What difference does it make if viruses are strain-, rather than species-specific?

Abstract

Theoretical work has suggested an important role of lytic viruses in controlling the diversity of their prokaryotic hosts. Yet, providing strong experimental or observational support (or refutation) for this has proven evasive. Such models have usually assumed “host groups” to correspond to the “species” level, typically delimited by 16S rRNA gene sequence data. Recent model developments take into account the resolution of species into strains with differences in their susceptibility to viral attack. With strains as the host groups, the models will have explicit viral control of abundance at strain level, combined with explicit predator or resource control at community level, but the direct viral control at species level then disappears. Abundance of a species therefore emerges as the combination of how many strains, and at what abundance, this species can establish in competition with other species from a seeding community. We here discuss how species diversification and strain diversification may introduce competitors and defenders, respectively, and that the balance between the two may be a factor in the control of species diversity in mature natural communities. These models can also give a dominance of individuals from strains with high cost of resistance; suggesting that the high proportion of “dormant“ cells among pelagic heterotrophic prokaryotes may reflect their need for expensive defense rather than the lack of suitable growth substrates in their environment.

Temperate phages as self-replicating weapons in bacterial competition

“…In particular, we numerically calculate the Duganella sp. growth rate during the exponential phase as r D = log 2 (D(t exp )) − log 2 (D(0)) t exp (9) over the time interval [0,t exp ] for which dC dt ≥ ε…”

“…Their ubiquity and the observation that globally they are responsible for the turnover of vast amounts of microbial biomass every second [3,4,5], has lead to the suggestion that they may play an important role in structuring bacterial communities and maintaining microbial diversity [6]. In particular, theoretical and experimental studies show that they can regulate competitively dominant species or even specific strains via a mechanism termed "Kill the Winner" [7,8,9]. This allows for the coexistence of less competitive species that would otherwise be excluded, thus promoting diversity.…”

A Generalist Protist Predator Enables Coexistence in Multitrophic Predator-Prey Systems Containing a Phage and the Bacterial Predator Bdellovibrio

“…All experiments were conducted in a resource-rich environment that may lead to selection for increased growth rates in small populations (Hairston et al, 1970). Exploitation of new resources had been already theoretically concluded to be a necessity for the evolution of bacterial strains under phage predation (Thingstad et al, 2015). It would be, therefore, interesting to see if the evolved Klebsiella strains would show reduced growth in less complex media.…”

Isolates as models to study bacterial ecophysiology and biogeochemistry

“…In particular, the interaction between the outer membrane proteins and phage attachment (Guttman et al 2005). Thingstad et al (2015) have proposed a model to account for phage resistance and the number of bacterial taxa in a given habitat. Based on their model, we visualize the virus host interaction in a closed substrate controlled space as follows: Imagine an initial number of cells of a bacterial species that utilizes the available food source in full.…”