Unprecedented loss of ammonia assimilation capability in a urease-encoding bacterial mutualist

BMC Genomics

Research Article

Laura E Williams¹  Jennifer J Wernegreen² 

[1] The Institute for Genome Sciences and Policy, Duke University, Durham, NC, USA;The Institute for Genome Sciences and Policy, Duke University, Durham, NC, USA;Nicholas School of the Environment, Duke University, Durham, NC, USA;

关键词: Glutamine Synthetase;    Intergenic Sequence;    Genome Reduction;    Homopolymeric Tract;    Read Dataset;   

DOI  :  10.1186/1471-2164-11-687

 received in 2010-09-16, accepted in 2010-12-02,  发布年份 2010

来源: Springer

【 摘 要 】

BackgroundBlochmannia are obligately intracellular bacterial mutualists of ants of the tribe Camponotini. Blochmannia perform key nutritional functions for the host, including synthesis of several essential amino acids. We used Illumina technology to sequence the genome of Blochmannia associated with Camponotus vafer.ResultsAlthough Blochmannia vafer retains many nutritional functions, it is missing glutamine synthetase (glnA), a component of the nitrogen recycling pathway encoded by the previously sequenced B. floridanus and B. pennsylvanicus. With the exception of Ureaplasma, B. vafer is the only sequenced bacterium to date that encodes urease but lacks the ability to assimilate ammonia into glutamine or glutamate. Loss of glnA occurred in a deletion hotspot near the putative replication origin. Overall, compared to the likely gene set of their common ancestor, 31 genes are missing or eroded in B. vafer, compared to 28 in B. floridanus and four in B. pennsylvanicus. Three genes (queA, visC and yggS) show convergent loss or erosion, suggesting relaxed selection for their functions. Eight B. vafer genes contain frameshifts in homopolymeric tracts that may be corrected by transcriptional slippage. Two of these encode DNA replication proteins: dnaX, which we infer is also frameshifted in B. floridanus, and dnaG.ConclusionsComparing the B. vafer genome with B. pennsylvanicus and B. floridanus refines the core genes shared within the mutualist group, thereby clarifying functions required across ant host species. This third genome also allows us to track gene loss and erosion in a phylogenetic context to more fully understand processes of genome reduction.

【 授权许可】

CC BY   
© Williams and Wernegreen; licensee BioMed Central Ltd. 2010