Biogeographic patterns of aerobic anoxygenic phototrophic bacteria reveal an ecological consistency of phylogenetic clades in different oceanic biomes

Anne-Catherine Lehours,Christian Jeanthon,Dominique Boeuf,François Enault

doi:10.1038/s41598-018-22413-7

Abstract

In marine environments, aerobic anoxygenic phototrophic (AAP) bacterial assemblages vary in space and along environmental gradients but the factors shaping their diversity and distribution at different taxonomic levels remain poorly identified. Using sets of sequences encoding the M sub-unit of the photosynthetic apparatus from different oceanic regions, we prioritized the processes underlying AAP bacterial biogeographical patterns. The present analysis offers novel insights into the ecological distribution of marine AAP bacteria and highlights that physiological constraints play a key role in structuring AAP bacterial assemblages at a global scale. Salinity especially seems to favor lineage-specific adaptations. Moreover, by inferring the evolutionary history of habitat transitions, a substantial congruence between habitat and evolutionary relatedness was highlighted. The identification of ecological cohesive clades for AAP bacteria suggests that prediction of AAP bacterial assemblages is possible from marine habitat properties.

Highlights

Anoxygenic phototrophic bacteria were long considered to be ecological oddities from specialized habitats[1] limiting their relevance for the biosphere
To gain a more accurate picture of the factors governing the ecology of aerobic anoxygenic phototrophic (AAP) bacteria, their diversity was investigated in different oceanic regions, and several studies have attempted to connect the observed patterns with environmental variables
The pufM dataset used in this study was assembled from sequences previously generated from 27 samples collected during 4 cruises (PROSOPE, BOUM, ARCTIC and MALINA) which took place between 1999 and 2009 in different oceanic regions (Mediterranean, North Pacific to Western Beaufort Sea, Barents and Norwegian seas; Fig. 1a)

Summary

Introduction

Anoxygenic phototrophic bacteria were long considered to be ecological oddities from specialized habitats[1] limiting their relevance for the biosphere. Determining how environmental conditions control the ecology of AAP bacteria, at a fine taxonomic resolution (i.e., sufficient to identify lineages with distinct traits), is critical for understanding how these organisms populate the oceans and contribute to global carbon cycling Following this idea, the objectives of the present study were (i) to provide elements establishing the role of the environmental context in structuring AAP bacterial diversity, (ii) to prioritize the processes (i.e, deterministic vs stochastic) responsible for generating AAP bacterial patterns in marine environments, (iii) to determine if a link between phylogeny and habitat preferendum exists. We analyzed the sequence polymorphism of the gene encoding for the M subunit of the core photosynthetic apparatus (pufM gene) of AAP bacteria in contrasted oceanic provinces encompassing different marine regions, distinct nutrient status and oceanic regimes, various temperatures, salinities and depths

Objectives

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Results

Conclusion