Characterization of optimal growth conditions and carotenoid production of strain Rhodotorula mucilaginosa HP isolated from larvae of Pieris rapae

Yeasts have been studied because of their production of a pigment known as carotenoid with potential application in food and feed supplements. A carotenoid‐producing yeast was isolated from the larvae of Pieris rapae, named HP. The strain HP was identified as Rhodotorula mucilaginosa classified by its carbohydrate fermentation pattern and physiological tests. Rhodotorula mucilaginosa HP produces several exogenous enzymes: alkaline phosphatase, esterase, leucine arylamidase, valine arylamidase, acid phosphatase and β‐glucosidase. Using response surface methodology, selected medium components (yeast extract, malt extract, peptone, glucose) were tested to find the optimum conditions for carotenoid production and the growth of R. mucilaginosa HP. Central composite design was used to control the concentrations of medium components. Peptone and glucose had the largest effects on carotenoid production and cell growth of R. mucilaginosa HP, respectively. The estimated optimal growth conditions of R. mucilaginosa HP were: yeast extract 3.23%, malt extract 2.84%, peptone 6.99% and glucose 12.86%. The estimated optimal conditions for carotenoid production were: yeast extract 2.17%, malt extract 2.11%, peptone 5.79% and glucose 12.46%. These results will assist in the formulation of an appropriate culture medium for optimal carotenoid production of R. mucilaginosa HP for commercial use.     

Cloning and Functional Expression of cDNA Encoding Pheromone Δ9 Acyl-CoA Desaturase of the Tobacco Cutworm, Spodoptera litura (Lepidoptera: Noctuidae)

ABSTRACT A cDNA encoding pheromone Δ9 acyl-CoA desaturase, Slit KPSE was isolated from sex pheromone gland of the tobacco cutworm, Spodoptera litura which uses a diene unsaturated fatty acid (UFA) derivative, Z9E11-14 : 2 as a major pheromone component. The fulllength open reading frame coding region of Slit KPSE was inserted in a yeast shuttle vector, YEpOLEX, and two kinds of yeast ( Saccharomyces cerevisiae ) mutant strains were transformed with the recombinant vector. In the desaturase-deficient ole 1 strain, Slit KPSE expressed a complementary enzyme producing two kinds of diene UFAs, more 9–16 : 1 and less 9–18 : 1 at a ratio of 1 : 0.74 exhibiting a typical functional characteristics as one of the pheromone Δ9 acyl-CoA desaturase lineage group, KPSE, but no Δ9 14C monoene was detectable because of too small amount of 14C saturated fatty acid precursor to be reliably used by Slit KPSE in the transformed cells. However, the another transformed yeast strain elo 1 which is deficient of elongase 1, an enzyme converting 14C to 16C hydrocarbon substrate, was supplemented with some myristic acid (14 : 0) in the medium, and produced a significant amount of 9–14 : 1 in due to a much enhanced level of the 14C substrate suggesting that Slit KPSE may be responsible for making the Δ9 double bond on the diene pheromone component.     

PRODUCTION OF GERMLINE CHIMERIC CHICKENS BY TRANSFER OF CULTURED PRIMORDIAL GERM CELLS

Primordial germ cells (PGCs) from stage 27 (5.5-day-old) Korean native ogol chicken embryonic germinal ridges were cultured in vitro for 5 days. As in in vivo culture, these cultured PGCs were expected to have already passed beyond the migration stage. Approximately 200 of these PGCs were transferred into 2.5-day-old white leghorn embryonic blood stream, and then the recipient embryos were incubated until hatching. The rate of hatching was 58.8% in the manipulated eggs. Six out of 60 recipients were identified as germline chimeric chickens by their feather colour. The frequency of germline transmission of donor PGCs was 1.3–3.1% regardless of sex. The stage 27 PGCs will be very useful for collecting large numbers of PGCs, handling of exogenous DNA transfection during culture, and for the production of desired transgenic chickens.     

Growth and Grazing Rates of the Marine Planktonic Ciliate Strombidinopsis sp. on Red-Tide and Toxic Dinoflagellates

ABSTRACT We investigated growth and grazing rates of Strombidinopsis sp. when feeding on several species of red-tide and/or toxic dinoflagellates. Strombidinopsis sp. one of the largest aloricate choreotrichs so far reported, grew well on Lingulodinium polyedrum, Gymnodinium sanguineum, Scrippsiella trochoidea, Cochlodinium polykrikoides , and Prorocentrum minimum , but failed to grow on Amphidinium carterae. Specific growth rates of Strombidinopsis sp. increased rapidly with increasing prey density up to ca. 100 ng C ml^-1, but were saturated or increased slightly at higher concentrations. Maximum specific growth rates of Strombidinopsis sp. on various prey species were 1.38 day^-1 for C. polykrikoides , 1.27 for G. sanguineum , 1.06 for P. minimum , 0.83 for L. polyedrum , and 0.67 for S. trochoidea. Threshold prey concentrations (where net growth = 0) were 12–38 ng C ml^-1. Maximum ingestion and clearance rates of Strombidinopsis sp. were 353 ng C grazer^-1 day^-1 and 110 μ, l grazer^-1 h^-1, respectively. Strombidinopsis sp. exhibited higher maximum growth, ingestion, and clearance rates than the mixotrophic dinoflagellate Fragilidium cf. mexicanum or the heterotrophic dinoflagellates Protoperidinium cf. divergens and P. crassipes , when grown on the same prey species. In addition, the sequence of prey species arranged according to growth response of Strombidinopsis sp. differed considerably from those of Fragilidium cf. mexicanum, Protoperidinium cf. divergens , and P. crassipes.     

Description of a New Planktonic Mixotrophic Dinoflagellate Paragymnodinium shiwhaense n. gen., n. sp. from the Coastal Waters off Western Korea: Morphology,Pigments, and Ribosomal DNA Gene Sequence

ABSTRACT. The mixotrophic dinoflagellate Paragymnodinium shiwhaense n. gen., n. sp. is described from living cells and from cells prepared by light, scanning electron, and transmission electron microscopy. In addition, sequences of the small subunit (SSU) and large subunit (LSU) rDNA and photosynthetic pigments are reported. The episome is conical, while the hyposome is hemispherical. Cells are covered with polygonal amphiesmal vesicles arranged in 16 rows and containing a very thin plate‐like component. There is neither an apical groove nor apical line of narrow plates. Instead, there is a sulcal extension‐like furrow. The cingulum is as wide as 0.2–0.3 × cell length and displaced by 0.2–0.3 × cell length. Cell length and width of live cells fed Amphidinium carterae were 8.4–19.3 and 6.1–16.0 μm, respectively. Paragymnodinium shiwhaense does not have a nuclear envelope chamber nor a nuclear fibrous connective (NFC). Cells contain chloroplasts, nematocysts, trichocysts, and peduncle, though eyespots, pyrenoids, and pusules are absent. The main accessory pigment is peridinin. The sequence of the SSU rDNA of this dinoflagellate (GenBank AM408889) is 4% different from that of Gymnodinium aureolum, Lepidodinium viride, and Gymnodinium catenatum, the three closest species, while the LSU rDNA was 17–18% different from that of G. catenatum, Lepidodinium chlorophorum, and Gymnodinium nolleri. The phylogenetic trees show that this dinoflagellate belongs within the Gymnodinium sensu stricto clade. However, in contrast to Gymnodinium spp., cells lack nuclear envelope chambers, NFC, and an apical groove. Unlike Polykrikos spp., which have a taeniocyst–nematocyst complex, P. shiwhaense has nematocysts without taeniocysts. In addition, P. shiwhaense does not have ocelloids in contrast to Warnowia spp. and Nematodinium spp. Therefore, based on morphological and molecular analyses, we suggest that this taxon is a new species, also within a new genus.     

Morphological Oogenesis in the out1 Mutant of Drosophila melanogaster Meigen (Diptera: Drosophilidae)

ABSTRACT The sex-linked, recessive otu¹ mutant of Drosophila melanogaster was studied cytologically to reveal the effect of the otu gene mutation on oogenesis. Consequently, the germarium of the otu¹ mutant was found to be larger as compared to the normal fertile one and contains many undifferentiated tumor cells resembling cystocytes. Each ovary consists of three types of ovarioles; ovarioles with only a germarium, ovarioles with a germarium and one tumor chamber, and ovarioles with a germarium and two tumor chambers. In the otu¹ germarium, the mesodermal follicle cells invade the clusters of different number of tumor cells at the posterior region of the germarium in order to make the tumor chamber and the dividing frequency of the tumor cells in the first tumor chamber was six times more than in the second tumor chamber. Follicle cells surrounding the tumor chamber are morphologically normal, but the number of the follicle cells becomes less as the tumor chambers move down contrary to the fertile one. The otu¹ mutant female never lays the egg and the formation of the vitelline membrane is incomplete. The otu¹ mutant tumor cells also showed characteristics of certain rapidly dividing cells and its nucleus is lobulated.     

Growth and Grazing Rates of the Heterotrophic Dinoflagellate Polykrikos kofoidii on Red-Tide and Toxic Dinoflagellates

We investigated growth rates, grazing rates, and prey selection of Polykrikos kofoidii when feeding on several species of red-tide and/or toxic dinoflagellates. Polykrikos kofoidii ingested all prey species used in this study, exhibiting positive growth on Lingulodinium polyedrum, Scrippsiella trochoidea, Ceratium furca, Gymnodinium catenatum, Gyrodinium impudicum, Prorocentrum micans, and the toxic dinoflagellate Amphidinium carterae, but not on P. minimum. Specific growth rates of P. kofoidii increased rapidly with increasing density of L. polyedrum, S. trochoidea, C. furca, and G. catenatum before saturating between 500-2,000 ng C ml(-1). Specific growth rates increased continuously when P. kofoidii was fed the other prey species. Maximum specific growth rates of P. kofoidii on G. catenatum (1.12 d(-1)), S. trochoidea (0.97 d(-1)), and L. polyedrum (0.83 d(-1)) were higher than those on C. furca (0.35 d(-1)), A. carterae (0.10 d(-1)), P. micans (0.06 d(-1)), G. impudicum (0.06 d(-1)), and P. minimum (-0.03 d(-1)). Threshold prey concentrations (where net growth = 0) were 54-288 ng C ml(-1). Maximum ingestion and clearance rates of P. kofoidii on these dinoflagellates were 5-24 ng C pseudocolony(-1) d(-1) and 1.0-5.9 microl pseudocolony(-1) h(-1), respectively. Polykrikos kofoidii strongly selected L. polyedrum over S. trochoidea in prey mixtures. Polykrikos kofoidii exhibited higher maximum growth, ingestion, and clearance rates than previously reported for the mixotrophic dinoflagellate Fragilidium cf. mexicanum or the heterotrophic dinoflagellates Protoperidinium cf. divergens and P. crassipes, when grown on the same prey species. Grazing coefficients calculated by combining field data on abundances of Polykrikos spp. and co-occurring red-tide dinoflagellate prey with laboratory data on ingestion rates obtained in the present study suggest that Polykrikos spp. sometimes have a considerable grazing impact on prey populations.     

The Ecological Roles of Heterotrophic Dinoflagellates in Marine Planktonic Community1

Heterotrophic dinoflagellates are ubiquitous and often abundant protists in marine environments. Recently, several novel predator-prey relationships between heterotrophic dinoflagellates and other planktonic organisms have been discovered and shown to have diverse ecological roles. Heterotrophic dinoflagellates are predators on a wide array of prey items, including phytoplankton, copepod eggs, and early naupliar stages. They are in turn important prey for some metazoa. Some heterotrophic dinoflagellates are predators of and simultaneously prey for other dinoflagellates. These newly discovered predator-prey relationships may influence our conventional view of energy flow and carbon cycling in the marine planktonic community.