Environmental Viscosity Modulates Interbacterial Killing during Habitat Transition

ABSTRACT Symbiotic bacteria use diverse strategies to compete for host colonization sites. However, little is known about the environmental cues that modulate interbacterial competition as they transition between free-living and host-associated lifestyles. We used the mutualistic relationship betwee...

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Autores principales:	Lauren Speare, Stephanie Smith, Fernanda Salvato, Manuel Kleiner, Alecia N. Septer
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2020
Materias:	Aliivibrio fischeri aggregation competition proteomics type VI secretion Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/31535ec94f7d477da0307b1754bb67b5
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spelling	oai:doaj.org-article:31535ec94f7d477da0307b1754bb67b52021-11-15T15:56:58ZEnvironmental Viscosity Modulates Interbacterial Killing during Habitat Transition10.1128/mBio.03060-192150-7511https://doaj.org/article/31535ec94f7d477da0307b1754bb67b52020-02-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.03060-19https://doaj.org/toc/2150-7511ABSTRACT Symbiotic bacteria use diverse strategies to compete for host colonization sites. However, little is known about the environmental cues that modulate interbacterial competition as they transition between free-living and host-associated lifestyles. We used the mutualistic relationship between Eupyrmna scolopes squid and Vibrio fischeri bacteria to investigate how intraspecific competition is regulated as symbionts move from the seawater to a host-like environment. We recently reported that V. fischeri uses a type VI secretion system (T6SS) for intraspecific competition during host colonization. Here, we investigated how environmental viscosity impacts T6SS-mediated competition by using a liquid hydrogel medium that mimics the viscous host environment. Our data demonstrate that although the T6SS is functionally inactive when cells are grown under low-viscosity liquid conditions similar to those found in seawater, exposure to a host-like high-viscosity hydrogel enhances T6SS expression and sheath formation, activates T6SS-mediated killing in as little as 30 min, and promotes the coaggregation of competing genotypes. Finally, the use of mass spectrometry-based proteomics revealed insights into how cells may prepare for T6SS competition during this habitat transition. These findings, which establish the use of a new hydrogel culture condition for studying T6SS interactions, indicate that V. fischeri rapidly responds to the physical environment to activate the competitive mechanisms used during host colonization. IMPORTANCE Bacteria often engage in interference competition to gain access to an ecological niche, such as a host. However, little is known about how the physical environment experienced by free-living or host-associated bacteria influences such competition. We used the bioluminescent squid symbiont Vibrio fischeri to study how environmental viscosity impacts bacterial competition. Our results suggest that upon transition from a planktonic environment to a host-like environment, V. fischeri cells activate their type VI secretion system, a contact-dependent interbacterial nanoweapon, to eliminate natural competitors. This work shows that competitor cells form aggregates under host-like conditions, thereby facilitating the contact required for killing, and reveals how V. fischeri regulates a key competitive mechanism in response to the physical environment.Lauren SpeareStephanie SmithFernanda SalvatoManuel KleinerAlecia N. SepterAmerican Society for MicrobiologyarticleAliivibrio fischeriaggregationcompetitionproteomicstype VI secretionMicrobiologyQR1-502ENmBio, Vol 11, Iss 1 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	Aliivibrio fischeri aggregation competition proteomics type VI secretion Microbiology QR1-502
spellingShingle	Aliivibrio fischeri aggregation competition proteomics type VI secretion Microbiology QR1-502 Lauren Speare Stephanie Smith Fernanda Salvato Manuel Kleiner Alecia N. Septer Environmental Viscosity Modulates Interbacterial Killing during Habitat Transition
description	ABSTRACT Symbiotic bacteria use diverse strategies to compete for host colonization sites. However, little is known about the environmental cues that modulate interbacterial competition as they transition between free-living and host-associated lifestyles. We used the mutualistic relationship between Eupyrmna scolopes squid and Vibrio fischeri bacteria to investigate how intraspecific competition is regulated as symbionts move from the seawater to a host-like environment. We recently reported that V. fischeri uses a type VI secretion system (T6SS) for intraspecific competition during host colonization. Here, we investigated how environmental viscosity impacts T6SS-mediated competition by using a liquid hydrogel medium that mimics the viscous host environment. Our data demonstrate that although the T6SS is functionally inactive when cells are grown under low-viscosity liquid conditions similar to those found in seawater, exposure to a host-like high-viscosity hydrogel enhances T6SS expression and sheath formation, activates T6SS-mediated killing in as little as 30 min, and promotes the coaggregation of competing genotypes. Finally, the use of mass spectrometry-based proteomics revealed insights into how cells may prepare for T6SS competition during this habitat transition. These findings, which establish the use of a new hydrogel culture condition for studying T6SS interactions, indicate that V. fischeri rapidly responds to the physical environment to activate the competitive mechanisms used during host colonization. IMPORTANCE Bacteria often engage in interference competition to gain access to an ecological niche, such as a host. However, little is known about how the physical environment experienced by free-living or host-associated bacteria influences such competition. We used the bioluminescent squid symbiont Vibrio fischeri to study how environmental viscosity impacts bacterial competition. Our results suggest that upon transition from a planktonic environment to a host-like environment, V. fischeri cells activate their type VI secretion system, a contact-dependent interbacterial nanoweapon, to eliminate natural competitors. This work shows that competitor cells form aggregates under host-like conditions, thereby facilitating the contact required for killing, and reveals how V. fischeri regulates a key competitive mechanism in response to the physical environment.
format	article
author	Lauren Speare Stephanie Smith Fernanda Salvato Manuel Kleiner Alecia N. Septer
author_facet	Lauren Speare Stephanie Smith Fernanda Salvato Manuel Kleiner Alecia N. Septer
author_sort	Lauren Speare
title	Environmental Viscosity Modulates Interbacterial Killing during Habitat Transition
title_short	Environmental Viscosity Modulates Interbacterial Killing during Habitat Transition
title_full	Environmental Viscosity Modulates Interbacterial Killing during Habitat Transition
title_fullStr	Environmental Viscosity Modulates Interbacterial Killing during Habitat Transition
title_full_unstemmed	Environmental Viscosity Modulates Interbacterial Killing during Habitat Transition
title_sort	environmental viscosity modulates interbacterial killing during habitat transition
publisher	American Society for Microbiology
publishDate	2020
url	https://doaj.org/article/31535ec94f7d477da0307b1754bb67b5
work_keys_str_mv	AT laurenspeare environmentalviscositymodulatesinterbacterialkillingduringhabitattransition AT stephaniesmith environmentalviscositymodulatesinterbacterialkillingduringhabitattransition AT fernandasalvato environmentalviscositymodulatesinterbacterialkillingduringhabitattransition AT manuelkleiner environmentalviscositymodulatesinterbacterialkillingduringhabitattransition AT aleciansepter environmentalviscositymodulatesinterbacterialkillingduringhabitattransition
_version_	1718427078569754624

Environmental Viscosity Modulates Interbacterial Killing during Habitat Transition

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