Abstract
Complex environmental conditions can significantly affect bacterial genome size by unknown mechanisms. The So0157-2 strain of Sorangium cellulosum is an alkaline-adaptive epothilone producer that grows across a wide pH range. Here, we show that the genome of this strain is 14,782,125 base pairs, 1.75-megabases larger than the largest bacterial genome from S. cellulosum reported previously. The total 11,599 coding sequences (CDSs) include massive duplications and horizontally transferred genes, regulated by lots of protein kinases, sigma factors and related transcriptional regulation co-factors, providing the So0157-2 strain abundant resources and flexibility for ecological adaptation. The comparative transcriptomics approach, which detected 90.7% of the total CDSs, not only demonstrates complex expression patterns under varying environmental conditions but also suggests an alkaline-improved pathway of the insertion and duplication, which has been genetically testified, in this strain. These results provide insights into and a paradigm for how environmental conditions can affect bacterial genome expansion.
Highlights
Complex environmental conditions can significantly affect bacterial genome size by unknown mechanisms
The So0157-2 strain of Sorangium cellulosum is an alkaline-adaptive epothilone producer that grows across a wide pH range
It is known that genome expansion can occur via acquisition of exogenous genetic materials by horizontal gene transfer (HGT) or by genome duplication[25,26]
Summary
Complex environmental conditions can significantly affect bacterial genome size by unknown mechanisms. The comparative transcriptomics approach, which detected 90.7% of the total CDSs, demonstrates complex expression patterns under varying environmental conditions and suggests an alkaline-improved pathway of the insertion and duplication, which has been genetically testified, in this strain. These results provide insights into and a paradigm for how environmental conditions can affect bacterial genome expansion. The relatively large genome sizes of aerobic myxobacteria seem to be consistent with their complex social activity and comprehensive environmental adaptation These bacteria possess complex regulatory networks consisting of many sigma factors and kinases that respond to fluctuating environments[14,15]. The data suggest the existence of an unique alkaline pH-improved pathway formed through the incorporation of exogenous genetic materials and the duplication of internal genes
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