Showing papers in "Journal of Phycology in 1968"

Simple conditions for growth of unicellular blue‐green algae on plates

Abstract: The efficiencies of plating of 2 cultures of unicellular blue-green algae, 1 coccoid and 1 rod-shaped, were studied systematically. Reproducible colony growth and accurate viable counts are dependent on the use of a low agar concentration, and on the sterilization of the agar separately from the mineral components of the medium.

Some observations on the vertical migration ofdinoflagellates (1) (2).

Abstract: The technique of measuring chlorophyll concentration in vivo by fluorometric analysis has been adapted to studying the diurnal migration of dino-flagellates in the sea and also in a deep tank (3 m in diameter by 10 m deep). The downward migration of Ceratium furca was followed during a bloom off the California coast. The main band of cells migrated from the upper 2 m to a depth of 5 m about 2 hr after sunset, and was dispersed between 5 and 16 m 4.5 hr after sunset. Cultures of Gonyaulax polyedra and Cachonina niei both migrated to the surface of the deep lank during illumination and migrated downward during darkness at a rate of 1-2 mjhr. The downward migration was observed to begin before the light was turned off, indicating that migration is correlated with a cellular periodicity which is to some extent independent of the light regime. Further evidence for such a periodicity was afforded by observations that C. niei start to migrate up in the water column before start of the light period. Nitrogen-limited cells of G. polyedra showed no diurnal migration, but within 1 day after addition of a nitrogen source they recovered their full migratory ability. Cells of C. niei, however, continued to migrate during 5 days of N-starvation, although they did not concentrate in the upper 1/2 m as did the control cells.

On pigments, growth, and photosynthesis of phaeodactylum tricornutum(1) (2).

Abstract: SUMMARY A maximum growth rate with doubling time of 18 hr at 18 C could be maintained. Continuous cultures at about half maximum growth rate provided cells for study of pigments and photosynthesis. The light intensity curve of photosynthesis had no unusual features and showed light-saturated rates of 30-35 μl O2/mrn3-hr at 18 C. Pigment analysis showed chlorophylls a and c (a/c ratio = 4), fucoxanthin, β-carotene, and diadinoxanthin. Growth under red light (±660 mμ) altered pigments only by decrease in chlorophyll c to about one-half the content obtained under clear tungsten lamps. The large and anomalous spectral shift in fucoxanthin following organic solvent extraction runs confirmed, but efforts to isolate a native fucoxanthin were unsuccessful. Spectral analysis of acetone extracts and sonicated cell preparations allowed estimate of fractional absorption by each component pigment. The analysis shows that chlorophyll a and fucoxanthin are the principal light absorbing pigments and that absorption by other carotenoids is very small.

Uptake of nitrate and nitrite by ditylum brightwellii-kinetics and mechanisms(1) (2).

Abstract: Ditylum brightwellii grown on NO2 - as a nitrogen source took up and assimilated NO2 - only in the light, apparently via a photosynthetic nitrite reductase. Assimilation was inhibited by dichlorophenyldimethylurea (DCMU), KCN, partially by 2,4 dinitrophenol, and by NO3 -. Kinetics of inhibition of NO2 - assimilation by NO3 - appeared to be "competitive." D. brightwellii cells grown on NO2 - took up NO3 - in both light and dark and in both cases the uptake was inhibited by p-chloromercuribenzoate, but not by DCMU, KCN, or by NO2 -. Most of the NO3 - taken up in the dark was recovered unchanged from the cells. However only 40% of NO3 - taken up in light was recovered from the cells and no NO2 - was found. This suggests that a photosynthetic nitrate reduction mechanism was active in these cells. DCMU inhibited the light-induced NO3 - reduction. This mechanism of NO3 - reduction is distinct from that involving NADH nitrate reductase in D. brightwellii since the concentration of the latter enzyme is very low in cells grown on NO2 -. Saturation kinetics were observed for NO2 - and NO3 - uptake. Half-saturation concentrations (Ks values) were 4 and 2 μM, respectively. These values are compared with those obtained for NO2 - and NO3 - assimilation by other unicellular algae. The comparisons show lower Ks values in oceanic species compared with tide-pool or freshwater algae and they support the idea that Ks values for NO3 - assimilation may provide a key to understanding species succession when this is due to declining: nitrate concentrations in the sea.

The effect of growth environment on the physiology of algae: light intensity(1) (2).

Abstract: SUMMARY Measurements were made of growth, pigmentation, photosynthesis, respiration, quinone Hill reaction, cell morphology, and structure as a function of growth light intensity for various algae. These processes showed varying degrees of dependency upon light intensity and are discussed with reference to algal classification. Eighteen algae, examples from 10 taxonomic divisions, were studied.

Electron and phase-contrast microscopy of sexual reproduction in chlamydomonas moewusii(1).

Abstract: The sexual process of C. moewusii from gametic activation through germination of the zygote has been studied with phase-contrast and electron microscopy. Long strands emerging from the gametic flagellar tips are the site of early flagellar attraction which is followed by union of compatible flagella within common flagellar sheaths. The gametic connecting strand is formed by coordinated elongation of the plasma papillae of a gametic pair and the penetration of the former through their wall papillae while the flagella are in intimate association. After the free-swimming period, the gametic pairs aggregate in a second period of clumping. The connecting strand is abscised and extruded during plas-mogamy as are the flagellar basal bodies. Evidence is presented which suggests union of the gametic plastids, and stages in karyogamy are illustrated. Formation of the wall layers, accumulation of starch and lipids, and changes in plastid organization in the maturing and germinating zygote are described as is the formation of the gonal walls.

Ultrastructure of the thermophilic blue-green alga, synechococcus lividus copeland(1).

Abstract: The ultrastructure of Synechococcus lividus Copeland, a thermophilic blue-green alga, was studied in thin sections. The cell envelope reveals striking similarities with that of some gram-negative bacteria. In contrast to bacteria and to many other species of blue-green algae, ribosomes are predominantly found in the central nuclear region and appear to be associated with the DNA fibrils. Thylakoids (photo-synthetic lamellae) are arranged as concentric shells, around the nuclear equivalent, lying nearly parallel to one another and to the plasma membrane. Both plasma and thylakoidal membranes, as described by other authors for different Cyanophyceae, are of the unit membrane dimension and morphology. Various types of intracellular inclusions are found: (1) Lipid inclusions, located in the cytoplasm are similar to the osmiophilic globules of higher plant chloroplasts. (2) Polyphosphate inclusions (or volutin) resembling those of other species are generally found at the cell poles but within the nuclear region. (3) Polyhedral inclusions also located in the nuclear region are clearly recognized to be different from the polyphosphate bodies, but their function remains unknown.

Ultrastructure of porphyridium aerugineum a blue-green colored rhodophytan(1,2,3) .

Abstract: The ulstrastructural study on Porphyridium aerugineum showed vesicles in the peripheral cytoplasm which contain fibrous material similar in appearance to the cell sheath. In most respects the morphology of P. aerugineum, a freshwater form, is very similar to that of P. cruenturn, a marine species. However, there is a marked difference in the shape of the phycobilisomes which are attached to the chloroplast lamellae. In P. cruentum the phycobilisomes are always spherical or oblate, whereas in P. aerugineum they are disk shaped. The possibility is considered that the shape of the phycobilisomes may be determined by the phycoerythrin and phycocyanin content.

The behavior of oscillatoria terebriformis in hot springs(1).

Abstract: Oscillatoria terebriformis, occurring from 54 to about 35 C in eastern Oregon hot springs, forms dense reddish-brown surface mats which are held together by the interwoven nature of the trichomes and not by a gel-like matrix, thus retaining the flexibility inherent in free trichome motility. The trichomes demonstrate gliding, flexional, and contractile movements. When the trichomes are interconnected, the mat contracts or retracts essentially as a unit in response to high light intensity (ca. 100 cm/hr) or supraoptimal temperature (ca. 2 cm/hr). Under lower light intensity and optimal temperature, the mat expands by the gliding movements of individual trichomes (1-3 cm/hr). Probable positive and negative phototopotactic responses of trichomes to low and high light intensities, respectively, also influence the density of the surface mat. Thus, the population of Oscillatoria is able to adjust its position and density rapidly by migrations and contractions, remaining almost always within the full optimal temperature range and fairly well xuithin the optimal light conditions as well.

Detection of limiting or surplus nitrogen in algae and aquatic weeds(1).

Abstract: The rate of NH4 +-N absorption by algae and aquatic weeds in the dark has been shown to be 4-5 times greater for plants which are N-limited as compared to plants with sufficient available N. Eight species of green algae, 2 blue-green algae, 2 diatoms, and 3 aquatic weeds were used to demonstrate the usefulness of the test in determining if available N was in surplus or limited supply in a particular environment. The test was shown not to differentiate between blue-green algae capable of fixing N (4 species) from media with NO3 -N or without combined nitrogen. The factors influencing the results of NH4(+) -N absorption tests have been investigated. In order to differentiate between plants with sufficient available N and those which are N limited, the rate of NH4 (+) -N absorption (0.1 mg N) over 1-hr incubation in the dark by 10-20 mg of algae or aquatic weed tissues is measured. The relatively simple analysis for NH4 (+) -N in the samples makes it very easy to follow the changing N nutrition of plants in cultures with a limited N supply or in the presence of possible N sources.

Culture and heterotrophy of the freshwater dinoflagellate, peridinium cinctum fa. ovoplanum lindeman(1).

Abstract: A defined minimal medium was developed for an axenic strain of Peridinium (Indiana Culture No. LB 1336). Thiamine, biotin, and vitamin B12 did not stimulate growth. Of 15 organic carbon sources tried in light, fructose, galactose, glucose, malate, malonate, and pyruvate enhanced growth but propionate retarded growth. In dark-grown cultures only media with succinate permitted growth above the survival level. Stimulation of growth by organic carbon sources was markedly pH dependent.

Morphology and reproduction of the red alga acrochaetium pectinatum in culture(1) (2).

Abstract: The life history of the marine red alga Acrochaetium pectinatum (Kylin) Hamel was studied in unialgal culture using supplemented natural seawater media. The tetrasporophytes are larger than the gametophytes, have a compact filamentous basal system, and produce monosporangia and tetrasporangia. Mono-spores give rise to tetrasporophytes. Tetraspores develop into small gametophytes with unicellular bases. The gametophytes are heterothallic when small (usually less than 500 μ) but as some females become larger (2-3 mm) they produce spermatangia as well as carpogonia. Gametophytes may bear mono-sporangia in addition to carpogonia or spermatangia. These monospores give rise to gametophytes. Fertilization of the carpogonia has not been observed. The tetrasporophytes produce only monosporangia in day-lengths of 12-16 hr, but both tetrasporangia and monosporangia are formed in daylengths of 6-10 hr. Tetrasporangial production is reduced at 15 C compared with 10 C. Light intensity in the range of 5-200 ft-c (cool white fluorescent lighting) has no apparent influence on induction of tetrasporangia. Induction of tetrasporangia is not a photoperiodic response because their development is not inhibited by a brief light break in the middle of the dark period in short daylengths. Plastid morphology, origin, and frequency of sporangia and vegetative branching are variable during the ontogeny, and consequently are somewhat unreliable as taxonomic criteria. Differences in basal systems between gametophytes and tetrasporophytes also indicate that this feature, which is used to distinguish major subgeneric groupings in Acrochaetium, may not be as useful as previously thought.

Production of male gametes and auxospores in the centric diatoms cyclotella meneghiniana and c. cryptica(1) (2).

Abstract: SUMMARY Vegetative cells of Cyclotella meneghiniana Kutzing form male gametes and anxospores following transfer from a synthetic freshwater medium to a modified artificial seawater. Both spermatogenesis and auxospore formation are correlated with an increase in the Na+ concentration in the medium. Spermatogenesis can also be induced in C. cryptica Reimann, Lewin, and Guillard in artificial seawater with an adjusted sodium level.

Electron microscopy of the lichen physcza azpolia (ehrh.) nyl.(1,2).

Abstract: The ultrastructure of the lichen Physcia aipolia was studied in the desiccated and hydrated states. No significant structural variation between these 2 states was noted for the fungus. The fungus contains unusual ellipsoidal structures heretofore unobserved. Their possible role in the formation of membrane is discussed. The plasmalemma of the fungus is convoluted while that of the alga is smooth. The convoluted projections have a "double-unit membrane" structure similar to fingerlike projections of the ellipsoidal bodies. With Os O4 fixation crystals are pre-served, enclosed in unit membrane sacs which extend to the convoluted surface. The pyrenoid of the associated alga does not produce starch in the desiccated condition, and electron-dense granules are present in the matrix associated with chloroplast lamellae which enter this area. In the hydrated condition, the alga contains abundant starch in the pyrenoid region, and the electron-dense granules are displaced to the preriphery of the pyrenoid starch. Mitochondria, endo-plasmic reticulum, and ribosomes are not clearly defined in the desiccated state while they are more so in the hydrated condition. Golgi bodies were not observed in the either lichen component. Finally, no fine structural basis for indicating an exchanged of materials between the alga and fungus was observed except, possibly, the convoluted plasmalemma of the fungus and the smooth plasmalemma of the alga.

B12 specificity of marine centric diatoms(1, 2).

Abstract: 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).

Electron microscopic studies of extraplastidic astaxanthin in haematococcus(1) (2).

Abstract: The ketonic carotenoid astaxanthin accumulates in perinuclear cytoplasm characterized by a network of ribosome-coated endoplnsmic reticulum segments, free ribosomes, dictyosomes in active stages of vesicle formation, and mitochondria The pigment granules form in the ground substance and not within any organelle or vesicle Coalescence of the globular granules results from increasing quantities of astaxanthin formed as the cells age The gross differences in fixation image following glzitaraldehyde-KMnO4 and glutaraldehyde-Os O4 are illustrated, and the need for n variety of fixations upon which interpretations are bused is emphasized The bright red coloration of akinetes is due to a masking of the chlorophyll by the massive astaxnnthin deposits rather than m y break-down of the chloroplast thylakoids

Morphological variation in pterocladia pyramidale

Abstract: Seven Pacific species of Pterocladia and European collections of P. capillacea were examined. Ten morphological criteria were assessed in specimens of P. pyramiclale from 10 intertidal and subtidal populations in San Diego, California. The observations obtained from these populations were compared with descriptions and specimens of P. complanata from southern and Baja California; P. mexicana, P. robusta, P. okamurai, and P. okamurai f. densa from the Galapagos Islands and Baja California; and P. tenuis and P. densa from Japan. All these taxa were found conspecific with P. pyramidale. Pterocladia capillacea from Europe, using the same characters, was not distinct from the Pacific assemblage. These two taxa should be united under the name of Pterocladia capillacea (Gmelin) Bornet & Thuret (1876). Pterocladia capillacea (= P. pyramidale) grows under varied conditions and exhibits various growth forms accordingly, in southern California. Variation between several forms seems related to the degree of exposure to light, temperature, and surf action; such forms are recognizable in herbarium collections from other parts of the world. Abundant fertile material occurs in southern California.

Chloroplast development and ultrestructure in the freshwater red alga batrachospermum(1).

Abstract: Chloroplast development and ultrastructure of the freshwater red alga Batrachospermum moniliforme are described. Chloroplasts develop from proplastids which have a double-membraned chloroplast envelope and a parallel double-membraned outer photo-synthetic lamella. Of these 2 double-membraned structures of the proplastid, only the outermost pho-tosynthetic lamella functions in production of further lamellae. The mature chloroplast consists of 2 or more concentric lamellae and a variable number of nonconcentric lamellae. These lamellae are not dense, uninterrupted sheets as described for other red algae, but are largely constructed of tubules, lying side by side, that form interrupted lamellar sheets. The possible physiological significance of lamellar interruptions in providing path-ways for movement of materials in the chloroplast stroma is discussed.

Studies in some foliose red algae of the pacific coast. iii. dumontiaceae, weeksiaceae, kallymeniaceae(1).

Abstract: The female reproductive structures and their development, and the vegetative structure are studied in 17 species of red algae in the Cryptonemiales (Rhodophyceae). Three genera, Weeksia, Constantinea, and the type species of Leptocladia, are removed from the Dumontiaceae to a newly created family, the Weeksiaceae, because of differing postfertilization events leading to the development of the gonimoblast from a cell of the carpogonial branch. Three genera of Dumontiaceae are studied: Pikea, including P. californica, the type species, and Pikea robusta a newly described species; Dilsea californica, and a newly described species of Neodilsea, a genus heretofore known only from the northwestern Pacific. Two transfers are made from the genus Leptocladia, 1 to Farlowia, as F. conferta, and 1 to Rhodophyllis (Gigartinales) as R. peruviana. Three species in the Kallymeniaceae are redescribed: Kallymenia pacifica, a rare and nearly unknown species from southern California and adjacent Pacific Mexico; K. norrisii from central California; and K. oblongifructa from Washington, Oregon, and northern California.

Carotenoid pigments of the dinoflagellate glenodinium foliaceum stein(1) (2).

Abstract: The marine dinoflagellate, Glenoclinium foliaceum Stein, has been shown to contain fucoxanthin, instead of peridinin, as the major xanthophyll. In addition, 2 carotenes-β-carotene and a compound with spectral properties reminiscent of isomerized y-carotene-and 2 xanthophylls-diadinoxanthin and an unidentified compound-were also isolated. These results support an earlier work that indicated the possible presence of fucoxanthin in some members of the Pyrrophyta.

The carotenoids of four blue-green algae(1).

Abstract: The carotenoids of 4 species of blue-green algae, Anabaena variabilis, Phormidium persicinum, P. ectocarpi, and P. fragile, were investigated. In each, ft-carotene was a major pigment and the only carotene detected. The xanthophylls present in Anabaena variabilis were echinenone, canthaxanthin, and myxo-xanthophyll. Each of the Phormidium species contained zeaxanthin as the major xanthophyll. In each, this was accompanied by trace amounts of echinenone and isocryptoxanthin. In addition, 2 new xanthophylls, spectrally resembling ^-carotene, were found in Phormidium persicinum and P. ectocarpi, while another, with a spectrum similar to that of myxoxanthophyll, was found in P. fragile.

Studies At Oyster Bay In Jamaica, West Indies. Iv. Observations On The Morphology And Asexual Cycle Of Pyrodinium Bahamense Plate(1) (2)

Abstract: The morphology and asexual cycle of the luminescent armoured dinoflagellate, Pyrodinium bahamense Plate, were examined in situ and in vitro. Several previously unreported aspects of the cycle are described. Attempts to induce the formation of these alternate life stages by imposing new conditions were unsuccessful.

Observations on the fine structure of oedogonium. v. evidence for the de novo formation of pyrenoids in zoospores of oe. cardiacum(1) (2) (3).

Abstract: Ultrastructural studies of the chloroplasts of zoospores and developing zoospores of Oedogonium carcliacum have disclosed the occurrence of numerous incipient pyrenoids. A single developing zoospore may possess several score of these structures which appear to arise de novo in the chloroplast stroma and seem to lack any direct association with mature pyrenoids which are also present in the cells. The incipient pyrenoids lack the associated starch grains and the membrane-limited channels characteristic of mature pyrenoids, but they are readily recognized in the chloroplasts since they demonstrate a greater granularity and electron density than the surrounding chloroplast stroma. The granularity and electron density of the incipient pyrenoids match the ultra-structural appearance of the matrix of mature pyrenoids. The smallest of the incipient pyrenoids examined from serial sections had a maximum diameter of less than 0.3 μ. This may be compared with the size of mature pyrenoids, many with a maximum diameter of over 5.0 μ. In all the zoospores and developing zoospores examined, only one mature pyrenoid was observed in an apparent stage of division.

Ultrastructure of spongiochloris typica during senescence(1) (2).

Abstract: The ultrastructural changes which occurred during senescence in the stationary phase of growth of the unicellular green alga Spongiochloris typica were observed. The cell wall consists of a membrane like primary wall and an inner secondary wall which becomes progressively thickened with age of the culture. During senescence the lamellae become more compact within the chloroplast. The major feature of aging is the appearance of lipid bodies which eventually come to occupy a major portion of the cell lumen. The ultrastructural changes observed to occur during senescence are discussed in relation to physiological data.

Control of colony and unicell formation in a synchronized scenedesmus(1) (2).

Abstract: Colony formation in a synchronized Scenedesmus could be controlled by the addition of 0.05% Na3 citrate or 85 μM EDTA to modified Bristol's medium. No unicells were formed; only S. quadricauda-like or S. longispina-type colonies were observed in young cultures grown in that medium. A colony population could be made completely unicellular in 2 days if grown in soil-Bristol's medium and transferred daily. The pleomorphic Scenedesmus was examined in synchronized culture. When the organism was grown in a defined medium in a 15-hr light /9-hr dark cycle on a roller tube rotator at 2-6 rpm and transferred daily, synchrony of cell division and release of the products were achieved. In a synchronized culture 2 doublings/day were recorded, with most cytoplasmic cleavages and all releasing of daughter cells taking place in the dark period. In many observations with several synchronized strains of Scenedesmus, no fixed pattern of release of daughter products from mother cells or colonies was detected. Colonies or unicells had their full spine complement at the time of release. As a cell or colony aged the spines sometimes increased in thickness. Other Scenedesmus strains were examined to provide supporting data.

An ultrastructural study of vegetative cell division in oedogonium borisianum12

Abstract: SUMMARY Vegetative cell division in Oedogonium borisianum is initiated by the formation of a 3-layered ring adjacent to the wall in the upper portion of the cell. This structure enlarges by the coalescence of vesicles. When the ring is fully developed, the parent wall splits adjacent to the ring, and the ring expands into a cylinder, which becomes the cuticle of the upper daughter cell. The lateral wall then forms between this cuticle and the plasmalemma of the cell. Concurrent with ring development and expansion, the nucleus migrates to a position in the center of the cell and karyokinesis occurs. Commencing with late telophase, evidence of transverse wall formation becomes apparent. The zone between the daughter nuclei contains a layer of microtubules in a plane parallel to the plane in which the transverse wall will develop. Subsequently a random coalescence of vesicles occurs along this plane. During the latter stages of this process, the ring expands and the plane of the transverse wall moves upward to the base of the ring cylinder. The completed transverse wall then fuses at is periphery with the newly formed lateral wall.

Unialgal cultures of cladophora glomerata (l.) kütz.(1) (2) : i. response to temperature.

Abstract: Unialgal cultures of Cladophora glomerata (L.) Kutz. grew with increasing vigor at temperatures between 15 and 30 C. Vegetative cells were killed upon freezing or when exposed to temperatures above 30 C. No growth occurred at 5 C and only slight growth was observed at 10 C. Effects of near lethal temperature on C. glomerata were dependent upon the duration of exposure in addition to the actual temperature attained. The response of this alga to various temperatures under culture conditions is in accord with tolerance limits established for naturally occurring populations. It seems probable that the annual periodicity of C. glomerata is regulated in large measure by seasonal variations in water temperature, greatest abundance coinciding with water temperatures between 15 and 30 C.

New species of halimeda: a taxonomic reappraisal(1) (2).

Abstract: A study of new Halimeda material available from the International Indian Ocean Expedition, and of type and other specimens not previously available to me, further indicated that Halimeda opuntia is a composite of species rather than a single species. The characteristics of some of its infraspecific taxa differ sufficiently from typical H. opuntia that I have elevated them to species. Extended diagnoses of three, H. hederacea, H. minima, and H. distorta, are given in this paper. Some characteristics new in Halimeda taxonomy are introduced, and distinguishing macroscopic and microscopic characteristics for the new species are discussed. Available ecological data are included.

Taxonomic confusion concerning certain filamentous blue-green algae(1).

Abstract: Throughout a long history many filamentous bacteria may have been identified in natural collections as blue-green algae. This problem has been especially acute regarding the thermophilic species of hot springs, especially at the higher temperatures. It is suggested that in the absence of pure cultures, the minimal criteria for distinguishing filamentous bacteria from blue-green algae microscopically should be: (1) observation of the chlorophyll fluorescence with a fluorescent microscope and (2) demonstration of light-dependent (14) CO2 fixation autoradiographically. Pure cultures of a number of filamentous thermophiles have been obtained from habitats at temperatures above 60 C. These cultures resemble microscopically the natural material, grow only heterot rophically, and do not contain chlorophyll.

Axilosphaera and heterotetracystis, new chlorosphaeracean genera from tennessee soil(1) (2).

Abstract: Two new chlorosphaeracean genera were isolated into axenic culture from soil collected in cedar glades in Cedars of Lebanon State Forest, Wilson County, Tennessee. The distinguishing characteristics of the new monotypic genus Axilosphaera include an axile (asymmetric) ckloroplast with at least 1 pyrenoid and Chlamydomonas-type (walled) zoospores. A. vegetata is the type species. Reproduction is by dissociation of daughter cells following vegetative cell division, by zoospores, and by aplanospores. The new polytypic genus Heterotetracystis, comprising 3 species, H. akinetos, H. macrogranulosa, and H. intermedia, is characterized by a parietal chloroplast with at least 1 pyrenoid and walled zoospores with flagella of unequal length. Reproduction is by dissociation of daughter cells following vegetative cell division and by zoospores. H. akinetos is designated as the type species.