Cloning, sequencing and distribution of the Salmonella typhimurlum LT2 siaiidase gene, nanH, provides evidence for interspecies gene transfer

The Salmonella typhimurium LT2 sialidase (neuraminidase, EC 3.2.1.18) structural gene, nanH, has been cloned and sialidase overproduced from multicopy plasmids in Escherichia coli. Sialidase expression was regulated positively by cAMP. In contrast, certain Tn1000 insertions located upstream of nanH coding sequences reduced sialidase activity. A nanH chromosomal insertion mutation constructed by marker exchange demonstrated a single sialidase gene copy in S. typhimurium LT2. The complete nucleotide sequence of nanH, encoding a 41,300 dalton polypeptide, was determined and the derived primary structure was similar to sialidases from Clostridium perfringens, Clostridium sordellii, Bacteroides fragilis, and Trypanosoma cruzi. Comparative sequence analysis, including codon usage and secondary structure predictions, indicated that the S. typhimurium and clostridial sialidases are homologous, strongly suggestive of an interspecies gene transfer event. At least two primary sequence motifs of the bacterial enzymes were detected in influenza A virus sialidases. The predicted secondary structure of the bacterial enzymes was strikingly similar to viral sialidase. From the population distribution of nanH detected within a collection of salmonellae, it was apparent that S. typhimurium obtained its nanH copy most recently from Salmonella arizonae. S. typhimurium LT2 is thus a genetic mosaic that differs from other strains of even the same serotype by nanH plus potentially additional characters linked to nanH. These results have relevance to the evolution and function of sialidases in pathogenic microbes, and to the origin of the sialic acids.     

Enzymatic characterization of oral and non-oral black-pigmented Bacteroides species

The purpose of this study was to investigate the production of various enzymes by oral and non-oral black-pigmented Bacteroides species using chromogenic substrates. The 19 substrates present in the API ZYM system did not differentiate between B. melaninogenicus, B. denticola, B. loescheii and B. levii. The asaccharolytic black-pigmented Bacteroides species showed each species specific enzyme activity, however, differences were based on one enzyme only as far as B. asaccharolyticus and B. endodontalis are concerned. An extended number of 40 chromogenic substrates were tested in order to find more species specific enzyme. With a set of 20 substrates it appeared to be possible to discriminate between all species tested. The possibility to use enzymes for the identification of black-pigmented Bacteroides is discussed.     

Studies on 9-amino-6-chloro-2-methoxy acridine fluorescence quenching and enhancement in relation to energy transduction in spheroplasts and intact cells of the cyanobacterium Plectonema boryanum

The fluorescent probe 9-amino-6-chloro-2-methoxy acridine was used to study the energy transduction in the thylakoid and cell membranes of the cyanobacterium Plectonema boryanum. Apart from light-driven electron transfer, the dark endogenous respiration also leads to energization resulting in an ACMA fluorescence response, that is sensitive to the electron flow inhibitor 2, 5-dibromo-3-methyl-6-isopropyl-p-benzoquinone, to the energy transfer inhibitors dicyclohexylcarbodiimide and venturicidine and to the uncoupler 5-chloro-3-t-butyl-2-chloro-4-nitrosalicylanilide.In spheroplasts, in which the cell membranes have lost their capacity to maintain a proton gradient, the respiration-and light-induced ACMA fluorescence changes (quenching) are similar to those in chloroplasts. In intact cells a combination of reversible quenching and enhancement of ACMA fluorescence was found. This dualistic behaviour is supposedly caused by an opposite orientation of the thylakoid and cell membranes. ACMA quenching at the level of the thylakoids was obtained either by respiratory or photosynthetic electron transfer and gave similar responses to those obtained in the spheroplasts. The slower ACMA fluorescence enhancement, only observed in cells with intact cell membranes, also evoked by both respiration and light-induced energization is sensitive to the compounds mentioned above and in addition to KCN.Our results support the view [8] that dark oxidation of substrates by O₂ proceeds via the thylakoid membrane and terminates at a CN^- sensitive oxidase located in the cell membrane which requires the involvement of a mobile cytoplasmic redox mediator.Abbreviations ACMA 9-amino-6-chloro-2-methoxy acridine - chl a chlorophyll a - DBMIB 2, 5-dibromo-3-methyl-6-isopropyl-p-benzoquinone - DCCD dicyclohexylcarbodiimide - DNP dinitrophenol - DNP-INT dinitrophenyl ether of 2-iodo-4-nitrothymol - FCCP carbonylcyanide-p-trifluoro-methoxy phenylhydrazone - S-13 5-chloro-3-t-butyl-2-chloro-4-nitrosalicylanilide - tricine N-2 (2-Hydroxy-1, 1-bis (hydroxymethyl) ethyl)-glycine - Tris Tris (hydroxymethyl) amino methane     

Proteolytic activity of black-pigmented Bacteroides strains

Abstract The proteolytic activity of several black-pigmented Bacteroides species was measured. Bacteroides gingivalis was the only species having collagenolytic activity. General proteolytic activity on gelatin and Azocoll was shown in cultures of B. gingivalis, B. asaccharolyticus, B. endodontalis, B. intermedius, B. corporis and to a lesser extent B. melaninogenicus; B. loescheii did not show proteolytic activity. When culture filtrates were tested, B. gingivalis showed high cell free proteolytic activity, whereas the other species had only very weak cell free activity. Growth curves of B. gingivalis revealed two distinct proteolytic activities; general proteolytic activity was found during the logarithmic growth phase, whereas a second peak containing high collagenolytic activity was found after prolonged incubation of cells showing autolysis.     

Ets proteins: new factors that regulate immunoglobulin heavy-chain gene expression.

We used a DNA-protein interaction screening method to isolate a cDNA, Erg-3, whose product binds to a site, designated pi, present in the immunoglobulin (Ig) heavy-chain gene enhancer. Erg-3 is an alternatively spliced product of the erg gene and contains an Ets DNA-binding domain. Fli-1 and PU.1, related Ets proteins, also bind to the same site. In addition, PU.1 binds to a second site, designated microB, in the Ig heavy-chain enhancer. We demonstrate that the pi binding site is crucial for Ig heavy-chain gene enhancer function. In addition, we show that Erg-3 and Fli.1, but not PU.1, can activate a reporter construct containing a multimer of protein-binding sites, synergistically with helix-loop-helix protein E12. We discuss how combinatorial interactions between members of the helix-loop-helix and Ets families may account for the tissue specificity of these proteins.     

Effect of culture filtrates of black-pigmented Bacteroides species on the matrix production of chick embryo chondrocytes in vitro

Antonie van Leeuwenhoek -     

Pleomorphism inScenedesmus quadricauda (Turp) Bréb. (Chlorophyceae)

A clone ofScenedesmus quadricauda, isolated from Tjeukemeer, exhibits a high degree of morphological variation in synchronized cultures. Cells are synchronized by light-dark cycles. During the photoperiod they build up the capacity to divide. First division into 2- and 4-celled coenobia is induced, then during the second half of the photoperiod the induction of division into 8 unicells takes place. Division itself and the subsequent liberation of daughter cells occur in the dark period.By giving a definite photoperiod the formation of either coenobia or unicellular stages is determined. The formation of both coenobia and unicells is followed using a light microscope. In both cases only the pattern of cytokinesis is similar. After cytokinesis the unicells become ovoid in shape and form two spines at each pole. They are released from the parental wall as separate cells and show remarkable similarity to theChodatella-like cells described by SWALE (1967) and FOTT (1968). The coenobial cells elongate, adhere to one another and each of the two outmost cells forms two spines (SMITH, 1914).     

IMPROV-ED trial: eHealth programme for faster recovery and reduced healthcare utilisation after CABG

Netherlands Heart Journal - After coronary artery bypass grafting (CABG), healthcare utilisation is high and is partly unplanned. eHealth applications have been proposed to reduce healthcare...