Acinetobacter baumannii is among the most prevalent bacterial causes of combat-related infections on the battlefield. Antibiotic resistance and a poor understanding of the protective host immune responses make treatment difficult. Here, we report the genome sequences of four clinical Acinetobacter baumannii-A. calcoaceticus complex isolates exhibiting significant differences in virulence in a mouse sepsis model.
First identified in 1982 as a human pathogen, enterohemorrhagic Escherichia coli of the O157:H7 serotype is a major cause of food-borne acquired human infections. Here, we report the genome sequence of the first known strain of this serotype isolated in the United States.
Piscirickettsia salmonis is a Gram-negative intracellular fish pathogen that has a significant impact on the salmon industry. Here, we report the genome sequence of P. salmonis strain LF-89. This is the first draft genome sequence of P. salmonis, and it reveals interesting attributes, including flagellar genes, despite this bacterium being considered nonmotile.
First identified in 1982, Escherichia coli O157:H7 is the dominant enterohemorrhagic serotype underlying food-borne human infections in North America. Here, we report the genomes of twenty-six strains derived from patients and the bovine reservoir. These resources enable detailed whole-genome comparisons and permit investigations of genotypic and phenotypic plasticity.
We sequenced four strains of Bacillus subtilis and the type strains for two closely related species, Bacillus vallismortis and Bacillus mojavensis. We report the high-quality Sanger genome sequences of B. subtilis subspecies subtilis RO-NN-1 and AUSI98, B. subtilis subspecies spizizenii TU-B-10(T) and DV1-B-1, Bacillus mojavensis RO-H-1(T), and Bacillus vallismortis DV1-F-3(T).
Title: Genome signatures of Escherichia coli O157:H7 isolates from the bovine host reservoir Eppinger M, Mammel MK, Leclerc JE, Ravel J, Cebula TA Ref: Applied Environmental Microbiology, 77:2916, 2011 : PubMed
Cattle comprise a main reservoir of Shiga toxin-producing Escherichia coli O157:H7 (STEC). The significant differences in host prevalence, transmissibility, and virulence phenotypes among strains from bovine and human sources are of major interest to the public health community and livestock industry. Genomic analysis revealed divergence into three lineages: lineage I and lineage I/II strains are commonly associated with human disease, while lineage II strains are overrepresented in the asymptomatic bovine host reservoir. Growing evidence suggests that genotypic differences between these lineages, such as polymorphisms in Shiga toxin subtypes and synergistically acting virulence factors, are correlated with phenotypic differences in virulence, host ecology, and epidemiology. To assess the genomic plasticity on a genome-wide scale, we have sequenced the whole genome of strain EC869, a bovine-associated E. coli O157:H7 isolate. Comparative phylogenomic analysis of this key isolate enabled us to place accurately bovine lineage II strains within the genetically homogenous E. coli O157:H7 clade. Identification of polymorphic loci that are anchored both in the chromosomal backbone and horizontally acquired regions allowed us to associate bovine genotypes with altered virulence phenotypes and host prevalence. This study catalogued numerous novel lineage II-specific genome signatures, some of which appear to be associated intimately with the altered pathogenic potential and niche adaptation within the bovine rumen. The presented extended list of polymorphic markers is valuable in the development of a robust typing system critical for forensic, diagnostic, and epidemiological studies of this emerging human pathogen.
To gain insights into the origin and genome evolution of the plague bacterium Yersinia pestis, we have sequenced the deep-rooted strain Angola, a virulent Pestoides isolate. Its ancient nature makes this atypical isolate of particular importance in understanding the evolution of plague pathogenicity. Its chromosome features a unique genetic make-up intermediate between modern Y. pestis isolates and its evolutionary ancestor, Y. pseudotuberculosis. Our genotypic and phenotypic analyses led us to conclude that Angola belongs to one of the most ancient Y. pestis lineages thus far sequenced. The mobilome carries the first reported chimeric plasmid combining the two species-specific virulence plasmids. Genomic findings were validated in virulence assays demonstrating that its pathogenic potential is distinct from modern Y. pestis isolates. Human infection with this particular isolate would not be diagnosed by the standard clinical tests, as Angola lacks the plasmid-borne capsule, and a possible emergence of this genotype raises major public health concerns. To assess the genomic plasticity in Y. pestis, we investigated the global gene reservoir and estimated the pangenome at 4,844 unique protein-coding genes. As shown by the genomic analysis of this evolutionary key isolate, we found that the genomic plasticity within Y. pestis clearly was not as limited as previously thought, which is strengthened by the detection of the largest number of isolate-specific single-nucleotide polymorphisms (SNPs) currently reported in the species. This study identified numerous novel genetic signatures, some of which seem to be intimately associated with plague virulence. These markers are valuable in the development of a robust typing system critical for forensic, diagnostic, and epidemiological studies.
To gain insights into the evolutionary origin, emergence, and pathogenicity of the etiologic agent of plague, we have sequenced the genomes of four Yersinia pestis strains isolated from the zoonotic rodent reservoir in foci of endemic plague in China. These resources enable in-depth studies of Y. pestis sequence variations and detailed whole-genome comparisons of very closely related genomes from the supposed site of the origin and the emergence of global pandemics of plague.
Zoonotic infections are a growing threat to global health. Chlamydia pneumoniae is a major human pathogen that is widespread in human populations, causing acute respiratory disease, and has been associated with chronic disease. C. pneumoniae was first identified solely in human populations; however, its host range now includes other mammals, marsupials, amphibians, and reptiles. Australian koalas (Phascolarctos cinereus) are widely infected with two species of Chlamydia, C. pecorum and C. pneumoniae. Transmission of C. pneumoniae between animals and humans has not been reported; however, two other chlamydial species, C. psittaci and C. abortus, are known zoonotic pathogens. We have sequenced the 1,241,024-bp chromosome and a 7.5-kb cryptic chlamydial plasmid of the koala strain of C. pneumoniae (LPCoLN) using the whole-genome shotgun method. Comparative genomic analysis, including pseudogene and single-nucleotide polymorphism (SNP) distribution, and phylogenetic analysis of conserved genes and SNPs against the human isolates of C. pneumoniae show that the LPCoLN isolate is basal to human isolates. Thus, we propose based on compelling genomic and phylogenetic evidence that humans were originally infected zoonotically by an animal isolate(s) of C. pneumoniae which adapted to humans primarily through the processes of gene decay and plasmid loss, to the point where the animal reservoir is no longer required for transmission.
The first reported Far East scarlet-like fever (FESLF) epidemic swept the Pacific coastal region of Russia in the late 1950s. Symptoms of the severe infection included erythematous skin rash and desquamation, exanthema, hyperhemic tongue, and a toxic shock syndrome. The term FESLF was coined for the infection because it shares clinical presentations with scarlet fever caused by group A streptococci. The causative agent was later identified as Yersinia pseudotuberculosis, although the range of morbidities was vastly different from classical pseudotuberculosis symptoms. To understand the origin and emergence of the peculiar clinical features of FESLF, we have sequenced the genome of the FESLF-causing strain Y. pseudotuberculosis IP31758 and compared it with that of another Y. pseudotuberculosis strain, IP32953, which causes classical gastrointestinal symptoms. The unique gene pool of Y pseudotuberculosis IP31758 accounts for more than 260 strain-specific genes and introduces individual physiological capabilities and virulence determinants, with a significant proportion horizontally acquired that likely originated from Enterobacteriaceae and other soil-dwelling bacteria that persist in the same ecological niche. The mobile genome pool includes two novel plasmids phylogenetically unrelated to all currently reported Yersinia plasmids. An icm/dot type IVB secretion system, shared only with the intracellular persisting pathogens of the order Legionellales, was found on the larger plasmid and could contribute to scarlatinoid fever symptoms in patients due to the introduction of immunomodulatory and immunosuppressive capabilities. We determined the common and unique traits resulting from genome evolution and speciation within the genus Yersinia and drew a more accurate species border between Y. pseudotuberculosis and Y. pestis. In contrast to the lack of genetic diversity observed in the evolutionary young descending Y. pestis lineage, the population genetics of Y. pseudotuberculosis is more heterogenous. Both Y. pseudotuberculosis strains IP31758 and the previously sequenced Y. pseudotuberculosis strain IP32953 have evolved by the acquisition of specific plasmids and by the horizontal acquisition and incorporation of different genetic information into the chromosome, which all together or independently seems to potentially impact the phenotypic adaptation of these two strains.
Helicobacter pylori infection of humans is so old that its population genetic structure reflects that of ancient human migrations. A closely related species, Helicobacter acinonychis, is specific for large felines, including cheetahs, lions, and tigers, whereas hosts more closely related to humans harbor more distantly related Helicobacter species. This observation suggests a jump between host species. But who ate whom and when did it happen? In order to resolve this question, we determined the genomic sequence of H. acinonychis strain Sheeba and compared it to genomes from H. pylori. The conserved core genes between the genomes are so similar that the host jump probably occurred within the last 200,000 (range 50,000-400,000) years. However, the Sheeba genome also possesses unique features that indicate the direction of the host jump, namely from early humans to cats. Sheeba possesses an unusually large number of highly fragmented genes, many encoding outer membrane proteins, which may have been destroyed in order to bypass deleterious responses from the feline host immune system. In addition, the few Sheeba-specific genes that were found include a cluster of genes encoding sialylation of the bacterial cell surface carbohydrates, which were imported by horizontal genetic exchange and might also help to evade host immune defenses. These results provide a genomic basis for elucidating molecular events that allow bacteria to adapt to novel animal hosts.
Predatory bacteria remain molecularly enigmatic, despite their presence in many microbial communities. Here we report the complete genome of Bdellovibrio bacteriovorus HD100, a predatory Gram-negative bacterium that invades and consumes other Gram-negative bacteria. Its surprisingly large genome shows no evidence of recent gene transfer from its prey. A plethora of paralogous gene families coding for enzymes, such as hydrolases and transporters, are used throughout the life cycle of B. bacteriovorus for prey entry, prey killing, and the uptake of complex molecules.
To understand the origin and emergence of pathogenic bacteria, knowledge of the genetic inventory from their nonpathogenic relatives is a prerequisite. Therefore, the 2.11-megabase genome sequence of Wolinella succinogenes, which is closely related to the pathogenic bacteria Helicobacter pylori and Campylobacter jejuni, was determined. Despite being considered nonpathogenic to its bovine host, W. succinogenes holds an extensive repertoire of genes homologous to known bacterial virulence factors. Many of these genes have been acquired by lateral gene transfer, because part of the virulence plasmid pVir and an N-linked glycosylation gene cluster were found to be syntenic between C. jejuni and genomic islands of W. succinogenes. In contrast to other host-adapted bacteria, W. succinogenes does harbor the highest density of bacterial sensor kinases found in any bacterial genome to date, together with an elaborate signaling circuitry of the GGDEF family of proteins. Because the analysis of the W. succinogenes genome also revealed genes related to soil- and plant-associated bacteria such as the nif genes, W. succinogenes may represent a member of the epsilon proteobacteria with a life cycle outside its host.
