Table of Contents
International Journal of Evolutionary Biology
Volume 2011, Article ID 634505, 5 pages
Research Article

Phylogenetic and Guanine-Cytosine Content Analysis of Symbiobacterium thermophilum Genes

Agricultural Bioinformatics Research Unit, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan

Received 10 September 2010; Revised 20 October 2010; Accepted 5 November 2010

Academic Editor: Shinji Kondo

Copyright © 2011 Hiromi Nishida and Choong-Soo Yun. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Although the bacterium Symbiobacterium thermophilum has a genome with a high guanine-cytosine (GC) content (69%), it belongs to a low GC content bacterial group. We detected only 18 low GC content regions with 5 or more consecutive genes whose GC contents were below 65% in the genome of this organism. S. thermophilum has 66 transposase genes, which are markers of transposable genetic elements, and 38 (58%) of them were located in the low GC content regions, suggesting that Symbiobacterium has a similar gene silencing system as Salmonella. The top hit (best match) analyses for each Symbiobacterium protein showed that putative horizontally transferred genes and vertically inherited genes are scattered across the genome. Approximately 25% of the 3338 Symbiobacterium proteins have the highest similarity with the protein of a phylogenetically distant organism. The putative horizontally transferred genes also have a high GC content, suggesting that Symbiobacterium has gained many DNA fragments from phylogenetically distant organisms during the early stage of Firmicutes evolution. After acquiring genes, Symbiobacterium increased the GC content of the horizontally transferred genes and thereby maintained a genome with a high GC content.