Biology subjects

Sanchez-Baracaldo, P.

Publications and source records attributed to Sanchez-Baracaldo, P..

5 recordsLinked to original sources

bioRxiv2024

Early-branching cyanobacteria up-regulate superoxide dismutase activity under a simulated early Earth anoxic atmosphere.

The evolution of oxygenic photosynthesis during the Archean (4-2.5 Ga), required the presence of complementary reducing pathways to maintain the cellular redox balance. While the timing of the evolution of superoxide dismutases (SODs), enzymes that convert superoxide to hydrogen peroxide, within the Bacteria and Archaea is not resolved, SODs containing copper and zinc in the reaction centre (CuZnSOD) were the first SODs estimated to appear in photosynthetic cyanobacteria, [≥] 2.93 Ga. Here we analysed the SOD gene expression and activity in the deep branching strain, Pseudanabaena sp. PCC7367. It releases more O2 and exhibits significantly higher growth rates (p<0.001) and protein and glycogen contents (p<0.05) under anoxic conditions compared to control cultures grown under present oxygen rich atmospheres in low CO2 (LC) or high CO2 (HC), prompting the question as to whether this correlates to higher cellular SOD activity under anoxic Archean simulated conditions. Expression of sodB encoding an iron containing SOD (FeSOD) and sodC, encoding a CuZnSOD, strongly correlated with increased extracellular O2 levels (p<0.001), while transcription of sodA, encoding a manganese containing (MnSOD), correlated to SOD activity during the day (p=0.019), when medium O2 concentrations were the highest. Cytosolic SOD activity was significantly higher (p<0.001) in anoxic cultures, two hrs before nightfall compared to oxic growth conditions. Night-time combined sodABC transcription in stirred cultures was significantly reduced (p<0.05) under anoxic conditions at elevated CO2 levels, as were medium O2 levels (p[≤]0.001), when compared to cultures grown under present-day oxic conditions with low CO2. Total cytosolic SOD activity remained comparable, suggesting that the replacement rate of SOD is higher under modern-day conditions than on early Earth. Our data suggest that the early branching cyanobacterium Pseudanabaena sp. PCC7367 may have retained ancestral features permitting it to thrive in its ecological niche as a benthic mat in shallow water marine environments.

microbiology↗

bioRxiv2023

Evolution of Multicellularity Genes in the Lead Up to the Great Oxidation Event

Cyanobacteria are among the most morphologically diverse prokaryotic phyla on Earth. Their morphotypes range from unicellular to multicellular filaments, yet mechanisms underlying the evolution of filamentous morphologies remain unknown. Here, we implement phylogenomic, Bayesian molecular clock and gene-tree-species-tree reconciliation analyses to estimate when genes encoding cell-cell joining structures first evolved. We also characterise septal structures and measure intercellular communication rates in non-model and early-branching filamentous strains. Our results suggest that genes encoding septal proteins (namely sepJ, sepI, and fraE) and potentially pattern formation (hetR) evolved in the Neoarchaean [~]2.6-2.7 billion years (Ga) ago. Later, at the start of the Great Oxygenation Event [~]2.5 Ga, genes involved in cellular differentiation (namely hetZ, patU3 and hglK) appeared. Our results predict that early-branching lineages like Pseudanabaena were capable of intercellular communication, but further innovations in cellular differentiation were needed to drive ecological expansion on a scale large enough to permanently oxygenate Earths atmosphere.

evolutionary biology↗

bioRxiv2021

Lack of Fe(II) transporters in basal Cyanobacteria complicates iron uptake in ferruginous Archean oceans.

Introductory paragraphCyanobacteria oxygenated Earths atmosphere during the Great Oxygenation Event (GOE) through oxygenic photosynthesis. Their high iron requirement was presumed met by high levels of Fe(II) in the anoxic Archean ocean. Here we show that most basal Cyanobacteria cannot synthesize the primary Fe(II) transporter, FeoB. Relaxed molecular clock analyses estimate the arrival of FeoB, as well as the Fe(III) transporters, cFTR1 and FutB, in the Cyanobacteria after the GOE. Furthermore Pseudanabaena sp. PCC7367, a basal marine, benthic strain grown under simulated Archean conditions, constitutively expressed cftr1, even after the addition of Fe(II). By utilizing gene expression studies under a simulated Archean atmosphere, as well as comparative genomics, phylogenetics and molecular clock analyses, this study identified a need to reappraise iron uptake in ancestral Cyanobacteria, as genetic profiling suggests that scavenging of siderophore bound Fe(III), rather than Fe(II), appears to have been the means of iron acquisition prior to the GOE.

evolutionary biology↗

bioRxiv2020

Origin of photosynthetic water oxidation at the dawn of life

Oxygenic photosynthesis starts with the oxidation of water to O2, a light-driven reaction catalysed by photosystem II. Cyanobacteria are the only prokaryotes capable of water oxidation and therefore, it is assumed that relative to the origin of life and bioenergetics, the origin of oxygenic photosynthesis is a late innovation. However, when exactly water oxidation originated remains an unanswered question. Here we use relaxed molecular clocks to compare one of the two ancestral core duplications that are unique to water-oxidizing photosystem II, that leading to CP43 and CP47, with some of the oldest well-described events in the history of life. Namely, the duplication leading to the Alpha and Beta subunits of the catalytic head of ATP synthase, and the divergence of archaeal and bacterial RNA polymerases and ribosomes. We also compare it with more recent events such as the duplication of cyanobacteria-specific FtsH metalloprotease subunits, of CP43 variants used in a variety of photoacclimation responses, and the speciation events leading to Margulisbacteria, Sericytochromatia, Vampirovibrionia, and other clades containing anoxygenic phototrophs. We demonstrate that the ancestral core duplication of photosystem II exhibits patterns in the rates of protein evolution through geological time that are nearly identical to those of the ATP synthase, RNA polymerase, or the ribosome. Furthermore, we use ancestral sequence reconstruction in combination with comparative structural biology of photosystem subunits, to provide additional evidence supporting the premise that water oxidation had originated before the ancestral core duplications. Our work suggests that photosynthetic water oxidation originated closer to the origin of life and bioenergetics than can be documented based on species trees alone.

evolutionary biology↗

bioRxiv2017

Molecular evidence for the early evolution of photosynthetic water oxidation

Photosystem II is a photochemical reaction center that catalyzes the light-driven oxidation of water to molecular oxygen. Water oxidation is the distinctive photochemical reaction that permitted the evolution of oxygenic photosynthesis and the eventual rise of Eukaryotes. At what point during the history of life an ancestral photosystem evolved the capacity to oxidize water still remains unknown. Here we study the evolution of the core reaction center proteins of Photosystem II using sequence and structural comparisons in combination with Bayesian relaxed molecular clocks. Our results indicate that a homodimeric photosystem with sufficient oxidizing power to split water had already appeared in the early Archean about a billion years before the most recent common ancestor of all described Cyanobacteria capable of oxygenic photosynthesis, and well before the diversification of some of the known groups of anoxygenic photosynthetic bacteria. Based on a structural and functional rationale we hypothesize that this early Archean photosystem was capable of water oxidation and had already evolved some level of protection against the formation of reactive oxygen species, which would place primordial forms of oxygenic photosynthesis at a very early stage in the evolutionary history of life.

evolutionary biology↗