Research

Simple Porifera holobiont reveals complex interactions between the host, an archaeon, a bacterium, and a phage

This work explores the interactions within the simplest sponge holobiont described so far. It consists on the sponge host A. beatrix, and it's two microbial symbionts: an autotrophic ammonia-oxidizing archaeon (N. spongiisocia) and a bacterium (Z. abyssi). We identified an unique relationship involving nutrient exchange between these organisms, with the archaeon relying on sponge-derived ammonia, while the bacterium benefits from the fumarate produced by the archaeon. Additionally, a virus infecting the archaeon plays a key role in the vitamin B12 exchange in this system. This complex interaction may have broader implications for understanding symbiotic relationships in other ecosystems​.

Species-specific relationships between deep sea sponges and their symbiotic Nitrosopumilaceae:

This work investigates the relationships between deep-sea sponges and their microbial symbionts, specifically ammonia-oxidizing archaea (AOA) from the Nitrosopumilaceae family. The study finds that Nitrosopumilaceae dominate the microbial communities in several sponge species, particularly in Aphrocallistes sp., where they constitute 97.70% of the microbiome. These symbionts likely contribute to carbon fixation and nitrogen cycling through ammonium oxidation, providing energy and organic carbon for the sponge. The results suggest species-specific relationships between sponges and Nitrosopumilaceae, possibly indicating vertical transmission of symbionts, a rare phenomenon in shallow-water sponges.

Carbon fixation pathways across the bacterial and archaeal tree of life

This work explored the distribution of carbon fixation pathways (CFPs) among bacteria and archaea, using 52,515 metagenome-assembled genomes (MAGs). The study identified CFPs in 1,007 bacterial and archaeal genomes, expanding known pathways like the reverse tricarboxylic acid cycle, 3-hydroxypropionate bi-cycle, and Calvin-Benson-Bassham cycle to previously unrecognized phyla, such as Thermoplasmatota and Elusimicrobiota. These findings highlight a broader diversity of microorganisms contributing to global primary production and carbon sinks than previously understood, emphasizing the ecological role of CFPs.

Novel metabolic pathways supporting life in the deep sea: 

During his PhD, Alessandro Garritano aims to better understand how symbionts support life in the deep sea. His project aims to explore microbiomes and their metabolic activities in a deep-sea petrol extraction site. He will focus particularly on the microbiomes that are living in symbiotic relationships with corals and sponges, the major habitat-forming organisms in the deep sea. Coral reefs and sponge gardens appear to survive and grow very well close to these areas and we hypothesize that this is due to unique metabolic capabilities of the symbiont microbiomes. In this sense, it is postulated that the microbiomes can utilize “unusual” carbon and energy sources as well as different carbon fixation pathways to convert those into useful nutrients and energy for the coral and sponge host.

Biological production of H2 and CH4 using POME as raw material: 

In his Masters, Alessandro Garritano focused on the anaerobic fermentation of palm oil mill wastewater (POME) using a mixed microbial consortium. The aim was to produce hydrogen and methane from POME in order to generate energy in a decentralized manner for remote areas in Brazil. Amongst his achievements, he  developed a gas chromatography method to quantify free fatty acids as well as started a new line of research in my former lab aiming the production of methane from the post-fermentation media after the initial hydrogen production. Furthermore, he discovered that a pre-hydrolysis step with an enzimatic prepataion of Ricinus communis can greatly increase hydrogen yield for most agro-industrial wastewaters.