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Identification of Culturable Oligotrophic Bacteria within Naturally Occurring Bacterioplankton Communities of the Ligurian Sea by 16S rRNA Sequencing and Probing 总被引:10,自引:0,他引:10
L. Giuliano M. De Domenico E. De Domenico M.G. Höfle M.M. Yakimov 《Microbial ecology》1999,37(2):77-85
Abstract
Typical marine bacteria (i.e., obligately oligotrophic) that were numerically dominant members of naturally occurring marine
communities were identified by cloning and sequencing the amplified 16S rRNA genes obtained from dilution cultures of the
original samples. The data reported here refer to two different habitats of a marine pelagic environment (28 miles offshore,
in the northwestern Mediterranean Sea). The samples were taken from the water column at two representative layers, i.e., the
30-m depth, corresponding to the chlorophyll maximum layer, and the 1800-m depth, representative of a deep, oligotrophic environment.
Three major lineages were found in the 16S rDNA clone libraries prepared from the two samples, two of which could be assigned
to the Vibrio and the Rhodobacter groups. The third lineage was a distant relative of the genus Flavobacterium, but it was not closely related to any marine isolate. Six oligonucleotide probes, either complementary to the conserved sequence
domains or selectively hybridizing to the clone sequences, were designed for use as hybridization group-specific and strain-specific
probes. A single-mismatch discrimination between certain probes and nontarget sequences was demonstrated by detecting the
probes' specificity at different hybridization and washing conditions. The screening of the clone libraries with the obtained
probes revealed that neither the 30-m sample higher dilution nor the 1800-m one were pure cultures. While some representatives
of the Vibrio group were found in both the surface and the deep sample, the members of the Flavobacterium and Rhodobacter lineages were detected only in the deep and the euphotic layers, respectively. We suggest an approach for analyzing autochthonous
marine bacteria able to grow in unamended seawater.
Received: 19 May 1998; Accepted: 29 October 1998 相似文献
25.
Strains of paramyxovirus type 1 (PMV-1) have been isolated from diseased racing pigeons in Sweden. One of these isolates was selected for studies of the pathogenicity and contagiousness in chickens. The same isolate was previously found to have a high intravenous pathogenicity index (IVPI) in 6 weeks old chickens. In three experiments it was found that the PMV-1 isolate was very pathogenic for 1 week old chickens but not pathogenic for 120 day old pullets inoculated intranasally and ocularly. Symptoms in the young chickens were similar to those seen in the neurotropic form of Newcastle disease. The mortality was high and the incubation period 5–11 days. The disease easily spread to young chickens kept in contact with diseased birds. The microscopic examination revealed an interstitial nonpurulent pneumonia and a nonpurulent encephalitis in the young chickens. In the pullets the only finding was a mild encephalitis. PMV-1 was recovered from all young chickens but not from the pullets. Both the chickens and the inoculated pullets developed antibodies to PMV-1. 相似文献
26.
Bruce M. Taylor Ronald W. Sarver Gregory Fici Roger A. Poorman Barry S. Lutzke Antonio Molinari Thomas Kawabe Karl Kappenman Allen E. Buhl Dennis E. Epps 《The protein journal》2003,22(1):31-40
The time dependency of the spontaneous aggregation of the fibrillogenic β-Amyloid peptide, Aβ1–40, was measured by turbidity, circular dichroism, HPLC, and fluorescence polarization. The results by all methods were comparable and they were most consistent with a kinetic model where the peptide first slowly forms an activated monomeric derivative (AM), which is the only species able to initiate, by tetramerization, the formation of linear aggregates. The anti-Aβ antibody 6E10, raised against residues 1–17, at concentrations of 200–300 nM delayed significantly the aggregation of 50 μM amyloid peptide. The anti–Aβ antibody 4G8, raised against residues 17–24, was much less active in that respect, while the antibody A162, raised against the C-terminal residues 39–43 of the full-length Aβ was totally inactive at those concentrations. Concomitant with the aggregation experiments, we also measured the time dependency of the Aβ1–40–induced toxicity toward SH-EP1 cells and hippocampal neurons, evaluated by SYTOX Green fluorescence, lactate dehydrogenase release, and activation of caspases. The extent of cell damage measured by all methods reached a maximum at the same time and this maximum coincided with that of the concentration of AM. According to the kinetic scheme, the latter is the only transient peptide species whose concentration passes through a maximum. Thus, it appears that the toxic species of Aβ1–40 is most likely the same transient activated monomer that is responsible for the nucleation of fibril formation. These conclusions should provide a structural basis for understanding the toxicity of Aβ1–40 in vitro and possibly in vivo. 相似文献
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Background
Identifying essential genes in bacteria supports to identify potential drug targets and an understanding of minimal requirements for a synthetic cell. However, experimentally assaying the essentiality of their coding genes is resource intensive and not feasible for all bacterial organisms, in particular if they are infective. 相似文献28.
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Catherine E. Rogers Karl R. Mattox Kenneth D. Stewart 《American journal of botany》1980,67(5):774-783
Chlorokybus atmophyticus has a sarcinoid growth habit and produces scale-covered zoospores. Flagella are laterally inserted and attached internally to a multilayered structure characteristic of the Charophyceae. There are two kinds of pyrenoid in each cell, a feature previously observed in only one scaly green flagellate. C. atmophyticus demonstrates that the sarcinoid growth habit arose independently at least twice in the green algae and cannot be used to define taxonomic groups unless combined with other criteria. It is further concluded that C. atmophyticus should be classified in a separate family Chlorokybaceae and a separate order Chloroky bales. 相似文献