Seminar Details

How did microbial phosphate acquisition uncover ubiquity of microbial mixotrophy in the open ocean?

Date

26/04/2017

Lecturers

Prof. Mikhail Zubkov - National Oceanography Centre, Southampton, UK

Abstract

Oligotrophic subtropical gyres are the largest oceanic ecosystems covering >40% of the Earth’s surface. In these ecosystems the smallest eukaryotic algae showed remarkable growth capacity by doubling their ten-hundred times bigger cells in only twice the time taken by the cyanobacterial cells. Nonetheless, energetic superiority of complex eukaryotic CO2-fixing cells succumbed to high nutrient transport efficiency of simple prokaryotic CO2-fixing cells. Different types of photosynthesis are used by main bacterioplankton groups to enhance uptake of sparse macronutrients. To acquire phosphate the ubiquitous Prochlorococcus and SAR11 bacteria use an extracellular buffer of labile phosphate up to 5-40 times larger than the amount of phosphate required to replicate their chromosomes. Control of phosphate uptake by prokaryotes suggests that algae should obtain phosphate indirectly. And indeed algae exercise their energetic superiority by feeding on bacterioplankton. Furthermore, because of their higher abundance, it is the smallest mixotrophic algae, rather than heterotrophic flagellates, that dominate bacterivory in the photic layer. The above findings advance our basic understanding of microbial food web functioning in the open ocean.

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