Meningitis and bacteremia by nonhemolytic Group B Streptococcus strain: A whole genome analysis

Group B streptococcus (GBS) is a leading cause of neonatal infections. Most isolates are β-hemolytic, and their activity is considered to be pivotal for GBS pathogenicity. We report a case of a neonate with meningitis caused by nonhemolytic GBS. The patient developed meningitis 3 days after birth. Genotyping was performed and the characteristics of the strain (GCMC97051) identified by whole genome sequence using next generation sequencing. GCMC97051 possesses genetic alterations such as disruption of cylA by IS1381A insertion and a frameshift mutation in cylE, resulting in a lack of hemolysis. Thus, nonhemolytic GBS can retain the potential to cause invasive infections.     

A Study of Conformational Equilibria in Chain Molecules. I. Liquid n-Butane

Abstract

We have performed molecular dynamics simulations for liquid n-butane in order to understand liquid structures in terms of both inter- and intra-molecular interactions. Each n-butane molecule consists of four sites interacting with LJ potential and only a dihedral angle is taken into account as the internal degree of freedom. The population of gauche conformations with respect to the ideal gas state is found to increase in the liquid state. To investigate how the intermolecular interaction affects the dihedral angle distribution, we also adopt the repulsive LJ potential (RLJ) model. It is found that the nearest neighbor packing of the methyl and/or methylene groups can be approximately represented by using only the repulsive interaction. From the dihedral angle distribution, however, the rate of the shift of RLJ model to gauche is larger than that of LJ model and the attractive force also plays a significant role in the conformational equilibrium.     

Calculation of Vapour-Liquid Equilibria of Lennard-Jones Binary Systems by the Gibbs Ensemble Monte Carlo Simulation

Abstract

The Gibbs ensemble Monte Carlo simulation has been used to calculate vapour-liquid equilibria of a Lennard-Jones (LJ) binary mixture. The mixture studied is the LB-2-1 model which has been used in our previous calculations on PVT relation and density-dependent local composition. The P-x-y relation has been established at two different temperatures and used to determine vapour-liquid coexistence region in the PVTx space.     

Ranging behavior of Mahale chimpanzees: a 16 year study

We have analyzed the ranging patterns of the Mimikire group (M group) of chimpanzees in the Mahale Mountains National Park, Tanzania. During 16 years, the chimpanzees moved over a total area of 25.2 or 27.4 km², as estimated by the grid-cell or minimum convex polygon (MCP) methods, respectively. Annually, the M group used an average of 18.4 km², or approximately 70 %, of the total home-range area. The chimpanzees had used 80 % of their total home range after 5 years and 95 % after 11 years. M group chimpanzees were observed more than half of the time in areas that composed only 15 % of their total home range. Thus, they typically moved over limited areas, visiting other parts of their range only occasionally. On average, the chimpanzees used 7.6 km² (in MCP) per month. Mean monthly range size was smallest at the end of the rainy season and largest at the end of the dry season, but there was much variability from year to year. The chimpanzees used many of the same areas every year when Saba comorensis fruits were abundant between August and January. In contrast, the chimpanzees used several different areas of their range in June. Here range overlap between years was relatively small. Over the 16 years of the study we found that the M group reduced their use of the northern part of their range and increased their frequency of visits to the eastern mountainous side of their home range. Changes in home-range size correlated positively with the number of adult females but not with the number of adult males. This finding does not support a prediction of the male-defended territory model proposed for some East African chimpanzee unit-groups.     

Development of Biotin-Prototrophic and -Hyperauxotrophic Corynebacterium glutamicum Strains

To develop the infrastructure for biotin production through naturally biotin-auxotrophic Corynebacterium glutamicum, we attempted to engineer the organism into a biotin prototroph and a biotin hyperauxotroph. To confer biotin prototrophy on the organism, the cotranscribed bioBF genes of Escherichia coli were introduced into the C. glutamicum genome, which originally lacked the bioF gene. The resulting strain still required biotin for growth, but it could be replaced by exogenous pimelic acid, a source of the biotin precursor pimelate thioester linked to either coenzyme A (CoA) or acyl carrier protein (ACP). To bridge the gap between the pimelate thioester and its dedicated precursor acyl-CoA (or -ACP), the bioI gene of Bacillus subtilis, which encoded a P450 protein that cleaves a carbon-carbon bond of an acyl-ACP to generate pimeloyl-ACP, was further expressed in the engineered strain by using a plasmid system. This resulted in a biotin prototroph that is capable of the de novo synthesis of biotin. On the other hand, the bioY gene responsible for biotin uptake was disrupted in wild-type C. glutamicum. Whereas the wild-type strain required approximately 1 μg of biotin per liter for normal growth, the bioY disruptant (ΔbioY) required approximately 1 mg of biotin per liter, almost 3 orders of magnitude higher than the wild-type level. The ΔbioY strain showed a similar high requirement for the precursor dethiobiotin, a substrate for bioB-encoded biotin synthase. To eliminate the dependency on dethiobiotin, the bioB gene was further disrupted in both the wild-type strain and the ΔbioY strain. By selectively using the resulting two strains (ΔbioB and ΔbioBY) as indicator strains, we developed a practical biotin bioassay system that can quantify biotin in the seven-digit range, from approximately 0.1 μg to 1 g per liter. This bioassay proved that the engineered biotin prototroph of C. glutamicum produced biotin directly from glucose, albeit at a marginally detectable level (approximately 0.3 μg per liter).     

Top-down motif engineering of a cytokine receptor for directing ex vivo expansion of hematopoietic stem cells

The technique to expand hematopoietic stem cells (HSCs) ex vivo is eagerly anticipated to secure an enough amount of HSCs for clinical applications. Previously we developed a scFv-thrombopoietin receptor (c-Mpl) chimera, named S-Mpl, which can transduce a proliferation signal in HSCs in response to a cognate antigen. However, a remaining concern of the S-Mpl chimera may be the magnitude of the cellular expansion level driven by this molecule, which was significantly less than that mediated by endogenous wild-type c-Mpl. In this study, we engineered a tyrosine motif located in the intracellular domain of S-Mpl based on a top-down approach in order to change the signaling properties of the chimera. The truncated mutant (trunc.) and an amino-acid substitution mutant (Q to L) of S-Mpl were constructed to investigate the ability of these mutants to expand HSCs. The result showed that the truncated and Q to L mutants gave higher and considerably lower number of the cells than unmodified S-Mpl, respectively. The proliferation level through the truncated mutant was even higher than that of non-transduced HSCs with the stimulation of a native cytokine, thrombopoietin. Moreover, we analyzed the signaling properties of the S-Mpl mutants in detail using a pro-B cell line Ba/F3. The data indicated that the STAT3 and STAT5 activation levels through the truncated mutant increased, whereas activation of the Q to L mutant was inhibited by a negative regulator of intracellular signaling, SHP-1. This is the first demonstration that a non-natural artificial mutant of a cytokine receptor is effective for ex vivo expansion of hematopoietic cells compared with a native cytokine receptor.     

Structural Analysis of an Extracellular Polysaccharide of Porodisculus pendulus

The aroL gene, encoding shikimate kinase of Brevibacterium lactofermentum, a coryneform glutamic acid-producing bacterium, was cloned. Recombinant plasmids containing the aroL gene caused elevated levels of shikimate kinase synthesis in B. lactofermentum. It was found that in addition to the aroL gene, the aroB and aroE genes, encoding dehydroquinate synthase and shikimate dehydrogenase, respectively, also existed on these recombinant plasmids, in complementation tests with various Escherichia coli and B. lactofermentum aromatic amino acid auxotrophs. The aroL, aroB and aroE genes of B. lactofermentum are located closely on the cloned DNA fragment, in that order. It was shown that at least these three aro genes form a cluster on the chromosome of B. lactofermentum.     

Isolation and Constitution of a Xylan from Bamboo

A xylan from bamboo culm was isolated by extraction with aikali of chlorite holocellulose and fractional precipitation as a copper complex. The structure was investigated by means of examination of acid components by controlled hydrolysis, methylation analysis, and periodate oxidation. As a result, 4-O-methyl-α-D-glucuronic acid and 2-O-(4-O-methyl-α-D-glucopyranosyluronic acid) D-xylose were isolated and identified as acid components of the bamboo xylan. Hydrolysis of the fully methylated products afforded 2,3,5-tri-O- methyl-L-arabinose (1.6 moles), 2,3,4-tri-O-methyl-D-xylose (1.2 moles), 2,3,4,6-tetra-O-methyl-D-glucose(0.4 moles), 2,3-di-O-methyl-D-xylose (35.8 moles) and mono-O-methyl-D-xylose (2.6 moles). In addition to the above methylated sugars, 2,3,4-tri-O-methyl-D-glucuronic acid and partially methylated aldobiouronic acid were separated by cellulose column chromatography and identified. These results suggest that the bamboo xylan consists mainly of a linear backbone of 1,4-linked β-D-xylopyranose unit, to which L-arabinofuranose and 4-O-methyl-D-glucuronic acid were attached as a single side chain unit at C₂ or C₃.

Additional evidence for a linear chain structure has been given by periodate oxidation. On oxidation by periodate, the bamboo xylan consumed 1.09 moles of periodate and produced 0.05 mole of formic acid per anhydroxylose unit.