Microorganisms inhabiting cold environments have gained increasing attention in recent decades due to their unique adaptation mechanisms that enable survival under extreme conditions. Growing evidence indicates that some cold-adapted bacteria possess phenotypic and genomic traits linked to pathogenicity, raising concerns about their potential environmental and public health relevance. Here, we characterized three culturable bacteria isolated from human-impacted snow in the French Alps (Chamrousse) and coastal Greenland (Nuuk). Snow samples were cultured on R2A medium, and isolates were identified by Sanger sequencing as Peribacillus, Sphingomonas, and Subtercola. Temperature tolerance, haemolytic activity, and antibiotic susceptibility were assessed by culture-based assays, while whole-genome sequencing was used to screen for antibiotic resistance and virulence-associated genes using reference databases. Only the Peribacillus isolate tolerated 37 °C and showed α-haemolysis. Antibiotic susceptibility testing indicated full susceptibility in Peribacillus, while Sphingomonas and Subtercola showed reduced susceptibility to a limited number of antibiotics, mainly to cefotaxime, chloramphenicol, and colistin. Genomes encoded genes associated with efflux, target modification, motility/adhesion, and stress adaptation, indicating environmental resilience rather than clinical pathogenicity. Overall, these isolates displayed limited pathogenic phenotypes with genomic traits primarily supporting environmental adaptation and survival.
Rahnella species are environmentally versatile bacteria widely distributed in terrestrial and aquatic ecosystems; however, the genomic basis of formaldehyde detoxification and stress adaptation in cryoconite-associated Rahnella remains poorly understood. In this study, we performed phylogenomic, comparative genomic, pan-genomic, stress-response, and functional analyses of Rahnella sp. PAMC25617 isolated from polar cryoconite to investigate glutathione (GSH)-dependent formaldehyde detoxification and its evolutionary conservation. Genome-based phylogeny, average nucleotide identity (ANI), and digital DNA–DNA hybridization (dDDH) analyses demonstrated that PAMC25617 represents a distinct genomic lineage within the genus Rahnella. The draft genome comprised 5.33 Mb with a GC content of 52
Palaeococcus pacificus DY20341T, a hyperthermophilic archaeon from deep sea hydrothermal sediments, grows at temperature range from 50 to 90 ℃ (Topt = 80℃). To explore the molecular basis of its thermal adaptation, we identified six representative hyperthermostable proteins from its cytosolic fraction that remained soluble after a stringent in vitro heat treatment at 100 °C. MALDI-TOF mass spectrometry identified these as an inorganic pyrophosphatase (PPase), a 5’-methylthioadenosine phosphorylase (MTAP), and four putative transporter components (one TRAP and three ABC transporter solute-binding proteins). RT-qPCR analysis revealed that the transcription of all six corresponding genes was significantly upregulated when the growth temperature was elevated from 80 °C to 90 °C, suggesting a potential role in the cellular response to heat stress. Biochemical characterization of the recombinant PPase demonstrated remarkable thermostability and an optimal temperature of 90 °C. Kinetic analysis revealed high catalytic efficiency, with a maximal specific activity of 590 ± 30 U/mg and a strong substrate affinity ( K_m = 6.24 µM). Phylogenetic analysis of the identified thermostable MTAP (PAP_00250) revealed its evolutionary origin from hyperthermophilic archaea, distinguishing it clearly from a second MTAP homolog (PAP_07050) in the genome, which aligns with mesophilic bacteria. The structural stability of the identified ABC and TRAP transporter components hypothesizes that efficient nutrient scavenging remains critical at extreme temperatures. Together, these findings provide valuable insights into the stable molecular machinery and potential physiological strategies enabling P. pacificus to thrive in hydrothermal environments.
This study aimed to evaluate L-asparaginase (L-ASNase) production by fungi isolated from soils across different Antarctic islands. Out of 138 isolates, 33 filamentous fungi and 5 yeasts exhibited enzymatic activity in solid culture media. Filamentous fungi were identified by sequencing the Internal Transcribed Spacer (ITS) region, while yeasts were identified using the D1/D2 domains of the 26 S rDNA gene. The blue filamentous fungus Antarctomyces F13.CR.LASP exhibited a maximum L-ASNase productivity of 0.76 U/L. Regarding the yeasts, the isolate Vishniacozyma victoriae G.L11 reached a productivity of 0.17 U/L, while corresponding values for glutaminase and urease were 0.11 and 0.06 U/L, respectively. Furthermore, V. victoriae G.L11 was capable of producing the enzyme using different low-cost substrates, particularly pineapple peel waste, which yielded 5.17 U/L. In this scenario, future optimization could further enhance L-asparaginase production levels by these fungi, providing valuable insights into the biotechnological potential of Antarctic fungi.
