Physiological performance of intertidal coralline algae during a simulated tidal cycle

Intertidal macroalgae endure light, desiccation, and temperature variation associated with sub‐merged and emerged conditions on a daily basis. Physiological stresses exist over the course of the entire tidal cycle, and physiological differences in response to these stresses likely contribute to spatial separation of species along the shore. For example, marine species that have a high stress tolerance can live higher on the shore and are able to recover when the tide returns, whereas species with a lower stress tolerance may be relegated to living lower on the shore or in tidepools, where low tide stresses are buffered. In this study, we monitored the physiological responses of the tidepool coralline Calliarthron tuberculosum (Postels and Ruprecht) E.Y. Dawson and the nontidepool coralline Corallina vancouveriensis Yendo during simulated tidal conditions to identify differences in physiology that might underlie differences in habitat. During high tide, Corallina was more photosynthetically active than Calliarthron as light levels increased. During low tide, Corallina continued to out‐perform Calliarthron when submerged in warming tidepools, but photosynthesis abruptly halted for both species when emerged in air. Surprisingly, pigment composition did not differ, suggesting that light harvesting does not account for this difference. Additionally, Corallina was more effective at resisting desiccation by retaining water in its branches. When the tide returned, only Corallina recovered from combined temperature and desiccation stresses associated with emergence. This study broadens our understanding of intertidal algal physiology and provides a new perspective on the physiological and morphological underpinnings of habitat partitioning.     

In vitro resistance mechanisms of Neisseria meningitidis against neutrophil extracellular traps

Neisseria meningitidis (Nm) is a leading cause of septicemia in childhood. Nm septicemia is unique with respect to very quick disease progression, high in vivo bacterial replication rate and its considerable mortality. Nm circumvents major mechanisms of innate immunity such as complement system and phagocytosis. Neutrophil extracellular traps (NETs) are formed from neutrophils during systemic infection and are suggested to contain invading microorganisms. Here, we investigated the interaction of Nm with NETs. Both, meningococci and spontaneously released outer membrane vesicles (SOMVs) were potent NET inducers. NETs were unable to kill NET bound meningococci, but slowed down their proliferation rate. Using Nm as model organism we identified three novel mechanisms how bacteria can evade NET‐mediated killing: (i) modification of lipid A of meningococcal LPS with phosphoethanolamine protected Nm from NET‐bound cathepsin G; (ii) expression of the high‐affinity zinc uptake receptor ZnuD allowed Nm to escape NET‐mediated nutritional immunity; (iii) binding of SOMVs to NETs saved Nm from NET binding and the consequent bacteriostatic effect. Escape from NETs may contribute to the most rapid progression of meningococcal disease. The induction of NET formation by Nm in vivo might aggravate thrombosis in vessels ultimately directing to disseminated intravascular coagulation (DIC).     

Differential community development of fouling species on the pearl oysters Pinctada fucata, Pteria penguin and Pteria chinensis (Bivalvia, Pteriidae)

A field experiment documented the development of fouling communities on two shell regions, the lip and hinge, of the pearl oyster species Pinctada fucata, Pteria penguin and Pteria chinensis. Fouling communities on the three species were not distinct throughout the experiment. However, when each species was analysed separately, fouling communities on the lip and hinge of P. penguin and P. chinensis were significantly different during the whole sampling period and after 12 weeks, respectively, whereas no significant differences could be detected for P. fucata. There was no significant difference in total fouling cover between shell regions of P. fucata and P. chinensis after 16 weeks; however, the hinge of P. penguin was significantly more fouled than the lip. The most common fouling species (the hydroid Obelia bidentata, the bryozoan Parasmittina parsevalii, the bivalve Saccostrea glomerata and the ascidian Didemnum sp.) showed species-specific fouling patterns with differential fouling between shell regions for each species. The role of the periostracum in determining the community development of fouling species was investigated by measuring the presence and structure of the periostracum at the lip and hinge of the three pearl oyster species. The periostracum was mainly present at the lip of the pearl oysters, while the periostracum at the hinge was absent and the underlying prismatic layer eroded. The periostracum of P. fucata lacked regular features, whereas the periostracum of P. penguin and P. chinensis consisted of a regular strand-like structure with mean amplitudes of 0.84 microm and 0.65 microm, respectively. Although the nature and distribution of fouling species on the pearl oysters was related to the presence of the periostracum, the periostracum does not offer a fouling-resistant surface for these pearl oyster species.     

Preliminary crystallographic analysis of trypanothione reductase from Crithidia fasciculata

Trypanothione reductase, a flavoprotein disulfide reductase specific to trypanosomatid parasites, has been crystallized by vapor diffusion of a protein solution (10 mg/ml) against 22% polyethylene glycol (average Mr 8000) containing 100 mM-ammonium sulfate. Crystals of a size suitable for structure determination by X-ray diffraction have been obtained by seeding protein solutions with smaller crystals. The space-group is P21 (a = 60.9 A, b = 161.8 A, c = 58.4 A, beta = 99.1 degrees). The molecular mass and volume of the unit cell suggest that there is a dimer of the enzyme in the asymmetric unit, and this is confirmed by self-rotation functions calculated using data to 4.5 A resolution. The crystals diffract to beyond 3 A resolution. Crystals of another P21 form (a = 91.3 A, b = 114.4 A, c = 92.0 A, beta = 141.3 degrees) are observed to grow under similar conditions.     

Response of the Photosynthetic Apparatus in Dunaliella salina (Green Algae) to Irradiance Stress

The response of the photosynthetic apparatus in the green alga Dunaliella salina, to irradiance stress was investigated. Cells were grown under physiological conditions at 500 millimoles per square meter per second (control) and under irradiance-stress conditions at 1700 millimoles per square meter per second incident intensity (high light, HL). In control cells, the light-harvesting antenna of photosystem I (PSI) contained 210 chlorophyll a/b molecules. It was reduced to 105 chlorophyll a/b in HL-grown cells. In control cells, the dominant form of photosystem II (PSII) was PSII_α(about 63% of the total PSII) containing >250 chlorophyll a/b molecules. The smaller antenna size PSII_β centers (about 37% of PSII) contained 135 ± 10 chlorophyll a/b molecules. In sharp contrast, the dominant form of PSII in HL-grown cells accounted for about 95% of all PSII centers and had an antenna size of only about 60 chlorophyll a molecules. This newly identified PSII unit is termed PSII_γ. The HL-grown cells showed a substantially elevated PSII/PSI stoichiometry ratio in their thylakoid membranes (PSII/PSI = 3.0/1.0) compared to that of control cells (PSII/PSI = 1.4/1.0). The steady state irradiance stress created a chronic photoinhibition condition in which D. salina thylakoids accumulate an excess of photochemically inactive PSII units. These PSII units contain both the reaction center proteins and the core chlorophyll-protein antenna complex but cannot perform a photochemical charge separation. The results are discussed in terms of regulatory mechanism(s) in the plant cell whose function is to alleviate the adverse effect of irradiance stress.     

Modified nucleoside-dependent transition metal binding to DNA analogs of the tRNA anticodon stem/loop domain

Biologically active DNA analogs of tRNA^Phe (tDNA^Phe) were used to investigate metal ion interaction with tRNA-like structures lacking the 2OH. Binding of Mg²⁺ to the 76 oligonucleotide tDNA^Phe, monitored by circular dichroism spectroscopy, increased base stacking and thus the conformational stability of the molecule. Mg²⁺ binding was dependent on a d(m⁵C) in the anticodon region. In contrast to Mg²⁺, Cd²⁺ decreased base stacking interactions, thereby destabilizing the molecule. Since alterations in the anticodon region contributed to most of the spectral changes observed, detailed studies were conducted with anticodon hairpin heptadecamers (tDNA_AC ^Phe). The conformation of tDNA_AC ^Phe-d(m⁵C) in the presence of 1 mm Cd²⁺, Co²⁺, Cr²⁺, Cu²⁺, Ni²⁺, Pb²⁺, VO²⁺ or Zn²⁺ differed significantly from that of the biologically active structure resulting from interaction with Mg²⁺, Mn²⁺ or Ca²⁺. Nanomolar concentrations of the transition metals were sufficient to denature the tDNA_AC ^Phe-d(m⁵C) structure without catalyzing cleavage of the oligonucleotide. In the absence of Mg²⁺ and at [Cd²⁺] to [tDNA_Ac ^Phe-d(m⁵C)] ratios of approximately 0.2–1.0, tDNA_AC ^Phe-d(m⁵C₄₀) formed a stable conformation with one Cd²⁺ bound with a K _d = 3.7 × 10^-7. In contrast to Mg²⁺, Cd²⁺ altered the DNA analogs without discriminating between modified and unmodified tDNA_AC ^Phe. This ability of transition metals to disrupt higher order DNA structures, and possibly RNA, at M concentrations, in vitro, demonstrates that these structures are potential targets in chronic metal exposure, in vivo.     

A large-subunit mitochondrial ribosomal DNA sequence translocated to the nuclear genome of two stone crabs (Menippe)

Two DNA sequences that appear to be homologous to large-subunit mitochondrial ribosomal RNA genes have been identified in the stone crabs Menippe mercenaria and M. adina. Amplification from whole genomic DNA by polymerase chain reaction (PCR) with oligonucleotide primers based on conserved portions of large-subunit mitochondrial rRNA genes consistently amplified two products of similar length (565 and 567 bp). These products differed at 3% of their nucleotide bases, and could be distinguished by a HindIII site. Only one of these sequences (designated the A sequence) was detected by PCR in purified mitochondrial DNA. The other (designated the B sequence) hybridized to total genomic DNA at a level consistent with a nuclear genome location. It is unlikely that the type B product would have been recognized as a nuclear copy by examination of its sequence alone. This is the first report of a mitochondrial gene sequence translocated into the nuclear genome of a crustacean.      

Similar local,but different systemic,metabolomic responses of closely related pine subspecies to folivory by caterpillars of the processionary moth

Plants respond locally and systemically to herbivore attack. Most of the research conducted on plant–herbivore relationships at element and molecular levels have focused on the elemental composition or/and certain molecular compounds or specific families of defence metabolites showing that herbivores tend to select plant individuals or species with higher nutrient concentrations and avoid those with higher levels of defence compounds. We performed stoichiometric and metabolomics, both local and systemic, analyses in two subspecies of Pinus sylvestris under attack from caterpillars of the pine processionary moth, an important pest in the Mediterranean Basin. Both pine subspecies responded locally to folivory mainly by increasing relative concentrations of terpenes and some phenolics. Systemic responses differed between pine subspecies, and most of the metabolites presented intermediate concentrations between those of the affected parts and unattacked trees. Our results support the hypothesis that foliar nutrient concentrations are not a key factor for plant selection by adult female processionary moths for oviposition, since folivory was not associated with any of the elements analysed. Phenolic compounds generally did not increase in the attacked trees, questioning the suggestion of induction of phenolics following folivory attack and the anti‐feeding properties of phenolics. Herbivory attack produced a general systemic shift in pines, in both primary and secondary metabolism, which was less intense and chemically different from the local responses. Local pine responses were similar between pine subspecies, while systemic responses were more distant.     

Earth Mover’s Distance (EMD): A True Metric for Comparing Biomarker Expression Levels in Cell Populations

Changes in the frequencies of cell subsets that (co)express characteristic biomarkers, or levels of the biomarkers on the subsets, are widely used as indices of drug response, disease prognosis, stem cell reconstitution, etc. However, although the currently available computational “gating” tools accurately reveal subset frequencies and marker expression levels, they fail to enable statistically reliable judgements as to whether these frequencies and expression levels differ significantly between/among subject groups. Here we introduce flow cytometry data analysis pipeline which includes the Earth Mover’s Distance (EMD) metric as solution to this problem. Well known as an informative quantitative measure of differences between distributions, we present three exemplary studies showing that EMD 1) reveals clinically-relevant shifts in two markers on blood basophils responding to an offending allergen; 2) shows that ablative tumor radiation induces significant changes in the murine colon cancer tumor microenvironment; and, 3) ranks immunological differences in mouse peritoneal cavity cells harvested from three genetically distinct mouse strains.