James A. Nienow

Extremophiles: Dry Environments (Including Cryptoendoliths)

Microorganisms in desert environments can form rich assemblages in spite of the harsh environmental conditions. These include extensive biological soil crusts dominated by cyanobacteria, lichens, and mosses in semiarid and arid regions, and epilithic, endolithic, and hypolithic phototrophic associations wherever suitable substrata are available. In the more arid regions, the cyanobacterial Chroococcidiopsis gains in importance. The extent of these associations depends on the moisture availability, the hyperarid core of the Atacama being near the limits of life on Earth. Survival of desert microorganisms in these environments is dependent on their ability to survive extended periods in the desiccated state. Low water activity and desiccation can result in damage to cell membranes, oxidation and photooxidation of macromolecules, and desiccation-induced breaks in DNA. Endolithic and hypolithic growth can alleviate the damage by prolonging the period of activity and reducing the amount of photooxidative damage. Biological adaptations include the production of exopolysaccharide sheaths; the production of compatible solutes, especially trehalose; the production of UV-blocking chemicals such as scytonemin and mycosporine-like amino acids; and the possible use of special DNA-repair mechanisms such as are found in radiation-resistant bacteria.

Fine structure, taxonomy and systematics of Reimerothrix (Fragilariaceae: Bacillariophyta), a new genus of synedroid diatoms from Florida Bay, USA

Abstract Reimerothrix floridensis A.K.S.K. Prasad gen. & sp. nov., a monotypic genus of Fragilariaceae (Bacillariophyta), is described from Florida Bay, USA. It forms rosettes of cells and grows epiphytically. The cells are narrowly linear and arcuate or straight and have a single plate-shaped plastid. The valves are inflated at their central part and have greatly elongated, drawn-out ends (projections). The central part of the valve has a wide lanceolate sternum and is almost free of areolation, except at the valve face-mantle junction, where there is a single row of poroid areolae. Over most of the elongate projections the valve bears a single row of areolae, but near the apices the areolae are irregularly distributed in two rows. The polar mantle bears pore fields with two or three rows of poroids, which are larger than those on the valve face, and two to four short spines. A single rimoportula is found at each apex; its external opening is a simple pore and its internal opening is usually orientated perpendicular to the apical axis. The valve mantle is hyaline, except at the apices. The cingulum is composed of two to four open, porous bands. Reimerothrix is compared with genera in the Fragilariaceae and Toxariaceae.

The centric diatom genus Cyclotella, (Stephanodiscaceae: Bacillariophyta) from Florida Bay, USA, with special reference to Cyclotella choctawhatcheeana and Cyclotella desikacharyi, a new marine species related to the Cyclotella striata complex†

A.K.S.K. Prasad and J.A. Nienow. 2006. The centric diatom genus Cyclotella, (Stephanodiscaceae: Bacillariophyta) from Florida Bay, USA, with special reference to Cyclotella choctawhatcheeana and Cyclotella desikacharyi, a new marine species related to the Cyclotella striata complex. Phycologia 45: 127–140. DOI: 10.2216/05-13.1 A new marine species of the centric diatoms of the genus Cyclotella, Cyclotella desikacharyi A.K.S.K. Prasad collected from several localities in Florida Bay, USA, where it is a dominant part of the planktonic assemblage, is described by means of light and scanning electron microscopy. Cyclotella desikacharyi is characterized by the presence of dense striae (14–19 in 10 µm) in the marginal zone and small granules all through the surface of the valve, including the central area, fultoportulae on the valve mantle located on every second or third interstria, each surrounded by three satellite pores, a pronounced tangential undulation, 3–17 valve-face fultoportulae in an arc on the uplift of the undulation and numerous discoid plastids. The new species is compared with Cyclotella striata complex; C. desikacharyi closely resembles C. striata in valve dimensions and in the structure and arrangement of alveolate striae, and in the presence of three satellite pores surrounding each fultoportula on the valve mantle; it differs from it in the stria density and the presence of siliceous granules on the entire valve surface. The new species is compared with the other closely related marine members of the genus, Cyclotella stylorum and Cyclotella litoralis. Cyclotella choctawhatcheeana Prasad, originally described from the northern Gulf Coast of Florida, is also recorded in several localities in Florida Bay and its global distribution is discussed. The evolution of euryhalinity in the genus Cyclotella is also discussed in brief.

Marine diatom genus Climaconeis (Berkeleyaceae, Bacillariophyta): two new species, Climaconeis koenigii and C. colemaniae, from Florida Bay, USA

Abstract Two new species of marine, epipelic, biraphid diatoms of the genus Climaconeis, Climaconeis koenigii A.K.S.K Prasad and C. colemaniae A.K.S.K Prasad, collected from several localities in Florida Bay, USA, are described by means of light and scanning electron microscopy. Climaconeis koenigii is characterized by extremely long and narrow arcuate cells (200–468 μm long and 2–4 μm wide) with fine striae, straight rather than curved central raphe endings, and 48–72 H-shaped plastids and by the absence of stauros and associated pores. Climaconeis colemaniae closely resembles C. scopulorioides in valve shape and in the structure and arrangement of the striae, polar mantle slits, central stauros, and two isolated pores in the central area; it differs from it in the stria density and the number of plastids. The new species are compared with other members of the genus, including the generitype C. lorenzii, which is also found in Florida Bay, and C. inflexa. A revised artificial key to the known species of Climaconeis is also provided.

THE MARINE DIATOM GENUS TRYBLIOPTYCHUS HENDEY (THALASSIOSIRACEAE, COSCINODISCOPHYCEAE): FINE STRUCTURE, TAXONOMY, SYSTEMATICS AND DISTRIBUTION

Detailed examination of the fine structure of frustules in Tryblioptychus cocconeiformis (Grunow ex Cleve) Hendey, the generitype, supports its placement in the family Thalassiosiraceae, as suggested by Simonsen (1979). Its taxonomic relationships are discussed. An account of its geographical distribution is also presented. Examination of original illustrations and descriptions suggests that Cyclotella crassa Tynni, a marine diatom described from the Persian Gulf, is probably conspecific with Tryblioptychus cocconeiformis.

Plicate Species of the Diatom Genus Thalassiosira (Bacillariophyta) from the Atlantic and Gulf Coasts of Southeastern United States, with the Description of T. livingstoniorum sp. nov.

ABSTRACT. Long-term observations of a marine planktonic plicate Thalassiosira species, T. cedarkeyensis Prasad, from the Gulf coasts of Florida, Alabama, and Mississippi and the Atlantic coasts of Florida and Georgia demonstrate its wide occurrence in the southeastern United States and its ability to form extensive blooms. We also report for the first time its ability to form typical Thalassiosira chains, linking sibling cells by threads of chitin. A closely related and co-occurring diatom, T. livingstoniorum, is described on the basis of investigations conducted during 2000–2011 as a new species from many localities in Apalachee Bay on the Gulf coast and Indian River Lagoon on the Atlantic coast of Florida. It differs from T. cedarkeyensis in areola density, presence of continuous cribra on loculate areolae, arrangement and distribution of valve processes, and the number of satellite pores surrounding the valve-face fultoportulae. We have not yet found any evidence of chain formation in T. livingstoniorum. Thalassiosira cedarkeyensis and T. livingstoniorum can be easily distinguished in Naphrax-mounted preparations in light microscopy (LM), and they represent two different groups (lineages?) of plicate species with reference to internal cribrum structure of the loculate areolae. Their differences may justify placement in two different genera. Although T. cedarkeyensis (which has individual cribra on the proximal siliceous layer like T. hyperborea) is abundant and widespread on the Gulf and Atlantic coasts of the southeastern United States, T. livingstoniorum (which has continuous cribra like T. lacustris) has been found, thus far, only in Florida coastal waters. Comparisons are made between these two species and the other morphologically similar extant and extinct plicate species. Thalassiosira livingstoniorum and T. cedarkeyensis, although widespread and frequently encountered during warmer months, may be easily overlooked sources of primary production in the nutrient-rich northeastern Gulf of Mexico.

Livingstonia (Thalassiosirales, Bacillariophyta), a new genus of fultoportulate centric diatoms from an Atlantic coastal plain river in Florida, southeastern United States

Prasad A.K.S.K and Nienow J.A. 2011. Livingstonia (Thalassiosirales, Bacillariophyta), a new genus of fultoportulate centric diatoms from an Atlantic coastal plain river in Florida, southeastern United States. Phycologia 50: 264–280. DOI: 10.2216/09-89.1 A morphological and taxonomic account of Livingstonia palatkaensis, a new genus and species of centric diatoms belonging to the order Thalassiosirales Glezer & Makarova, is provided. Descriptions are based on material collected from the St. Johns River, a major, highly colored blackwater river in the Atlantic coastal plain in the southeastern United States. Scanning electron microscopic observations clearly show that although the valve structure in Livingstonia shares broad similarities with the genera Thalassiosira and Skeletonema, the types of the two fultoportulate families Thalassiosiraceae and Skeletonemataceae, respectively, it is sufficiently dissimilar to warrant the description of a new genus. Livingstonia is characterized by the presence of compound marginal processes, each formed from the external extension of a fultoportula and a semielliptical hyaline hood or cover. The areolae have semicontinuous internal cribra. A single rimoportula is present near the valve center. No fultoportulae are found at or near the center of the valve face. Furthermore, Livingstonia lacks connecting threads of marginal fultoportulae and an external extension of the rimoportula on the valve face, a combination of features that is unusual in the genus Skeletonema. Livingstonia is also distinguished from two recently described freshwater genera in the Thalassiosiraceae from the southeastern United States, Cyclotubicoalitus and Spicaticribra, in having a rimoportula away from the margin but close to the center of the valve and in other key characteristics. A note on another freshwater, co-occurring, more frequent and widespread, chain-forming, closely related diatom, Skeletonema potamas, is also included. Livingstonia is tentatively placed in the family Thalassiosiraceae.

Hemoglobin aggregates studied under static and dynamic conditions involving the formation of nanobacteria-like structures

Hemoglobin aggregates studied under static and dynamic conditions involving the formation of nanobacteria-like structures Laser light scattering and scanning electron microscopy (SEM) are used to study hemoglobin in the aqueous phase. The impact that salts [NaCl, Ca3(PO4)2] and iron oxide nanoparticles have on the hemoglobin size are also studied. The first set of experiments examined hemoglobin aggregates in the aqueous phases in the presence of salts and nanoparticles. Aqueous phase samples were then dehydrated and examined using SEM. The resulting structures resemble those observed in nanobacteria studies conducted in other labs. This study demonstrates that aggregates of hemoglobin and various salts found in a physiological environment can produce structures that resemble nanobacteria. Agregati hemoglobina proučavani pod statičkim i dinamičkim uvjetima uključujući i nastajanje struktura poput nanobakterija Metoda dinamičkog rasapa svjetlosti i pretražna elektronska mikroskopija (SEM) koriš tene su za proučavanje hemoglobina u vodenoj fazi. Nadalje, ispitivan je utjecaj soli [NaCl, Ca3(PO4)2] i nanočestica oksida željeza na veličinu hemoglobina. U prvom setu pokusa proučavani su agregati hemoglobina u vodenoj fazi u prisutnosti soli i nanočestica. Vodena faza je dehidrirana i ostatak analiziran pomoću pretražne elektronske mikroskopije. Agregati hemoglobina i različitih soli pronađeni u fiziološkim uvjetima čine strukture slične nanobakterijama.

Fine structure and ecology of Nanoneis longta in the northeastern Gulf of Mexico with a revised definition of the species

A population of the rarely reported diatom Nanoneis longta was observed over a period of more than two years in the northeastern Gulf of Mexico. This permitted a detailed examination of the fine structure of the valve in scanning and transmission electron microscopy. The population matched the basic features of the original description of the species, but displayed a greater size range. Our use of SEM revealed the presence of a novel structure, the porticus marginalis, along the perimeter of the valve. The species was most abundant below the thermocline, at depths between 25 and 125 m, and from summer to early fall. An emended definition of the species to accommodate the observed size range and the new feature is included.