The Persistence of Parasitic Plasmids

Abstract

The conditions under which plasmids are predicted to persist remain controversial. Here, we reevaluate the ordinary differential equations used previously to model plasmid persistence and conclude that the parameter space required for maintenance is far less stringent than has been supposed. Strikingly, our model demonstrates that purely parasitic plasmids may persist, even in the absence of heterogeneity in the host population, and that this persistence is expressed by oscillations or damped oscillations between the plasmid-bearing and the plasmid-free class.

The interplay between relatedness and horizontal gene transfer drives the evolution of plasmid-carried public goods

“…All plasmid-carrying offspring produce a public good which generates a benefit that is shared by all individuals within the same patch. The cost of producing the public good to the producer individual is represented by C (this includes the baseline cost of plasmid carriage, where we can write C ¼ C C þ C G , where C G is the cost of public goods production and C C is the cost of plasmid carriage [18]) and the benefit of producer behaviour (shared by all individuals within the same patch j) is represented by B. Public goods, for example, production of b-lactamase, which confers antibiotic resistance [8] or secreted virulence factors [32] are often horizontally transferred in bacteria.…”

What traits are carried on mobile genetic elements, and why?

“…Such models also provide powerful tools for studying the ecology and evolution of plasmids (Bergstrom et al, 2000;Smith, 2001;Lili et al, 2007). By ignoring copy number within cells, and simply assuming that a given cell will either be susceptible to plasmid infection or infected by a plasmid, we can model the dynamics as follows:…”

“…However, many mobile elements do exert costs on their hosts (Diaz Ricci and Hernandez, 2000;Fox et al, 2008), raising the question as to how costly and poorly transmissible MGEs can persist within a genome Stewart and Levin, 1977;Bergstrom et al, 2000;Lili et al, 2007). Stewart and Levin (1977) built one of the first models to analyse plasmid persistence, and argued that plasmids could not persist under low rates of HGT.…”

“…Stewart and Levin (1977) built one of the first models to analyse plasmid persistence, and argued that plasmids could not persist under low rates of HGT. This has provoked a debate as to whether horizontal transfer is sufficient for mobile elements to persist in populations because of their costs on host fitness (see, for example, Bergstrom et al, 2000;Lili et al, 2007;Slater et al, 2008). The persistence of any parasite is fundamentally determined by its rate of horizontal transmission (Anderson and May, 1992), which can be readily measured for plasmids and has been found to vary over eight orders of magnitude among plasmids of E. coli (Dionisio et al, 2002).…”

Mathematical Modeling of the Transmission and Control of Foodborne Pathogens and Antimicrobial Resistance at Preharvest

“…4). Horizontal gene transfer can be modeled as a contagious process (Lili et al, 2007). The term that describes how sensitive bacteria acquire the plasmid by contact with resistant bacteria is similar to the transmission term use for the SIR models; b NsNr N , where b is the conjugate rate and N s , N r , and N are the sensitive, resistant, and total bacteria populations, respectively.…”