A plasmidic beta -lactamase which hydrolyzes cephamycins was first detected and reported in 1989. At that time its description was restricted to phenotypic characteristics. We analyzed the nucleotide ...sequence of its gene and explored its genetic relationship with other bla genes. The deduced amino acid sequence of the bla sub(CMY-1) product was compared with those of other known plasmidic cephamycinases and of chromosomal AmpC beta -lactamases. The results indicate that the relationship of CMY-1 is closest to MOX-1 among the plasmidic cephamycinases and to AmpC of Pseudomonas aeruginosa among the chromosomal cephalosporinases. We conclude that the plasmidic cephamycinases described up to now may be classified into three families, as follows: CMY-1, MOX-1, and FOX-1 with AmpC of P. aeruginosa; CMY-2, BIL-1, and LAT-1 with AmpC of Citrobacter freundii; and MIR-1 with AmpC of Enterobacter cloacae. Plasmidic cephamycinases are now recognized as clinically relevant class C beta -lactamases.
Plasmidic extended-spectrum beta -lactamases of Ambler class A are mostly inactive against ceftibuten. Salmonella typhimurium JMC isolated in Argentina harbors a bla gene located on a plasmid ...(pMVP-5) which confers transferable resistance to oxyiminocephalosporins, aztreonam, and ceftibuten. The beta -lactamase PER-2 (formerly ceftibutenase-1; CTI-1) is highly susceptible to inhibition by clavulanate and is located at a pI of 5.4 after isoelectric focusing. The bla sub(PER-2) gene was cloned and sequenced. The nucleotide sequence of a 2.2-kb insert in vector pBluescript includes an open reading frame of 927 bp. Comparison of the deduced amino acid sequence of PER-2 with those of other beta -lactamases indicates that PER-2 is not closely related to TEM or SHV enzymes (25 to 26% homology). PER-2 is most closely related to PER-1 (86.4% homology), an Ambler class A enzyme first detected in Pseudomonas aeruginosa. An enzyme with an amino acid sequence identical to that of PER-1, meanwhile, was found in various members of the family Enterobacteriaceae isolated from patients in Turkey. Our data indicate that PER-2 and PER-1 represent a new group of Ambler class A extended-spectrum beta -lactamases. PER-2 so far has been detected only in pathogens (S. typhimurium, Escherichia coli, Klebsiella pneumonia, Proteus mirabilis) isolated from patients in South America, while the incidence of PER-1-producing strains so far has been restricted to Turkey, where it occurs both in members of the family Enterobacteriaceae and in P. aeruginosa.
With regard to the transportation sector, an efficient powertrain technology contributes to sustainable lowering of CO2 emissions. Due to the periodic or continuous operation in boundary and mixed ...friction, minimization of friction losses in automobile gearboxes offers massive potential in terms of efficiency improvement and saving fossil fuels. In close cooperation between the Surface Engineering Institute (IOT) and the Gear Research Center (FZG), the aim of this work was to reduce friction losses in powertrain by diamond-like carbon (DLC) coatings on highly loaded gears under severe rolling–sliding conditions. The zirconium based DLC coatings ZrCg (a:C-H/ZrCg) and nanocomposite ZrC (a-C:H/ZrC) were deposited by physical vapor deposition (PVD) at IOT. The industrial DLC coating DLC-REF1 served as reference. Application-related tribological tests of lubricated highly-loaded rolling–sliding contacts were performed in a twin-disc test-rig and a gear efficiency test-rig at FZG. Calculations and measurements of relative lubricant film thickness confirmed that the tribological model tests covered the entire friction regime from boundary and mixed friction to fluid friction (elasto-hydrodynamic lubrication, EHL). Despite complete separation of the coated surfaces, the Coefficient of Friction was reduced by 35% using ZrCg coated discs in the twin-disc test-rig. Practical investigations of DLC coated gears in the FZG gear efficiency test-rig revealed that compared to uncoated gears friction losses in EHL were reduced by up to 25% using the industrial reference DLC-REF1 and 39% using ZrCg, especially at higher loads and higher circumferential speeds. This yet widely unknown favorable effect of DLC coatings under EHL conditions was attributed to the thermophysical properties of DLC coatings and confirmed by simulations of real rolling–sliding contacts at FZG. Wetting analyses of tribological surfaces were analyzed determining the surface properties, interfacial tension and surface energy, of the DLC coatings and the gear oils by means of contact angle measurements. The adhesion energy was calculated from contact angle data. Correlation analyses revealed a clear impact of the interfacial tension and adhesion energy on the frictional behavior under boundary and fluid friction conditions. It was found that a higher adhesion energy (good wetting) contributes to a lower CoF under boundary and mixed friction conditions as well as in the fluid friction regime (EHL).
•Wetting of gear oils on DLC was statistically correlated with frictional behavior.•High adhesion energy (low spreading parameter) leads to low Coefficient of Friction.•DLC (a-C:H/ZrCg) on gears reduces friction by 39% in the fluid friction regime.•Thermal conductivity and specific heat capacity of DLC are decisive factors.•Simulations of flash temperature of rolling contacts confirm this assumption.
To determine the intraspecific variability of microscopic organisms such as dinophytes is challenging, but can be achieved using cultured material. Unusual morphologies of
Peridinium tuberosum
...assigned to the
Peridinium cinctum
species group have been described as bulges on the posterior end of the cell a hundred years ago and more, but its taxonomic significance is unclear at present. We collected field material in Germany and Poland in order to establish strains to study cell morphology using light and scanning electron microscopy. For the cultured material, DNA sequence data from the rRNA operon was gained as well and included in molecular phylogenetics (including 22 new partial rRNA sequences). Two new, closely related ribotypes were detected, and all strains showed the principle morphology of
P
.
cinctum
having an asymmetric epitheca, a large first apical plate and a sulcus extending onto the epitheca. In the single-strain GeoM*979 assigned to one of the two new ribotypes, cells with bulges appeared rarely but consistently, mostly on the hypotheca, but other variations also occurred. Overall, cells of this strain display traits not observed before while studying cultured
P. cinctum
, and this distinction is further supported by molecular data and additional details of epithecal opening. However, there does not remain enough information to determine strain GeoM*979 as a separate species (namely
P. tuberosum
) and therefore, it is identified as
Peridinium
aff.
cinctum
until further notice.
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