The Aeromonas salmonicida plasmidome: a model of modular evolution and genetic diversity

Abstract

High‐throughput genomic sequencing has helped to reveal the plasmidome of Aeromonas salmonicida. This literature review provides an overview of A. salmonicida’s rich plasmidome by presenting all the plasmids identified so far, addressing their biological importance and the functional links between them. The plasmids of A. salmonicida, especially those bearing antibiotic resistance genes, can provide clues about interactions of this species with other pathogens (animals and humans), as is the case for pRAS3‐3432 and Chlamydia suis or pSN254b and Salmonella enterica. In addition to antibiotic resistance, plasmids play an important role in the virulence of A. salmonicida, particularly for the subspecies salmonicida and the plasmid pAsa5, which carries genes for the type‐three secretion system, a virulence factor essential for the bacterium. The A. salmonicida plasmidome also has many cryptic plasmids with no known biological function, but which can be used for the acquisition of new genetic elements. Striking examples are pAsa7 and pAsaXII that provide, respectively, resistance to chloramphenicol and formaldehyde and are derivatives of cryptic pAsa2.

Systematic Analysis of the Stress-Induced Genomic Instability of Type Three Secretion System in Aeromonas salmonicida subsp. salmonicida

“…Some plasmids, such as the cryptic plasmids pAsa1, pAsa2, and pAsa3, are found in nearly all the strains [16,20]. Other plasmids, especially the antibiotic resistance plasmids, are distributed heterogeneously [21]. Considering the non-uniform distribution of plasmids, we wanted to know if the presence or absence of some plasmids was a factor in the strain's ability to lose their TTSS.…”

Genomic Perspectives on Aeromonas salmonicida subsp. salmonicida Strain 890054 as a Model System for Pathogenicity Studies and Mitigation of Fish Infections

“…In addition, 890054 possesses all four small cryptic plasmids (Supplementary Table 6) from the core A. salmonicida subsp. salmonicida plasmidome proposed by Vincent et al (2020) as well as AsaGEI1a which is typically found in about 1/3 of the North American A. salmonicida subsp. salmonicida strains (Emond-Rheault et al, 2015).…”

“…salmonicida for infection challenges. This may lead to difficulties in repeating and generalizing results, in part due to the tremendous genomic diversity within the accessory genome of this subspecies (Attéré et al, 2017;Massicotte et al, 2019;Vincent et al, 2020).…”

Microbe Profile: Aeromonas salmonicida: an opportunistic pathogen with multiple personalities

“…salmonicida is very rich in mobile genetic elements. Among these elements, several plasmids carry multidrug resistance genes or virulence factors [3]. In the salmonicida subspecies, almost all of the genes encoding the type three secretion system (TTSS), a major virulence factor, are found on a large plasmid called pAsa5 [4].…”