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Phenotypic and Physiological Characterization of the Epibiotic Interaction Between TM7x and Its Basibiont Actinomyces

Bor, Batbileg and Poweleit, Nicole and Bois, Justin S. and Cen, Lujia and Bedree, Joseph K. and Zhou, Z. Hong and Gunsalus, Robert P. and Lux, Renate and McLean, Jeffrey S. and He, Xuesong and Shi, Wenyuan (2016) Phenotypic and Physiological Characterization of the Epibiotic Interaction Between TM7x and Its Basibiont Actinomyces. Microbial Ecology, 71 (1). pp. 243-255. ISSN 0095-3628. PMCID PMC4688200.

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Despite many examples of obligate epibiotic symbiosis (one organism living on the surface of another) in nature, such an interaction has rarely been observed between two bacteria. Here, we further characterize a newly reported interaction between a human oral obligate parasitic bacterium TM7x (cultivated member of Candidatus Saccharimonas formerly Candidate Phylum TM7), and its basibiont Actinomyces odontolyticus species (XH001), providing a model system to study epiparasitic symbiosis in the domain Bacteria. Detailed microscopic studies indicate that both partners display extensive morphological changes during symbiotic growth. XH001 cells manifested as short rods in monoculture, but displayed elongated and hyphal morphology when physically associated with TM7x. Interestingly, these dramatic morphological changes in XH001 were also induced in oxygen-depleted conditions, even in the absence of TM7x. Targeted quantitative real-time PCR (qRT-PCR) analyses revealed that both the physical association with TM7x as well as oxygen depletion triggered up-regulation of key stress response genes in XH001, and in combination, these conditions act in an additive manner. TM7x and XH001 co-exist with relatively uniform cell morphologies under nutrient-replete conditions. However, upon nutrient depletion, TM7x-associated XH001 displayed a variety of cell morphologies, including swollen cell body, clubbed-ends, and even cell lysis, and a large portion of TM7x cells transformed from ultrasmall cocci into elongated cells. Our study demonstrates a highly dynamic interaction between epibiont TM7x and its basibiont XH001 in response to physical association or environmental cues such as oxygen level and nutritional status, as reflected by their morphological and physiological changes during symbiotic growth.

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Bois, Justin S.0000-0001-7137-8746
Additional Information:© 2015 Springer Science+Business Media New York. Received: 6 August 2015; Accepted: 11 November 2015. Published online: 23 November 2015. We thank the members of the Shi and Lux laboratories for their feedback and invaluable discussion. We also thank Melissa Agnello for providing extensive editing of the manuscript. We thank the Chemistry and Biochemistry instrumentation facility at UCLA for providing access to the confocal microscope. This work was supported in part by grants from the National Institutes of Health (1R01DE023810-01) and Oral Health-Research Postdoctoral Training Program (B.B., UCLA School of Dentistry T90 award). The authors declare that they have no conflict of interests.
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UCLA School of DentistryUNSPECIFIED
Subject Keywords:Obligate; Epibiont; Symbiosis; Bacterial interaction; TM7; Actinomyces
Issue or Number:1
PubMed Central ID:PMC4688200
Record Number:CaltechAUTHORS:20151201-151719120
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:62519
Deposited By: Tony Diaz
Deposited On:03 Dec 2015 02:47
Last Modified:23 Apr 2020 22:43

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