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The genome sequence of Blochmannia floridanus: comparative analysis of reduced genomes.

ABSTRACT: Bacterial symbioses are widespread among insects, probably being one of the key factors of their evolutionary success. We present the complete genome sequence of Blochmannia floridanus, the primary endosymbiont of carpenter ants. Although these ants feed on a complex diet, this symbiosis very likely has a nutritional basis: Blochmannia is able to supply nitrogen and sulfur compounds to the host while it takes advantage of the host metabolic machinery. Remarkably, these bacteria lack all known genes involved in replication initiation (dnaA, priA, and recA). The phylogenetic analysis of a set of conserved protein-coding genes shows that Bl. floridanus is phylogenetically related to Buchnera aphidicola and Wigglesworthia glossinidia, the other endosymbiotic bacteria whose complete genomes have been sequenced so far. Comparative analysis of the five known genomes from insect endosymbiotic bacteria reveals they share only 313 genes, a number that may be close to the minimum gene set necessary to sustain endosymbiotic life.

SUBMITTER: Gil R

PROVIDER: S-EPMC170928 | biostudies-literature | 2003 Aug

REPOSITORIES: biostudies-literature

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The genome sequence of Blochmannia floridanus: comparative analysis of reduced genomes.

Gil Rosario R Silva Francisco J FJ Zientz Evelyn E Delmotte François F González-Candelas Fernando F Latorre Amparo A Rausell Carolina C Kamerbeek Judith J Gadau Jürgen J Hölldobler Bert B van Ham Roeland C H J RC Gross Roy R Moya Andrés A

Proceedings of the National Academy of Sciences of the United States of America 20030728 16

Bacterial symbioses are widespread among insects, probably being one of the key factors of their evolutionary success. We present the complete genome sequence of Blochmannia floridanus, the primary endosymbiont of carpenter ants. Although these ants feed on a complex diet, this symbiosis very likely has a nutritional basis: Blochmannia is able to supply nitrogen and sulfur compounds to the host while it takes advantage of the host metabolic machinery. Remarkably, these bacteria lack all known ge ...[more]

PMID: 12886019

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Project description:The transcriptome of Blochmannia floridanus, the endosymbiont of the carpenter ant Camponotus floridanus, is presented during eight developmental stages of its holometabolous host by use of a whole genome DNA-macroarray. The detected transcription patterns indicate the presence of local transcription units as well as global regulatory mechanisms. Yet, the overall regulation scale is very modest, rarely exceeding a factor of three which is in line with the low number of transcriptional regulators present in this reduced genome. A large number of genes show differential expression in different life stages and a distinct expression pattern of genes possibly involved in symbiotic function as compared to housekeeping genes is apparent. However, these transcriptional changes are small as compared to the changes in the number of bacteria during host development which is highest in pupae and in young imagines. Control of replication of the bacteria in certain life stages may therefore be the decisive parameter influencing overall gene expression of Blochmannia in the animal. The few highly expressed genes like those encoding molecular chaperones exhibit a significantly higher G+C-content than moderately expressed genes. Keywords: Host stage-dependent gene expression C. floridanus laboratory colonies were maintained under constant conditions at 25°C with a 12 h light cycle in artificial nests and fed twice a week with cockroaches (Nauphoeta cinerea), Bhatkar agar (Bhatkar and Whitcomb, 1970), and honey water (50% wt/wt) ad libitum. Developmental stages were defined as L1 (very young larvae, still clustered), L2 (older larvae, approx. 2-4 mm), P1 (pupae before metamorphosis), P2 (pupae after metamorphosis, still uncolored), P3 (pupae shortly before eclosion with dark abdomens), W1 (workers shortly after eclosion, not completely melanized, no aggressive behavior), W2 (fully melanized adult workers from the nest, age not distinguishable), and W3 (adult workers from isolated subcolonies, at least 4 months old). For RNA preparations, midguts of the respective life stage (L2 - W3) were dissected and bacteria were isolated by homogenization and centrifugation. Endosymbionts from small larvae (L1) were isolated from whole animals. RNA for each cDNA array experiment was isolated from individual bacterial preparations; from L1 to W2, each developmental stage was represented by at least three independent experiments and samples from at least three different ant colonies. Two ant colonies (C79 and C118) were represented in every stage from L1 to W2 with additional samples from six other colonies. Old W3 workers were collected from two isolated subcolonies derived from the same mother colony, each sampled in duplicate.

Project description:Enterococci are among the leading causes of hospital-acquired infections in the United States and Europe, with Enterococcus faecalis and Enterococcus faecium being the two most common species isolated from enterococcal infections. In the last decade, the proportion of enterococcal infections caused by E. faecium has steadily increased compared to other Enterococcus species. Although the underlying mechanism for the gradual replacement of E. faecalis by E. faecium in the hospital environment is not yet understood, many studies using genotyping and phylogenetic analysis have shown the emergence of a globally dispersed polyclonal subcluster of E. faecium strains in clinical environments. Systematic study of the molecular epidemiology and pathogenesis of E. faecium has been hindered by the lack of closed, complete E. faecium genomes that can be used as references.In this study, we report the complete genome sequence of the E. faecium strain TX16, also known as DO, which belongs to multilocus sequence type (ST) 18, and was the first E. faecium strain ever sequenced. Whole genome comparison of the TX16 genome with 21 E. faecium draft genomes confirmed that most clinical, outbreak, and hospital-associated (HA) strains (including STs 16, 17, 18, and 78), in addition to strains of non-hospital origin, group in the same clade (referred to as the HA clade) and are evolutionally considerably more closely related to each other by phylogenetic and gene content similarity analyses than to isolates in the community-associated (CA) clade with approximately a 3-4% average nucleotide sequence difference between the two clades at the core genome level. Our study also revealed that many genomic loci in the TX16 genome are unique to the HA clade. 380 ORFs in TX16 are HA-clade specific and antibiotic resistance genes are enriched in HA-clade strains. Mobile elements such as IS16 and transposons were also found almost exclusively in HA strains, as previously reported.Our findings along with other studies show that HA clonal lineages harbor specific genetic elements as well as sequence differences in the core genome which may confer selection advantages over the more heterogeneous CA E. faecium isolates. Which of these differences are important for the success of specific E. faecium lineages in the hospital environment remain(s) to be determined.

Dataset Information

The genome sequence of Blochmannia floridanus: comparative analysis of reduced genomes.

Publications

The genome sequence of Blochmannia floridanus: comparative analysis of reduced genomes.

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