Comparative Genomic Study of Polar Lichen-Associated Hymenobacter sp. PAMC 26554 and Hymenobacter sp. PAMC 26628 Reveals the Presence of Polysaccharide-Degrading Ability Based on Habitat

Enhanced remediation of co-contaminated agricultural soils under cold stress by immobilized bacterial agents: A perspective based on abundance differences

This study explored the enhanced remediation effects and microbial mechanisms of the immobilized microbial agent B&Ma19, compared to the microbial agent Ma19, in cold-region farmland co-contaminated with antibiotics and heavy metals during winter. B&Ma19 achieved superior fluoroquinolone degradation and significantly reduced the bioavailability of copper and zinc, while Ma19 treatment only reduced the content of available zinc. Microbial community analysis revealed that B&Ma19 promoted the proliferation of Firmicutes and increased the relative abundance of rare taxa during the freeze-thaw and freezing phases. Functional predictions indicated that B&Ma19 enhanced the expression of proteins in the winter microbial community involved in resistance to antibiotics, metabolic activity, and nutrient acquisition capacity. A random forest model identified Sporosarcina as a potential key genus for co-contamination remediation. Moreover, increased in overall community dispersal limitation and reduced drift-driven succession were observed. The co-occurrence network became more stable, characterized by a higher proportion of moderately abundant keystone taxa. Mantel tests showed that B&Ma19 weakened the correlation between antibiotic resistance genes (ARGs) and mobile genetic elements, and reduced the impact of temperature fluctuations on contaminant concentrations. In contrast, Ma19 strengthened ARG-antibiotic associations. These findings provide a theoretical basis for bioremediation of co-contaminated farmland in cold regions.

Bioprospecting Antarctic Microorganisms: Investigating Hymenobacter psoromatis PAMC26554 for Biochemical Potential

Microorganisms from the genus Hymenobacter are known for their distinctive traits, yet their secondary metabolite (SM) production has not been thoroughly investigated. In this study, we examined the biosynthetic potential of SMs from Hymenobacter psoromatis PAMC26554, which was isolated from Antarctic lichen. In silico analysis identified biosynthetic gene clusters (BGCs) for terpenes, non-ribosomal peptide synthetases (NRPSs), and polyketide synthases (PKSs), indicating the strain's potential for novel SM production. Optimization of culture conditions showed that R2A medium at 15°C supported growth. HPLC analysis revealed phenylacetic acid (PAA) as a notable compound, which was characterized by ESI-MS and NMR, marking the first isolation of PAA from the genus Hymenobacter. In addition, bioactivity assays indicated moderate lipase inhibition by PAA, while molecular docking studies revealed stable interactions with the enzyme, demonstrating that hydrogen bonding and π-π stacking contribute to its lipase inhibitory activity. In summary, this research highlights the genus Hymenobacter as a potential source for secondary metabolite discovery, with PAA exemplifying its unexplored biochemical capabilities.

Lichens and Health-Trends and Perspectives for the Study of Biodiversity in the Antarctic Ecosystem

Lichens are an important vegetative component of the Antarctic terrestrial ecosystem and present a wide diversity. Recent advances in omics technologies have allowed for the identification of lichen microbiomes and the complex symbiotic relationships that contribute to their survival mechanisms under extreme conditions. The preservation of biodiversity and genetic resources is fundamental for the balance of ecosystems and for human and animal health. In order to assess the current knowledge on Antarctic lichens, we carried out a systematic review of the international applied research published between January 2019 and February 2024, using the PRISMA model (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). Articles that included the descriptors "lichen" and "Antarctic" were gathered from the web, and a total of 110 and 614 publications were retrieved from PubMed and ScienceDirect, respectively. From those, 109 publications were selected and grouped according to their main research characteristics, namely, (i) biodiversity, ecology and conservation; (ii) biomonitoring and environmental health; (iii) biotechnology and metabolism; (iv) climate change; (v) evolution and taxonomy; (vi) reviews; and (vii) symbiosis. Several topics were related to the discovery of secondary metabolites with potential for treating neurodegenerative, cancer and metabolic diseases, besides compounds with antimicrobial activity. Survival mechanisms under extreme environmental conditions were also addressed in many studies, as well as research that explored the lichen-associated microbiome, its biodiversity, and its use in biomonitoring and climate change, and reviews. The main findings of these studies are discussed, as well as common themes and perspectives.

Revealing the diversity of bacteria and fungi in the active layer of permafrost at Spitsbergen island (Arctic) - Combining classical microbiology and metabarcoding for ecological and bioprospecting exploration

Arctic soils are constantly subjected to extreme environmental conditions such as low humidity, strong winds, high salinity, freeze-thaw cycles, UV exposition, and low nutrient availability, therefore, they have developed unique microbial ecosystems. These environments provide excellent opportunities to study microbial ecology and evolution within pristine (i.e. with limited anthropogenic influence) regions since the High Arctic is still considered one of the wildest and least explored environments on the planet. This environment is also of interest for the screening and recovery of unique microbial strains suitable for various biotechnological applications. In this study, a combination of culture-depended and culture-independent approaches was used to determine the cultivation bias in studies of the diversity of cold-active microorganisms. Cultivation bias is a reduction in recovered diversity, introduced when applying a classical culturing technique. Six different soil types, collected in the vicinity of the Polish Polar Station Hornsund (Spitsbergen, Norway), were tested. It was revealed that the used media allowed recovery of only 6.37 % of bacterial and 20 % of fungal genera when compared with a culture-independent approach. Moreover, it was shown that a combination of R2A and Marine Broth media recovered as much as 93.6 % of all cultivable bacterial genera detected in this study. Based on these results, a novel protocol for genome-guided bioprospecting, combining a culture-dependent approach, metabarcoding, next-generation sequencing, and genomic data reuse was developed. With this methodology, 14 psychrotolerant, multi-metal-resistant strains, including the highly promising Rhodococcus spp., were obtained. These strains, besides increased metal tolerance, have a petroleum hydrocarbon utilization capacity, and thus may be good candidates for future bioremediation technologies, also suited to permanently cold regions.

Chronicle of Research into Lichen-Associated Bacteria

Lichens are mutually symbiotic systems consisting of fungal and algal symbionts. While diverse lichen-forming fungal species are known, limited species of algae form lichens. Plasticity in the combination of fungal and algal species with different eco-physiological properties may contribute to the worldwide distribution of lichens, even in extreme habitats. Lichens have been studied systematically for more than 200 years; however, plasticity in fungal-algal/cyanobacterial symbiotic combinations is still unclear. In addition, the association between non-cyanobacterial bacteria and lichens has attracted attention in recent years. The types, diversity, and functions of lichen-associated bacteria have been studied using both culture-based and culture-independent methods. This review summarizes the history of systematic research on lichens and lichen-associated bacteria and provides insights into the current status of research in this field.

Hymenobacter cyanobacteriorum sp. nov., isolated from a freshwater reservoir during the cyanobacterial bloom period

A Gram-negative, red-colored, and rod-shaped bacterial strain, DH14^T, was isolated from a eutrophic reservoir. The 16S rRNA gene sequence analysis showed that strain DH14^T was most closely related to Hymenobacter terrigena (98.3% similarity) and Hymenobacter terrae (98.1%). The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain DH14^T and its related type strains were below 82.9% and 27.2%, respectively. Strain DH14^T contained iso-C_15:0 (32.6%), anteiso-C_15:0 (14.0%), and summed feature 3 (C_16:1 ω6c and/or C_16:1 ω7c) (25.8%) as major cellular fatty acids. The main polar lipids were phosphatidylethanolamine, two unidentified aminophospholipids, and one unidentified lipid. The respiratory quinone was menaquinone 7 (MK-7). The genomic DNA G + C content was 62.1%. These evidences support the classification of strain DH14^T as a novel species in the genus Hymenobacter, for which the name Hymenobacter cyanobacteriorum sp. nov. is proposed. The type strain is DH14^T (= KCTC 92040^T = LMG 32425^T).

Complete genome sequencing and comparative CAZyme analysis of Rhodococcus sp. PAMC28705 and PAMC28707 provide insight into their biotechnological and phytopathogenic potential

Study of carbohydrate-active enzymes (CAZymes) can reveal information about the lifestyle and behavior of an organism. Rhodococcus species is well known for xenobiotic metabolism; however, their carbohydrate utilization ability has been less discussed till date. This study aimed to present the CAZyme analysis of two Rhodococcus strains, PAMC28705 and PAMC28707, isolated from lichens in Antarctica, and compare them with other Rhodococcus, Mycobacterium, and Corynebacterium strains. Genome-wide computational analysis was performed using various tools. Results showed similarities in CAZymes across all the studied genera. All three genera showed potential for significant polysaccharide utilization, including starch, cellulose, and pectin referring their biotechnological potential. Keeping in mind the pathogenic strains listed across all three genera, CAZymes associated to pathogenicity were analyzed too. Cutinase enzyme, which has been associated with phytopathogenicity, was abundant in all the studied organisms. CAZyme gene cluster of Rhodococcus sp. PAMC28705 and Rhodococcus sp. PAMC28707 showed the insertion of cutinase in the cluster, further supporting their possible phytopathogenic properties.