STEROLS OF 14 SPECIES OF MARINE DIATOMS (BACILLARIOPHYTA)1

The sterol compositions of 14 species of marine diatoms were determined by gas chromatography and gas chromatography-mass spectrometry. A variety of sterol profiles were found. The sterols 24-methylcholesta-5,22E-dien-3β-ol, cholest-5-en-3β-ol, and 24-methylcholesta-5,24(28)-dien-3β-ol, previously described as the most common sterols found in diatoms, were major sterols in only a few of the species. In light of this and other recent data, it is clear that these three sterols are not typical constituents of many diatom species. Most of the centric species examined had 24-methylcholesta-5,24(28)-dien-3β-ol and 24-methylcholest-5-en-3β-ol as two of their major sterols. The exception was Rhizosolenia setigera, which possessed cholesta-5,24-dien-3β-ol as its single major sterol. In contrast to the centric species, the pennate diatoms examined did not have any particular sterols common to most species. Minor levels ofΔ⁷-sterols, rarely found in large amounts in diatoms, were found in four species. C₂₉sterols were found in many species; seven contained 24-ethylcholest-5-en-3β-ol and three contained 24-ethylcholesta-5,22E-dien-3β-ol, reinforcing previous suggestions that C₂₉ sterols are not restricted to higher plants and macroalgae. 24-Ethylcholesta-5,22E-dien-3β-ol may prove to be useful for taxonomy of the genus Amphora and the order Thalassiophysales. A major sterol of Fragilaria pinnata was the uncommon algal sterol 23,24-dimethylcholesta-5,22E-dien-3β-ol. Cholesta-5,24-dien-3β-ol was the only sterol found in the culture of Nitzschia closterium. This differed from previous reports of 24-methylcholesta-5,22E-dien-3β-ol as the single major sterol in N. closterium. Two C₂₈ sterols possessing an unusual side chain were found in Thalassi-onema nitzschioides, a C_28:2 sterol (16%) and a C_28:1 sterol in lower abundance (2.5%), which may be 23-methylcholesta-5,22E-dien-3β-ol and 23-methyl-5α-cholest-22E-en-3β-ol, respectively. The species Cylindrotheca fusiformis, T. nitzschioides, and Skeletonema sp. may be useful as direct sources of cholesterol in mariculture feeds due to their moderate to high content of this sterol.     

EFFECT OF BLUE-GREEN LIGHT ON PHOTOSYNTHETIC PIGMENTS AND CHLOROPLAST STRUCTURE IN THE MARINE DIATOM STEPHANOPYXIS TURRIS1

Blue-green light increased the chlorophyll concentration and chloroplast number of cells of Stephanopyxis turris (Grev.) Ralfs, compared to white light controls. Light fields for growth were 400 μW·cm^?2 (12:12 LD cycles). Chlorophyll increased up to 100%/cell, but no change in the ratio of chlorophylls to major carotenoids occurred. The effect was, therefore, not that of complementary chromatic adaptation. At the same time, blue-green light enhanced the photosynthetic fixation of CO₂. At the ultrastructure level, an increase in, and rearrangement of, the thylakoid system occurred.     

EFFECT OF POLYCARBONATE CONTAINERS ON THE GROWTH OF TWO SPECIES OF MARINE DIATOMS1

Two species of marine diatoms [Skeletonema costatum (Greville) Cleve and Thalassiosira pseudonana (Hustedt) Hasle and Heimdal] were grown in glass and polyarbonate containers. S. costatum exhibited a signzJicantly lower exponential growth rate and maximal yield and a signajcantly longer lag phase when grown in polycarbonate. Exponential growth rate and maximal yield of T. pseudonana was significantly reduced (P < 0.05 in all cases). This study suggests that a difference in diatom growth between glass and polyarbonate containers might arise in certain cases. However, such a difference may not be detectable with all biomass measurement techniques or with low within-treatment replication.     

EFFECT OF BLUE-GREEN LIGHT ON PHOTOSYNTHETIC PIGMENTS AND CHLOROPLAST STRUCTURE IN UNICELLULAR MARINE ALGAE FROM SIX CLASSES1

The photosynthetic pigments of 17 species of unicellular marine algae grown in white and blue-green light were examined. Blue-green light (400 μW·cm^?2; 12:12 LD cycle) caused major chlorophyll increases (55–146%) in five diatoms, one dinoflagellate and one cryptomonad; minor chlorophyll increases (17–39%) in two diatoms, two dinoflagellates, one prymnesiophyte (haptophyte), one chrysophyte and one chlorophyte; and no chlorophyll increase in two diatoms and one pyrmnesiophyte (haptophyte). The relative proportions of major chlorophylls and carotenoids did not change, but in six of eight species tested small increases in the concentration of chlorophyll c occurred. Blue-green light caused a small increase in the concentration of phycoerythrin relative to chlorophyll a in the cryptomonad. A larger number of thylakoids per chloroplast were observed in six species grown in blue-green light compared to white light controls. The ultrastructure changes observed depended not only on the magnitude of the chlorophyll increase but also on the architecture of the chloroplast.     

INTRASPECIFIC COMPARISONS OF NITRATE UPTAKE IN THREE MARINE DIATOMS1

Short-term (within 5 min) and long-term (≤2 h) rates of nitrate uptake were determined for the marine diatoms, Nitschiella longissima (Cleve), Skeletonema costatum (Greville) Cleve and Asterionella japonica (Cleve). Pigment levels, cell carbon, nitrogen and cell volume were also determined for cells in the logarithmic and stationary phases of growth. For each species, one clone isolated from oligotrophic coastal water and one clone isolated from eutrophic coastal water were compared. Long-term NO₃^? uptake typically followed saturation kinetics describable by the Michaelis-Menten expression. Under experimental conditions, half-saturation constants ranged from 0.6 to 2.2 μM NO₃^?. Generally, the oligotrophic clones had lower Ks and V_max (on a per cell basis) than their eutrophic counterparts, though this was only statistically significant in one pair of clones. Eutrophic and oligotrophic clones also differed in their short-term response to nutrient addition; oligotrophic clones showed greatest rate of uptake at the lowest nitrate addition while uptake by eutrophic clones increased with increasing nitrate concentration. However, all clones had very similar V_max values expressed on a dry weight basis. Under N-starvation, cellular C and pigment levels (and N to a lesser extent) generally declined more in eutrophic than in oligotrophic clones. While the differences between inshore and offshore clones were not great, the results are consistent with the hypothesis that eutrophic waters support algae which grow faster and are less conservative biochemically than cells in oligotrophic waters.     

CHANGES IN EMISSION SPECTRA OF PHOTOSYNTHETIC PIGMENTS IN VIVO

1. The effects of 3-(4'-chlorophenyl)-1, 1-dimethylurea (CMU)onthe fluorescence of photosynthetic pigments in vivo wereinvestigatedin blue-green, red and brown algae and in isolatedspinach chloroplasts.CMU caused an increase in steady statelevel of fluorescenceof chlorophyll a, but did not influencethe fluorescence ofphycobilins. The spectrum of the fluorescenceincrement hada peak at 685 m/µ and a shoulder at 730–740mµ.These two bands probably arise from chlorophyll a(C_f684) belongingto pigment system II.
2. On excitation of chlorophylla in a red alga, Porphyra yezoensis,a fluorescence band witha peak at 720 mµ was observedbesides a shoulder at 685mµ. The 720 m band is inferredto arise from chlorophylla (probably, C_f-1) in pigment systemI.
3. On addition of CMUto the algal cells, the induction of fluorescencewas modifiedto take a simple time course. The induction wasobserved onlywith respect to the fluorescence of chlorophylla, but not inthe fluorescence of phycobilins. The spectrumof the "transient"fluorescence showed two emission bands ofchlorophyll a at 685mµ and 740 mµ, and was quitesimilar in form tothe spectrum of the CMU-caused increase insteady state fluorescence.
4. These facts were interpreted in terms of the correlation offluorescence of chlorophyll a and the photochemical reactionsof photosynthesis

(Received July 20, 1967; )     

PHOTOSYNTHETIC PIGMENT ORGANIZATION IN DIATOMS (BACILLARIOPHYCEAE)1

The isolation and characterization of six pigment-protein complexes from five diatom species (Phaeodactylum tricornutum Bohlin, Chaetoceros gracilis Schutt, Nitzschia sp. Mono Lake, Nitzschia laevis Hust. and Thalassiosira pseudonana (Hust.) Hasle and Heimdal) was accomplished by membrane dissociation with digitonin followed by gel electrophoresis. Six analogous complexes obtained from all species were correlated in spectral characteristics and relative mass with complexes from higher plants obtained by the same procedure. The largest of these complexes, comprising about 15% of the total Chl a, contained reaction centers of Photosystem I (PSI) and antenna pigments (LHC₁).Some PSI complexes also separated from LHC₁ in the gel. For the first time in diatoms, a Photosystem II complex was isolated and identified from its position in the gels, absorption and fluorescence spectra, lack of P700, and enrichment carotene. Three antenna pigment-protein complexes in addition to LHC₁ occurred in varying proportion under different experimental conditions but in sum, they accounted for 70% of the total Chl a. All three bands were highly enriched in Chl c and fucoxanthin, although the ratio of Chl c/ xanthophyll decreased between the slowest migrating LHC₂ and fastest moving LHC₄ LHC₃ contained the highest proportio of pigment-protein and was composed primarily of polypeptides of about 18,000 D. Essentially all α- and β-carotene was bound to the reaction center complexes. The Nitzschia from Mono Lake differed from the other species in that PSI complexes could not be readily dissociated from its membrane by digitonin treatment, a characteristic which may reflect a different chloroplast membrane structure in this alga.     

CARBON FIXATION IN CULTURED MARINE BENTHIC DIATOMS1

The enzyme activity of ribulose 1, 5-bisphosphate carboxylase-oxygenase (RuBisCO) and phosphoenolpyruvate carboxylase (PEPC) was measured in four species of marine benthic diatoms isolated from subtidal sediments of Graveline Bayou, Mississippi. Enzyme activities were measured in cultures of Amphora micrometra Giffen, A. tenerrima Aleem and Hustedt, Nitzschia fontifuga Cholnoky, and Nitzschia vermicularis Grunow that were grown at light levels supporting μ_max and at light-limiting irradiances. All four species exhibited similar RuBisCO: PEP ratios (range = 1–1.8) at μ_max the lowest ratio (0.4) was observed in A. micrometra. Reduced light levels increased PEPC relative to that measured at μ_max in two species. Two-dimensional paper chromatography was used to determine the first products of carbon fixation in A. micrometra After a 15 s incorporation period, the first product of photosynthetic carbon fixation was 3-phosphoglycerate even though this alga had a PEPC activity that was three times higher than that of RuBisCO. After 30 s, over 50% of the recovered radioactivity was still in this compound. Stable carbon isotope analyses of a mixture of the four pennate diatoms also suggest the predominant carbon fixation pathway in these benthic diatoms was similar to C3 plants.     

光合细菌H3菌株色素分析

H3菌株系由盐田微生物层中分离获得的光合细菌株。具有丰富的天然色素。经活细胞色素光谱吸收峰值测定,色素经有机溶剂提取、硅胶薄板层析、SDS－PAGE电泳等,结果表明H3菌株的主要色素包括细菌叶绿素a、细菌脱镁叶绿素（Bacteriophaeophytin）和三种类胡萝卜素。总胡萝卜素含量占细胞于重的0．6％,胡萝卜素蛋白复合体的分子量约11,000.培养条件的差异对色素形成及相对含量有不同程度的影响。     

PHOTOACCLIMATION OF PHOTOSYNTHESIS IRRADIANCE RESPONSE CURVES AND PHOTOSYNTHETIC PIGMENTS IN MICROALGAE AND CYANOBACTERIA1

The photosynthesis‐irradiance response (PE) curve, in which mass‐specific photosynthetic rates are plotted versus irradiance, is commonly used to characterize photoacclimation. The interpretation of PE curves depends critically on the currency in which mass is expressed. Normalizing the light‐limited rate to chl a yields the chl a‐specific initial slope (α^chl). This is proportional to the light absorption coefficient (a^chl), the proportionality factor being the photon efficiency of photosynthesis (φ_m). Thus, α^chl is the product of a^chl and φ_m. In microalgae α^chl typically shows little (<20%) phenotypic variability because declines of φ_m under conditions of high‐light stress are accompanied by increases of a^chl. The variation of α^chl among species is dominated by changes in a^chl due to differences in pigment complement and pigment packaging. In contrast to the microalgae, α^chl declines as irradiance increases in the cyanobacteria where phycobiliproteins dominate light absorption because of plasticity in the phycobiliprotein:chl a ratio. By definition, light‐saturated photosynthesis (P_m) is limited by a factor other than the rate of light absorption. Normalizing P_m to organic carbon concentration to obtain P_m^C allows a direct comparison with growth rates. Within species, P_m^C is independent of growth irradiance. Among species, P_m^C covaries with the resource‐saturated growth rate. The chl a:C ratio is a key physiological variable because the appropriate currencies for normalizing light‐limited and light‐saturated photosynthetic rates are, respectively, chl a and carbon. Typically, chl a:C is reduced to about 40% of its maximum value at an irradiance that supports 50% of the species‐specific maximum growth rate and light‐harvesting accessory pigments show similar or greater declines. In the steady state, this down‐regulation of pigment content prevents microalgae and cyanobacteria from maximizing photosynthetic rates throughout the light‐limited region for growth. The reason for down‐regulation of light harvesting, and therefore loss of potential photosynthetic gain at moderately limiting irradiances, is unknown. However, it is clear that maximizing the rate of photosynthetic carbon assimilation is not the only criterion governing photoacclimation.     

B12 SPECIFICITY OF MARINE CENTRIC DIATOMS1, 2

Twenty-one species (23 isolates) of marine diatoms were examined for their capacity to utilize analogs of cyanocobalamin for growth at the ecologically significant concentration of 4 ng 1-¹. Yields due to the analogs were compared to those produced by B₁₂. Responses of the various clones to the analogs were not all-or-none, but varied continuously; thus, assigning the clones to the conventional B₁₂ specificity types is a convenient but arbitrary classification. The use of 10 and 1% levels of response is suggested for such classification. At the 10% level of response, 11 clones had coliform, 4 lactobacillus, and 8 mammalian specificity patterns. At the 1% response level, 14 had coliform, 5 lactobacillus, and 4 mammalian specificities. All clones exceed the 10% response level on all benzimi-dazole-containine analogs tested. Few clones showed definite enough patterns of response to make them potentially useful for differential bioassay. The clones suggested are clone 675-D (Bidclulphia sp.?), clone F^;-3 (Fragilaria sp.?), and the estuarine clone of Cyclotella nana (3H).     

PIGMENTS OF THE DINOFLAGELLATE PERIDINIUM BALTICUM AND ITS PHOTOSYNTHETIC ENDOSYMBIONT1

An examination of the pigments of the binucleate dinoflagellate Peridinium balticum (Levander) Lemmerman revealed the presence of chlorophylls a, c₁ and c₂ and the carotenoids: fucoxanthin (most abundant), diadinoxanthin, diatoxanthin, an unidentified fucoxanthin-like xanthophyll, β-carotene, γ-carotene and astaxanthin. A comparison of the pigments of P. balticum and P. foliaceum (Stein) Biecheler, also a binucleate dinoflagellate, demonstrated similar compositions. However P. balticum lacked the β-carotene precursors (e.g. phytoene) which accumulated outside the chloroplast in P. foliaceum. This study indicates that P. balticum and P. foliaceum are closely related; each species is a heterotrophic dinoflagellate with a photosynthetic endosymbiont taxonomically affiliated with the Chrysophyta (Chrysophyceae or Bacillariophyceae).     

ASSAY OPTIMIZATION AND REGULATION OF UREASE ACTIVITY IN TWO MARINE DIATOMS

An in vitro urease enzyme assay was developed for the marine diatoms Thalassiosira pseudonana Hasle et Heimdal (clone 3H) and T. weissflogii (Grunow) Fryxell et Hasle (clone Actin). This assay involves the colorimetric measurement of ammonium following the hydrolysis of urea in crude cell homogenates and it is the first assay to account for the rate of nitrogen assimilation in both species grown on urea as the sole nitrogen source. Urease activity was found to be present regardless of nitrogen source, although activities showed distinctly different patterns depending on the species examined and form of nitrogen supplied. Under nitrogen-replete conditions, urease activity in T. pseudonana was present constitutively when grown on NH₄⁺ and upregulated when grown on NO₃⁻ or urea. In nitrogen-replete T. weissflogii , urease activity was present at high constitutive levels regardless of the nitrogen source and showed no upregulation. Nitrogen starvation did not upregulate activity in either species.     

北京地区51种蚜虫的染色体组型

本文报道了通过改进蚜虫染色体制片方法,对北京地区51种常见蚜虫的染色体进行研究的结果。在这51种蚜虫中,染色体数目范围由2n=4至2n=18,出现频率最高的为2n=8、10、12。根据染色体的长度和形态,总结出8种蚜虫染色体组型,并将这几种组型与两种蚜虫分类系统进行对照,在较高级的分类水平上,讨论了这二种分类系统安排与细胞学证据的相符程度。     

ULTRASTRUCTURAL AND PHYSIOLOGICAL DIFFERENCES IN SOYBEANS WITH GENETICALLY ALTERED LEVELS OF PHOTOSYNTHETIC PIGMENTS

Soybeans displaying incomplete dominance for leaf pigmentation possess chloroplasts with characteristic shape and organization of photosynthetic membranes. The chloroplasts of light green plants lack grana typical of dark green or a field type (Beeson) but normally possess doubled thylakoids. Achlorophyllous lethal yellow plants have thylakoids reduced to single spiralled membranes. The yellow plants lack a waxy cuticle over the leaf surface which is characteristic of all other soybeans examined, and they lack catalase activity in microbodies. Photosynthetic rates in the light green plants are at least as high as in the fully pigmented ones and photorespiration levels are not significantly different. Thus, in light green plants greater efficiency of enzymatic processes in photosynthesis apparently offsets the inhibitory activities associated with photorespiration. Single allele alterations from dark green to light green and light green to lethal yellow appear to alter a variety of structures and functions.