Niche-partitioning of ubiquitous, abundant and previously neglected marine bacteria: a case study of Rhodospirillales

Abstract

Marine microbes stand for a great part of the global biodiversity and play key roles in the oceans. However, investigating their diversity and ecology has been extremely challenging due to sampling and methodological constraints. Current molecular and bioinformatic tools together with recent large-scale oceanographic cruises (e.g. Tara Oceans and Malaspina) have helped the scientific community to assess the global ocean's planktonic diversity with an unprecedented depth of analysis. For instance, temperature has been found to be the strongest selective pressure on microbial communities in the global ocean. This is a very relevant finding since the ocean has rapidly warmed during the last two centuries and recent climate change reports project further warming for this century. Niche-partitioning refers to the mechanism through which natural selection leads competing species into different niches and it has been previously described in marine microbes. During my PhD project we found a clear niche-partitioning pattern driven by temperature across space (latitude and depth) and time in Rhodospirillales, an ubiquitous, abundant, but previously neglected group of marine bacteria. This BEPE project brings together classic ecological theory, state-of-the-art molecular techniques and culture-independent methods to explore the biology and ecology of a potentially important, but previously neglected marine bacterial group (Rhodospirillales) in the global ocean. To achieve this goal, we will combine spatial data from two global oceanographic cruises (Tara Oceans and Malaspina), one regional cruise (HotMix Mediterranean Cruise) and a time-series data from a marine microbial observatory (in the NW Mediterranean). Furthermore, we plan to look for genes and mechanisms underpinning the adaptation of this ubiquitous bacterial group to contrasting temperature niches. We also aim to refine the taxonomy and define the ecological and functional capabilities of uncultured marine bacteria within Rhodospirillales by using comparative genomics of single-cell amplified genomes (SAGs) and metagenome amplified genomes (MAGs). (AU)