Wear testing of crosslinked polyethylene: wear rate variability and microbial contamination.

The wear performance of two types of crosslinked polyethylene (Marathon™ and XLK™, DePuy Synthes Inc., Warsaw, IN) was evaluated in a pin-on-disc wear tester, a hip wear simulator, and a knee wear simulator. Sodium azide was used as the microbial inhibitor in the calf serum-based lubricant. In the pin-on-disc wear tester, the Marathon wear rate of 5.33±0.54mm(3)/Mc was significantly lower (p=0.002) than the wear rate of 6.43±0.60mm(3)/Mc for XLK. Inversely, the Marathon wear rate of 15.07±1.03mm(3)/Mc from the hip wear simulator was 2.2-times greater than the XLK wear rate of 6.71±1.03mm(3)/Mc from the knee wear simulator. Differences in implant design, conformity, GUR type, and kinematic test conditions were suggested to account for the difference between the wear rates generated in the different types of wear testing apparati. In all wear tests, sodium azide was ineffective at inhibiting microbial growth in the lubricant. Eight different organisms were identified in the lubricant samples from the wear tests, which suggested the necessity of using an alternative, more effective microbial inhibitor. Careful sample preparation and thorough cleaning has shown to improve the consistency of the wear results. The wear rates generated in the hip and knee wear simulators closely reflected the wear behaviour of Marathon and XLK reported in published data that were tested under similar conditions.

[Genetic collections: problems of formation, conservation and use]. / Geneticheskie kollektsii: problemy formirovaniia, sokhraneniia i ispol'zovaniia.

Classification of plant genepool collections are presented, the principal tasks worked on by collections are examined. Databases on genepool collections of the Institute of Cytology and Genetics of Syberian Branch of Russian Academy of Sciences (Russia) and the National Centre for Plant Genetic Resources of Ukraine are described. Principles of formation of genepool collections, their existing problems, the methods of maintenance of their viability and genetical authenticity are discussed. Necessary amount of collection accessions, differences and specificity of their reproduction and multiplication aims and tasks are proved. Gradations of the permissible changes of accessions in connection with the type and the purpose of collections are proposed. The necessity of specialized periodical edition on genepool collecting is emphasized.

Isolation of an antimicrobial compound from Impatiens balsamina L. using bioassay-guided fractionation.

By using brine shrimp (Artemia salina) lethality test-guided fractionation, a single bioactive compound (LC(50)=26 ppm) was isolated from the 95% ethanol extract of the dried aerial parts of Impatiens balsamina L. and subsequently identified as 2-methoxy-1,4-naphthoquinone (MNQ). The structure of MNQ was confirmed by UV, FT-IR, MS, and 1-and 2-D NMR spectroscopy. The antimicrobial activity of MNQ was evaluated using 12 bacterial and eight fungal strains. Five gram-positive and two gram-negative bacteria as well as all eight fungi (including multi-drug resistant strains) tested were highly sensitive to MNQ. A tea prepared according to traditional methods was found to contain sufficient MNQ to account for its antimicrobial properties.

[Analysis of isogenic lines of the soft wheat carrying dominant alleles of Bg, Hg, and Rg1 genes using microsatellite and protein markers]. / Analiz izogennykh linii miagkoi pshenitsy, nesushchikh dominantnye alleli genov Bg, Hg i Rg1, s pomoshch'iu mikrosatellitnykh i belkovykh markerov.

To determine tight linkage between morphological and molecular markers of the first homologous group of chromosomes of common wheat, microsatellite analysis of six near-isogenic lines with marker dominant alleles controlling back color (Bg; 1AS) and hairy glume (Hg; 1AS) and two lines bearing the dominant alleles of the gene for red glume color (Rgl; 1BS) was conducted. The component composition of gliadins in these lines was studied. Tight linkage of Bg, Hg, and Gli-A1 genes with a microsatellite marker Xgwm136 (1AS) and of Rg1 and Gli-B1 genes with markers Xgwm33 and Xgwm550 (1BS) was shown. Based on the results obtained and literature data, the most probable order of morphological and molecular markers on chromosomes of common wheat was determined. On chromosome 1AS, from the centromere to the telomere, the markers are located as follows: Xgwm136-Gli-A1-BgHg; on chromosome 1BS, in the same direction: Xgwm33-Gli-B1-Rg1-Xgwm550.

Physiological adaptations involved in alkane assimilation at a low temperature by Rhodococcus sp. strain Q15.

We examined physiological adaptations which allow the psychrotroph Rhodococcus sp. strain Q15 to assimilate alkanes at a low temperature (alkanes are contaminants which are generally insoluble and/or solid at low temperatures). During growth at 5 degrees C on hexadecane or diesel fuel, strain Q15 produced a cell surface-associated biosurfactant(s) and, compared to glucose-acetate-grown cells, exhibited increased cell surface hydrophobicity. A transmission electron microscopy examination of strain Q15 grown at 5 degrees C revealed the presence of intracellular electron-transparent inclusions and flocs of cells connected by an extracellular polymeric substance (EPS) when cells were grown on a hydrocarbon and morphological differences between the EPS of glucose-acetate-grown and diesel fuel-grown cells. A lectin binding analysis performed by using confocal scanning laser microscopy (CSLM) showed that the EPS contained a complex mixture of glycoconjugates, depending on both the growth temperature and the carbon source. Two glycoconjugates [beta-D-Gal-(1-3)-D-GlcNAc and alpha-L-fucose] were detected only on the surfaces of cells grown on diesel fuel at 5 degrees C. Using scanning electron microscopy, we observed strain Q15 cells on the surfaces of octacosane crystals, and using CSLM, we observed strain Q15 cells covering the surfaces of diesel fuel microdroplets; these findings indicate that this organism assimilates both solid and liquid alkane substrates at a low temperature by adhering to the alkane phase. Membrane fatty acid analysis demonstrated that strain Q15 adapted to growth at a low temperature by decreasing the degree of saturation of membrane lipid fatty acids, but it did so to a lesser extent when it was grown on hydrocarbons at 5 degrees C; these findings suggest that strain Q15 modulates membrane fluidity in response to the counteracting influences of low temperature and hydrocarbon toxicity.

[Use of RAPD- and STS-analysis for marking genes of a homeologic group from chromosome 5 of common wheat]. / Ispol'zovanie RAPD- i STS-analiza dlia markirovaniia genov piatoi gomeologicheskoi gruppy khromosom miagkoi pshenitsy.

The search for STS (sequence-tagged site) and RAPD (random amplified polymorphic DNA) markers tightly linked to some genes of homeologous group 5 chromosomes of common wheat Triticum aestivum L., more specifically, awns inhibitor genes (B1), vernalization response gene (Vrn1), and homeologous chromosome pairing gene (Ph1), was conducted. To estimate the linkage of the gene with the marker, wheat lines marked with recessive alleles b1 and vrn1 were used. RELP (restriction fragment length polymorphism) and SSR (simple sequence repeat) analyses of isogenic wheat lines were conducted to characterize the chromosomal region transferred to the isogenic line from the donor parent. In RAPD analysis of isogenic wheat lines marked with recessive alleles b1 and vrn1, 95 arbitrary primers were used. To develop STS markers, analysis of the primary structure of RELP markers Xpsr426 and Xcdo504, tightly linked to the Vrn1 gene, and the Xpsr1201 marker, located at the Ph1 locus, was carried out. Two markers that are tightly linked to the Vrn1 gene (5AL)--RAPD marker Xr405 and STS marker Xsts426--were obtained in this work. In addition, there is every reason to believe that Xsts426 can be used as a PCR marker of genes Vrn2 (5BL) and Vrn3 (5DL), while Xsts1201, of the gene Ph1 (5BL).

Functions of S-layers.

Although S-layers are being increasingly identified on Bacteria and Archaea, it is enigmatic that in most cases S-layer function continues to elude us. In a few instances, S-layers have been shown to be virulence factors on pathogens (e.g. Campylobacter fetus ssp. fetus and Aeromonas salmonicida), protective against Bdellovibrio, a depository for surface-exposed enzymes (e.g. Bacillus stearothermophilus), shape-determining agents (e.g. Thermoproteus tenax) and nucleation factors for fine-grain mineral development (e.g. Synechococcus GL 24). Yet, for the vast majority of S-layered bacteria, the natural function of these crystalline arrays continues to be evasive. The following review up-dates the functional basis of S-layers and describes such diverse topics as the effect of S-layers on the Gram stain, bacteriophage adsorption in lactobacilli, phagocytosis by human polymorphonuclear leukocytes, the adhesion of a high-molecular-mass amylase, outer membrane porosity, and the secretion of extracellular enzymes of Thermoanaerobacterium. In addition, the functional aspect of calcium on the Caulobacter S-layer is explained.

Unusually Stable Spinae from a Freshwater Chlorobium sp.

A green Chlorobium sp. with spinae, strain JSB1, was isolated from an enrichment culture previously obtained from Fayetteville Green Lake, N.Y. (J. S. Brooke, J. B. Thompson, T. J. Beveridge, and S. F. Koval, Arch. Microbiol. 157:319-322, 1992). Cells were gram-negative, nonmotile rods which contained bacteriochlorophyll c and chlorosomes. Spinae were best seen by transmission electron microscopy in thin sections of cells fixed in the presence of tannic acid. High-resolution scanning electron microscopy showed the spinae randomly distributed at the cell surface and at the junctions between cells. Spinae were physically sheared from cells and isolated from the culture supernatant by ultrafiltration. As observed by electron microscopy, spinae demonstrated unusual structural stability when exposed for 1 h at 37 deg C to chemical treatments such as hydrogen bond-breaking agents, detergents, metal-chelating agents, proteases, and organic solvents. They were stable for 1 h at 37 deg C over the pH range 2.3 to 9.9 and in 1 M HCl and 1 M NaOH. The structural integrity of the spinae was also maintained when spinae were subjected to harsher treatments of autoclaving in 2% (wt/vol) sodium dodecyl sulfate and exposure to dithiothreitol at pH 9 for 1 h at 100 deg C. Partially dissociated spinae were obtained after 5 h at 100 deg C in 1 M HCl and 1 M NaOH. In acid, the tubular spinae became amorphous structures, with no helical striations visible. In alkali, the spinae had dissociated into irregular aggregates of disks. Since both high temperature and extremes of pH were required to achieve partial dissociation of the spinae, the strength of the structure presumably comes from covalent bonding.

Physical characterization of the flagella and flagellins from Methanospirillum hungatei.

Flagellar filaments from Methanospirillum hungatei GP1 and JF1 were isolated and subjected to a variety of physical and chemical treatments. The filaments were stable to temperatures up to 80 degrees C and over the pH range of 4 to 10. The flagellar filaments were dissociated in the detergents (final concentration of 0.5%) Triton X-100, Tween 20, Tween 80, Brij 58, N-octylglucoside, cetyltrimethylammonium bromide, and Zwittergent 3-14, remaining intact in only two of the detergents tested, sodium deoxycholate and 3-[(3-cholamidopropyl)-dimethyl-ammonio]-1-propanesulfonate (CHAPS). Spheroplasting techniques were used to separate the internal cells from the complex sheath, S-layer (cell wall), and end plugs of M. hungatei. The flagellar basal structure was visualized after solubilization of membranes by CHAPS or deoxycholate. The basal structure appeared to be a simple knob with no apparent ring or hook structures. The multiple, glycosylated flagellins constituting the flagellar filaments were cleaved by proteases and cyanogen bromide. The cyanogen bromide-generated fragments of M. hungatei GP1 flagellins were partially sequenced to provide internal sequence information. In addition, the amino acid composition of each flagellin was determined and indicated that the flagellins are distinct gene products, rather than differentially glycosylated forms of the same gene product.

Relatedness of the flagellins from methanogens.

Purified flagellar filaments isolated from six methanogens were composed of multiple flagellins. Two flagellins were present in Methanococcus deltae (Mr = 34,000 and 32,000), Methanoculleus marisnigri (Mr = 31,000 and 25,500) and Methanococcus jannaschii (Mr = 31,000 and 27,500), three in Methanothermus fervidus (Mr = 34,000, 25,000 and 24,000) and four or more in both Methanococcus vannielii and Methanococcus maripaludis (Mr ranging from 27,500 to 32,000). The flagellins of M. fervidus and M. deltae reacted positively with glycoprotein-specific stains. The flagellins of M. deltae, M. maripaludis and M. vannielii were closely related to those of M. voltae based on cross-reactivity with antisera raised against M. voltae flagellins and homology with flagellin-specific oligonucleotide probes to the N-terminus and leader peptide of M. voltae flagellins. Similarities appear to exist among the flagellins of M. fervidus, M. marisnigri and Halobacterium halobium based on cross-reactivity with antisera produced against the flagella of Methanospirillum hungatei JF1. The N-termini of the flagellins from the mesophilic Methanococcus spp. and M. marisnigri show homology with the N-termini of other archaebacterial flagellins. These N-termini may undergo a modification involving removal of a leader peptide.

Correlation between glycosylation of flagellin proteins and sensitivity of flagellar filaments to Triton X-100 in methanogens.

The flagellins of Methanospirillum hungatei strains JF1 and GP1, Methanococcus deltae, and Methanothermus fervidus are glycosylated. Isolated flagellar filaments from these organisms are dissociated by low concentrations (0.5% (v/v)) of Triton X-100. Flagellar filaments from other methanogens (Methanococcus voltae, Methanococcus vannielii and Methanoculleus marisnigri) composed of non-glycosylated flagellins are resistant to Triton X-100 treatment. Consequently, the isolation techniques (employing Triton X-100) used to isolate basal body-hook-filament complexes in eubacteria may not be applicable to many methanogens.

Effect of paracrystalline protein surface layers on predation by Bdellovibrio bacteriovorus.

We determined that paracrystalline protein surface arrays (S layers) protected gram-negative eubacteria from predation by Bdellovibrio bacteriovorus. Aquaspirillum serpens VHA and MW5 and Aquaspirillum sinuosum were resistant to predation by B. bacteriovorus 6-5-S when fully covered by their S layers. The S layer of Aeromonas salmonicida A449 protected the cells from predication by B. bacteriovorus 109J. A predacious, plaque-forming vibrio that lysed an S-layer- variant of Caulobacter crescentus but was not predacious on the parental strain which possessed an S layer was isolated from raw sewage. Since S layers are stable components of many bacterial surfaces in nature, they can provide this protective function in both aquatic and terrestrial habitats where Bdellovibrio spp. are found.

Isolation, characterization, and cellular insertion of the flagella from two strains of the archaebacterium Methanospirillum hungatei.

In high (45 mM)-phosphate medium, Methanospirillum hungatei strains GP1 and JF1 grew as very long, nonmotile chains of cells that did not possess flagella. However, growth in lower (3 or 30 mM)-phosphate medium resulted in the production of mostly single cells and short chains that were motile by means of two polar tufts of flagella, which transected the multilayered terminal plug of the cell. Electron microscopy of negatively stained whole mounts revealed a flagellar filament diameter of approximately 10 nm. Flagellar filaments were isolated from either culture fluid or concentrated cell suspensions that were subjected to shearing. Flagellar filaments were sensitive to treatment with both Triton X-100 and Triton X-114 at concentrations as low as 0.1% (vol/vol). The filaments of both strains were composed of two flagellins of Mr 24,000 and 25,000. However, variations in trace element composition of the medium resulted in the production of a third flagellin in strain JF1. This additional flagellin appeared as a ladderlike smear on sodium dodecyl sulfate-polyacylamide gels with a center of intensity of Mr 35,000 and cross-reacted with antisera produced from filaments containing only the Mr-24,000 and -25,000 flagellins. On sodium dodecyl sulfate-polyacrylamide gels, all flagellins stained by the thymol-sulfuric acid and Alcian blue methods, suggesting that they were glycosylated. This was further supported by chemical deglycosylation of the strain JF1 flagellins, which resulted in a reduction in their apparent molecular weight on sodium dodecyl sulfate-polyacylamide gels. Heterologous reactions to sera raised against the flagella from each strain were limited to the Mr-24,000 flagellins.

Chemotaxis in Listeria monocytogenes.

Listeria monocytogenes is a flagellated bacterium with a characteristic tumbling motion. It is intriguing to speculate that directional motility might facilitate penetration of the intestinal epithelium or selective colonization of the central nervous system or gravid uterus. There are conflicting reports on the extent of flagellation and degree of motility at temperatures corresponding to the internal environment of the mammalian host. No studies of chemotaxis in Listeria have been reported. We examined Listeria for flagella, motility, and chemotaxis after growth at 10 degrees, 24 degrees, 30 degrees, 37 degrees and 40 degrees C. Listeria grown at all temperatures possessed flagella and were motile to at least some degree. Those grown at 24 degrees or 30 degrees C were the most abundantly flagellated and the most vigorously motile. The bacteria were able to swim towards tryptose at all temperatures and toward glucose at all temperatures except 40 degrees C.

Isolation of flagella from the archaebacterium Methanococcus voltae by phase separation with Triton X-114.

The flagella of Methanococcus voltae were isolated by using three procedures. Initially, cells were sheared to release the filaments, which were purified by differential centrifugation and banding in KBr gradients. Flagella were also prepared by solubilization of cells with 1% (vol/vol) Triton X-100 and purified as described above. Both of these techniques resulted in variable recovery and poor yield of flagellar filaments. Purification of intact flagella (filament, hook, and basal body) was achieved by using phase transition separation with Triton X-114. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified flagella revealed two major proteins, with molecular weights of 33,000 and 31,000. This result indicates the likely presence of two flagellins. The filament had a diameter of 13 nm. The basal structure consisted of a small knob, while a slight thickening of the filament immediately adjacent to this area was the only evidence of a hook region. Flagella from three other Methanococcus species were isolated by this technique and found to have the same ultrastructure as flagella from M. voltae. Isolation of flagella from three eubacteria and another methanogen (Methanospirillum hungatei [M. hungatii]) by the phase separation technique indicated that the detergent treatment did not affect the structure of basal bodies. Intact ring structures and well-differentiated hook regions were apparent in each of these flagellar preparations.

Ultrastructure and biochemistry of the cell wall of Methanococcus voltae.

The ultrastructure and chemical composition of the cell wall of the marine archaebacterium Methanococcus voltae were studied by negative-staining and freeze-etch electron microscopy and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. M. voltae possesses a single regularly structured (RS) protein layer external to the plasma membrane. Freeze-etch preparations of cells indicated that the protein subunits are hexagonally arranged with a center-to-center spacing of approximately 10 nm. The extracted RS protein had a molecular weight of 76,000. It was present on envelopes prepared by shearing in a French press, osmotic lysis, or sonication, as indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. NaCl was not required for attachment of the RS protein to the underlying plasma membrane. The hexagonal array could be demonstrated by platinum shadowing and freeze-etching of envelopes, but negative staining in the abscence of NaCl failed to stabilize the array. The RS protein could be solubilized by urea, guanidine hydrochloride, dithiothreitol, and several detergents, including Nonidet P-40, Triton X-100, and Tween 20. However, the most specific release of the wall protein from envelopes occurred after a heat treatment in HEPES (N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid) buffer at 50 to 60 degrees C.

The superficial protein arrays on bacteria.

In nature, many bacteria possess a surface layer of regularly-structured protein subunits which is probably essential for survival in many ecological niches. These paracrystalline layers perform a variety of functions among the diverse groups of bacteria in which these superficial arrays have been detected.

The isolation of surface array proteins from bacteria.

The methods used for the isolation of regularly structured (RS) surface array proteins of a range of prokaryotes are described. Most RS proteins can be selectively solubilized from envelope preparations with low concentrations of urea or guanidine hydrochloride. Sodium dodecyl sulfate - polyacrylamide gel electrophoresis analysis of the protein extracts shows that most RS arrays are composed of a single polypeptide that may contain carbohydrate. The molecular weight of the proteins varies from 41 000 to 200 000. Possible reasons for the presence of more than one polypeptide in RS protein preparations are discussed, as well as the evidence for proteolytic degradation of some RS proteins during isolation. Structural features of the RS proteins are described and the importance of protein conformation to assembly of the arrays is indicated.