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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 73 (1990), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The photoorientation of Peridinium gatunense, which causes massive algal blooms each year in Lake Kinneret (Israel), is characterized using a microcomputer-controlled video immage system. The cells show positive phototaxis under a wide light irradiance range from 1 lx up to about 18 klx, i.e., to about fifth of the natural solar radiation measured on the water surface. Above 20 klx diaphototactic movement of the cells is observed. The action spectrum of photoorientation based on fluence rate-response curves shows little activity below 520 nm and a peak of 640 nm. No obvious effect of photosynthetic inhibitors (DCMU and DBMIB) was found on phototaxis, although motility of the cells is drastically affected in the presence of high concentrations of these inhibitors. The results suggest that the photsynthetic mechanism is not involved in photoperception of phototactically active radiation. The ecological significance of photoorientation of the cells is discussed in this paper.
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  • 2
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A molecular typing approach for Campylobacter jejuni was applied with restriction fragment length polymorphism (RFLP) analysis of a 702-bp PCR-amplified portion of the flagellin-A (flaA) gene. We analyzed a total of 179 strains, including 69 independent clinical isolates from diarrheic patients in Japan, 85 isolates in China, and 25 heat-stable (HS) serotype strains by Penner and Hennessy ((1980) J. Clin. Microbiol. 12, 732–737). Six AfaI, seven MboI, and five HaeIII RFLPs were found in the 702-bp flaA segment from the 179 strains. Using a combination of these three enzymes, 25 separate RFLP groups were recognized. While 59 of 154 (38.3%) strains obtained in Japan and China were nontypeable by the HS antigenic scheme, all but two of 154 (98.7%) could be typed by RFLP typing. All 11 isolates of HS-19 strains, which are frequently isolated from Guillain-Barré syndrome (GBS) patients, showed an identical RFLP pattern (Cj-1), and Cj-1 consisted only of HS-19 strains. This suggests that the HS-19:Cj-l strain is distinct among C. jejuni strains. This molecular typing method provides a rapid and reliable typing scheme for epidemiological studies of C. jejuni, and may also be useful for the analysis of C. jejuni subtypes from GBS patients.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 128 (1995), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract This paper presents a hypothesis on the importance of initial microbial adhesion in the overall process of biofilm formation. The hypothesis is based on the realization that dynamic shear conditions exist in many environments, such as in the oral cavity, or on rocks and ship hulls. Recognizing that an entire biofilm is detached during high shear once the bond between the initially adhering organisms and a surface (often constituted through a so-called ‘conditioning film’) is broken, it becomes clear that research should focus on detachment rather than adhesion. Experiments were done in a parallel plate flow chamber in which attempts were made to detach adhering oral streptococci from glass by applying a high shear caused by the passage of a bubble, giving an air-liquid interface. Detachment of streptococci from bare glass and from an initially adhering actinomycete strain appeared not to occur. However, substantial detachment of adhering streptococci occurred when adhesion was mediated through a salivary conditioning film, presumably because of cohesive failure in the conditioning film.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 244 (2005), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Antrodia camphorata (A. camphorata) is a rare medicinal fungus with antioxidative, vasorelaxtative, anti-inflammatory and anti-hepatitive effects. However, the neuroprotective effect has not been studied. By using serum deprivation-induced apoptosis in neuronal-like PC12 cells as a cell stress model, we found that A. camphorata is effective in preventing serum-deprived apoptosis. Inhibitors of both a serine/threonine kinase and a specific protein kinase A (PKA) inhibited the protective effect of A. camphorata, indicating that A. camphorata prevents serum-deprived PC12 cell apoptosis through a PKA-dependent mechanism. A transcription inhibitor, actinomycin D, and a protein synthesis inhibitor, cyclohexamide, both attenuated the protective effect of A. camphorata, indicating a requirement for gene expression for protection by A. camphorata. On the other hand, A. camphorata also increased phosphorylated CREB, a transcription factor, which is H-89-inhibitable in this study, suggesting the possibility that A. camphorata prevents serum deprivation-induced PC12 cell apoptosis through a PKA/CREB-dependent pathway.
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  • 5
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The spatial arrangement of two strains of oral bacteria adhering on glass was studied in order to investigate cooperative effects in their adhesion mechanisms. Streptococcus salivarius HB was a strain which possessed several classes of fibrillar surface appendages, whereas on the cell surface of S. mutants NS no surface appendages could be identified. The bacteria were deposited from a flowing suspension with various buffer concentrations on the bottom glass plate of a parallel plate flow cell and were observed directly with a video camera mounted on a phase contrast microscope. The positions of all adhering bacteria were determined by means of automated real time image analysis and subsequently employed for calculating radial and angular pair distribution functions. Pair distribution functions indicate the average relative number density of bacteria around one deposited bacterium as a function of the radial distance or the angular orientation relative to the flow direction. From the calculated pair distribution functions of both bacterial strains it was concluded that cooperative effects contributed to the adhesion of S. salivarius HB, but not to adhesion of S. mutants NS. It was suggested that these cooperative effects originate from the surface appendages of S. salivarius HB.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 28 (1985), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Paraquat-resistant Escherichia coli mutants were isolated. The mutants were 10- to 50-fold more resistant to paraquat than the wild type. The wild type was more responsive to the presence of paraquat by inducing higher levels of the manganese-containing superoxide dismutase (MnSOD). Thus, in minimal medium, 0.1 mM paraquat caused a 5-fold increase in MnSOD in the wild type while it had no effect on the level of MnSOD in the mutants. Yet, 50 mM paraquat exerted a dramatic induction of SOD in the mutant strains when grown in trypticase soy yeast extract (TSY) medium. In TSY medium, catalase was not significantly affected by paraquat in all the strains tested. Resistance to paraquat in these mutant strains is, therefore, unrelated to their capacity to detoxify superoxide or hydrogen peroxide.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 25 (1984), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The surface free energies (γb) of a variety of oral streptococci were determined from contact angle measurements on bacterial deposits, using the concept of dispersion and polar components. At least four strains of each species were tested. Strains of Streptococcus mutans, S. sanguis and S. salivarius possessed relatively high surface free energies (103 ± 12 mJ · m−2) and at the species level no significant difference was found. In contrast, the strains of S. mitis had remarkably low surface free energies (45 ± 14 mJ · m−2). S. milleri appeared to be a heterogeneous species, showing surface free energies over a range of 32–119 mJ · m−2. No significant differences were observed between laboratory strains and strains freshly isolated from the oral cavity.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 23 (1984), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The structure of a cell wall-associated glycoprotein, supposed to be involved in host-related adherence of Streptococcus salivarius (K+) strains, was investigated. The Mr of the two major subclasses of the glycoprotein was estimated to be in the range of 230 000 to 295 000, both in the presence of SDS and under non-denaturating conditions. Circular dichroism spectra indicated an α-helix content of 45%. Electron microscopic observation of rotary shadowed individual molecules showed fibrillar structures with an average length of 870 ± 40 Å and a width of 75 ± 6 Å. The glycoprotein is presumably identical with a class of long fibrils found on the surface of these cells.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 73 (1990), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The effects of artificial and solar UV-B radiation on the gravitactic (formerly called geotactic) orientation of the freshwater dinoflagellate Peridinium gatunense were measured under artificial UV-B radiation and in a temperature-controlled growth chamber under solar radiation in Portugal. Circular histograms of gravitaxis show the impairement of orientation after UV irradiation. The degree of orientation, quantified using the Rayleigh test and top quadrant summation, decreased as the exposure time to the radiation prolonged. The effects of artifical UV-B radiation on orientation are stronger than those of solar radiation, probably because the radiation source emits higher fluence rates below 300 nm than found in solar radiation. After UV radiation, the gravitactic orientation under artificially increased acceleration at 2 g was drastically affected.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 128 (1995), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Homologous internal controls were used as competitor DNA in the polymerase chain reaction for the quantitative detection of mycoplasma DNA. PCR primer sets were designed on the basis of the most conserved nucleotide sequences of the 16S rRNA gene of mycoplasma species. Amplification of this gene was examined in five different mycoplasma species: Mycoplasma orale, M. hyorhinus, M. synoviae, M. gallisepticum and M. pneumonias. To evaluate the primers, a number of different cell lines were assayed for the detection of mycoplasma infections. All positive cell lines showed a distinct product on agarose gels while uninfected cells showed no DNA amplification. Neither bacterial nor eukaryotic DNA produced any cross-reaction with the primers used, thus confirming their specificity. Internal control DNA to be used for quantitation was constructed by modifying the sizes of the wild-type amplified products and cloning them in plasmid vectors. These controls used the same primer binding sites as the wild-type and the amplified products were differentiated by a size difference. The detection limits for all the mycoplasma species by competitive quantitative PCR were estimated to range from 4 to 60 genome copies per assay as determined by ethidium bromide-stained agarose gels. These internal standards also serve as positive controls in PCR-based detection of mycoplasma DNA, and therefore accidental contamination of test samples with wild-type positive controls can be eliminated. The quantitative PCR method developed will be useful in monitoring the progression and significance of mycoplasma in the disease process.
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