Abstract: Thermophilic fungi constitute an interesting study model for understanding ecologi-cal mechanisms of adaptation in diverse environments and have attractive toolboxes with a wide range of biotechnological applications. This work describes for the first time an endophytic and thermophilic strain of Aspergillus brasiliensis that was isolated in the crater of the active volcano "El Chichonal" in Mexico. The average temperature of the collection site was around 60 °C and the soil pH was moderately acidic. The complete genome of A. brasiliensis E_15.1 was sequenced and assembled in about 37 Mb of genomic DNA. We performed a comprehensive phylogenomic anal-ysis for the precise taxonomic identification of this species as a novel strain of Aspergillus brasil-iensis. Likewise, the predicted coding sequences were classified according to various functions including Carbohydrate-Active Enzymes (CAZymes), biosynthetic gene clusters of secondary metabolites (BGCs), and metabolic pathways associated with plant growth promotion. Among the functional traits identified was the degradation of chitin, chitooligosaccharides, xylan, and cellulose, as well as the biosynthesis of clavaric acid, a triterpene with antitumor activity due to its ability to inhibit Farnesyl-protein transferase. In addition to the genomic analysis, a set of en-zymatic assays confirmed the thermostability of extracellular xylanases, cellulases of A. brasili-ensis E_15.1. Our findings suggest that the enzymatic repertoire of A. brasiliensis E_15.1 has a high potential for industrial application due to its thermostability and can promote plant growth at high temperatures. Finally, this strain constitutes an interesting source of terpenoids with pharmacological activity.

Considering the increasing interest in understanding the biotic component of methane removal from our atmosphere, it becomes essential to study the physiological characteristics and genomic potential of methanotroph isolates, especially their traits allowing them to adapt to elevated growth temperatures. The genetic signatures of Methylocaldum species have been detected in many terrestrial and aquatic ecosystems. A small set of representatives of this genus has been isolated and maintained in culture. The genus is commonly described as moderately thermophilic, with the growth optimum reaching 50oC for some strains. Here, we present a comparative analysis of genomes of three Methylocaldum strains—two terrestrial M. szegediense strains (O-12 and Norfolk) and one marine strain Methylocaldum marinum (S8). The examination of the core genome inventory of this genus uncovers significant redundancy in primary metabolic pathways, including the machinery for methane oxidation (numerous copies of pmo genes) and methanol oxidation (duplications of mxaF, xoxF1-5 genes), three pathways for one-carbon (C1) assimilation, and two methods of carbon storage (glycogen and polyhydroxyalkanoates). We also investigate the genetics of melanin production pathways, as a key feature of the genus.

Protein tyrosine phosphatases (PTPs) of the polymerase and histidinol phosphatases (PHP) superfamily with characteristic phosphatase activity dependent on divalent metal ions are found in many gram-positive bacteria. Although members of this family are co-purified with metal ions, they still require the exogenous supply of metal ions for full activation. However, the specific roles these metal ions play during catalysis are yet to be well understood. Here, we report the metal ion requirement for phosphatase activities of S. aureus Cap8C and L. rhamnosus Wzb. AlphaFold-predicted structures of the two PTPs suggest that they are members of the PHP family. Like other PHP phosphatases, the two enzymes have catalytic preference for Mn2+, Co2+, and Ni2+ ions. Cap8C and Wzb show an unusual thermophilic property with optimum activities over 75oC. Pre-incubation experiments show that the two enzymes are not inherently thermostable suggesting that certain catalytic step(s) in the reaction mechanism has a high activation energy. Consistent with this model, the activity-temperature profiles of the two enzymes are dependent on the divalent metal ion activating the enzyme.

The volatile fatty acids (VFAs) productions, as well as particulate organics decomposition, soluble chemical oxygen demand (SCOD) yield, and the VFAs production pathways, of mesophilic and thermophilic anaerobic fermentation were investigated. Batch experiments showed that the decomposition rate of volatile suspended solids (VSS), particulate carbohydrate (P-C) and particulate protein (P-P) followed the first-order kinetic model at different temperature. However, the intermediates， accumulated in the process of protein or carbohydrate digestion had a more significant inhibitory effect on the production of VFAs during the mesophilic anaerobic acidification process. Thermophilic fermentation led to more accumulation of VFAs compared to mesophilic fermentation. Then 13C stable isotope labeling experiment demonstrated that, acetic (HAc), propionic (HPr) and butyric (HBu) could be produced from carbohydrate and protein digestion, but valeric (HVa) was only generated from the degradation of protein. Finally, the possible pathway of HVa synthesis was proposed.