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Predicting gene expression levels from codon biases in alpha-proteobacterial genomes.
Samuel Karlin1, Melanie J Barnett, Allan M Campbell
1Department of Mathematics, Stanford University, Stanford, CA 94305, USA. karlin@math.stanford.edu
Summary
Predicted highly expressed genes in five alpha-proteobacterial genomes show conserved aerobic respiration pathways are highly expressed. Glycolysis and flagellar gene expression varies, with Caulobacter crescentus exhibiting unique TonB-dependent receptor expression.
Area of Science:
- Genomics
- Microbiology
- Proteobacteria
Background:
- Alpha-proteobacteria exhibit diverse lifestyles and pathogenic potentials.
- Gene expression patterns provide insights into cellular functions and adaptations.
- Comparative genomics aids in understanding evolutionary relationships and functional divergence.
Purpose of the Study:
- To analyze predicted highly expressed (PHX) genes in five complete high G+C alpha-proteobacterial genomes.
- To identify conserved and variable gene expression patterns across different species and their ecological niches.
- To investigate the genomic location and functional categories of PHX genes.
Main Methods:
- Bioinformatic analysis of five complete alpha-proteobacterial genomes: Sinorhizobium meliloti, Mesorhizobium loti, Caulobacter crescentus, Agrobacterium tumefaciens, and Brucella melitensis.
- Identification and categorization of predicted highly expressed (PHX) genes.
- Comparative analysis of PHX gene distribution across chromosomes and megaplasmids.
- Functional annotation of PHX genes, focusing on metabolic pathways and motility structures.
Main Results:
- PHX genes are predominantly located on the main chromosome in genomes with multiple chromosomes/megaplasmids.
- Tricarboxylic acid cycle and aerobic respiration genes are consistently PHX across all five genomes.
- Glycolysis and fermentation genes are generally not PHX, with exceptions in Mesorhizobium loti and Brucella melitensis.
- Flagellar gene expression varies, being high in Mesorhizobium loti and Caulobacter crescentus, but low in Sinorhizobium meliloti and Agrobacterium tumefaciens.
- Caulobacter crescentus displays a high number of PHX TonB-dependent receptors, potentially for nutrient uptake.
Conclusions:
- Aerobic respiration pathways are a conserved highly expressed feature in these alpha-proteobacteria.
- Gene expression strategies for energy metabolism and motility differ among these species.
- The high expression of TonB-dependent receptors in Caulobacter crescentus suggests specialized nutrient acquisition mechanisms.