Saturation of penicillin-binding protein 1 by β-lactam antibiotics in growing cells of Bacillus licheniformis

With the help of a new highly sensitive method allowing the quantification of free penicillin-binding proteins (PBPs) and of an integrated mathematical model, the progressive saturation of PBP1 by various β-lactam antibiotics in growing cells of Bacillus licheniformis was studied. Although the results confirmed PBP1 as a major lethal target for these compounds, they also underlined several weaknesses in our present understanding of this phenomenon. In growing cells, but not in resting cells, the penicillin target(s) appeared to be somewhat protected from the action of the inactivators. In vitro experiments indicated that amino acids, peptides and depsipeptides mimicking the peptide moiety of the nascent peptidoglycan significantly interfered with the acylation of PBP1 by the antibiotics. In addition, the level of PBP1 saturation at antibiotic concentrations corresponding to the minimum inhibitory concentrations was not constant, suggesting that additional, presently undiscovered, factors might be necessary to account for the experimental observations.     

High frequency of-β-hexosaminidase deficiency in lymphoblastoid cell lines

The activity of seven lysosomal enzymes was determined in 25 lymphoblastoid cell lines. These lines included normal controls transformed with Epstein-Barr virus, Burkitt's lymphomas and other lymphomas with or without EBV genome.Four lines were deficient in total β-hexosaminidase activity. The deficiency was as severe as that of the variant O (Sandhoff's disease) of clinical β-hexosaminidase deficiency. The electrophoretic pattern was also similar to that observed in Sandhoff's disease.The possible mechanisms explaining the high frequency of β-hexosaminidase deficiency in lymphoblastoid cell lines are discussed.     

Trophoblastin, an antiluteolytic protein present in early pregnancy in sheep.

Trophoblastin, an antiluteolytic component from the embryo, was identified in the ewe by the means of intrauterine injections of homogenates from trophoblasts at 14--16 days pregnancy. Homogenates from embryos and their membranes at 21--23 days pregnancy did not extend the life of the corpus luteum, suggesting that trophoblastin synthesis occurs for only a short period. The trophoblastin was thermolabile (80 degrees C for 30 min) and inactivated by pronase. Treatment of ewes with oCS, hCG, and extracts of 120-day placentae did not affect the time of luteolysis. The protein appears to be insoluble at pH 7 or 8, but to dissolve readily at pH 9.6. After injection of homogenates or extracts from 15--16-day-old trophoblasts, the initial CL were maintained for more than 1 month in most cyclic recipient ewes. Surgical removal of embryos at 21--23 days resulted in luteal maintenace for more than 1 month in over 50% of the operated animals. All the maintained CL were secretory although their average weight was about one-half of that CL of normal pregnancy, suggesting the existence of complementary luteotrophic placental factors. The uteri of most of these pseudopregnant ewes were distended with a clear, sterile fluid.     

Sequences homologous to Tc(s) transposable elements ofCaenorhabditis elegans are widely distributed in the phylum nematoda

Summary To have a better understanding of the evolutionary history of mobile elements within the nematodes, we examined the distribution and the conservation of homologues to transposable elements fromCaenorhabditis elegans (Tc1, Tc2, Tc3, Tc4, Tc5, and FB1) in 19 nematode species belonging to the class Secernentea. Our results show that Tc1 elements display a distribution restricted to the family Rhabditidae with poor conservation. The Tc2 and FB1 homologous elements have the same patchy distribution within the Rhabditidae. They were only found inCaenorhabditis and inTeratorhabditis. The Tc3 element is widely distributed among nematode species. Tc3 homologous elements are present in the majority of the Rhabditidae but also in two genera within the family Panagrolaimidae, and inBursaphelenchus, which belongs to the order Aphelenchida. Tc4 and Tc5 homologues show the most limited distribution of all tested elements, being strictly limited toC. elegans. These data indicate that in some cases, the distribution of transposable elements in the nematode cannot be explained by strict vertical transmission. The distribution of Tc3, Tc4, and Tc5 suggests that horizontal transmission may have occurred between reproductively isolated species during their evolutionary history.     

DNA sequence analysis of the lamB gene from Klebsiella pneumoniae: implications for the topology and the pore functions in maltoporin.

Summary We have determined the sequence of the lamB gene from Klebsiella pneumoniae. It encodes the precursor to the LamB protein, a 429 amino acid polypeptide with maltoporin function. Comparison with the Escherichia coli LamB protein reveals a high degree of homology, with 325 residues strictly identical. The N-terminal third of the protein is the most conserved part of the molecule (1 change in the signal sequence, and 13 changes up to residue 146 of the mature protein). Differences between the two mature proteins are clustered mainly in six regions comprising residues 145–167, 173–187, 197–226, 237–300, 311–329, and 367–387 (K. pneumoniae LamB sequence). The most important changes were found in regions predicted by the two-dimensional model of LamB folding to form loops on the cell surface. In vivo maltose and maltodextrin transport properties of E. coli K 12 and K. pneumoniae strains were identical. However, none of the E. coli K12 LamB-specific phages was able to plaque onto K. pneumoniae. Native K. pneumoniae LamB protein forms highly stable trimers. The protein could be purified by affinity chromatography on starch-Sepharose as efficiently as the E. coli K12 LamB protein, indicating a conservation of the binding site for dextrins. However, none of the monoclonal antibodies directed against native E. coli K12 LamB protein recognized native purified K. pneumoniae LamB protein. These data indicate that most of the variability occurs within exposed regions of the protein and provide additional support for the proposed model of LamB folding. The fact that the N-terminal third of the protein is highly conserved is in agreement with the idea that it is part of, or constitutes, the pore domain located within the transmembranous channel and that it is not accessible from the cell surface.     

Blood lactic acid level changes during acidosis induced by hydrochloric acid perfusion]

An increase in H+ ions concentration by infusion of hydrochloric acid produces a reduction in lactacidemia. This phenomenon is a result of the inhibitory effect of acidosis on phosphofructokinase producing a diminution of intracellular glycolysis.     

Molecular Epidemiology of Carbapenem Non-Susceptible Acinetobacter baumannii in France

Carbapenem-resistant Acinetobacter baumannii have emerged globally. The objective of this study was to investigate the epidemiology, clonal diversity and resistance mechanisms of imipenem non-susceptible A. baumannii isolates in France. Between December 2010 and August 2011, 132 notifications were collected, including 37 outbreaks corresponding to 242 cases (2 to 55 per cluster). Multilocus sequence typing, pulsed-field gel electrophoresis (PFGE) and characterisation of carbapenemase-encoding genes were performed on 110 non-repetitive isolates. Gene bla _OXA-23 was the most frequently detected (82%), followed by bla _OXA-24 (11%) and bla _OXA-58 (7%). Eleven sequence types (ST) were distinguished, among which sequence types ST1, ST2 (64%), ST20, ST25, ST85 and ST107. Isolates from epidemiological clusters had the same ST and resistance genes, indicating probable transmission within centres. In contrast, PFGE types of isolates differed among centres, arguing against transmission among centers. This study provides the first epidemiological snapshot of the population of A. baumannii with reduced susceptibility to carbapenems from France, and further underlines the predominance of international clones.