Sequence analysis of the gene encoding alternansucrase, a sucrose glucosyltransferase from Leuconostoc mesenteroides NRRL B-1355

The gene encoding alternansucrase (ASR) from Leuconostoc mesenteroides NRRL B-1355, an original sucrose glucosyltransferase (GTF) specific to alternating alpha-1,3 and alpha-1,6 glucosidic bond synthesis, was cloned, sequenced and expressed into Escherichia coli. Recombinant enzyme catalyzed oligoalternan synthesis from sucrose and maltose acceptor. From sequence comparison, it appears that ASR possesses the same domains as those described for GTFs specific to either contiguous alpha-1,3 osidic bond or contiguous alpha-1,6 osidic bond synthesis. However, the variable region and the glucan binding domain are longer than in other GTFs (by 100 and 200 amino acids respectively). The N-catalytic domain which presents 49% identity with the other GTFs from L. mesenteroides possesses the three determinants potentially involved in the glucosyl enzyme formation.     

Amylosucrase from Neisseria polysaccharea: novel catalytic properties

Amylosucrase is a glucosyltransferase that synthesises an insoluble alpha-glucan from sucrose. The catalytic properties of the highly purified amylosucrase from Neisseria polysaccharea were characterised. Contrary to previously published results, it was demonstrated that in the presence of sucrose alone, several reactions are catalysed, in addition to polymer synthesis: sucrose hydrolysis, maltose and maltotriose synthesis by successive transfers of the glucosyl moiety of sucrose onto the released glucose, and finally turanose and trehalulose synthesis - these two sucrose isomers being obtained by glucosyl transfer onto fructose. The effect of initial sucrose concentration on initial activity demonstrated a non-Michaelian profile never previously described.     

An essential function of the C. elegans ortholog of TPX2 is to localize activated aurora A kinase to mitotic spindles

In vertebrates, the microtubule binding protein TPX2 is required for meiotic and mitotic spindle assembly. TPX2 is also known to bind to and activate Aurora A kinase and target it to the spindle. However, the relationship between the TPX2-Aurora A interaction and the role of TPX2 in spindle assembly is unclear. Here, we identify TPXL-1, a C. elegans protein that is the first characterized invertebrate ortholog of TPX2. We demonstrate that an essential role of TPXL-1 during mitosis is to activate and target Aurora A to microtubules. Our data suggest that this targeting stabilizes microtubules connecting kinetochores to the spindle poles. Thus, activation and targeting of Aurora A appears to be an ancient and conserved function of TPX2 that plays a central role in mitotic spindle assembly.     

Intracellular nickel accumulation by Pseudomonas aeruginosa and its chemical nature

AIMS: To investigate intracellular localization of nickel and its chemical nature in Pseudomonas aeruginosa. METHODS AND RESULTS: Transmission electron micrographs of Ni-loaded bacteria exhibited a darkened electron opaque zone throughout the cell periphery. Energy dispersive X-ray analysis confirmed the deposition of metallic nickel. Cell fractionation revealed that 88% of the accumulated nickel was restricted to the periplasm and membrane. X-ray diffraction patterns ascertained the chemical nature of cellular Ni as phosphide (Ni5P4, NiP2 and Ni12P5) and carbide (Ni3C) crystals. CONCLUSION: Pseudomonas aeruginosa accumulated nickel as its phosphide and carbide crystal mostly in the cell envelope region, indicating the predominant role of phosphoryl and carboxyl/carbonyl groups of cell wall/membrane components in cation sequestration. SIGNIFICANCE AND IMPACT OF THE STUDY: The data contribute significantly to a better understanding of bacteria-metal interaction and will be useful in developing biotechnological strategies for toxic metal bioremediation.     

Antiprotozoal alkaloids from Galanthus trojanus

Two new alkaloid N-oxides, 1-O-acetyldihydromethylpseudolycorine N-oxide, and 11-hydroxyvittatine N-oxide, ten known alkaloids; arolycoricidine, haemanthamine, O-methylnorbelladine, narcidine, dihydrolycorine, 8-O-demethylmaritidine, stylopine and protopine, nicotinic acid and tyramine were isolated from Galanthus trojanus A.P. Davis & N. Özhatay (Amaryllidaceae). The chemical structures of the isolates were elucidated by UV, IR, MS, CD, 1D and 2D NMR experiments. The in vitro antiprotozoal and cytotoxic potentials of the compounds were also evaluated.     

Isolation,molecular characterization and antibiotic resistance of Shiga Toxin–Producing Escherichia coli (STEC) from buffalo in India

In total, 363 Escherichia coli were isolated from 165 faecal samples of healthy buffaloes in West Bengal, India. Twenty‐four of these isolates (6·61%) were found to carry at least one gene characteristic for Shiga toxin–producing Escherichia coli (STEC). These STEC strains belonged to 13 different O‐serogroups. The stx₁ gene was present in 23 (95·8%) of total STEC isolates, whereas 20 (83·3%) STEC isolates carried the gene stx_2. Twelve strains of E. coli (50% of total STEC isolates) possessed enterohaemolysin (ehxA) gene in combination with others. Fourteen (58·33%) isolates found to possess saa gene. However, no E. coli was detected harbouring gene for intimin protein (eaeA). Of 23 stx₁‐positive isolates, seven (30·43%) were positive for genes of the stx_1C subtype. Of the 20 isolates with the stx₂ gene, 25% (5/20) possessed stx_2C and 10% (2/20) possessed stx_2d gene. The phylogenetic analysis after RAPD of STEC strains revealed six major clusters. The isolated STEC strains were resistant most frequently to erythromycin (95·83%), cephalothin (62·5%), amikacin (54·17%), kanamycin (45·83%) and gentamicin (41·67%) group of antibiotics. No ESBL‐producing (bla_CTXM, bla_TEM, bla_SHV) or quinolone resistance gene (qnrA) was detected in the STEC isolates.

Significance and Impact of the Study

The buffaloes from different districts of West Bengal, India, are important reservoir of multidrug‐resistant Shiga toxin–producing Escherichia coli (STEC). India is home to more than 56% of world buffalo population, traditionally raised by farmers. So, there is a major risk of transmission of STEC among the human population of this part of the globe. However, there is no prevalence study of STEC from healthy or diarrhoeic buffalo in India. The present study reports for the first time in India about isolation, molecular characterization and antibiotic resistance pattern of STEC in healthy buffaloes.     

A Prospective Study of the Causes of Febrile Illness Requiring Hospitalization in Children in Cambodia

BackgroundFebrile illnesses are pre-eminent contributors to morbidity and mortality among children in South-East Asia but the causes are poorly understood. We determined the causes of fever in children hospitalised in Siem Reap province, Cambodia.ConclusionWe identified a microbiological cause of fever in almost 50% of episodes in this large study of community-acquired febrile illness in hospitalized children in Cambodia. The range of pathogens, antimicrobial susceptibility, and co-morbidities associated with mortality described will be of use in the development of rational guidelines for infectious disease treatment and control in Cambodia and South-East Asia.     

The Effects of Chromium Complex and Level on Glucose Metabolism and Memory Acquisition in Rats Fed High-Fat Diet

Conditions in which glucose metabolism is impaired due to insulin resistance are associated with memory impairment. It was hypothesized that supplemental chromium (Cr) may alleviate insulin resistance in type 2 diabetes and consequently improve memory acquisition, depending upon its source and level. In a complete randomized design experiment, male Wistar rats (n=60; weighing 200-220 g) were fed either normal (8%, normal diet (ND)) or high-fat (40%, high-fat diet (HFD)) diet and supplemented with Cr as either chromium-glycinate (CrGly) or chromium-acetate (CrAc) at doses of 0, 40, or 80 μg/kg body weight (BW) via drinking water from 8 to 20 weeks of age. Feeding HFD induced type 2 diabetes, as reflected by greater glucose/insulin ratio (2.98 vs. 2.74) comparing to feeding ND. Moreover, HFD rats had greater BW (314 vs. 279 g) and less serum (53 vs. 68 μg/L) and brain (14 vs. 24 ng/g) Cr concentrations than ND rats. High-fat diet caused a 32% reduction in expressions of glucose transporters 1 and 3 (GLUTs) in brain tissue and a 27% reduction in mean percentage time spent in the target quadrant and a 38% increase in spatial memory acquisition phase (SMAP) compared with ND. Compared with supplemental Cr as CrAc, CrGly was more effective to ameliorate response variables (i.e., restoration of tissue Cr concentration, enhancement of cerebral GLUTs expressions, and reduction of the glucose/insulin ratio and SMAP) in a dose-response manner, especially in rats fed HFD. Supplemental Cr as CrGly may have therapeutic potential to enhance insulin action and alleviate memory acquisition in a dose-dependent manner, through restoring tissue Cr reserve and enhancing cerebral GLUTs expressions.