Insights into Genomic Variation within Salmonella enterica

Advances in molecular microbiology, comparative genomics and data mining have allowed us to uncover new insights into genome structure within bacterial species. To evolve, Bacteria gains and loses genes and other genomic sequences to adapt to specific ecological niches [1]. Thus, the intraspecies genomic variation found in numerous bacterial species has highlighted the need of analyzing genome composition to define bacterial species [1]. Fortunately, Whole-Genome Sequence Analysis (WGSA) has uncovered the dynamic nature of genomic plasticity and the consequent extensive genetic diversity in Bacteria [2]. Currently, microbiological research has been focused on WGSA within-species to identify molecular or virulence determinants. These studies could accelerate our understanding of bacterial pathogenesis and strains-specific traits of virulence; key factors in improving bacterial surveillance and development of antibacterial treatments or vaccines [3]. Herein, we investigate the genomic variation within Salmonella enterica as an example of the potential of comparative analysis of WGSA to uncover intraspecies variation. A total of 1,604 S. enterica whole genomes were analyzed. This dataset comprised 38 different serotypes (Table 1) retrieved from the Integrated Microbial Genomes (IMG) system [4]. Serotypes with at least 3 genomes available were used for bioinformatics analyses. Intraspecies traits of genomic variation were assessed for each of the selected serotypes. Briefly, it was found that the genome size S. enterica serotypes varies considerably; for example, serotype Muenchen, in average, possess the largest genome size (5.00 Mbp) whereas Paratyphi possess the smallest (4.59 Mbp). Unexpectedly, a high variation in the genome size was observed in each serotype (Figure 1 and Table 1).