Knowledge of the complete genomic DNA sequence of an organism allows a systematic approach to defining its genetic components. The genomic sequence provides access to the complete structures of all genes, including those without known function, their control elements, and, by inference, the proteins they encode, as well as all other biologically important sequences. Furthermore, the sequence is a rich and permanent source of information for the design of further biological studies of the organism and for the study of evolution through cross-species sequence comparison. The power of this approach has been amply demonstrated by the determination of the sequences of a number of microbial and model organisms. The next step is to obtain the complete sequence of the entire human genome. Here we report the sequence of the euchromatic part of human chromosome 22. The sequence obtained consists of 12 contiguous segments spanning 33.4 megabases, contains at least 545 genes and 134 pseudogenes, and provides the first view of the complex chromosomal landscapes that will be found in the rest of the genome.

An extracellular particle approximately 40 nM in diameter was detected in culture supernatant from the fastidious bacterium Rochalimaea henselae. This particle has at least three associated proteins and contains 14 kbp linear DNA segments that are heterogeneous in sequence. The 14 kbp DNA was also present in R. henselae cells as an extrachromosomal element for all 14 strains tested. Despite attempts to induce lysis of R. henselae, plaque formation was not observed. A similar particle, also containing 14 kbp DNA, was observed in Bartonella bacilliformis, and may be analogous to a bacteriophage that has been described elsewhere for B. bacilliformis.

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