We present here the complete genome sequence of a common avian clone of Pasteurella multocida, Pm70. The genome of Pm70 is a single circular chromosome 2,257,487 base pairs in length and contains 2,014 predicted coding regions, 6 ribosomal RNA operons, and 57 tRNAs. Genome-scale evolutionary analyses based on pairwise comparisons of 1,197 orthologous sequences between P. multocida, Haemophilus influenzae, and Escherichia coli suggest that P. multocida and H. influenzae diverged Ϸ270 million years ago and the ␥ subdivision of the proteobacteria radiated about 680 million years ago. Two previously undescribed open reading frames, accounting for Ϸ1% of the genome, encode large proteins with homology to the virulence-associated filamentous hemagglutinin of Bordetella pertussis. Consistent with the critical role of iron in the survival of many microbial pathogens, in silico and wholegenome microarray analyses identified more than 50 Pm70 genes with a potential role in iron acquisition and metabolism. Overall, the complete genomic sequence and preliminary functional analyses provide a foundation for future research into the mechanisms of pathogenesis and host specificity of this important multispecies pathogen.I t has been more than a century since Louis Pasteur conducted experiments with Pasteurella multocida (Pm), first demonstrating that laboratory attenuated bacteria could be used for the development of vaccines (1). Despite this seminal discovery, the molecular mechanisms for infection and virulence of Pm have remained largely undetermined, and this organism has continued to cause a wide range of diseases in animals and humans. It is the causative agent of fowl cholera in domesticated and wild birds, hemorrhagic septicemia in cattle, atrophic rhinitis in swine, and is the most common source of infection in humans because of dog and cat bites (2, 3).Because the genomic DNA sequence encodes all of the heritable information responsible for microbial replication, virulence, host specificity, and ability to evade the immune system, a comprehensive knowledge of a pathogen's genome provides all of the necessary information required for cost-effective and targeted research into disease prevention and treatment. To better understand the molecular basis for Pm's virulence, pathogenicity, and host specificity, we sequenced the genome of a common avian isolate recovered from a recent case of fowl cholera in chickens. The analysis identified a total of 2,014 open reading frames, including several encoding putative virulence factors. In particular, Pm has two genes with significant homology to the filamentous hemagglutinin gene in Bordetella pertussis, as well as more than 50 genes with a potential role in iron uptake and metabolism. The analysis also provides strong evidence that Pm and its close relative, Hemophilus influenzae (Hi), diverged Ϸ270 million years ago (mya) and that the ␥ subdivision of the proteobacteria, a group that contains many of the pathogenic Gram-negative organisms, radiated Ϸ680 mya. Materials and Meth...

Leptospirosis is an important zoonosis of worldwide distribution. Humans become infected via exposure to pathogenic Leptospira spp. from infected animals or contaminated water or soil. The availability of genome sequences for Leptospira interrogans, serovars Lai and Copenhageni, has opened up opportunities to examine global transcription profiles using microarray technology. Temperature is a key environmental factor known to affect leptospiral protein expression. Leptospira spp. can grow in artificial media at a range of temperatures reflecting conditions found in the environment and the mammalian host. Therefore, transcriptional changes were compared between cultures grown at 20°C, 30°C, 37°C, and 39°C to represent ambient temperatures in the environment, growth under laboratory conditions, and temperatures in healthy and febrile hosts. Data from direct pairwise comparisons of the four temperatures were consolidated to examine transcriptional changes at two generalized biological conditions representing mammalian physiological temperatures (37°C and 39°C) versus environmental temperatures (20°C and 30°C). Additionally, cultures grown at 30°C then shifted overnight to 37°C were compared with those grown long-term at 30°C and 37°C to identify genes potentially expressed in the early stages of infection. Comparison of data sets from physiological versus environmental experiments with upshift experiments provided novel insights into possible transcriptional changes at different stages of infection. Changes included differential expression of chemotaxis and motility genes, signal transduction systems, and genes encoding proteins involved in alteration of the outer membrane. These findings indicate that temperature is an important factor regulating expression of proteins that facilitate invasion and establishment of disease.

The sex pheromone plasmids in Enterococcus faecalis are one of the most efficient conjugative plasmid transfer systems known in bacteria. Plasmid transfer rates can reach or exceed 10 ؊1 transconjugants per donor in vivo and under laboratory conditions. We report the completion of the DNA sequence of plasmid pCF10 and the analysis of the transcription profile of plasmid genes, relative to conjugative transfer ability following pheromone induction. These experiments employed a mini-microarray containing all 57 open reading frames of pCF10 and a set of selected chromosomal genes. A clear peak of transcription activity was observed 30 to 60 min after pheromone addition, with transcription subsiding 2 h after pheromone induction. The transcript activity correlated with the ability of donor cells to transfer pCF10 to recipient cells. Remarkably, aggregation substance (Asc10, encoded by the prgB gene) was present on the cell surface for a long period of time after pheromone-induced transcription of prgB and plasmid transfer ability had ceased. This observation could have relevance for the virulence of E. faecalis.The advent of microarray technology allows for a comprehensive analysis of gene expression patterns associated with various biological processes, providing insights into complex regulatory networks. One of the most complex processes is the transfer of large portions of genetic material from a donor cell into a recipient cell by means of conjugation. The plasmids of the sex pheromone family in Enterococcus faecalis are among the most efficient bacterial conjugation systems known (16). The family consists of over 20 plasmids and shows extensive sequence homologies (28). E. faecalis strains can host several of these plasmids. This is exemplified by strain V583, the first vancomycin-resistant isolate in the United States (45), chosen for genome sequencing by The Institute for Genomic Research (TIGR; www.tigr.org). V583 contains two sex pheromone plasmids with homology to the well-characterized pAD1 (pTEF1) and pCF10 (pTEF2) plasmids, respectively. The complete sequences for the pheromone plasmids pAD1 and pAM373 became available recently (14,19). Analysis of the sequences of this group of plasmids allows comparisons and insights into the evolution of these elements.Although the sex pheromone plasmids can be disseminated among enterococcal populations very efficiently, plasmid transfer is highly regulated and only induced by recipient cells in close proximity to plasmid donors. The recipient cells secret 7-to 8-amino-acid-long hydrophobic sex pheromones that are bound by a plasmid-encoded binding protein (44, 51). The pheromone is then taken up into the cell (32) and releases a transcriptional block of the PrgX/TraA family of repressors (5). One of the early transcripts after induction encodes for the surface protein aggregation substance (AS) (9). Expression of AS results in tight physical contact between donor and recipient, allows for plasmid transfer rates of up to 10 Ϫ1 transconjugants/donor (16), and is nece...