Paul W. Johnson

IN-SITU MORPHOLOGY AND OCCURRENCE OF EUCARYOTIC PHOTOTROPHS OF BACTERIAL SIZE IN THE PICOPLANKTON OF ESTUARINE AND OCEANIC WATERS1

Concentrates of the picoplankton (0.2–2.0 μm) sized fraction from the euphotic zone of estuarine and oceanic waters were examined by transmission electron microscopy. In addition to the numerous phototrophic procaryotes (chroococcoid cyanobacteria) previously reported, small phototrophic eucaryotes were observed in 20 of 25 samples examined. Micromonas pusilla (Butcher) Manton and Parks, a 1 × 1.5 μm flagellate, was abundant in estuarine samples in summer. Similar sized cells of non‐flagellated chlorophytes, either Nannochloris Naumann or Chlorella Beijerinck, were observed sporadically in many samples. The most ubiquitous microalga was a scaled, non‐flagellated prasinophyte that occurred at 9 of 15 different locations on 15 of 20 sampling dates in water samples from Iceland to the Caribbean Sea, This tiny alga (0.5 to 1.0 μm in diam.) is probably the smallest known photo‐trophic eucaryote and has not heretofore been described. Enrichment cultures using conventional techniques on several cruises yielded only the Chlorella‐type of green alga, as well as numerous isolates of unicellular chroococcoid cyanobacteria.

Ultrastructure and ecology of Aureococcus anophagefferens gen. et sp. nov. (Chrysophyceae): the dominant picoplankter during a bloom in Narragansett Bay, Rhode Island, summer 1985

Observations of a marked cessation of feeding in filter feeding animals maintained in flowing Narragansett Bay seawater in June 1985 drew our attention to a bloom of a golden alga 2 μm in diameter at unprecedented populations of 109 cells. L−1. This picoplankter lacked morphological features useful in discriminating it from other similar sized forms with either phase contrast or epifluorescence light microscopy. Natural populations of picoplankton, obtained from the height of the bloom until its decline, were examined in thin section with transmission electron microscopy. A cell with a single chloroplast, nucleus, and mitochondrion and an unusual exocellular polysaccharide‐like layer was apparently the bloom alga. The ultrastructure of this alga is consistent with that of the Chrysophyceae, and a new genus and species, Aureococcus anophagefferens is described.

Dissolved Organic Matter and Heterotrophic Microneuston in the Surface Microlayers of the North Atlantic

Dissolved organic carbon, carbohydrates, and adenosine triphosphate in the size fractions 0.2 to 3 micrometers and 3 to 1000 micrometers are significantly enriched in the upper 150-micrometer surface layer compared to subsurface water, mean enrichment factors being 1.6, 2.0, 2.5, and 3.1, respectively. When calculated as a 0.1-micrometer microlayer of wet surfactants, the mean concentration of organic matter was 2.9 grams per liter, of which carbohydrates accounted for 28 percent. The data for plant pigments and particulate adenosine triphosphate indicated that bacterioneuston was enriched at seven of nine stations while phagotrophic protists were enriched at five stations. Instances of enrichment and inhibition were verified by cultural data for bacteria and amoebas. The observations indicate that the surface microlayers are largely heterotrophic microcosms, which can be as rich as laboratory cultures, and that an appreciable part of the dissolved organic carbon is carbohydrate of phytoplankton origin, released and brought to the surface by migrating and excreting phagotrophic protists.

The first methane-oxidizing bacterium from the upper mixing layer of the deep ocean:Methylomonas pelagica sp. nov.

Methane enrichment of twenty-three 100-ml portions of seawater from three stations in the Sargasso Sea yielded the same obligate type I methanotroph. It is pigmented white, requires NaCl, grows well in seawater with either methane or methanol, but not on other C1 compounds nor on C−C bonded organic matter, and it uses either ammonia or nitrate but not dinitrogen as a nitrogen source. Formaldehyde is produced in marked amounts from methanol. Growth occurs at 20° and 30°C but not at 10°C and is inhibited in natural sunlight. Representative isolates from each hydrographic station assimilate one-carbon units via the ribulose monophosphate pathway for formaldehyde fixation, and have a DNA base composition of 49 mol% guanine plus cytosine. The type strain, NCMB 2265, has been namedMethylomonas pelagica sp. nov. This upper ocean methanotroph may obtain its C1 substrates in situ from particles of algal debris that become anoxic, ferment, and accumulate in the thermocline to form a false benthos.

DESCRIPTION AND CHARACTERIZATION OF THE ALGAL SPECIES AUREOUMBRA LAGUNENSIS GEN. ET SP. NOV. AND REFERRAL OF AUREOUMBRA AND AUREOCOCCUS TO THE PELAGOPHYCEAE1

The Texas brown tide alga (strain TBA‐2) is described as Aureoumbra lagunensis Stockwell, DeYoe, Hargraves, et Johnson, gen. et sp. nov. Pigment composition, chloroplast structure, and 18s ribosomal RNA gene sequence data indicate that A. lagunensis and the east coast brown tide alga Aureococcus anophagefferens (originally placed in the Chrysophyceae) belong in the class Pelagophyceae. The new genus Aureoumbra with A. lagunensis as the type species differs from Aureococcus in 18s ribosomal RNA gene sequence, pyrenoid form, nitrogen physiology, and possession of basal bodies. The genus Aureococcus is placed in the order Pelagomonadates and family Pelagomonadaceae while ordinal placement of Aureoumbra is deferred.

Ultrastructure and Ecology of Perispira ovum (Ciliophora: Litostomatea): An Aerobic, Planktonic Ciliate that Sequesters the Chloroplasts, Mitochondria, and Paramylon of Euglena proxima in a Micro‐oxic Habitat

ABSTRACT. High resolution sampling of the stratified water column in a fjord‐like ecosystem revealed a green‐pigmented planktonic ciliate that was found to be a ravenous predator of Euglena proxima. The vertical distributions of both predator and prey were coincident, and maximum populations occurred across the transition from oxic to anoxic water. This ciliate was identified as Perispira ovum (family Spathidiidae; Order Haptorida). P. ovum was observed by transmission electron microscopy to retain not only the chloroplasts, but also the mitochondria and paramylon reserve of its algal prey. A mechanism of sequestration of algal organelles is demonstrated for the first time. This mechanism includes: recognition, capture, and ingestion of prey; rupture and release of algal cell contents; and enrobing of individual organelles and paramylon by the host vacuolar membrane. The structural integrity, peripheral location, and association with host endoplasmic reticulum suggests the sequestered organelles may be functional within P. ovum. The occurrence and high biomass of this aerobic ciliate in an oxygen‐limited environment also suggests that the sequestered chloroplasts are photosynthetically active and may provide additional substrates (such as oxygen) and metabolic capabilities that are crucial for its survival.

WIDESPREAD OCCURRENCE OF THE OCEANIC ULTRAPLANKTER, PRASINOCOCCUS CAPSULATUS (PRASINOPHYCEAE), THE DIAGNOSTIC “GOLGI‐DECAPORE COMPLEX” AND THE NEWLY DESCRIBED POLYSACCHARIDE “CAPSULAN”

A nonmotile green nanoalga was isolated from the waters over the Cayman Trench in March 1979 and has been maintained in culture as clone URI 266G (CCMP 1202). It was observed to form a copious polysaccharide capsule that presumably originated in the Golgi body and was secreted through a crown of 10 pores in the cell wall, the “decapore.” This multilaminate apical area, lying adjacent to the Golgi, underwent structural changes during morphogenesis. The polysaccharide precursors that coalesced to form the capsule apparently became stainable and visible as they exited the decapore when they cross‐linked with divalent ions in seawater. Cell wall precursors, or a cell wall lamina, surrounded the daughter cells both during synchronous binary fission and after cell separation, with the maternal capsule perhaps acting as a template. Similar prasinophyte isolates have been obtained from widespread areas of the North Atlantic and were divided into two subgroups on the basis of their pigment complement (Hooks et al. 1988). One subgroup, typified by clone Ω 48‐23 (CCMP 1203), was described by Guillard et al. (1991) as Pycnococcus provasolii Guillard within a new family, the Pycnococcaceae. The other subgroup, typified by clone URI 266G (CCMP 1202), contained two unique carotenoids, one of which was uriolide (Foss et al. 1986). Subsequently, Miyashita et al. (1993) described an alga from the western Pacific Ocean that is indistinguishable from URI 266G in both pigment composition and ultrastructure that they named Prasinococcus capsulatus Miyashita et Chihara and placed tentatively in the Pycnococcaceae. They described a curious asexual budding fission. Here we suggest an alternative form of cell division analogous to that observed in the other described Pycnococcaceae. We used theultrastructure of cells in exponential and stationary phases of growth to illustrate synchronous asexual binary fission, the “Golgi‐decapore complex,” and its apparent role in capsule formation. A unique sulfated and carboxylated polyanionic polysaccharide named capsulan is released from this complex.

Ammonia removal by selective ion exchange, a backup system for microbiological filters in closed-system aquaculture

Abstract Nitrification by biological filters in closed-system aquaculture is the primary method for removing ammonia from the culture water. This paper examines experimentally the process of selective ion exchange as an alternative to biological oxidation of ammonia. We propose that an inexpensive ion exchange column would be useful as a backup system to the microbiological filters, or as an alternate system used while treating diseased animals in culture so as not to harm the nitrifying bacteria of the main biological filters.

Nanostructured Materials Synthesis in a Mixed Surfactant Mesophase

ABSTRACT The mixed surfactant system of bis (2-ethylhexyl) sodium sulfosuccinate (AOT) and α-phosphatidylcholine (lecithin) forms a rigid gel-like mesophase in the presence of equal volumes of water and a hydrocarbon (isooctane). Small angle neutron scattering (SANS) results indicate that these structures undergo transitions from columnar hexagonal geometries to lamellar geometries depending on the water content and/or the temperature. The system is used to synthesize nanostructured ceramics (silica) in the aqueous microphase. Interpenetrating networks of poly-(hydroxyethylmethacrylate) and poly(styrene) are also synthesized using the aqueous microphase to support the water soluble monomer (hydroxyethyl methacrylate) and the organic microphase (styrene). SANS results indicate that the template structure is maintained during materials synthesis.

Amphiphilic Templates in the Synthesis of Nanostructured Composites — from Particles to Extended Structures

Surfactant self-assembly is used to develop templates for materials synthesis. The reverse micelle microstructure of the anionic, AOT, serves as a template for the enzymatic synthesis of polymer microspheres and the encapsulation of nanoparticles within these microspheres. Transformation from reverse micelles to a rigid organohydrogel structure is conducted through the addition of the zwitterionic phospholipid, lecithin. The gel serves as a template for the extended synthesis of silica networks and provides opportunities to synthesize polymer-inorganic structured nanocomposites.