Biology subjects

Cerruti, M.

Publications and source records attributed to Cerruti, M..

5 recordsLinked to original sources

bioRxiv2025

Combined Raman Microscopy and Transmission Electron Microscopy shows the co-existence of whitlockite crystals and carbonated hydroxyapatite-mineralized collagen fibrils in human calcified aortic valves

Aortic valve stenosis (AS), the leading valvular disease in aging populations, is driven by complex extracellular matrix (ECM) modifications and progressive calcification. Despite its clinical significance, the molecular mechanisms underlying AS remain poorly understood, limiting therapeutic options to invasive valve replacement. This study employs Raman microscopy, a label-free imaging technique, and its integration with transmission electron microscopy (TEM) to elucidate the biochemical and ultrastructural changes in stenotic aortic valves. High-resolution spectroscopic imaging revealed distinct extracellular matrix modification across different regions, involving elastin degradation, cholesterol deposition, and mineral formation, comprising not only hydroxyapatite (cHAp) but also whitlockite. Elastin-rich domains associated with cHAp deposition exhibited cross-link degradation, while collagen matrices supported mineralized phases with varying mineral-to-matrix ratios that, in heavily mineralized regions, went far above those of mature human bone. For the first time we demonstrated whitlockite as a mineral deposit in calcified aortic valves, in areas with different degrees of calcification. This implies that this Mg containing mineral, which has been considered a precursor to cHAp in pathological calcification, forms independently, challenging prevailing models of calcification. The combination of Raman and TEM showed how bone-like cHAp mineralized collagen matrix in later stages engulfs the initial non-physiological whitlockite deposits. This correlative multimodal approach advances our understanding of AS by capturing spatially resolved chemical and structural dynamics at the nanoscale. The findings highlight Raman microscopys potential for probing calcification mechanisms across diverse tissue types and suggest its role in identifying novel therapeutic targets. This study underscores the value of integrative imaging methodologies in unraveling complex pathological processes and advancing patient care.

biochemistry↗

bioRxiv2021

Syntrophy between fermentative and purple phototrophic bacteria for carbohydrate-based wastewater treatment

Fermentative chemoorganoheterotrophic bacteria (FCB) and purple photoorganoheterotrophic bacteria (PPB) are two interesting microbial guilds to process carbohydrate-rich wastewaters. Their interaction has been studied in axenic pure cultures or co-cultures. Little is known about their metabolic interactions in open cultures. We aimed to harness the competitive and syntrophic interactions between PPB and FCB in mixed cultures. We studied the effect of reactor regimes (batch or continuous, CSTR) and illumination modes (continuous irradiation with infrared light, dark, or light/dark diel cycles) on glucose conversions and the ecology of the process. In batch, FCB outcompeted (>80%) PPB, under both dark and infrared light conditions. In CSTR, three FCB populations of Enterobacteriaceae, Lachnospiraceae and Clostridiaceae were enriched (>70%), while Rhodobacteraceae relatives of PPB made 30% of the community. Fermentation products generated from glucose were linked to the dominant FCB. Continuous culturing at a dilution rate of 0.04 h-1 helped maintain FCB and PPB in syntrophy: FCB first fermented glucose into volatile fatty acids and alcohols, and PPB grew on fermentation products. Direct supply of carboxylates like acetate under infrared light enriched for PPB (60%) independent of reactor regimes. Ecological engineering of FCB- and PPB-based biorefineries can help treat and valorize carbohydrate-based waste feedstocks. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=115 SRC="FIGDIR/small/444055v1_ufig1.gif" ALT="Figure 1"> View larger version (14K): org.highwire.dtl.DTLVardef@1ee41forg.highwire.dtl.DTLVardef@12d74aorg.highwire.dtl.DTLVardef@f46351org.highwire.dtl.DTLVardef@a47706_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2020

Effects of light/dark diel cycles on the photoorganoheterotrophic metabolism of Rhodopseudomonas palustris for differential electron allocation to PHAs and H2

Light/dark cycles can impact the electron distribution in Rhodopseudomonas palustris, a hyperversatile photoorganoheterotrophic purple non-sulfur bacterium (PNSB). Dynamic conditions during diel cycles are important for the physiology of PNSB, but the coupling between illumination patterns and redox balancing has not been extensively studied. For survival and growth, Rhodopseudomonas has developed different mechanisms to allocate electrons under dynamic growth conditions. Products such as hydrogen and poly-{beta}-hydroxyalkanoates (PHAs) can form alternative electron sinks. A continuous culture, fed with a balanced nutrients medium, was exposed to three different conditions: 24 h continuous infrared illumination, 16h light/8h dark, and 8h light/16h dark. Light and dark phase durations in a cycle determined the energy availability level (light) and the attainment of a stationary state. Under long dark phases, the acetate substrate accumulated to levels that could not be depleted by growth in the light. Under short dark phases, acetate was rapidly consumed in the light with most of the phototrophic growth occurring under acetate-limiting conditions. Under diel cycles, substrate uptake and growth were unbalanced and Rhodopseudomonas shunted the excess of carbon and electron flow first toward PHAs production. Only secondarily, when PHA storage got saturated, the electron excess was redirected toward H2. A numerical model described well the dynamics of biomass and nutrients during the different light/dark cycle regimes. The model simulations allowed determination of stoichiometric and kinetic parameters for conversion by Rhodopseudomonas. Understanding the inherent process dynamics of diel light cycles in purple sulfur bacteria cultures would enable optimization procedures for targeted bioproduct formation. ImportancePurple non-sulfur bacteria (PNSB) are important anoxygenic phototrophic microorganisms that take part in numerous environmental processes, based on their metabolic versatility. Rhodopseudomonas palustris is a model photosynthetic bacterium of the PNSB guild. Light cycles influence deeply its physiology. Poly-{beta}-hydroxyalkanoates (PHAs) and biohydrogen are two of the most studied metabolic products of Rhodopseudomonas, because of their biotechnology potential besides involvement in carbon and electron allocations in its metabolism. Their production mechanisms have often been described as competitive, but the rationale behind the production of one or the other compound has not been elucidated. Here, we found that under light / dark cycles an excess of organic substrate was first directed toward PHAs production, and only when this pathway was saturated H2 was produced. Understanding the dynamics of carbon and electron allocation under intermittent light cycles enhances our knowledge on PNSB metabolisms and paves ways to manage the formation of targeted bioproducts.

microbiology↗

bioRxiv2020

Control tools to selectively produce purple bacteria for microbial protein in raceway reactors

Purple non-sulfur bacteria (PNSB) show potential for microbial protein production on wastewater as animal feed. They offer good selectivity (i.e. uneven community with high abundance of one species) when grown anaerobically in the light. However, the cost of a closed anaerobic photobioreactor (PBR) is prohibitive for protein production. While open raceway reactors are cheaper, their feasibility to selectively grow PNSB is thus far unexplored. This study developed tools to boost PNSB abundance in the biomass of a raceway reactor fed with volatile fatty acids as carbon source. For oxygen availability as tool, not stirring in the night (i.e. reduced oxygen supply) elevated the PNSB abundance from 8% to 20%. For light availability as tool, a 24-h illumination increased the PNSB abundance from 8% to 31% compared to a 12-h light/12-h dark regime. A reactor run at 2-d sludge retention time at the highest surface-to-volume ratio (10 m2 m-3 increased light availability) showed productivities up to 0.2 g protein L-1 d-1 and the highest PNSB abundance (78%). The estimated production cost is {euro}1.9 kg-1 dry weight (vs. PBR {euro}11.4 kg-1 dry weight). This study pioneered in PNSB-based microbial protein production in raceways, yielding cost efficiency along with high selectivity when avoiding the combined availability of oxygen, COD and darkness. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=89 SRC="FIGDIR/small/912980v1_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@c5e3borg.highwire.dtl.DTLVardef@1fe8d28org.highwire.dtl.DTLVardef@e5630borg.highwire.dtl.DTLVardef@1c99bf3_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2020

Enriching and aggregating purple non-sulfur bacteria in an anaerobic sequencing-batch photobioreactor for nutrient capture from wastewater

Purple non-sulfur bacteria (PNSB), a guild of anoxygenic photomixotrophic organisms, rise interest to capture nutrients from wastewater in mixed-culture bioprocesses. One challenge targets the aggregation of PNSB biomass through gravitational separation from the treated water to facilitate its retention and accumulation, while avoiding the need for membranes. We aimed to produce an enriched, concentrated, well-settling, nutrient-removing PNSB biomass using sequencing batch regimes (SBR) in an anaerobic photobioreactor. The stirred tank was fed with a synthetic influent mimicking loaded municipal wastewater (430-860 mg CODAc LInf-1, COD:N:P ratio of 100:36:4-100:11:2 m/m/m), operated at 30{degrees}C and pH 7, and continuously irradiated with infrared (IR) light (>700 nm) at 375 W m-2. After inoculation with activated sludge at 0.1 g VSS L-1, PNSB were rapidly enriched in a first batch of 24 h: the genus Rhodobacter reached 54% of amplicon sequencing read counts. SBR operations at volume exchange ratio of 50% with decreasing hydraulic retention times (48 to 16 h; 1 to 3 cycles d-1) and increasing volumetric organic loading rates (0.2 to 1.3 kg COD m-3 d-1) stimulated the aggregation (compact granules of 50-150 m), settling (sedimentation G-flux of 4.7 kg h-1 m-2), and accumulation (as high as 3.8 g VSS L-1) of biomass. The sludge retention time (SRT) increased freely from 2.5 to 11 d without controlled sludge wasting. Acetate, ammonium, and orthophosphate were removed simultaneously (up to 96% at a rate of 1.1 kg COD m-3 d-1, 77% at 113 g N m-3 d-1, and 73% at 15 g P m-3 d-1) with a COD:N:P assimilation ratio of 100:6.7:0.9 (m/m/m). Competition for substrate and photons occurred in the PNSB guild. SBR regime shifts sequentially selected for Rhodobacter (90%) under shorter SRT and non-limiting acetate concentrations during reaction phases, Rhodopseudomonas (70%) under longer SRT and acetate limitation, and Blastochloris (10%) under higher biomass concentrations. We highlighted the benefits of a PNSB-based SBR process for biomass accumulation and simultaneous nutrient capture at substantial rates, and its underlying microbial ecology. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=121 SRC="FIGDIR/small/899062v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@1f167bdorg.highwire.dtl.DTLVardef@1d1c1e2org.highwire.dtl.DTLVardef@fe591org.highwire.dtl.DTLVardef@1a8c4e3_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIPNSB were highly enriched (90%) in an anaerobic stirred-tank photobioreactor. C_LIO_LIThe mixed-culture SBR process fostered PNSB biomass aggregation and accumulation. C_LIO_LIPNSB sludge reached 3.8 g VSS L-1 and a sedimentation G-flux of 4.7 kg h-1 m-2. C_LIO_LIPNSB enabled a high simultaneous removal of COD (96%), N (77%), and P (73%). C_LIO_LIRhodobacter, Rhodopseudomonas, and Blastochloris competed for acetate and photons. C_LI

bioengineering↗