Cargando…

Genome Evolution in the Obligate but Environmentally Active Luminous Symbionts of Flashlight Fish

The luminous bacterial symbionts of anomalopid flashlight fish are thought to be obligately dependent on their hosts for growth and share several aspects of genome evolution with unrelated obligate symbionts, including genome reduction. However, in contrast to most obligate bacteria, anomalopid symb...

Descripción completa

Detalles Bibliográficos
Autores principales: Hendry, Tory A., de Wet, Jeffrey R., Dougan, Katherine E., Dunlap, Paul V.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4987116/
https://www.ncbi.nlm.nih.gov/pubmed/27389687
http://dx.doi.org/10.1093/gbe/evw161
_version_ 1782448268649693184
author Hendry, Tory A.
de Wet, Jeffrey R.
Dougan, Katherine E.
Dunlap, Paul V.
author_facet Hendry, Tory A.
de Wet, Jeffrey R.
Dougan, Katherine E.
Dunlap, Paul V.
author_sort Hendry, Tory A.
collection PubMed
description The luminous bacterial symbionts of anomalopid flashlight fish are thought to be obligately dependent on their hosts for growth and share several aspects of genome evolution with unrelated obligate symbionts, including genome reduction. However, in contrast to most obligate bacteria, anomalopid symbionts have an active environmental phase that may be important for symbiont transmission. Here we investigated patterns of evolution between anomalopid symbionts compared with patterns in free-living relatives and unrelated obligate symbionts to determine if trends common to obligate symbionts are also found in anomalopid symbionts. Two symbionts, “Candidatus Photodesmus katoptron” and “Candidatus Photodesmus blepharus,” have genomes that are highly similar in gene content and order, suggesting genome stasis similar to ancient obligate symbionts present in insect lineages. This genome stasis exists in spite of the symbiont’s inferred ability to recombine, which is frequently lacking in obligate symbionts with stable genomes. Additionally, we used genome comparisons and tests of selection to infer which genes may be particularly important for the symbiont’s ecology compared with relatives. In keeping with obligate dependence, substitution patterns suggest that most symbiont genes are experiencing relaxed purifying selection compared with relatives. However, genes involved in motility and carbon storage, which are likely to be used outside the host, appear to be under increased purifying selection. Two chemoreceptor chemotaxis genes are retained by both species and show high conservation with amino acid sensing genes, suggesting that the bacteria may actively seek out hosts using chemotaxis toward amino acids, which the symbionts are not able to synthesize.
format Online
Article
Text
id pubmed-4987116
institution National Center for Biotechnology Information
language English
publishDate 2016
publisher Oxford University Press
record_format MEDLINE/PubMed
spelling pubmed-49871162016-08-22 Genome Evolution in the Obligate but Environmentally Active Luminous Symbionts of Flashlight Fish Hendry, Tory A. de Wet, Jeffrey R. Dougan, Katherine E. Dunlap, Paul V. Genome Biol Evol Research Article The luminous bacterial symbionts of anomalopid flashlight fish are thought to be obligately dependent on their hosts for growth and share several aspects of genome evolution with unrelated obligate symbionts, including genome reduction. However, in contrast to most obligate bacteria, anomalopid symbionts have an active environmental phase that may be important for symbiont transmission. Here we investigated patterns of evolution between anomalopid symbionts compared with patterns in free-living relatives and unrelated obligate symbionts to determine if trends common to obligate symbionts are also found in anomalopid symbionts. Two symbionts, “Candidatus Photodesmus katoptron” and “Candidatus Photodesmus blepharus,” have genomes that are highly similar in gene content and order, suggesting genome stasis similar to ancient obligate symbionts present in insect lineages. This genome stasis exists in spite of the symbiont’s inferred ability to recombine, which is frequently lacking in obligate symbionts with stable genomes. Additionally, we used genome comparisons and tests of selection to infer which genes may be particularly important for the symbiont’s ecology compared with relatives. In keeping with obligate dependence, substitution patterns suggest that most symbiont genes are experiencing relaxed purifying selection compared with relatives. However, genes involved in motility and carbon storage, which are likely to be used outside the host, appear to be under increased purifying selection. Two chemoreceptor chemotaxis genes are retained by both species and show high conservation with amino acid sensing genes, suggesting that the bacteria may actively seek out hosts using chemotaxis toward amino acids, which the symbionts are not able to synthesize. Oxford University Press 2016-06-07 /pmc/articles/PMC4987116/ /pubmed/27389687 http://dx.doi.org/10.1093/gbe/evw161 Text en © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. http://creativecommons.org/licenses/by-nc/4.0/ This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com
spellingShingle Research Article
Hendry, Tory A.
de Wet, Jeffrey R.
Dougan, Katherine E.
Dunlap, Paul V.
Genome Evolution in the Obligate but Environmentally Active Luminous Symbionts of Flashlight Fish
title Genome Evolution in the Obligate but Environmentally Active Luminous Symbionts of Flashlight Fish
title_full Genome Evolution in the Obligate but Environmentally Active Luminous Symbionts of Flashlight Fish
title_fullStr Genome Evolution in the Obligate but Environmentally Active Luminous Symbionts of Flashlight Fish
title_full_unstemmed Genome Evolution in the Obligate but Environmentally Active Luminous Symbionts of Flashlight Fish
title_short Genome Evolution in the Obligate but Environmentally Active Luminous Symbionts of Flashlight Fish
title_sort genome evolution in the obligate but environmentally active luminous symbionts of flashlight fish
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4987116/
https://www.ncbi.nlm.nih.gov/pubmed/27389687
http://dx.doi.org/10.1093/gbe/evw161
work_keys_str_mv AT hendrytorya genomeevolutionintheobligatebutenvironmentallyactiveluminoussymbiontsofflashlightfish
AT dewetjeffreyr genomeevolutionintheobligatebutenvironmentallyactiveluminoussymbiontsofflashlightfish
AT dougankatherinee genomeevolutionintheobligatebutenvironmentallyactiveluminoussymbiontsofflashlightfish
AT dunlappaulv genomeevolutionintheobligatebutenvironmentallyactiveluminoussymbiontsofflashlightfish