Use of a deviant mitochondrial genetic code in yellow-green algae as a landmark for segregating members within the phylum

Several algae that were previously classified in the phylum Xanthophyta (yellow-green algae) were assigned in 1971 to a new phylum, Eustigmatophyta. It was anticipated that the number of algae reclassified to Eustigmatophyta would increase. However, due to the fact that the morphological characteristics that segregate eustigmatophytes from other closely related algae can be only obtained through laborious electron microscopic techniques, the number of members in this phylum have increased rather slowly. We attempted, therefore, to segregate two closely related groups of algae, eustigmatophytes and yellow-green algae, on the basis of a molecular phylogenetic tree as a means of providing an alternative method of distinguishing these phyla. We analyzed the mitochondrial cytochrome oxidase subunit I (COXI) gene sequences of eight algae classified as xanthophyceans and found that six manifested the expected deviant genetic code where AUA codes for methionine (AUA/Met), but not for isoleucine (AUA/Ile) as in the universal genetic code. The other two, Monodus sp. (CCMP 505) and Ophiocytium majus (CCAP 855/1), which were presumed to be yellow-green algae, and all the examined eustigmatophytes utilized AUA for Ile. In addition, the phylogenetic tree of COXI gene sequences showed that the six yellow-green algae bearing the AUA/Met deviant code composed a tight clade with a bootstrap value of 100%. The phylogenetic tree of the corresponding sequences from Monodus sp. and Ophiocytium majus and the eustigmatophytes also composed a tight cluster, but with a bootstrap value of 92%. These results strongly suggest that two previously classified members of yellow-green algae belong to the phylum Eustigmatophyta. Therefore, examination of the mitochondrial genetic code in algae appears to be a potentially very useful genetic marker for classifying these organisms, especially when it is considered with the results obtained through a molecular phylogenetic tree. Received: 14 December 1996 / Accepted: 3 April 1997     

COMPARATIVE STUDIES OF PHOTOCHEMICAL OXIDATION-REDUCTION REACTIONS IN LAMELLAR FRAGMENTS OF VARIOUS ALGAE AND SPINACH

The activity of various electron carriers, including DPIP, spinachplastocyanin, mammalian cytochrome c, and Anabaena cytochrome553, as donor in the reaction induced by the photochemical systemI was examined with lamellar fragments of various algae andspinach. Reduced DPIP was an effective electron donor irrespective ofthe organisms, when it was supplied at a high concentration(10^–3 M). Spinach plastocyanin was effective in the reactionswith the lamellae of green algae, Euglena, diatom Phaeodactyrumand red algae Porphyra yezoensis and Porphyra sp. Yamamoto II,whereas it was inactive in the lamellae of blue-green algae.Horse-heart cytochrome c and Anabaena cytochrome 553 were activein the reaction with the lamellae of bluegreen algae. The formercytochrome was also active in the reactions in Porphyridiumand Cyanidium. The cytochromes were less active in the reactionsin which spinach plastocyanin acted as effective electron donor. The data were interpreted as that the photochemical system Iin bluegreen algae differs from that of other photosyntheticorganisms with respect to the properties of the site of theelectron-input. ¹ Present address: Nomura Research Institute for Technologyand Economics, Kamakura, Kanagawa. ² Present address: Ocean Research Institute, University of Tokyo,Nakano, Tokyo.     

A Membrane-like Structure on the Pollen Wall Surface in Brassica

In the mature Brassica pollen grain, the outermost wall layer,the exine, is surrounded by a trilamellar structure which presentssome of the morphological, cytochemical, enzymological and physico-chemicalcharacteristics of a biological membrane. This structure, designatedthe exinic outer layer (EOL), has been visualized and partiallycharacterized by electron microscope techniques. Its possibleinvolvement in the male-female recognition reaction is discussed. Brassica spp., pollen grain, exine surface, membrane-like structure, male-female recognition, electron microscopy     

A Yellow Marine Chiamydomonas: Morphology and Pigment Composition

A unicellular yellow marine microorganism was isolated fromwater samples collected in Hachinohe Harbor, on the northerncoast of Japan, and Off Tsushima Island, on the western coastof Japan, and its structure and pigment composition were investigated.Light and electron microscopy indicated that the alga belongsto the genus Chlamydomonas and it is identified as C. parkeae. Pigment analysis by high-performance liquid chromatography revealedthe presence of 2,4-divinylprotochlorophyllide (DVP) as a thirdchlorophyll in addition to chlorophylls a and b. Such a pigmentcomposition has been reported previously only for some prasinophytesamong autotrophically grown algae. With respect to carotenoids,the alga contains, in addition to the carotenoids of higherplants (neoxanthin, violaxanthin, zeaxanthin, lutein, ß-carotene),siphonaxanthin and siphonein (siphonaxanthin dodecenoate); thelatter have been detected previously only in marine benthiculvophycean algae and in some prasinophytes. However, the coexistenceof DVP, siphonein and siphonaxanthin in a single species hasnever been reported for either ulvophycean or prasinophyceanalgae. In addition to siphonaxanthin dodecenoate, the alga wasfound to contain two "siphoneins", siphonaxanthin decenate andsiphonaxanthin octanoate. ³ Present address: Nippon Roche Research Center, Kajiwara, Kamakura,Kanagawa, 247 Japan.     

The chloroplast pigments of some green and yellow-green algae

Pigment analysis carried out by thin-layer chromatography confirms that Chlorocloster engadinensis Vischer, C. solani George and Nephrodiella brevis Vischer are all green algae (Chlorophyceae) and not yellow-green algae (Xanthophyceae) as has been suggested. The pigments of Coccomyxa elongata Jaag, C. simplex (Pringsheim) Mainx and Pyrobotrys stellata Korshikov are also typical of green algae. The pigments of Pleurochloris commutata Pascher, P. magna Boye Petersen, Polyedriella helvetica Vischer et Pascher, Mischococcus sphaerocephalus Vischer and Tribonema aequale Pascher, are different to those of the green algae in accordance with their being classified as yellow-green algae. However, a detailed comparison of the pigments of Pleurochloris and Tribonema suggests that whilst both contain chlorophyll, α, β-carotene and esterified vaucheriaxanthin, the major xanthophyll in Pleurochloris corresponds to violaxanthin and not to antheraxanthin as in Tribonema.     

Zoospore Structure and Colony Formation in Pediastrum Spp. and Hydrodictyon reticulatum (L.) Langerheim

The process of daughter colony formation in Pediastrum biradiatumMeyen, P. tetras (Ehren-berg) Ralfs, P. duplex Meyen, and Hydrodictyonreticulatum (L.) Lagerheim has been investigated using lightmicroscopy and electron microscopy of thin sections. The precisedisposition of the organelles confers upon the zoospores ofthese algae a special symmetry of a type unusual for the Chlorophyta.Apart from this, the detailed ultrastructure of the zoosporeand young vegetative cells resembles that of other green algaepreviously investigated. A common sequence of events has beenfound to occur during colony formation in both Pediastrum andHydrodictyon, with a correlation between zoospore symmetry andthat of the colony produced. The changes involved in the transitionfrom a motile to a non-motile cell are considered, and appearto have features in common with this process in some other greenalgae. The early stages in wall deposition involve the simultaneousformation of two distinct layers and serve to stick togetherthe cells which by this time have collectively assumed the basicmorphological characteristics of the mature coenobia.     

Ultrastructure of Angiosperm Haustoria--A Review

It has been clear for many years that the evolution of parasitismin the angiosperms has taken place independently in a numberof unrelated groups (Kuijt, 1969). In other words, the parasiticorgans (haustoria) which both structurally and physiologicallyjoin host and parasite are remarkable instances of convergentevolution in these different groups. The main thread which canbe followed throughout the many anatomical studies which inthe past have been carried out on haustoria is the search forcommon denominators between various groups; that is, as to howmuch the haustoria of unrelated taxa have come to resemble eachother. When Solms-Laubach (1867–1868) more than a century agoreviewed the structure of angiosperm haustoria it required wellover one hundred pages to do so. Needless to say the bulk ofour present knowledge has been obtained since that time, andlight microscopy continues to unearth significant new information.In a recent review of haustorial anatomy (Kuijt, 1969), severalstructural parallelisms are noted. The advent of electron microscopyhas, since the latter review, resulted in a great deal of additionalinformation which has enabled certain comparisons between groupsto be made. Ultrastructural studies have quite naturally concentratedon the most readily available which, of course, are also thosewhich have been most i ntensively studied with the light microscopein the past. The haustoria of several families, such as Rafflesiaceae,Balanophoraceae, Hydnoraceae, and Lennoaceae, have scarcelybeen studied even with the light microscope. The purpose of the present paper is to give a general reviewof present knowledge of the ultrastructure of haustoria. Todo so we must of necessity ignore most recent purely anatomicalwork, except where relevant to the topics under discussion.Ultrastructural observations have been made on mistletoes (Arceuthobiumand Phthirusa, Loranthaceae), Santalaceae (several genera),Scrophulariaceae(Castilleja), Orobanchaceae (Orobanche) andConvolvulaccae (Cuscuta), in which order the discussion willproceed.     

The Effect of Available Nitrate and Ammonium-Nitrogen on the Growth of Two Nitrogen-Fixing Blue-Green Algae

The effect of combined nitrogen supplied as nitrate or ammonium-nitrogenon the growth of two nitrogen-fixing blue-green algae, Nostocentophytum and Calothrix scopulorum, has been studied. Thesespecies have been isolated from marine environments. Both algaegrew as vigorously on elemental nitrogen as in the presenceof combined nitrogen. Growth was equal at all levels of nitrate-nitrogenemployed but high levels of ammonium-nitrogen proved inhibitoryor even toxic to the algae. Nostoc was slightly more susceptibleto high ammonium-nitrogen levels than was Calothrix. Increasein pH of the medium from 7.2 to 8.4 increased the toxic effectof ammonium-nitrogen although relative growth at the variouslevels of nitrate-nitrogen was not affected. The results suggestthat the different effects of ammonium-nitrogen on the growthof freshwater and marine blue-green algae may be due in partat least to the different pH levels of freshwater and marineenvironments in which the algae grow, rather than to any inherentdifference between the two groups.     

中国萤火虫云南窗萤荧光素酶cDNA的克隆表达和序列分析(英文）

从一种来自中国日行性萤火虫（云南窗萤）发光器官mRNA中克隆、测序并表达了有功能的荧光素酶。云南窗萤荧光素酶的cDNA序列有1 647个碱基,编码548个氨基酸残基。从推测得到的氨基酸序列的比对分析得出：云南窗萤的荧光素酶与来自Lampyris noctiluca, L. turkestanicus和Nyctophila cf. caucasica三种萤火虫的荧光素酶有97.8%的序列一致性。从推测得出的氨基酸序列进行系统发育分析,其结果表明：云南窗萤和Lampyris+Nyctophila聚在一起, 与同属的发光强夜行性的萤火虫不形成的单系。云南窗萤荧光素酶在大肠杆菌中表达的条带大约70 kDa,并且在有荧光素存在时发出黄绿色荧光。对荧光素酶的结构模拟和分析表明,云南窗萤荧光素酶基因的氨基端和羧基端结构域之间的裂沟处存在这5个多肽环,这正是从其他荧光素酶推测得到的催化荧光反应时的底物结合位点。云南窗萤和窗萤属的其他3种萤火虫的荧光素酶相比,有13个不同氨基酸位点,位于模拟分子结构的表面。对于这些多肽环、不同氨基酸残基和晶体结构的进一步研究有利于解释日行和夜行性萤火虫荧光素酶的差异。     

Successional dynamics of the phytoplankton in the lower part of the river Ebro

The temporal and spatial dynamics of phytoplankton have beenstudied in four sites located along the last 60 km of the riverEbro, over a period of 1 year. Diatoms and green algae werethe most abundant groups; blue-green algae were frequent onlyin autumn. Asterionella formosa dominated the winter phytoplanktonassemblages. In autumn, spring and early summer centric diatomswere dominant: Aulacoseira granulata (Ehr.) Simonsen in autunm;Cyclotella sp. p1., Skeletonema potamos (Weber) Hasle and StephanodisciLssp. p1. in spring. A great abundance of green algae was observedduring the summer, mainly in the lower sites. In the sites closerto the mouth, the spring maximum of centric diatoms extendedto the summer. Mainly in the downstream sites, a remarkablegrowth of Acrinocyclus normanii f. subsalsa (Juhl.-Daunf.) Hustedtand Stephanodiscus hantzschii f tenuis (Hust.) Hak. & Stoerm.was added to green algae in the late summer. As has been investigatedthrough a principal component analysis, the phytoplankton temporalsuccession and longitudinal differences between the sites maybe affected by the variations in flow and the increase of waterconductivity downstream; both factors seem to act together.The river is rather homogeneous with respect to the phytoplanktonassemblages during the winter and spring months, and from latespring to the following autumn, differences greatly increaseboth in time and downstream.     

Electron Microscope Observations on the Zoospores of Pylaiella and Laminaria

The zoospores of Laminaria saccharina and Pylaiella litoralishave both been shown to possess a hairy front flagellum (Flimmergeissel).In both cases this is longer than the smooth hind flagellum.There is no proboscis. In Pylaiella it has been shown that thehairs are in two rows on the front flagellum and that they arisein pairs except at the extreme front end. Each hair has a jointedstructure and consists of a thicker basal portion which passesabruptly into a thin distal portion. There are signs of a loosetransparent skin covering the axis of the flagellum betweenthe rows of hairs. The axis has also been shown to be fibrillarin construction and to be capable of decomposing into elevenstrands, two of which are central. There is perhaps an intercalarymaterial in the axis in addition to the component fibrils.     

Further Observations with the Electron Microscope on Spermatozoids in the Brown Algae

Observations are recorded for Ascophyllum, Pelvetia, Himanthalia,and Dictyota in addition to Fucus which has already been describedin a previous paper. Fibrillar disintegration of cilia has beenobtained in all except Pelvetia, in each case to give nine peripheralstrands and a central pair. This corrects a previous error forthe hind flagellum of Fucus. Some facts are given regardingthe internal organs associated with the parts of the cilia insidethe body in Himanthalia and Dictyota. A proboscis similar tothat previously described for Fucus has been demohstrated inAscophyllum and Pelvetia, but is absent from Himanthalia andDictyota. Himanthalia differs from the other Fucoids in therelative lengths of front and hind flagella. Dictyota has onlya single flagellum. In all, the front flagellum is a Flimmergeisselwith two rows of hairs, which, in certain cases, notably Himanthalia;have very long hair points. In Himanthalia there is a largespine near the distal end of the front flagellum borne on onefibril of the peripheral series. In Dictyota there is a rowof smaller spines at the front end of the flagellum borne ina line between the two lateral rows of hairs. These spines inDictyot can be used as evidence regarding the internal symmetryof the whole cilium which is summarized in a diagram.     

Three-dimensional structures of the human α2-macroglobulin-methylamine and chymotrypsin complexes

The three-dimensional structures of chymotrypsin- and methylamine-treated negatively stained human α₂-macroglobulin have been determined by weighted back projection from electron microscope data. Projections of the reconstructions show good concordance with two-dimensional averages of both stained and frozen-hydrated molecules. The reconstructions reveal that the H-shaped front projection of the molecule is related to the smaller ellipsoidal end view by a rotation of 90° about the crossbar (minor axis) of the H. This finding is in agreement with tilt studies. The reconstruction of the α₂-macroglobulin-methylamine reveals an hour-glass shaped void which is filled by the two proteinase molecules in the reconstruction of α₂-macroglobulin-chymotrypsin. Protein plugs which appear to block the exterior entrances to the cavity may function to prevent access of proteins to the encapsulated proteinase and serve to block its escape. Extensive thresholding of each reconstruction leaves a “backbone” consisting of two side-by-side rod-like structures, suggesting that this is the arrangement of the two protomeric units which form the molecule. Both structures show some departure from the expected symmetry. The asymmetries are robust features of the reconstructions and may reflect structurally asymmetric features of the transformation from the native to the chymotrypsin-treated form of the molecule.     

Predation by ciliates on a metalimnetic Cryptomonas population: feeding rates, impact and effects of vertical migration

Deep algal maxima are frequently overlayed by dense populationsof ciliates, rotifers and crustaceans. This has been interpretedas evidence of heavy predation on the algae, although the impactof this predation has never been determined experimentally.We determined the vertical and seasonal distribution of thealga Cryptomonas phaseolus and its most relevant predators,the ciliates Coleps sp. and Prorodon sp., forming metalimneticmaxima in Lake Cisó. On several dates, in situ feedingrates of ciliates were determined by three independent methods:(i) epifluorescence counts of ingested algal cells togetherwith estimates of the food turnover time of the ciliates; (ii)in situ incubations with radioactively labeled algae: (iii)HPLC determination of alloxanthine content in the predator sizefraction. Feeding rates varied between 0.07 and 0.64 Cryptomonasciliate^–1 h^–1. We then calculated integrated predationon the algae. using the functional response of the ciliatesand the vertical distribution of each population. We found thateven though the ciliates were always food saturated, their predationimpact on Cryptomonas was not very large: as an average, 5–25%of the biomass of Cryptomonas was removed daily by the ciliates.Finally, we studied the effects of the diel vertical movementsof these populations on predation impact. By migrating intothe sulfide-rich hypolimnion during the night, Cryptomonas couldreduce its predation losses by 38%. Thus, the algae were protectedfrom predation during several hours of each diel cycle and maintaineda very large biomass throughout stratification, although thisresulted in a very slow growth. Slow growth, coupled to largebiomass, seems to be a general feature of metalimnetic accumulationsof organisms.     

Differences of the primer-independent phosphorylase isozyme in thermophilic and mesophilic algae

Kinetic studies of the primer-independent, aa phosphorylaseisozyme of two thermophilic algae, Cyanidium caldarium and Oscillatoriaprinceps, and two mesophilic algae, Spirogyra setiformis andChlorella pyrenoidosa, indicate that the isozyme of thermophilicspecies is more resistant to denaturation by heat, and has lessaffinity for the glucose-1-phosphate substrate than the sameisozyme of mesophilic algae. This points out the possibilitythat this enzyme's structure is more rigid in thermophiles andmay lack the flexible conformation found in the mesophilic isozyme.The evolutionary significance of thermophily as a primitivecharacter rather than an adaptive trait is discussed in thelight of studies with a low temperature variant strain of thethermophilic alga, Oscillatoria princeps, LTV. (Received November 15, 1972; )     

Observations on the Life History of the Haptophycean Alga Pleurochrysis scherffelii with Special Reference to the Microanatomy of the Different Types of Motile Cells

The coccolith-bearing phase of Pleurochrysis scherffelii hasbeen examined with the electron microscope for the first time.Coccolith and scale structure, haptonema morphology, and themicroanatomy of the protoplast have been recorded and shownto agree closely with those of Hymenomonas carterae and theHymenomonas stage of Apistonema previously investigated by thepresent author. Comparative observations have been made on thevegetative phase and non-coccolith-bearing swarmers of Pleurochrysisscherffelii and these differ significantly in scale morphologyfrom the coccolith-bearing phase although the haptonema of theswarmers is similar. Certain developmental observations havebeen included in the investigation and the taxonomic significanceof the findings is discussed in a preliminary way.     

Structure and protein distribution for the capsid of Caulobacter crescentus bacteriophage phiCbK

Electron microscope images of negatively stained empty capsids of Caulobacter crescentus bacteriophage φCbK have been analyzed by computer Fourier methods. Two-dimensional computer density maps for the distribution of material in the capsid wall have been obtained by computer Fourier filtering which made possible the complete separation of contributions from the front and back of the capsid including overlapping Fourier coefficients. After scaling for the capsid thickness, using a one-dimensional reconstruction of data from edge-on views of the capsid wall and using topographical information provided by low-angle metal shadowing, a three-dimensional density distribution has been derived. A model for the distribution of subunits in the capsid is proposed which places each of the two major capsid subunit proteins (which are present in a 2:1 ratio) in quasi-equivalent bonding environments. A tentative model is presented in which assembly of the capsid (an elongated T = 7l icosadeltahedron) is regulated by the bonding geometry of the penton proteins.     

Endosymbiosis in Hydra and the Evolution of Internal Defense System

Certain species of Chlorella have exploited an intracellularhabitat and occur naturally as cytobionts in Hydra viridissima.The algae evoke phagocytosis by Hydra digestive cells and aresequestered in individual phagosomes that migrate to the baseof the host cells and resist fusion with lysosomes. The abilityto resist digestion is closely correlated with release of extracellularcarbohydrate (maltose) by the algae. The established populationof algae grows at an average rate equal to or greater than thatof the host and a constant population density is maintained.The host regulates algal population density by expelling ordigesting excess algae, or by controlling algal cell division.The control mechanism is unknown but can be breached by additionof inorganic ions to the Hydra culture medium with the resultthat the algae overgrow the Hydra. The Hydra-Chlorella symbiosis is probably mutually beneficial,but conditions such as prolonged darkness (with or without feeding)can reduce the competitive fitness of the host since this conditionresults in heterotrophy by the algae at the expense of selectedhost substrates. The evolution of selective permeability toorganic substrates is a major feature of the successful colonizationof the intracellular habitat by symbiotic Chlorella.     

Scanning electron microscope study and computer analysis of taxonomic distances of the marine Podonidae (Cladocera)

The different theories about the taxonomic position of Europeanmarine Cladocera have been confronted with the results of comparativeinvestigations performed with scanning electron microscope andmathematical clustering analysis. It appears that both genera,Evadne and Podon, including the six species of Podonidae, haveto be considered as valid. ^*Research Assistant at the National Fund for Scientific Research.     

Quantitative relationship between two reaction centersin the photosynthetic system of blue-green algae

The quantitative relationship between reaction centers I andII was studied with blue-green algae Anabaena cylindrica, Anabaenavariabilis and Anacystis nidulans grown under different lightconditions. The number of reaction centers I was estimated fromthe P700 content and that of reaction centers II, from the O₂yield of repetitive short flashes. Supplementary determinationswere done with three other blue-green algae and one red alga.The maximum number of reaction centers II counted from the O₂yield of repetitive short flashes was markedly smaller thanthe total number of P700 in all algae tested when the algaewere grown under weak light; in the extreme case (Anabaena cylindrica),the ratio was only 0.258?0.015. This ratio became larger andclose to unity when the algae were grown under stronger light.Variation in the number of reaction centers in a single cellsuggested that reaction center I was a variable component. Ourresults indicate that the proportion of the two reaction centersmay markedly vary in blue-green algae depending on the growthconditions (Received November 13, 1978; )