Genome Mining Shows Ubiquitous Presence and Extensive Diversity of Toxin-Antitoxin Systems in Pseudomonas syringae.

Bacterial toxin-antitoxin (TA) systems consist of two or more adjacent genes, encoding a toxin and an antitoxin. TA systems are implicated in evolutionary and physiological functions including genome maintenance, antibiotics persistence, phage defense, and virulence. Eight classes of TA systems have been described, based on the mechanism of toxin neutralization by the antitoxin. Although studied well in model species of clinical significance, little is known about the TA system abundance and diversity, and their potential roles in stress tolerance and virulence of plant pathogens. In this study, we screened the genomes of 339 strains representing the genetic and lifestyle diversity of the Pseudomonas syringae species complex for TA systems. Using bioinformatic search and prediction tools, including SLING, BLAST, HMMER, TADB2.0, and T1TAdb, we show that P. syringae strains encode 26 different families of TA systems targeting diverse cellular functions. TA systems in this species are almost exclusively type II. We predicted a median of 15 TA systems per genome, and we identified six type II TA families that are found in more than 80% of strains, while others are more sporadic. The majority of predicted TA genes are chromosomally encoded. Further functional characterization of the predicted TA systems could reveal how these widely prevalent gene modules potentially impact P. syringae ecology, virulence, and disease management practices.

Sandwich-type tetranuclear lanthanide complexes with cucurbit[6]uril: from molecular compounds to coordination polymers.

Sandwich-type lanthanide complexes with macrocyclic ligand cucurbit[6]uril (C 36H 36N 24O 12, CB[6]) were synthesized under hydrothermal conditions from aqueous solutions of lanthanide(III) bromides, CB[6], and 4-cyanopyridine. According to X-ray analysis (Ln = La, Pr, Dy, Ho, Er, and Yb), the compounds with different structural types of lanthanide cores have a common fragment where the tetranuclear hydroxo complex is sandwiched between two macrocycles {(IN@CB[6])Ln 4(mu 3-OH) 4(IN@CB[6])} (6+) (IN = isonicotinate). The photoluminescence (for Ln = Eu) and Fourier transform ion cyclotron resonance mass spectra (for Ln = Pr, Dy, and Er) were studied. The compounds are used for the first time as precursors for the synthesis of lanthanide-silver heterometallic coordination polymers. The chainlike crystal structure of polymers (Ln = La, Pr, and Dy) is constituted by the sandwich complexes linked via the coordination of IN nitrogen atoms to the silver atoms.

The bivalent metal hypophosphites Sr(H2PO2)2, Pb(H2PO2)2 and Ba(H2PO2)2.

The structures of isomorphous monoclinic strontium and lead bis(dihydrogenphosphate), Sr(H2PO2)2 and Pb(H2PO2)2, and orthorhombic barium bis(dihydrogenphosphate), Ba(H2PO2)2, consist of layers of hypophosphite anions and metal cations exhibiting square antiprismatic coordination by O atoms. The Sr and Pb atoms are located on sites with point symmetry 2, and the Ba atoms are on sites with point symmetry 222. Within the layers, each anion bridges four metal cations.

The alkali hypophosphites KH2PO2, RbH2PO2 and CsH2PO2.

The structures of the hypophosphites KH(2)PO(2) (potassium hypophosphite), RbH(2)PO(2) (rubidium hypophosphite) and CsH(2)PO(2) (caesium hypophosphite) have been determined by single-crystal X-ray diffraction. The structures consist of layers of alkali cations and hypophosphite anions, with the latter bridging four cations within the same layer. The Rb and Cs hypophosphites are isomorphous.

Hexaaquanickel(II) bis(hypophosphite).

The structure of hexaaquanickel(II) bis(hypophosphite), [Ni(H(2)O)(6)](H(2)PO(2))(2), has been determined. The crystals are prismatic. The packing of the Ni and P atoms (not the entire hypophosphite anions) is the same as in the structures of [Co(H(2)O)(6)](H(2)PO(2))(2) and [Co(0.5)Ni(0.5)(H(2)O)(6)](H(2)PO(2))(2). The Ni(II) cations have a pseudo-face-centered cubic cell, with cell parameter a approximately= 10.216 A and tetrahedral cavities occupied by P atoms. The Ni(II) cation has crystallographically imposed twofold symmetry and has an octahedral coordination sphere consisting of six water O atoms, two of which also lie on the twofold axis. The planes of oppositely coordinated water molecules are in a cross conformation. The geometry of the hypophosphite anion is close to point symmetry mm2. The hypophosphite anions are hydrogen bonded to the coordinated water molecules.

Hexaaquacobalt(II) bis(hypophosphite) and hexaaquacobalt(II)/nickel(II) bis(hypophosphite).

The title compounds, hexaaquacobalt(II) bis(hypophosphite), [Co(H(2)O)(6)](H(2)PO(2))(2), and hexaaquacobalt(II)/nickel(II) bis(hypophosphite), [Co(0.5)Ni(0.5)(H(2)O)(6)](H(2)PO(2))(2), are shown to adopt the same structure as hexaaquamagnesium(II) bis(hypophosphite). The packing of the Co(Ni) and P atoms is the same as in the structure of CaF(2). The Co(II)(Ni(II)) atoms have a pseudo-face-centred cubic cell, with a = b approximately 10.3 A, and the P atoms occupy the tetrahedral cavities. The central metal cation has a slightly distorted octahedral coordination sphere. The geometry of the hypophosphite anion in the structure is very close to ideal, with point symmetry mm2. Each O atom of the hypophosphite anion is hydrogen bonded to three water molecules from different cation complexes, and each H atom of the hypophosphite anion is surrounded by three water molecules from further different cation complexes.

Copper(II) hypophosphite: the alpha- and beta-forms at 270 and 100 K, and the gamma-form at 270 K.

Copper(II) hypophosphite has been shown to exist as several polymorphs. The crystal structures of monoclinic alpha-, orthorhombic beta- and orthorhombic gamma-Cu(H(2)PO(2))(2) have been determined at different temperatures. The geometry of the hypophosphite anion in all three polymorphs is very close to the idealized one, with point symmetry mm2. Despite having different space groups, the structures of the alpha- and beta-polymorphs are very similar. The polymeric layers formed by the Cu atoms and the hypophosphite ions, which are identical in the alpha- and beta-polymorphs, stack in the third dimension in different ways. Each hypophosphite anion is coordinated to three Cu atoms. On cooling, a minimum amount of contraction was observed in the direction normal to the layers. The structure of the polymeric layers in the gamma-polymorph is quite different. There are two symmetry-independent hypophosphite anions; the first is coordinated to two Cu atoms, while the second is coordinated to four Cu atoms. In all three polymorphs, the Cu atoms are coordinated by six O atoms of six hypophosphite anions, forming tetragonal bipyramids; in the alpha- and beta-polymorphs, there are four short and two long Cu-O distances, while in the gamma-polymorph, there are four long and two short Cu-O distances.

Antigenic Variation and Some Biological Properties of Wild-Type Measles Virus Strain Buk and Vaccine Strain L-16.

In some measles virus strains protein synthesis is restricted or reduced at higher temperature incubation. But in wild-type Buk strain and L-16 vaccine strain no changes in viral protein synthesis at 40 degrees C were shown. Radiolabelled Buk and L-16 proteins were precipitated with reconvalescent sera, vaccinated children's sera, subacute sclerosing panencephalitis patients' sera and rabbit antisera. There are no differences in the autoradiograms. However, antigenic variations in Buk strain proteins were discovered by using mAbs in radioimmunoprecipitation analysis. Buk strain hemagglutinin (H protein) has low binding ability in epitopes II and III in comparison with L-16 strain. Analogous changes were found in the epitope II of Buk strain phosphoprotein. Nucleocapsid, fusion and membrane proteins of the two strains have the same interactions with mAbs. In order to investigate H protein affinity with antihemagglutinins and receptors for erythrocytes a modified test for HA-inhibiting antibodies was used. But incubation time for sera and tween-ether antigens was varied from 0 min to 1.5 h. In "0 min" incubation time hemagglutinin can bind with antihemagglutinins or receptors for erythrocytes. But H protein binds more readily with antibodies. Buk strain H protein revealed antihemagglutinins in higher titers than L-16 strain antigen.