Genomic Analysis of Phylotype I Strain EP1 Reveals Substantial Divergence from Other Strains in the Ralstonia solanacearum Species Complex

Abstract

Ralstonia solanacearum species complex is a devastating group of phytopathogens with an unusually wide host range and broad geographical distribution. R. solanacearum isolates may differ considerably in various properties including host range and pathogenicity, but the underlying genetic bases remain vague. Here, we conducted the genome sequencing of strain EP1 isolated from Guangdong Province of China, which belongs to phylotype I and is highly virulent to a range of solanaceous crops. Its complete genome contains a 3.95-Mb chromosome and a 2.05-Mb mega-plasmid, which is considerably bigger than reported genomes of other R. solanacearum strains. Both the chromosome and the mega-plasmid have essential house-keeping genes and many virulence genes. Comparative analysis of strain EP1 with other 3 phylotype I and 3 phylotype II, III, IV strains unveiled substantial genome rearrangements, insertions and deletions. Genome sequences are relatively conserved among the 4 phylotype I strains, but more divergent among strains of different phylotypes. Moreover, the strains exhibited considerable variations in their key virulence genes, including those encoding secretion systems and type III effectors. Our results provide valuable information for further elucidation of the genetic basis of diversified virulences and host range of R. solanacearum species.

Comparison of bacterial communities in soil samples with and without tomato bacterial wilt caused by Ralstonia solanacearum species complex

“…The method is described briefly as follows: each isolated strain was cultured in the CN liquid medium (about 72 h, 28°C, 200 rpm). The R. solanacearum strain EP1 [35] was selected as an indicator strain. It was cultured in CPG medium (casamino acid 1‰, peptone 1%, glucose 1%) until the OD 600 was 1.0.…”

Functional Analysis of Genes Comprising the Locus of Heat Resistance in Escherichia coli

“…coli strains are reflected in the genome plasticity of the species and the acquisition of mobile genetic elements or "lifestyle cassettes" that improve competitiveness in particular niches (1)(2)(3). A nomadic lifestyle also necessitates resistance to environmental stress encountered in extraintestinal niches, e.g., osmotic stress, starvation, or heat stress (4). Colonization of intestines of humans and domestic animals, genome plasticity and the acquisition of virulence factors, and stress resistance also relate to the role of E. coli as a foodborne pathogen (5).…”

“…Colonization of intestines of humans and domestic animals, genome plasticity and the acquisition of virulence factors, and stress resistance also relate to the role of E. coli as a foodborne pathogen (5). Thermal processes are frequently used for food preservation in industrial processing; accordingly, the heat resistance of E. coli often determines its persistence in processed foods (4).…”

“…The survival of E. coli at high temperature is increased by accumulation of compatible solutes, by adjustment of the membrane composition, and by protein homeostasis (4). The accumulation of compatible solutes in response to osmotic stress has broad implications for stress resistance, including heat resistance (4,6).…”

“…The survival of E. coli at high temperature is increased by accumulation of compatible solutes, by adjustment of the membrane composition, and by protein homeostasis (4). The accumulation of compatible solutes in response to osmotic stress has broad implications for stress resistance, including heat resistance (4,6). Membrane homeostasis during heat shock maintains biophysical properties and integrity of the membrane by increasing the proportion of saturated and cyclopropane fatty acids (7,8).…”