Winkler, M.-K. H. | bioRxiv Science

bioRxiv2026

Development of a Stabilized Alginate-based Hydrogel for Oral Delivery of Encapsulated Live Cultures and Allowing their Intact Passage Through the Digestive System.

Alginate hydrogels are widely used for biocompatible encapsulation due to their low cost, mild gelation conditions, and scalability; however, their limited mechanical strength and poor chemical stability under physiological conditions restrict their utility for oral delivery applications. In particular, the development of robust alginate formulations capable of surviving gastrointestinal salt and pH exposures is critical for advancing encapsulated microbial therapeutics for chronic kidney disease (CKD). In this study, we investigated the incorporation of ferric iron into calcium alginate networks as a strategy to enhance gel stability while maintaining biocompatibility. Using a three-ion competition approach, we achieved controlled introduction of ferric ions into calcium alginate gels without significantly altering bulk mechanical properties relative to standard calcium alginate. Although the initial ferric-containing gels displayed comparable modulus and structure, post-treatment with chitosan under mildly acidic conditions produced a dramatic increase in gel stability in physiological salt concentrations across both acidic and neutral pH environments. Ferric-containing gels formed at pH 4.6 absorbed negligible chitosan, in contrast to iron-free alginate gels, which incorporated substantial chitosan under identical conditions. These results support the formation of a thin, dense interfacial complex between chitosan, ferric ions, and alginate at the gel surface, which reinforces the matrix and inhibits dissolution. The resulting hybrid ferric-calcium alginate formulation enabled the production of sub-millimeter beads capable of encapsulating live Thauera aminoaromatica while preserving anaerobic p-cresol degradation activity at 37 {degrees}C using nitrate as an electron acceptor. Collectively, these findings establish ferric-modified alginate hydrogels as a promising, scalable platform for stable oral delivery of encapsulated microbial therapeutics.

bioengineering↗

bioRxiv2023

A novel order-level lineage of ammonia-oxidizing Thaumarchaeota is widespread in marine and terrestrial environments

Ammonia-oxidizing archaea (AOA) are among the most ubiquitous and abundant groups of Archaea on Earth, widely distributed in marine, terrestrial, and geothermal ecosystems. However, the genomic diversity, biogeography, and evolutionary process of AOA populations in subsurface environments are vastly understudied compared to those of marine and soil AOA. We here report a novel AOA order Candidatus Nitrosomirales that forms a deeply branching basal sister lineage to the thermophilic Ca. Nitrosocaldales. Metagenomic and 16S rRNA gene read mapping demonstrates the dominant presence of Nitrosomirales AOA in various groundwater environments and their widespread distribution across a range of geothermal, terrestrial, and marine habitats. Notably, terrestrial Nitrosomirales AOA show the genetic capacity of using formate as an alternative source of reductant and appear to have acquired key metabolic genes and operons from other mesophilic populations via horizontal gene transfer, including the genes encoding urease, nitrite reductase, and V-type ATPase. Potential metabolic versatility and acquired functions may facilitate their radiation into a variety of subsurface, marine, and soil environments. Molecular thermometer-based evolutionary analysis suggests that Nitrosomirales originated from thermophilic environments and transitioned into temperate habitats in parallel with Nitrososphaerales and Nitrosopumilales. We also provide evidence that terrestrial-marine habitat transitions occurred within each one of the four AOA orders, which reveals a more complex evolutionary trajectory of major AOA lineages than previously proposed. Together, these findings establish a robust taxonomic and evolutionary framework of AOA and provide new insights into the ecology and evolution of this globally abundant functional guild.

microbiology↗