Biology subjects

Sahonero-Canavesi, D. X.

Publications and source records attributed to Sahonero-Canavesi, D. X..

3 recordsLinked to original sources

bioRxiv2026

Towards understanding the bacterial biosynthesis of branched GDGTs: Identification of iso-diabolic acid-based tetraester and mixed ether/ester, membrane-spanning lipid intermediates in members of the Bacillota

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial membrane-spanning lipids (MSLs) resembling archaeal membrane lipids, as they form monolayers and are linked to glycerol backbones via ether bonds. Ubiquitous in soils, sediments, and aquatic environments, their distributions are widely applied as paleoclimate proxies for reconstructing past temperature and pH. Despite this, understanding of their biological origins and functional role in cells remain incomplete. While some Acidobacteria are known producers of brGDGTs, genomic evidence and environmental surveys indicate additional bacterial contributors. In this study, we report the first detection of potential brGDGT biosynthetic intermediates in Bacillota. Ultra-high pressure liquid chromatography high resolution multi-stage mass spectrometry (UHPLC-HRMSn) revealed membrane-spanning diglycerol lipids which contained iso-diabolic acid (13,16-dimethyl octacosanedioic acid)-derived alkyl chains. These diglycerol lipids displayed diverse structures, including tetraesters, mixed ester/ether combinations, and vinyl ether bonds. Additionally, open membrane spanning lipids analogous to brGTGTs were also identified. Notably, all brGDGT and brGTGT analogues were detected with a phosphatidylglycerol head group. Experiments showed that the two Bacillota strains, which produce these brGDGT biosynthetic intermediates, responded differently to changes in temperature and oxygen availability, suggesting that environmental regulation of brGDGT-related lipids is taxonomically dependent. Based on these findings, we propose a biosynthetic pathway for brGDGT formation and highlight the physiological implications for interpreting brGDGT-based paleoclimate proxies. This work expands the known diversity of bacterial sources of brGDGTs and provides new insights into the ecological and evolutionary significance of these lipids. IMPORTANCEBranched GDGTs (brGDGTs) are bacterial membrane spanning lipids which form a monolayer, linked through ether bonds to the glycerol backbone, characteristics more commonly found in archaeal membrane lipids. They are commonly used in paleoclimate proxies to assess past temperature and pH but their predictive power is hampered by the lack of information regarding their biological producers. Branched GDGTs have been detected in just a few species of the Acidobacteria but there are strong indications that other bacterial phyla also contribute to the pool of brGDGTs in the environment. Here, we report for the first time the production of potential brGDGT intermediates in Bacillota species. This study demonstrates that brGDGTs likely occur much more widespread in the bacterial domain than previously thought and opens a new chapter both in the understanding of the function of these membrane lipids and their use in paleoclimatology.

microbiology↗

bioRxiv2024

Combining 13C, 15N, and 2H to measure feeding and metabolic activity in marine, shallow-water sponges - A pilot study

BackgroundShallow-water sponges can reach high densities and have several functions in the ecosystem, such as, providing microhabitats for other species or being involved in benthic-pelagic coupling. They also have a fast cell turnover so they can serve as test animals for the development of new methods to measure the metabolic activity of individual organisms. Here, we measured the feeding and metabolic activity of the common intertidal sponge Halichondria panicea using a triple stable isotope labeling experiment with a 13C and 15N-enriched bacteria as substrate and 2H from deuterated water. We also constrained pathways of phospholipid-derived fatty acid (PLFA) biosynthesis in the sponge and its microbiome. MethodsSponges were collected in the Eastern Scheldt (North Sea) and incubated in 1% 2H-enriched seawater in the presence of 13C- and 15N-enriched substrate of inactivated bacteria for 12 h. Water samples for the analysis of dissolved inorganic carbon (DIC), 13C-DIC, and inorganic nutrients were taken at the begin and the end of the incubations, while oxygen concentration in the water was recorded continuously. Seawater incubations with the addition of substrate bacteria served as blanks and dead sponges incubated in 1% 2H-enriched seawater served as controls for the incorporation of 2H into inactive tissue. At the end of the experiment, sponges were sampled for bulk analyses of 13C, 15N, and 2H in sponge tissue, and for 13C and 2H incorporation into phospholipid-derived fatty acids (PLFAs). ResultsSponges consumed oxygen, nitrite, nitrate, and silicon, while they excreted ammonia and released 13C-DIC. They incorporated 4.82 mol 13C mmol C-1 d-1, 2.46 mol 15N mmol C-1 d-1, and 0.49 mol 2H mmol C-1 d-1 into bulk sponge tissue. The PLFAs extracted from the sponges contained on average 5.61 g 13C g-1 dry mass (DM) sponge and 5.43 ng 2H g-1 DM sponge. Most 13C was incorporated into bacteria-specific PLFAs derived from the substrate bacteria; 2H, in comparison, was mostly built in sponge-specific PLFAs. ConclusionH. panicea from the Eastern Scheldt were in a similar condition as starving specimens from the Baltic Sea which suggests that the large bivalve stocks in the Eastern Scheldt outcompete this sponge for food. During the incubation experiment, however, the sponges were well fed as indicated by the silicon and oxygen uptake rates. The significantly higher uptake rates of 2H by living sponges compared to dead sponges proved that deuterated water can be used to measure the metabolic activity of individual filter-feeding specimens, but more test with species of diverse biological traits and growth stages are recommended. Additionally, we suggest to focus on compound-specific 2H uptake, as these data were less affected by 1H exchange of non-covalently bound 1H. Assessing 13C- and 2H-enriched PLFAs of the incubated H. panicea also revealed that the sponge microbiome produced the bacteria-specific PLFAs i-C14:0, ai-C15:0, i-C17:0, and ai-C17:0 using C from the substrate bacteria. The ai-C15:0 was subsequently elongated and desaturated to build the sponge-specific PLFA ai-C25:2. Other sponge-specific PLFAs were formed using C14:0 and C16:0 from the sub-strate bacteria as precursors.

ecology↗

bioRxiv2022

Disentangling the lipid divide: Identification of key enzymes for the biosynthesis of unusual Membrane-spanning and Ether lipids in Bacteria

Bacterial membranes are composed of fatty acids (FAs) ester-linked to glycerol-3-phosphate, while archaea possess membranes made of isoprenoid chains ether-linked to glycerol-1-phosphate. Many archaeal species organize their membrane as a monolayer of membrane-spanning lipids (MSLs). Exceptions to this lipid divide are the production by some bacterial species of (ether-bound) MSLs, formed by tail-tail condensation of fatty acids resulting in the formation of (iso) diabolic acids (DAs), which are the likely precursors of paleoclimatological relevant branched glycerol dialkyl glycerol tetraether molecules. However, the enzymes responsible for their production are unknown. Here, we report the discovery of bacterial enzymes responsible for the condensation reaction of fatty acids and for ether bond formation, and confirm that the building blocks of iso-DA are branched iso-FAs. Phylogenomic analyses of the key biosynthetic genes reveal a much wider diversity of potential MSL (ether)-producing bacteria than previously thought, with significant implications for our understanding of the evolution of lipid membranes.

microbiology↗