Gulf Stream warm core rings: phytoplankton in two fall rings of different ages

Warm core ring (WCR) 82-H was sampled in September–October(1982) as a Gulf Stream meander pinched off and became a ring.It is compared with the 3-month-old WCR 81-D, visited September–October(1981). Although the rings have different histories, their phytoplanktonassemblages share some characteristics. Using cluster analysesbased on quantitative group counts, a station from one ringoccasionally clusters most closely with a station from the otherring, showing a similar balance of organisms. The younger ringat the time of sampling, WCR 82-H, had lower diversity, fewershelf species, and greater consistency between stations, exceptfor a high level of Oscillatoria in the meander before the ringpinched off. Interaction with slope water was seen principallyat the ring margin. WCR 81-D, on the other hand, showed a greatdeal of structure, and immediate dilutions with slope waterand the Gulf Stream were apparent, with higher diversity beforeand a week after such interactions. The upper water column ofwarm core rings, although showing evidence of physical mixing,can exhibit stratification of species, even after a storm.     

Multivariate statistical analysis of net diatom species distributions in the Southwestern Atlantic and Indian Ocean

Summary Vertical net haul diatom assemblages from near South Georgia, and from between Africa and Antarctica, were examined and compared. Variation among South Georgia stations was examined by principal component, cluster and canonical discriminant analyses. Diatom distributions provide evidence for at least two distinct water masses. The region north of the island is characterized by neritic, temperate diatoms and by an assemblage with low species diversity. The region south of the island is characterized by oceanic, antarctic species and relatively high species diversity. The regions are most distinct to the west of the island, intergrading east of the island. Within the north-south division, five station groupings were detected on the basis of distribution of dominant net diatoms. By comparing classical species ecological categorizations to results of principal component analysis, a neritic-oceanic factor was identified from net diatom distributions. This factor was common to both areas in spite of the fact that Biscoe and Agulhas collections were from different seasons.     

Freezing-Out Technique Applied to the Concentration of Biologically Active Materials

When applied to a dilute solution of folic acid and glucose, a freezing-out (with agitation) technique was shown to be an effective method of achieving a 20-fold reduction in volume with a loss of 10% of the active material being concentrated. Concentration of a stimulatory factor for Lactobacillus casei produced by Candida albicans in a complex medium was limited by the total solute concentration. Salts in the medium were concentrated to levels inhibitory for L. casei. The process is not selective and all solutes are concentrated.     

USE OF RIBOSOMAL DNA INTERNAL TRANSCRIBED SPACERS FOR PHYLOGENETIC STUDIES IN DIATOMS1

Sequence variation of ribosomal DNA internal transcribed spacers (ITS) among populations, species, and genera of the diatom genus Stephanodiscus was investigated. ITS 1 and ITS 2, including the 5.8S gene, were sequenced from geographically distant and nearby populations of S. niagarae Ehrenberg. In addition, repeats from S. hantzschii Grunow and Cyclotella meneghiniana Kützing were sequenced to determine the taxonomic range over which the ITS region could be used for diatom systematics. The morphologically distinct S. yellowstonensis Theriot & Stoermer, thought to have evolved from S. niagarae in Yellowstone Lake between 12,000 and 8000 years ago, also was sequenced to assess its relationship to nearby S. niagarae populations. The organization and relative sizes of ITS 1 and ITS 2 in Stephanodiscus species were similar to those reported for other eukaryotes. In general, ITS 2 was slightly larger and more variable than ITS 1. Cladistic analysis of ITS sequences did not resolve relationships of nearby S. niagarae and S. yellowstonensis populations. However, central North American S. niagarae populations were in a clade supported by two nucleotide changes. For Cyclotella, much of the ITS region was not alignable with that for Stephanodiscus species; therefore, generic-level comparison within the Thalassiosiraceae may not be possible. The variation (95–96% similarity) between S. hantzschii and other Stephanodiscus species suggests that interspecific relationships could be assessed with ITS sequences. Although S. yellowstonensis is morphologically distinct from S. niagarae, no autapomorphic nucleotide sites were identified. Two S. niagarae populations (Heart and Lewis Lakes), however, did possess autapomorphic ITS sites.     

PHYLOGENY OF THE ULVOPHYCEAE (CHLOROPHYTA): CLADISTIC ANALYSIS OF NUCLEAR-ENCODED rRNA SEQUENCE DATA1

Cladistic analysis of nuclear-encoded rRNA sequence data provided us with the basis for some new hypotheses of relationships within the green algal class Ulvophyceae. The orders Ulotrichales and Ulvales are separated from the clade formed by the remaining orders of siphonous and siphonocladous Ulvophyceae (Caulerpales, Siphonocladales /Cladophorales [S/C] complex, and the Dasycladales), by the Chlorophyceae and Pleurastrophyceae. Our results suggest that the Ulvophyceae is not a monophyletic group. Examination of inter- and intra-ordinal relationships within the siphonous and siphonocladous ulvophycean algae revealed that Cladophora, Chaetomorpha, Anadyomene, Microdictyon, Cladophoropsis and Dictyosphaeria form a clade. Thus the hypothesis, based on ultrastructural features, that the Siphonocladales and Cladophorales are closely related is supported. Also, the Caulerpales is a monophyletic group with two lineages; Caulerpa, Halimeda, and Udotea comprise one, and Bryopsis and Codium comprise the other. The Dasycladales (Cymopolia and Batophora) also forms a clade, but this clade is not inferred to be the sister group to the S/C complex as has been proposed. Instead, it is either the sister taxon to the Caulerpales or basal to the Caulerpales and S/C clade The Trentepohliales is also included at the base of the siphonous and siphonocladous ulvophycean clade. The Pleurastrophyceae, which, like the Ulvophyceae, posses a counter-clockwise arrangement of flagellar basal bodies, are more closely related to the Chlorophyceae than to the Ulvophyceae based on rRNA sequences. Thus, the arrangement of basal bodies does not diagnose a monophyletic group. Previously reported hypotheses of phylogenetic relationships of ulvophycean algae were tested. In each case, additional evolutionary steps were required to obtain the proposed relationships. Relationships of ulvophycean algae to other classes of green algae are discussed.     

Characterization of Epstein–Barr virus reactivation in a modeled spaceflight system

Epstein–Barr virus (EBV) is the causative agent of mononucleosis and is also associated with several malignancies, including Burkitt's lymphoma, Hodgkin's lymphoma, and nasopharyngeal carcinoma, among others. EBV reactivates during spaceflight, with EBV shedding in saliva increasing to levels ten times those observed pre‐and post‐flight. Although stress has been shown to increase reactivation of EBV, other factors such as radiation and microgravity have been hypothesized to contribute to reactivation in space. We used a modeled spaceflight environment to evaluate the influence of radiation and microgravity on EBV reactivation. BJAB (EBV‐negative) and Raji (EBV‐positive) cell lines were assessed for viability/apoptosis, viral antigen and reactive oxygen species expression, and DNA damage and repair. EBV‐infected cells did not experience decreased viability and increased apoptosis due to modeled spaceflight, whereas an EBV‐negative cell line did, suggesting that EBV infection provided protection against apoptosis and cell death. Radiation was the major contributor to EBV ZEBRA upregulation. Combining modeled microgravity and radiation increased DNA damage and reactive oxygen species while modeled microgravity alone decreased DNA repair in Raji cells. Additionally, EBV‐infected cells had increased DNA damage compared to EBV‐negative cells. Since EBV‐infected cells do not undergo apoptosis as readily as uninfected cells, it is possible that virus‐infected cells in EBV seropositive individuals may have an increased risk to accumulate DNA damage during spaceflight. More studies are warranted to investigate this possibility. J. Cell. Biochem. 114: 616–624, 2013. © 2012 Wiley Periodicals, Inc.     

Revisiting Ross and Sims (1971): toward a molecular phylogeny of the Biddulphiaceae and Eupodiscaceae (Bacillariophyceae)

The ocellate and pseudocellate diatoms in the Eupodiscaceae and Biddulphiaceae (respectively) are common inhabitants of the marine littoral (and plankton zone) with a rich fossil history making them important components of marine stratigraphic studies and good candidates for molecular dating work. These diatoms are important for un‐derstanding the phylogeny of the diatoms as a whole, as molecular phylogenies have blurred the traditional distinction between the pennate and multipolar non‐pennate diatoms. However, the convoluted taxonomic history of these groups has the potential to disrupt both stratigraphic and molecular dating studies. Although efforts have been made to examine frustule morphology of several ocellate and pseudocellate diatoms and develop a morphological scheme to define genera, very little work has been done to determine how these groups are interrelated. In this study, we use nuclear and chloroplast molecular markers to construct a phylogeny of a diverse sampling of Eupodiscaceae and Biddulphiaceae taxa. The ocellus‐bearing taxa (Eupodiscaceae) are monophyletic, and thus the ocellus may be a useful character in delimiting the Eupodiscaceae, the Biddulphiaceae are polyphyletic and scattered across a number of lineages of multipolar non‐pennate diatoms. Hypothesis testing aimed at assessing the likeliness of several morphology based hypotheses against the molecular data highlights uncertainty in both types of data. We present evidence that there are monophyletic genera within both the Biddulphiaceae and Eupodiscaceae, and recommend the taxa within the Odontella mobilensis/sinensis/regia clade be transferred to a new genus: Trieres Ashworth & Theriot.     

Complex spatial distribution and dynamics of an abundant Escherichia coli outer membrane protein, LamB

Advanced techniques for observing protein localization in live bacteria show that the distributions are dynamic. For technical reasons, most such techniques have not been applied to outer membrane proteins in Gram-negative bacteria. We have developed two novel live-cell imaging techniques to observe the surface distribution of LamB, an abundant integral outer membrane protein in Escherichia coli responsible for maltose uptake and for attachment of bacteriophage lambda. Using fluorescently labelled bacteriophage lambda tails, we quantitatively described the spatial distribution and dynamic movement of LamB in the outer membrane. LamB accumulated in spiral patterns. The distribution depended on cell length and changed rapidly. The majority of the protein diffused along spirals extending across the cell body. Tracking single particles, we found that there are two populations of LamB--one shows very restricted diffusion and the other shows greater mobility. The presence of two populations recalls the partitioning of eukaryotic membrane proteins between 'mobile' and 'immobile' populations. In this study, we have demonstrated that LamB moves along the bacterial surface and that these movements are restricted by an underlying dynamic spiral pattern.     

Listeria monocytogenes actin-based motility varies depending on subcellular location: a kinematic probe for cytoarchitecture

Intracellular Listeria monocytogenes actin-based motility is characterized by significant individual variability, which can be influenced by cytoarchitecture. L. monocytogenes was used as a probe to transmit information about structural variation among subcellular domains defined by mitochondrial density. By analyzing the movement of a large population of L. monocytogenes in PtK2 cells, we found that mean speed and trajectory curvature were significantly larger for bacteria moving in mitochondria-containing domains (generally perinuclear) than for bacteria moving in mitochondria-free domains (generally peripheral). Analysis of bacteria that traversed both mitochondria-containing and mitochondria-free domains revealed that these motile differences were not intrinsic to bacteria themselves. Disruption of mitochondrial respiration did not affect bacterial mean speed, speed persistence, or trajectory curvature. In contrast, microtubule depolymerization lead to decreased mean speed per bacterium and increased mean speed persistence of L. monocytogenes moving in mitochondria-free domains compared with untreated cells. L. monocytogenes were also observed to physically collide with mitochondria and push them away from the bacterial path of motion, causing bacteria to slow down before rapidly resuming their speed. Our results show that subcellular domains along with microtubule depolymerization may influence the actin cytoskeleton to affect L. monocytogenes speed, speed persistence, and trajectory curvature.