The regulation of Streptococcus mutans glucan-binding protein A expression

The S. mutans GBP-A is hypothesized to be constitutively expressed and to contribute to the sucrose-dependent colonization of S. mutans. To investigate GBP-A expression, a reporter gene encoding chloramphenicol acetyltransferase (CAT) was placed downstream of the gbpA promoter and CAT activity was measured under conditions that would be associated with the sucrose-dependent colonization of S. mutans. Expression of GBP-A was optimal under anaerobiosis and neutral pH conditions, and correlated with optimal growth. The addition of sucrose to the growth medium did not elevate the expression of GBP-A.     

DISTRIBUTION,PHYLOGENY, AND GROWTH OF COLD‐ADAPTED PICOPRASINOPHYTES IN ARCTIC SEAS1

Our pigment analyses from a year‐long study in the coastal Beaufort Sea in the western Canadian Arctic showed the continuous prevalence of eukaryotic picoplankton in the green algal class Prasinophyceae. Microscopic analyses revealed that the most abundant photosynthetic cell types were Micromonas‐like picoprasinophytes that persisted throughout winter darkness and then maintained steady exponential growth from late winter to early summer. A Micromonas (CCMP2099) isolated from an Arctic polynya (North Water Polynya between Ellesmere Island and Greenland), an ice‐free section, grew optimally at 6°C–8°C, with light saturation at or below 10 μmol photons·m^?2·s^?1 at 0°C. The 18S rDNA analyses of this isolate and environmental DNA clone libraries from diverse sites across the Arctic Basin indicate that this single psychrophilic Micromonas ecotype has a pan‐Arctic distribution. The 18S rDNA from two other picoprasinophyte genera was also found in our pan‐Arctic clone libraries: Bathycoccus and Mantoniella. The Arctic Micromonas differed from genotypes elsewhere in the World Ocean, implying that the Arctic Basin is a marine microbial province containing endemic species, consistent with the biogeography of its macroorganisms. The prevalence of obligate low‐temperature, shade‐adapted species in the phytoplankton indicates that the lower food web of the Arctic Ocean is vulnerable to ongoing climate change in the region.     

Muscle fatigue and contraction intensity modulates the complexity of surface electromyography

Nonlinear dynamical techniques offer a powerful approach for the investigation of physiological time series. Multiscale entropy analyses have shown that pathological and aging systems are less complex than healthy systems and this finding has been attributed to degraded physiological control processes. A similar phenomenon may arise during fatiguing muscle contractions where surface electromyography signals undergo temporal and spectral changes that arise from the impaired regulation of muscle force production. Here we examine the affect of fatigue and contraction intensity on the short and long-term complexity of biceps brachii surface electromyography. To investigate, we used an isometric muscle fatigue protocol (parsed into three windows) and three contraction intensities (% of maximal elbow joint moment: 40%, 70% and 100%). We found that fatigue reduced the short-term complexity of biceps brachii activity during the last third of the fatiguing contraction. We also found that the complexity of surface electromyography is dependent on contraction intensity. Our results show that multiscale entropy is sensitive to muscle fatigue and contraction intensity and we argue it is imperative that both factors be considered when evaluating the complexity of surface electromyography signals. Our data contribute to a converging body of evidence showing that multiscale entropy can quantify subtle information content in physiological time series.     

Association of Pinus banksiana Lamb. and Populus tremuloides Michx. seedling fine roots with Sistotrema brinkmannii (Bres.) J. Erikss. (Basidiomycotina)

Sistotrema brinkmannii (Bres.) J. Erikss. (Basidiomycotina, Hydanaceae), commonly regarded as a wood decay fungus, was consistently isolated from bareroot nursery Pinus banksiana Lamb. seedlings. S. brinkmannii was found in ectomycorrhizae formed by Thelephora terrestris Ehrh., Laccaria laccata (Scop.) Cooke, and Suillus luteus (L.) Roussel. In pure culture combinations with sterile P. banksiana and Populus tremuloides Michx. seedlings, S. brinkmannii colonized root cortical cells while not killing seedlings. Colonization by S. brinkmannii appeared to be intracellular but typical endo- or ectomycorrhizae were not formed. The fungus did not decay roots, although it was shown to produce cellulase in enzyme tests. Results suggest a unique association between S. brinkmannii and seedling roots that is neither mycorrhizal nor detrimental; its exact function remains to be elucidated.     

Song convergence in multiple urban populations of silvereyes (Zosterops lateralis)

Recent studies have revealed differences between urban and rural vocalizations of numerous bird species. These differences include frequency shifts, amplitude shifts, altered song speed, and selective meme use. If particular memes sung by urban populations are adapted to the urban soundscape, "urban-typical" calls, memes, or repertoires should be consistently used in multiple urban populations of the same species, regardless of geographic location. We tested whether songs or contact calls of silvereyes (Zosterops lateralis) might be subject to such convergent cultural evolution by comparing syllable repertoires of geographically dispersed urban and rural population pairs throughout southeastern Australia. Despite frequency and tempo differences between urban and rural calls, call repertoires were similar between habitat types. However, certain song syllables were used more frequently by birds from urban than rural populations. Partial redundancy analysis revealed that both geographic location and habitat characteristics were important predictors of syllable repertoire composition. These findings suggest convergent cultural evolution: urban populations modify both song and call syllables from their local repertoire in response to noise.     

Human Liver Cell Trafficking Mutants: Characterization and Whole Exome Sequencing

The HuH7 liver cell mutant Trf1 is defective in membrane trafficking and is complemented by the casein kinase 2α subunit CK2α’’. Here we identify characteristic morphologies, trafficking and mutational changes in six additional HuH7 mutants Trf2-Trf7. Trf1 cells were previously shown to be severely defective in gap junction functions. Using a Lucifer yellow transfer assay, remarkable attenuation of gap junction communication was revealed in each of the mutants Trf2-Trf7. Electron microscopy and light microscopy of thiamine pyrophosphatase showed that several mutants exhibited fragmented Golgi apparatus cisternae compared to parental HuH7 cells. Intracellular trafficking was investigated using assays of transferrin endocytosis and recycling and VSV G secretion. Surface binding of transferrin was reduced in all six Trf2-Trf7 mutants, which generally correlated with the degree of reduced expression of the transferrin receptor at the cell surface. The mutants displayed the same transferrin influx rates as HuH7, and for efflux rate, only Trf6 differed, having a slower transferrin efflux rate than HuH7. The kinetics of VSV G transport along the exocytic pathway were altered in Trf2 and Trf5 mutants. Genetic changes unique to particular Trf mutants were identified by exome sequencing, and one was investigated in depth. The novel mutation Ile34Phe in the GTPase RAB22A was identified in Trf4. RNA interference knockdown of RAB22A or overexpression of RAB22AI34F in HuH7 cells caused phenotypic changes characteristic of the Trf4 mutant. In addition, the Ile34Phe mutation reduced both guanine nucleotide binding and hydrolysis activities of RAB22A. Thus, the RAB22A Ile34Phe mutation appears to contribute to the Trf4 mutant phenotype.     

Gymnodinium smaydae n. sp., a New Planktonic Phototrophic Dinoflagellate from the Coastal Waters of Western Korea: Morphology and Molecular Characterization

The marine phototrophic dinoflagellate Gymnodinium smaydae n. sp. is described from cells prepared for light, scanning, and transmission electron microscopy. Also, sequences of the small (SSU) and large subunits (LSU) and the internal transcribed spacer region (ITS1–5.8S–ITS2) of ribosomal DNA were analyzed. This newly isolated dinoflagellate possessed nuclear chambers, nuclear fibrous connective, an apical groove running in a counterclockwise direction around the apex, and a major accessory pigment peridinin, which are four key features for the genus Gymnodinium. The epicone was conical with a round apex, while the hypocone was ellipsoid. Cells growing photosynthetically were 6.3–10.9 μm long and 5.1–10.0 μm wide, and therefore smaller than any other Gymnodinium species so far reported except Gymnodinium nanum. Cells were covered with polygonal amphiesmal vesicles arranged in 11 horizontal rows, and the vesicles were smaller than those of the other Gymnodinium species. This dinoflagellate had a sharp and elongated ventral ridge reaching half way down the hypocone, unlike other Gymnodinium species. Moreover, displacement of the cingulum was 0.4–0.6 × cell length while in other known Gymnodinium species it is less than 0.3 × cell length. In addition, the new species possessed a peduncle, permanent chloroplasts, pyrenoids, trichocysts, pusule systems, and small knobs along the apical furrow, but it lacked an eyespot, nematocysts, and body scales. The sequence of the SSU, ITS1–5.8S–ITS2, and LSU rDNA region differed by 1.5–3.8%, 6.0–17.4%, and 9.1–17.5%, respectively, from those of the most closely related species. The phylogenetic trees demonstrated that the new species belonged to the Gymnodinium clade at the base of a clade consisting of Gymnodinium acidotum, Gymnodinium dorsalisulcum, Gymnodinium eucyaneum, etc. Based on morphological and molecular data, we suggest that the taxon represents a new species, Gymnodinium smaydae n. sp.     

Lacustrine spatial distribution of landlocked Atlantic salmon populations assessed across generations by multilocus individual assignment and mixed-stock analyses

The objective of this study was to assess the spatiotemporal distribution of four landlocked Atlantic salmon (Salmo salar) populations during their sympatric feeding phase in lake St-Jean (Québec, Canada). A total of 1100 fish captured over a period of 25 years was genotyped at six microsatellite loci in order to assess the temporal stability of the relative proportion of each population in different lake sectors using both individual-based assignment and mixed-stock analysis. Estimates of relative proportions obtained from both methods were highly correlated. A nonrandom spatial distribution of populations was observed for each period and, despite the fact that the overall proportion of each population varied over time, the pattern of differential distribution remained generally stable over time. Furthermore, there were indications that the extent of horizontal spatial overlap among populations was negatively correlated with that of their genetic differentiation at both microsatellites and a major histocompatibility complex locus, and independent of the geographical distance between the rivers of origin. We discuss the hypothesis that the temporal stability of spatial distribution, the lack of an association between spatial partitioning and geographical distance between rivers of origin, and the apparent negative correlation between spatial overlap and genetic differentiation, reflect the outcome of selective pressures driving behavioural differences for spatial niche partitioning among populations.