Ecological and evolutionary role of specialized bacteria in algae health and carbon sequestration

Introduction

Marine algae fixing CO2 into organic matter is central to the global carbon cycle. While the food chain and marine bacteria consume roughly half of the fixed carbon, a harder-to-degrade fraction remains in the ocean, naturally sequestering CO2 and lessening climate change effects.

Importance of Algal Complex Glycans

This remaining fraction is mainly derived from algal complex glycans that provide structural support, defense against microbial pathogens, and can be a carbon source for the algae microbiome. The specialized bacteria feeding on complex glycans are integral to the algae microbiome, yet have been historically dismissed.

Project Focus

ERODERS focuses on the unidentified mechanisms supporting the interactions between bacteria feeding on complex fucose-containing sulfated polysaccharides (FCPS) and the (host) algae that produce them.

Hypothesis

I propose that specialized bacteria have co-evolved with algae and have a key role in unlocking glycans that maintain the algae microbiome and simultaneously modify the structure of glycans that participate in carbon sequestration processes.

Bacterial Groups of Interest

Bacteria belonging to the Verrucomicrobiota and Planctomycetota phyla are the only groups living on algae that carry the enzymes to consume FCSPs.

Methodology

Using a combination of cutting-edge approaches (multi-omic, visualization, and physiologic examination), we will expand into the unknown diversity and population structure of FCSP degrading bacteria on micro and macroalgae.

Experimental Design

To tease apart the effects on algae health, we will incubate the model brown algae Ectocarpus with FCSP-degrading bacteria under laboratory conditions and examine both the response of incubated bacteria and the impact on the algae growth and its microbiome.

Conclusion

This proposal presents a unique opportunity to unveil the microbial diversity and mechanisms that link bacteria to the metabolism of complex glycans involved in carbon sequestration processes and the evolutionary significance shaping the relationship between bacteria and hosts, with implications from marine to gut ecosystems.