Biology subjects

Contreras, G.

Publications and source records attributed to Contreras, G..

4 recordsLinked to original sources

bioRxiv2025

Metabolic engineering of Methanothermobacter thermautotrophicus ΔH for recombinant acetoin production

Thermophilic methanogens of the genus Methanothermobacter are established biocatalysts in power-to-gas applications, converting H2 and CO2 into CH4 through the process of methanogenesis. Further expanding this platform for the bioproduction of value-added compounds (power-to-x) has the potential to increase the economic viability of such processes. This requires a genetic toolset that enables the controlled expression of recombinant pathways. Here, we report the fully autotrophic inducible recombinant bioproduction of acetoin from H2 and CO2 in Methanothermobacter thermautotrophicus {Delta}H. To facilitate inducible gene expression, we implemented an anhydrotetracycline (aTc)-inducible promoter system, expanding our available set of promoters. The aTc-inducible system enabled controlled expression of a codon-optimized acetoin-production operon comprising the acetolactate synthase- and acetolactate decarboxylase-encoding genes from Streptococcus thermophilus. Batch cultivation at 42{degrees}C demonstrated aTc-dependent acetoin formation, yielding up to 0.45 {+/-} 0.08 mM acetoin. Fed-batch bioreactor experiments confirmed growth-coupled, recombinant acetoin production, while eliminating the non-specific acetoin accumulation that we observed during non-growth phases in batch cultivation. Continuous cultivation in a chemostat resulted in stable acetoin production rates of 1.28 {+/-} 0.07 {micro}mol L-{superscript 1} h-{superscript 1} at 42{degrees}C. Elevated temperatures led to reduced acetoin production, suggesting diminished activity or thermal instability of the heterologous enzymes. This study demonstrates the feasibility of value-added bioproduction in Methanothermobacter and establishes an inducible expression system suitable for pathway engineering in thermophilic methanogens. Together with genome-scale modeling and emerging enzyme engineering strategies, these results lay the foundation for developing robust, CH4-co-producing power-to-x bioprocesses with Methanothermobacter species.

microbiology↗

bioRxiv2025

Detection of zoonotic Cryptosporidium parvum in invasive beavers from southern Tierra del Fuego, Chile

Since their introduction to Tierra del Fuego in 1946, invasive beavers have expanded their population and caused extensive environmental degradation across the subantarctic region. Beaver dams have profoundly impacted peatlands, mature sub-Antarctic forests, and watercourses. Here, we report a pathogen in invasive beavers in Patagonia and discuss their potential role as a reservoir of waterborne zoonotic pathogens. We detected Cryptosporidium through microscopy using the Ziehl-Neelsen staining technique in beaver collected from southern Tierra del Fuego. Out of the 105 beavers examined, three tested positive to optical microscopy, which were then identified molecularly as Cryptosporidium parvum by sequence analysis of the 18S ribosomal DNA (rDNA). Given the potential impacts of Cryptosporidium parvum upon native species, wildlife, and human health, this finding highlights the potential risks associated with the ongoing expansion of beavers into other areas of the sub-Antarctic region. A potential role of invasive beavers as reservoirs of zoonotic Cryptosporidium spp. in Patagonia emphasizes the unknown consequences of human-introduced exotic species on pristine ecosystems.

bioengineering↗

bioRxiv2025

Closed State Structure of the Pore Revealed by Uncoupled Shaker K+ Channel

Voltage gated potassium (Kv) channels play key roles in numerous physiological processes from cellular excitability to immune response and are among the most important pharmaceutical targets. Despite recent advances in the structural determination of Kv channels, the closed state structure of strictly coupled Kv1 family remains elusive. Here, we captured the closed state structure of the pore in the Shaker potassium by uncoupling the voltage sensor domains from the pore domains. Ionic current, gating current and fluorescence measurements show that a conserved isoleucine residue in the S4-S5 linker region, plays a key role controlling the strength of the electromechanical coupling and the channel activation-deactivation equilibrium. Structural determination of completely uncoupled I384R mutant by single particle cryoEM revealed a fully closed pore in the presence of fully activated but non-relaxed voltage sensors. The putative conformational transitions from a fully open pore domain indicates a "roll and turn" movement along the whole length of the pore-forming S6 helices in sharp contrast to canonical gating models based on limited movements of S6. The rotational and translational movement posits two hydrophobic residues, one at inner cavity and the other at the bundle crossing region, directly at the permeation pathway, limiting the pore radius to less than 0.7[A]. Voltage clamp fluorimetry of wild type channel incorporating a fluorescent unnatural amino acid strongly supports the cryoEM structural model. Surprisingly, the selectivity filter was captured in a noncanonical state, unlike the previously described dilated or pinched filter conformations. With the present experiment results, we propose a new gating model for strictly coupled Kv1 channels and the molecular mechanism of interactions among different functional states.

biophysics↗

bioRxiv2025

Characterizing dog communities adjacents to key shorebird sites in Chile

Free-ranging domestic dogs can cause numerous negative impacts on public health, tourism, and the environment. Some of these impacts on wildlife are compounded and facilitated by human communities, for example through the provision of food, health care, and shelter, which altogether increase the dogs life expectancy. Shorebirds are one of the groups adversely affected by dogs through nest predation, behavioral changes, and persecution during foraging and roosting periods. In Chile, dogs are a ubicutous threat in wetlands. In this study, we characterized the dog populations at the mouth of the Lluta River (Chacalluta area) and the Coihuin wetland (Coihuin-Chamiza area), both of international importance for shorebirds. We estimated the total abundance of dogs, their seasonal survival, and demographic and behavioral traits by photographic capture-recapture methods in eight surveys of 6.6 km2 for Chacalluta and 2.0 km2 for Coihuin-Chamiza. We estimated a population size of 167 individuals in Chacalluta and 505 individuals in Coihuin-Chamiza, a relatively low survival rate in both sites, a healthy body status in more than 80% of the dogs, small group sizes (1-2 individuals), and movements of 1,000 to 3,000 meters between locations. We report patterns associated with human ownership, indicating irresponsible pet ownership. This information will be the basis for developing public policies and evaluating strategies to lessen their impact on shorebirds, such as demographic control of the animal population, reduction of abandonment, and promotion of responsible pet ownership practices.

zoology↗