Widespread distribution of prophages signaling the potential for adaptability and pathogenicity evolution of Ralstonia solanacearum species complex

• Published in: Genomics (San Diego, Calif.) Vol. 113; no. 3; pp. 992 - 1000
• Main Authors: Gonçalves, Osiel Silva, Souza, Flávia de Oliveira, Bruckner, Fernanda Prieto, Santana, Mateus Ferreira, Alfenas-Zerbini, Poliane
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-05-2021
• Subjects: Bacterial wilt; Bacteriophages; CRISPR-Cas; Genome, Bacterial; Humans; Inovirus; Prophages - genetics; Ralstonia solanacearum - genetics; Virulence; Virulence Factors - genetics; Bacteriophages; CRISPR-Cas; Bacterial wilt; Inovirus
• ISSN: 0888-7543; 1089-8646
• DOI: 10.1016/j.ygeno.2021.02.011

Integrated bacteriophages (prophages) can impact host cells, affecting their lifestyle, genomic diversity, and fitness. However, many basic aspects of how these organisms affect the host cell remain poorly understood. Ralstonia solanacearum is a gram-negative plant pathogenic bacterium that encompasses a great diversity of ecotypes regarded as a species complex (R. solanacearum Species Complex - RSSC). RSSC genomes have a mosaic structure containing numerous elements, signaling the potential for its evolution through horizontal gene transfer. Here, we analyzed 120 Ralstonia spp. genomes from the public database to identify prophage sequences. In total, 379 prophage-like elements were found in the chromosome and megaplasmid of Ralstonia spp. These elements encode genes related to host fitness, virulence factors, antibiotic resistance, and niche adaptation, which might contribute to RSSC adaptability. Prophage-like elements are widespread into the complex in different species and geographic origins, suggesting that the RSSC phages are ancestrally acquired. Complete prophages belonging to the families Inoviridae, Myoviridae, and Siphoviridae were found, being the members of Inoviridae the most abundant. Analysis of CRISPR-Cas spacer sequences demonstrated the presence of prophages sequences that indicate successive infection events during bacterial evolution. Besides complete prophages, we also demonstrated 14 novel putative prophages integrated into Ralstonia spp. genomes. Altogether, our results provide insights into the diversity of prophages in RSSC genomes and suggest that these elements may deeply affect the virulence and host adaptation and shaping the genomes among the strains of this important pathogen.
•379 prophage-like elements were found in the chromosome and megaplasmid of Ralstonia spp.•Prophage-like elements are widespread into the Ralstonia solanacearum Species Complex (RSSC).•Prophages belonging to the family Inoviridae are the most abundant in RSSC.•Fourteen novel putative prophages integrated into Ralstonia spp. genomes were described.