. Andrew C. Beattie Robert Spooner-Hart Grant A. Herron 《Experimental & applied acarology》2009,48(4):291-302
Occasional pesticide application in integrated pest management to at least part of a crop requires that any biological control
agents must re-invade previously sprayed areas in order that resurgent pests can be constrained. The ability of the phytoseiid
predatory mite Phytoseiulus persimilis to feed on adult two-spotted spider mite (TSSM) Tetranychus urticae on excised leaf discs in both control conditions and in a treatment with a sub lethal residue of agricultural mineral oil
(AMO) was assessed. The predator exhibited a Type II functional response with the asymptote significantly higher in the AMO
conditions due to the fact that the prey grew slower and reached a smaller size in this treatment. In terms of prey volume
eaten, the satiation level of the predator was unchanged by the AMO deposits. The numbers of eggs produced by adult P. persimilis females at densities of 4, 8 and 16 TSSM adult females/disc in the control were significantly higher than those in the AMO
treatment, but were similar for the higher density levels, 32 and 64 prey per disc. Thus the functional response in terms
of volume of prey eaten explained the numerical response in terms of predator eggs produced. The presence of AMO deposits
when the prey were at high density had no effect on predator efficiency (volume eaten) but resulted in a lower intake than
that in control conditions when there was a greater distance between prey. 相似文献
7.
Functional responses of predators are generally measured under laboratory conditions at rather high prey densities. This is
also true for the predation capability of the anthocorid predatory bug Orius sauteri (Poppius). To quantify the daily impact of one female Orius predator on its prey Thrips palmi Karny on greenhouse eggplants where the prey is present below the economic threshold density, we use its patch-leaving and
feeding behaviour on eggplant leaves with different prey numbers and scale up to the larger spatio-temporal scale of the greenhouse
and one foraging day by means of a simulation model. For this, we also use literature data on the distribution of T. palmi over eggplant leaves. The simulation results in a typical type II functional response for O. sauteri as a function of average T. palmi density: O. sauteri can find and eat approximately 10 prey items per day if T. palmi is present around its economic injury level. The daily mean number of prey eaten per O. sauteri predator, i.e., its predation capability, is highly sensitive to the actual baseline leaving tendency, the effect size of
the presence of prey on the baseline leaving tendency and the effect size of the encounter rate with prey thereon. 相似文献
8.
9.
Greenhouse and field experiments were conducted from 2005 to 2007 to determine the effectiveness of different release times
with the predatory mite, Neoseiulus californicus (McGregor), for control of the twospotted spider mite (TSSM), Tetranychus urticae Koch, in strawberries (Fragaria x ananassa Duchesne). The effect of N. californicus releases over time and on development of TSSM populations during a growing season were evaluated. Our hypothesis was that
repeated applications of N. californicus, which is currently recommended by biological control companies, might be unnecessary to attain season-long control of TSSM.
In greenhouse trials, three treatments consisting of releases of N. californicus at five-day intervals: day 0, day 5, and day 10, and an untreated control were evaluated. The treatment releases significantly
reduced TSSM below the control within five days of each release. Neoseiulus californicus significantly reduced TSSM in treatments with high densities (leaflets with ≥ 40 TSSM) below that of treatments with lower
densities (leaflets with ≤ 10 TSSM) demonstrating that if released at a predator: prey ratio of 1:10, timing of release does
not alter the effectiveness of N. californicus in controlling TSSM. However, we found that if the ratio of predator: prey remains adequate, N. californicus is a more efficient predator at high TSSM densities. Field studies included three treatments consisting of releases of N. californicus at one-month intervals. All treatments significantly reduced TSSM compared with the control plots (no releases). Releases
applied early in the season sustained TSSM significantly below those in the control plots for the whole season. Our results
indicate that one release of N. californicus is able to sustained control of TSSM in strawberry throughout a growing season if released when TSSM populations are low
early in the season in the southeastern United States. 相似文献
10.
The predatory mite Typhlodromus bagdasarjani Wainstein and Arutunjan (Acari: Phytoseiidae) is an indigenous and widespread species of the Middle East fauna. In this paper
we assess the effect of temperature on developmental rate and reproduction potential of T. bagdasarjani under laboratory conditions. The development of this species was determined at 15, 20, 25, 30, 35 and 37.5 ± 1°C, 60 ± 10%
RH and L16:D8 h photoperiod. The total developmental time averaged 28.2, 15.0, 8.9, 7.6, 7.2 and 7.4 days at 15–37.5°C, respectively,
when feeding on immature stages of two-spotted spider mite, Tetranychus urticae Koch. The lower developmental threshold (T
0
) and thermal constant (K) for the development of this predator were estimated 9.2°C and 162 degree-days by the Ikemoto linear model. The life table
parameters were estimated at 15–35°C. The shortest life span of females at 35°C was 45.0 days, followed by 50.7, 50.9, 103.3
and 136.8 days at 30, 25, 20 and 15°C, respectively. Mated females laid on average 19.9, 26.3, 41.1, 39.6 and 31.3 eggs per
female at 15–35°C, respectively. The intrinsic rate of increase (r
m
) and finite rate of increase (λ) increased significantly with increasing temperature. The r
m
values ranged from 0.021 (15°C) to 0.186 (35°C) days−1. The highest value of net reproductive rate (R
0) was 13.6 females progeny/female/generation at 25°C. The results demonstrated that T. bagdasarjani is well adapted to high temperatures. However, the efficiency to control spider mites may be affected by behavioral characteristics
of the predator and its prey under real conditions. 相似文献
11.
Surface inoculation dose–response and time–response bioassays and detached fruit bioassays were conducted with a novel South
African isolate of the Cryptophlebia leucotreta granulovirus (CrleGV-SA) against Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Noctuidae) neonate larvae. LC50 and LC90 values were estimated to be 4.095 × 103 and 1.185 × 105 OBs ml−1, respectively. LT50 and LT90 values were estimated to be 4 days 22 h and 7 days 8 h, respectively, categorising the virus as a fast or type 2 granulovirus.
There was a conspicuous difference in behaviour between larvae on inoculated diet and untreated diet, resulting in a significant
reduction in penetration of diet. Bioassays on detached Navel oranges revealed LC50 and LC90 values of 9.310 × 107 and 1.515 × 109 OBs ml−1, when using data on numbers of larvae per fruit rather than on numbers of infested fruit. Field trials will be conducted. 相似文献
12.
Willis RE White CR Merritt DJ 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(4):477-486
Trap-building, sit-and-wait predators such as spiders, flies and antlions tend to have low standard metabolic rates (SMRs)
but potentially high metabolic costs of trap construction. Members of the genus Arachnocampa (glowworms) use an unusual predatory strategy: larvae bioluminesce to lure positively phototropic insects into their adhesive
webs. We investigated the metabolic costs associated with bioluminescence and web maintenance in larval Arachnocampa flava. The mean rate of CO2 production ([(V)\dot] \dot{V}CO2) during continuous bioluminescence was 4.38 μl h−1 ± 0.78 (SEM). The mean [(V)\dot] \dot{V}CO2 of inactive, non-bioluminescing larvae was 3.49 ± 0.35 μl h−1. The mean [(V)\dot] \dot{V}CO2 during web maintenance when not bioluminescencing was 8.95 ± 1.78 μl h−1, a value significantly lower than that measured during trap construction by other predatory arthropods. These results indicate
that bioluminescence itself is not energetically expensive, in accordance with our prediction that a high cost of bioluminescence
would render the Arachnocampa sit-and-lure predatory strategy inefficient. In laboratory experiments, both elevated feeding rates and daily web removal
caused an increase in bioluminescent output. Thus, larvae increase their investment in light output when food is plentiful
or when stressed through having to rebuild their webs. As light production is efficient and the cost of web maintenance is
relatively low, the energetic returns associated with continuing to glow may outweigh the costs of continuing to attract prey. 相似文献
13.
Ana Sabatés Francesc Pagès Dacha Atienza Verónica Fuentes Jennifer E. Purcell Josep-María Gili 《Hydrobiologia》2010,645(1):153-165
Pelagic cnidarians are important consumers of zooplankton and ichthyoplankton in the world’s oceans, and thus harm fisheries
as competitors and predators of fish. This study examined the inshore-offshore distribution of pelagic cnidarians and the
trophic ecology of Pelagia noctiluca ephyrae (<12 mm diameter) and larger medusae in late spring 1995 in the NW Mediterranean Sea. The distribution of pelagic
cnidarians was closely related to the presence of the shelf-slope front with most species mainly concentrated close to the
front. Meroplanktonic antho- and leptomedusae predominated in coastal waters and more holoplanktonic trachy- and narcomedusae
occurred both in shelf and open sea waters. P. noctiluca was more abundant than other medusae, including hydromedusae. Siphonophores, particularly Muggiaea atlantica, outnumbered medusae at most stations. The diet of P. noctiluca ephyrae contained mainly copepods, but ~12% of the prey were fish larvae. P. noctiluca exhibited positive prey selection for chaetognaths and mollusc larvae in day and night samples, but fish larvae were positively
selected only at night. These differences may be related to the diel vertical distributions of P. noctiluca and their prey. Most of the ingested fish larvae belonged to the family Myctophidae, but anchovy and sparid larvae also were
found in the gastric pouches. The size of ingested fish larvae increased as ephyra diameter increased; however, in the larger
medusae (>12 mm) the number of prey increased with medusa size rather than the size of the larvae. The temporal and spatial
co-occurrence of P. noctiluca with early life stages of fish suggests that P. noctiluca may be an important predator on summer ichthyoplankton. 相似文献
14.
Badii MH Hernández-Ortiz E Flores AE Landeros J 《Experimental & applied acarology》2004,34(3-4):263-273
The aims of this study were: (a) determine the prey stage preference of female Euseius hibisci (Chant) (Phytoseiidae) at constant densities of different stages of Tetranychus urticae Koch (Tetranychidae), (b) assess the functional response of the predator females to the varying densities of eggs, larvae, or protonymphs of T. urticae, and (c) estimate the functional response of E. hibisci when pollen of Ligustrum ovalifolium was present as well. We conducted experiments on excised pieces of strawberry leaf arenas (Fragaria ananassa) under laboratory conditions of 25 ± 2 °C, 60 ± 5% RH and 12 h photophase. Our results indicated that the predator consumed significantly more prey eggs than other prey stages. Consumption of prey deutonymphs and adults was so low that they were excluded from the non-choice functional response experiments. The functional response on all food items was of type II. The two parameters of the functional response were estimated for each prey type by means of the adjusted non-linear regression model. The highest estimated value a (instantaneous rate of discovery) and the lowest value of Th (handling time, including digestion) were found for the predator feeding on prey eggs, and a was lowest and Th highest when fed protonymphs. Using the jack-knife method, the values for the functional response parameters were estimated. The values of a and Th produced by the model were similar among all prey types except for the eggs, which were different. Using pollen simultaneously with prey larvae decreased the consumption of the latter over the full range of prey densities The suitability of this predator for biological control of T. urticae on strawberry is discussed. 相似文献
15.
Three mite species are frequently found on vegetable crops in Italy: the pest Tetranychus urticae Koch (Acari: Tetranychidae), the predator Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) and the unspecialised feeder Tydeus californicus (Banks) (Acari: Tydeidae). In laboratory trials, the direct and residual effects of six insecticides recommended for the control of aphids, whiteflies and thrips in vegetable crops, (Biopiren® plus (pyrethrins), Confidor® (imidacloprid), Oikos® (azadirachtin), Plenum® (pymetrozine), Naturalis® (Beauveria bassiana) and Rotena® (rotenone)), were evaluated for the three mite species. All the products affected the mites and their effect was often favourable towards T. urticae and unfavourable towards N. californicus and T. californicus. Rotenone was more toxic to eggs than females of T. urticae. It was highly toxic to N. californicus and caused the death of all treated females of T. californicus. Pyrethrins and imidacloprid increased T. urticae fecundity, but decreased fecundity of N. californicus. Imidacloprid decreased T. californicus fecundity more than pyrethrins. Beauveria bassiana was not toxic to T. urticae and T. californicus, but induced high mortality in the progeny of treated females of N. californicus. Azadirachtin and pymetrozine were the least toxic to T. urticae and N. californicus, but decreased production of larvae in T. californicus. Implications for integrated pest management on vegetables are discussed. 相似文献
16.
Raquel Abad-Moyano Alberto Urbaneja Daniela Hoffmann Peter Schausberger 《Experimental & applied acarology》2010,50(4):329-341
The two-spotted spider mite, Tetranychus urticae, is one of the most problematic phytophagous pests in Spanish clementine orchards. The most abundant predatory mites in this
ecosystem are Euseius stipulatus, Phytoseiulus persimilis and Neoseiulus californicus. Euseius stipulatus is dominant but poorly adapted to utilize T. urticae as prey. It mainly persists on pollen and citrus red mite, Panonychus citri. A recent study suggested that the more efficacious T. urticae predators P. persimilis and N. californicus are negatively affected by lethal and non-lethal intraguild interactions with E. stipulatus. Here, we investigated the potential of N. californicus and P. persimilis to colonize and thrive on young clementine trees infested by T. urticae in presence and absence of E. stipulatus. Presence of E. stipulatus interfered with establishment and abundance of P. persimilis and negatively affected the efficacy of N. californicus in T. urticae suppression. In contrast, the abundance of E. stipulatus was not affected by introduction of a second predator. Trait-mediated effects of E. stipulatus changing P. persimilis and N. californicus behavior and/or life history were the most likely explanations for these outcomes. We conclude that superiority of E. stipulatus in intraguild interactions may indeed contribute to the currently observed predator species composition and abundance, rendering
natural control of T. urticae in Spanish clementine orchards unsatisfactory. Nonetheless, stronger reduction of T. urticae and/or plant damage in the predator combination treatments as compared to E. stipulatus alone indicates the possibility to improve T. urticae control via repeated releases of N. californicus and/or P. persimilis. 相似文献
17.
Islam S. Sobhy Awad A. Sarhan Ahmed A. Shoukry Gamal A. El-Kady Nasser S. Mandour Stuart R. Reitz 《BioControl》2010,55(6):753-765
The predatory bug Orius albidipennis (Reuter) (Hemiptera: Anthocoridae) has tremendous potential as a biological control agent, especially in its native range
around the Mediterranean Basin and East Africa. The need to exploit native biological control agents is growing in importance
as concerns over the introduction of non-native species continue to increase. However, little is known of the effects of different
prey on development and reproduction of O. albidipennis compared with other species of Orius. Therefore, we compared the development, survival, reproductive biology, and prey consumption of O. albidipennis when fed eggs of Ephestia kuehniella Zeller, Tetranychus urticae Koch, and Trialeurodes vaporariorum (Westwood), and larvae of Gynaikothrips ficorum (Marchal), under laboratory of 26 ± 1°C, 60 ± 10% RH and 16L:8D photoperiod. Individuals were reared from the neonate stage
until death on one of the four prey types. The type of prey had profound effects on all measured performance traits. The highest
survival rate was recorded for nymphs that were fed on E. kuehniella eggs, while the lowest survival rate was observed for those fed on T. vaporariorum eggs. The shortest nymphal period was recorded for nymphs fed on E. kuehniella eggs, while the longest was measured for those fed on T. urticae eggs. During the nymphal period, O. albidipennis consumed significantly more eggs of T. urticae than other prey types, whereas the lowest number of consumed prey were eggs of E. kuehniella. Adult females and males consumed significantly more T. urticae eggs than other types of prey. However, Orius albidipennis females showed the highest fecundity when fed on E. kuehniella eggs, and the lowest when fed on T. vaporariorum eggs. Adult females and males that fed on G. ficorum larvae had significantly longer life spans compared with those fed other prey. Because of their relatively rapid development
and high fecundity, O. albidipennis fed E. kuehniella eggs had a significantly higher net reproductive rate (Ro) and intrinsic rate of increase (r
m
) than O. albidipennis fed other prey types. Overall, eggs of E. kuehniella were the most suitable diet for nymphs and adults of O. albidipennis. Although less suitable, O. albidipennis could survive and reproduce on the other prey types, which is a favourable attribute in biological control agents. These
results on the effect of different prey types on development and reproduction of O. albidipennis will also contribute to the development of mass rearing programs for biological control agents in developing countries, such
as Egypt. 相似文献
18.
Two carotenoid 1,2-hydratase (CrtC) genes from the photosynthetic bacteria Rubrivivax gelatinosus and Thiocapsa roseopersicina were cloned and expressed in Escherichia coli in an active form and purified by affinity chromatography. The biochemical properties of the recombinant enzymes and their
substrate specificities were studied. The purified CrtCs catalyze cofactor independently the conversion of lycopene to 1-HO-
and 1,1′-(HO)2-lycopene. The optimal pH and temperature for hydratase activity was 8.0 and 30°C, respectively. The apparent K
m and V
max values obtained for the hydration of lycopene were 24 μM and 0.31 nmol h−1 mg−1 for RgCrtC and 9.5 μM and 0.15 nmol h−1 mg−1 for TrCrtC, respectively. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis revealed two protein bands of 44 and
38 kDa for TrCrtC, which indicate protein processing. Both hydratases are also able to convert the unnatural substrate geranylgeraniol
(C20 substrate), which functionally resembles the natural substrate lycopene. 相似文献
19.
Engineering <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis> for the production of pyruvate 总被引:1,自引:0,他引:1
A Corynebacterium glutamicum strain with inactivated pyruvate dehydrogenase complex and a deletion of the gene encoding the pyruvate:quinone oxidoreductase
produces about 19 mM l-valine, 28 mM l-alanine and about 55 mM pyruvate from 150 mM glucose. Based on this double mutant C. glutamicum △aceE △pqo, we engineered C. glutamicum for efficient production of pyruvate from glucose by additional deletion of the ldhA gene encoding NAD+-dependent l-lactate dehydrogenase (LdhA) and introduction of a attenuated variant of the acetohydroxyacid synthase (△C–T IlvN). The latter
modification abolished overflow metabolism towards l-valine and shifted the product spectrum to pyruvate production. In shake flasks, the resulting strain C. glutamicum △aceE △pqo △ldhA △C–T ilvN produced about 190 mM pyruvate with a Y
P/S of 1.36 mol per mol of glucose; however, it still secreted significant amounts of l-alanine. Additional deletion of genes encoding the transaminases AlaT and AvtA reduced l-alanine formation by about 50%. In fed-batch fermentations at high cell densities with adjusted oxygen supply during growth
and production (0–5% dissolved oxygen), the newly constructed strain C. glutamicum △aceE △pqo △ldhA △C–T ilvN △alaT △avtA produced more than 500 mM pyruvate with a maximum yield of 0.97 mol per mole of glucose and a productivity of 0.92 mmol g(CDW)−1 h−1 (i.e., 0.08 g g(CDW)
−1 h−1) in the production phase. 相似文献
20.
Yemendzhiev H Gerginova M Krastanov A Stoilova I Alexieva Z 《Journal of industrial microbiology & biotechnology》2008,35(11):1309-1312
Trametes versicolor 1 was shown to grow on phenol as its sole carbon and energy source. The culture growth and degradation ability dependence
on culture medium pH value was observed. The optimal pH value of a liquid Czapek salt medium was 6.5. The investigated strain
utilized completely 0.5 g/l phenol in 6 days. The dynamics of the phenol degradation process was investigated. The process
was characterized by specific growth rate μmax 0.33 h−1, metabolic coefficient k = 4.4, yield coefficient Y
x/s
= 0.23 and rate of degradation Q = 0.506 h−1. The intracellular activities of phenol hydroxylase (0.333 U/mg protein) and cis,cis-muconate lactonizing enzyme (0.41 U/mg protein) were demonstrated for the first time in this fungus. In an attempt to estimate
the occurrence of gene sequences in T. versicolor 1 related to phenol degradation pathway a dot blot analysis with total DNA isolated from this strain was performed. Two synthetic
oligonucleotides were used as hybridizing probes. One of the probes was homologous to the 5′end of phyA gene coding for phenol hydroxylase in Trichosporon cutaneum ATCC 46490. The other probe was created on the basis of cis,cis-muconate lactonizing enzyme coding gene in T. cutaneum ATCC 58094. The results of these investigations showed that T. versicolor 1 may carry genes similar to those of Trichosporon cutaneum capable to degrade phenol. 相似文献