The theoretical basis of universal identification systems for bacteria and viruses.

It is shown that the presence/absence pattern of 1000 random oligomers of length 12-13 in a bacterial genome is sufficiently characteristic to readily and unambiguously distinguish any known bacterial genome from any other. Even genomes of extremely closely-related organisms, such as strains of the same species, can be thus distinguished. One evident way to implement this approach in a practical assay is with hybridization arrays. It is envisioned that a single universal array can be readily designed that would allow identification of any bacterium that appears in a database of known patterns. We performed in silico experiments to test this idea. Calculations utilizing 105 publicly-available completely-sequenced microbial genomes allowed us to determine appropriate values of the test oligonucleotide length, n, and the number of probe sequences. Randomly chosen n-mers with a constant G + C content were used to form an in silico array and verify (a) how many n-mers from each genome would hybridize on this chip, and (b) how different the fingerprints of different genomes would be. With the appropriate choice of random oligomer length, the same approach can also be used to identify viral or eukaryotic genomes.

[Cloning of the sugar related biosynthesis gene cluster from Streptomyces tenebrarius H6].

Streptomyces tenebrarius H6 produces a complex of aminoglycoside antibiotics, such as apramycin, tobramycin and kanamycin B etc. To study the apramycin biosynthetic genes the genomic library from the Streptomyces tenebrarius H6 was established using E. coli/Streptomyces shuttle vector pKC505 by in vitro packing. The probability of finding a specific gene from the library composed of 3,000 colonies was over 99.9%. According to the highly conserved sequence of the genes involved in 6-deoxyhexose biosynthesis, primers were designed and 0.6 kb fragment homologous to strE gene was obtained by PCR. 30 positive clones were found from the genomic library of S. tenebrarius H6 with the 0.6 kb fragment as a probe. Overlapped regions were localized by Southern hybridization and putative sugar related biosynthetic gene cluster was mapped by restriction enzyme digestions. An ORF of dTDP-glucose-4,6-dehydratase gene consisted of 1,132 bp, designated as aprE, was obtained and submitted to GenBank under the accession number of AF306787. A DNA sequence highly homologous to strL coding dTDP-4-dehydrorhamnose reductase was found linked with aprE gene.

The synaptic basis of GABAA,slow.

Although two kinetically distinct evoked GABAA responses (GABAA,fast and GABAA,slow) have been observed in CA1 pyramidal neurons, studies of spontaneous IPSCs (sIPSCs) in these neurons have reported only a single population of events that resemble GABAA,fast in their rise and decay kinetics. The absence of slow sIPSCs calls into question the synaptic basis of GABAA,slow. We present evidence here that both evoked responses are synaptic in origin, because two classes of minimally evoked, spontaneous and miniature IPSCs exist that correspond to GABAA,fast and GABAA,slow. Slow sIPSCs occur infrequently, suggesting that the cells underlying these events have a low spontaneous firing rate, unlike the cells giving rise to fast sIPSCs. Like evoked GABAA,fast and GABAA,slow, fast and slow sIPSCs are modulated differentially by furosemide, a subtype-specific GABAA antagonist. Furosemide blocks fast IPSCs by acting directly on the postsynaptic receptors, because it reduces the amplitude of both miniature IPSCs and the responses of excised patches to applied GABA. Thus, in the hippocampus, parallel inhibitory circuits are composed of separate populations of interneurons that contact anatomically segregated and pharmacologically distinct postsynaptic receptors.

The contralaterally projecting neurons of the isthmic nucleus in five anuran species: a retrograde tracing study with HRP and cobalt.

The morphology of projection neurons of the isthmic nucleus was studied in Rana esculenta, R. nigromaculata, Bufo marinus, B. bufo gargarizans, and Xenopus laevis from a comparative anatomical point of view. The main point of this work was to provide an anatomical basis for electrophysiological studies. Neurons projecting to the ipsilateral optic tectum were labeled by retrograde transport of horseradish peroxidase and cobaltous lysine complex injected into the optic tectum. Contralaterally projecting cells were filled by injecting the tracer substances into the crossed isthmotectal tract. Cells of the anterior nonrim cortex and the rostral part of the medulla project to the ipsilateral tectum. A band of cells in the middle of the medulla, a few cells in the caudal part of the medulla, and most of the neurons in the rim cortex project to the contralateral tectum. Five types of neurons were distinguished in the rim cortex of R. esculenta. Most of them have piriform perikarya and their dendrites arborize in the rim neuropil. In the medulla of the isthmic nucleus of R. esculenta, seven types of neurons were distinguished. Most of these neurons also exist in the other species. Medullary cells are piriform, fusiform, or multipolar, and are variable in size and in dendritic arborization. The isthmic neurons of the two Ranae and Bufo species are similar. The dominant cell types in Xenopus are multipolar with extensive dendritic arborization, which occupies more space in the nucleus than in the other species. Neurons with narrow dendritic trees may represent a system of fine resolution, and those neurons with extensive dendritic arborization may belong to a coarser system.