Abstract
Epibacterium mobile BBCC367 is a marine bacterium that is common in coastal areas. It belongs to the Roseobacter clade, a widespread group in pelagic marine ecosystems. Species of the Roseobacter clade are regularly used as models to understand the evolution and physiological adaptability of generalist bacteria. E. mobile BBCC367 comprises two chromosomes and two plasmids. We used gel-free shotgun proteomics to assess its protein expression under 16 different conditions, including stress factors such as elevated temperature, nutrient limitation, high metal concentration, and UVB exposure. Comparison of the different conditions allowed us not only to retrieve almost 70% of the predicted proteins, but also to define three main protein assemblages: 584 essential core proteins, 2,144 facultative accessory proteins and 355 specific unique proteins. While the core proteome mainly exhibited proteins involved in essential functions to sustain life such as DNA, amino acids, carbohydrates, cofactors, vitamins and lipids metabolisms, the accessory and unique proteomes revealed a more specific adaptation with the expression of stress-related proteins, such as DNA repair proteins (accessory proteome), transcription regulators and a significant predominance of transporters (unique proteome). Our study provides insights into how E. mobile BBCC367 adapts to environmental changes and copes with diverse stresses.
Highlights
With oceans covering ∼70% of the planet’s surface they represent the largest habitat on Earth
For quantitative proteomics cells were pelleted by centrifugation at 8,000 g for 15 min and were stored at −80◦C until further use
The genome sequence of E. mobile BBCC367 consists of 4,712,067 bp, including 4,557 coding sequences (CDS) and 75 RNAs (15 rRNAs and 60 tRNAs)
Summary
With oceans covering ∼70% of the planet’s surface they represent the largest habitat on Earth. In contrast to blue water open oceans, coastal marine environments represent more heterogeneous habitats that provide a wider spectrum of accessible dissolved organic matter. These conditions favor copiotrophic generalist bacteria over specialists (Lauro et al, 2009). Epibacterium mobile BBCC367, formerly known as Ruegeria mobilis BBCC367 (Wirth and Whitman, 2018), a member of the Roseobacter clade (Lee et al, 2012), is a key component of marine bacterioplankton, as 15% of bacterial cells in the open ocean and 20% in coastal waters are members of this group from tropical to polar regions (Moran et al, 2007; Gram et al, 2010). Members of the Roseobacter clade feature diverse metabolic capabilities that foster their widespread abundance, in temperate and deep pelagic oceans (Luo and Moran, 2014)
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