Microbial experimental evolution as a novel research approach in the Vibrionaceae and squid-Vibrio symbiosis.

Michele K. Nishiguchi,William Soto

doi:10.3389/fmicb.2014.00593

Michele K. Nishiguchi, William Soto

Open Access

https://doi.org/10.3389/fmicb.2014.00593

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Abstract

The Vibrionaceae are a genetically and metabolically diverse family living in aquatic habitats with a great propensity toward developing interactions with eukaryotic microbial and multicellular hosts (as either commensals, pathogens, and mutualists). The Vibrionaceae frequently possess a life history cycle where bacteria are attached to a host in one phase and then another where they are free from their host as either part of the bacterioplankton or adhered to solid substrates such as marine sediment, riverbeds, lakebeds, or floating particulate debris. These two stages in their life history exert quite distinct and separate selection pressures. When bound to solid substrates or to host cells, the Vibrionaceae can also exist as complex biofilms. The association between bioluminescent Vibrio spp. and sepiolid squids (Cephalopoda: Sepiolidae) is an experimentally tractable model to study bacteria and animal host interactions, since the symbionts and squid hosts can be maintained in the laboratory independently of one another. The bacteria can be grown in pure culture and the squid hosts raised gnotobiotically with sterile light organs. The partnership between free-living Vibrio symbionts and axenic squid hatchlings emerging from eggs must be renewed every generation of the cephalopod host. Thus, symbiotic bacteria and animal host can each be studied alone and together in union. Despite virtues provided by the Vibrionaceae and sepiolid squid-Vibrio symbiosis, these assets to evolutionary biology have yet to be fully utilized for microbial experimental evolution. Experimental evolution studies already completed are reviewed, along with exploratory topics for future study.

Highlights

THE VIBRIONACEAE The family Vibrionaceae (Domain Bacteria, Phylum Proteobacteria, Class Gammaproteobacteria) encompass gram-negative chemoorganotrophs that are mostly motile and possess at least one polar flagellum (Farmer III and Janda, 2005; Thompson and Swings, 2006); the gut symbiont Vibrio halioticoli to the abalone Haliotis discus hannai has been described as non-motile (Sawabe et al, 1998)
Results demonstrated as V. fischeri adapted to E. tasmanica, the ability of the derived lines to grow along a salinity gradient significantly changed relative to the ancestor
Evolutionary differentiation occurred in the derived lines relative to the ancestor and to each other for biofilm formation, motility, bioluminescence, and carbon source metabolism, results consistent when compared to V. fischeri wild isolates obtained from light organs of E. scolopes and E. tasmanica specimens collected in the field (Soto et al, 2014)

Summary

Introduction

THE VIBRIONACEAE The family Vibrionaceae (Domain Bacteria, Phylum Proteobacteria, Class Gammaproteobacteria) encompass gram-negative chemoorganotrophs that are mostly motile and possess at least one polar flagellum (Farmer III and Janda, 2005; Thompson and Swings, 2006); the gut symbiont Vibrio halioticoli to the abalone Haliotis discus hannai has been described as non-motile (Sawabe et al, 1998). Work has shown V. fischeri are able to adapt to a novel squid host within 400 generations (Table 1), and such evolution may create tradeoffs in the ancestral animal host environment or in the free-living phase as a physiological correlated response to an important abiotic factor (Soto et al, 2012).

Results

Conclusion