Growth of Phytomonas serpens in a Defined Medium; Nutritional Requirements

ABSTRACT. Three strains of Phytomonas serpens two from tomatoes, Lycopersicon esculentum one from the insect Phtia picta (Hemiptera, Coreidae), were cultivated in a chemically defined medium developed from a defined medium for cultivating insect flagellates. Besides organic growth factors required by other insect trypanosomatids this flagellate requires, serine and inositol. Glutamine stimulates growth, and, surprisingly, does not require heme.     

Plant regeneration and somaclonal variation from cultured immature embryos of sister lines of rye and triticale differing in their content of heterochromatin

Summary Plants were regenerated from cultured immature embryos of two pairs of sister lines of triticale (X Triticosecale) cvs Rosner and Drira and five sister lines of rye (Secale cereale). The triticale lines differ in heterochromatic content of a particular rye chromosome (6R or 7R), while the rye lines differ in only one heterochromatic band. Variation in morphogenetic response was present between the triticale cultivars and between the rye lines. One of the rye lines (7RL+ +) showed a distinctive superior response in terms of somatic embryogenesis. These findings are discussed in relation to factors affecting morphogenetic response and genetic stability in culture.     

High apparent dielectric constant inside a protein reflects structural reorganization coupled to the ionization of an internal Asp

The dielectric properties of proteins are poorly understood and difficult to describe quantitatively. This limits the accuracy of methods for structure-based calculation of electrostatic energies and pK(a) values. The pK(a) values of many internal groups report apparent protein dielectric constants of 10 or higher. These values are substantially higher than the dielectric constants of 2-4 measured experimentally with dry proteins. The structural origins of these high apparent dielectric constants are not well understood. Here we report on structural and equilibrium thermodynamic studies of the effects of pH on the V66D variant of staphylococcal nuclease. In a crystal structure of this protein the neutral side chain of Asp-66 is buried in the hydrophobic core of the protein and hydrated by internal water molecules. Asp-66 titrates with a pK(a) value near 9. A decrease in the far UV-CD signal was observed, concomitant with ionization of this aspartic acid, and consistent with the loss of 1.5 turns of alpha-helix. These data suggest that the protein dielectric constant needed to reproduce the pK(a) value of Asp-66 with continuum electrostatics calculations is high because the dielectric constant has to capture, implicitly, the energetic consequences of the structural reorganization that are not treated explicitly in continuum calculations with static structures.     

Wild black-headed gulls (<Emphasis Type="Italic">Larus ridibundus</Emphasis>) as an environmental reservoir of <Emphasis Type="Italic">Salmonella</Emphasis> strains resistant to antimicrobial drugs

Salmonella were isolated from black-headed gulls (Larus ridibundus) in six locations in the Czech Republic from 1984 to 2005 (Chropyně and Nymburk in 1984–1986; Nové Mlyny, Bartošovice, and Hodonín in 1991–1994; and Nové Mlyny, Bartošovice, and Ostrava in 2005). Antimicrobial susceptibility was determined in 12 antimicrobial drugs using disk diffusion. Although 95% of Salmonella isolates (197 out of 207) were pansusceptible, the prevalences of resistance increased significantly from 1 (2%) out of 59 isolates in 1984–1986 and 3 (3%) out of 100 isolates in 1991–1994 to 6 (13%) out of 48 isolates in 2005. Furthermore, in 2005, two isolates were nalidixic acid-resistant and one isolate was multidrug-resistant Salmonella Typhimurium DT 104. These findings suggest that the occurrence of salmonellae in black-headed gulls depends to a large extent on the contamination where the gulls feed and possibly reflects the dissemination of these strains among farm animals and humans. Black-headed gulls may also become infected with resistant Salmonella and thus pose a potential risk of Salmonella contamination of surface water and animal feeds, and consequently dissemination.     

Reporter genes lucFF, luxCDABE, gfp, and dsred have different characteristics in whole-cell bacterial sensors

The selection of a genetic reporter can be difficult because of the wide range of genes available. In order to reduce the selection, we compared the performance of different reporter genes: firefly luciferase (Photinus pyralis lucFF), bacterial luciferase operon (Photorhabdus luminescens luxCDABE), green fluorescent protein (Aequorea victoria gfp), and red fluorescent protein (Discosoma sp. dsred) in whole-cell bacterial sensors. Escherichia coli sensor bacteria were engineered to contain a reporter plasmid that carries the reporter gene under the control of mercury- (mer from Tn21) or arsenite- (ars from R773) responsive regulatory units. Characteristics of the strains were studied by using different arsenite or mercury concentrations and incubation times. The lowest detectable concentration of analytes and the fastest responses were achieved with lucFF or luxCDABE as reporter genes. The fluorescent proteins, GFP and DsRed, gave responses at higher analyte concentrations and after significantly longer incubation times. The results indicate that luciferases are better reporters in whole-cell sensor bacteria.     

Stomaching Notch

The self‐renewal and differentiation of tissue stem cells must be tightly controlled. Unrestrained self‐renewal leads to over‐proliferation of stem cells, which may cause tumor formation, while uncontrolled differentiation leads to depletion of the stem cell pool. In this issue of The EMBO Journal, Demitrack et al (2015) show that the Notch pathway is a key regulator of Lgr5 antral stem cell self‐renewal and differentiation. Notch signaling controls the proliferation and differentiation of stem cells as well as gastric tissue growth, while uncontrolled Notch activity in stem cells leads to polyp formation.     

Application of biomaterials to advance induced pluripotent stem cell research and therapy

Derived from any somatic cell type and possessing unlimited self-renewal and differentiation potential, induced pluripotent stem cells (iPSCs) are poised to revolutionize stem cell biology and regenerative medicine research, bringing unprecedented opportunities for treating debilitating human diseases. To overcome the limitations associated with safety, efficiency, and scalability of traditional iPSC derivation, expansion, and differentiation protocols, biomaterials have recently been considered. Beyond addressing these limitations, the integration of biomaterials with existing iPSC culture platforms could offer additional opportunities to better probe the biology and control the behavior of iPSCs or their progeny in vitro and in vivo. Herein, we discuss the impact of biomaterials on the iPSC field, from derivation to tissue regeneration and modeling. Although still exploratory, we envision the emerging combination of biomaterials and iPSCs will be critical in the successful application of iPSCs and their progeny for research and clinical translation.     

Genetic portrait of Lisboa immigrant population from Cabo Verde with mitochondrial DNA analysis

Journal of Genetics -