Methanobactins: Structures, Biosynthesis, and Microbial Diversity

Metagenome-based microbial metabolic strategies to mitigate ruminal methane emissions using Komagataeibacter-based symbiotics

Global warming increasingly threatens organisms in equatorial regions, where temperatures often exceed physiological limits. Rumen methanogens are a major biological source of anthropogenic methane, a potent greenhouse gas. Therefore, ruminal methane mitigation strategies that preserve animal productivity are urgently needed. Our In vitro analysis of Holstein steer rumen fluid-integrating gas production, volatile fatty acid (VFA) profiles, and metagenomic data-demonstrated that kombucha, a fermented beverage, effectively reduces methane emissions by modulating ruminal fermentation. Rumen fluid was incubated for 60 h under three treatments (control, 3-NOP, and kombucha). During the initial 30 h, kombucha reduced methane by 15.07 % compared to the control but was 17.54 % higher than 3-NOP. In the subsequent 30 h, kombucha achieved sustained reductions of 34.72 % versus the control and 26.28 % versus 3-NOP, highlighting its uniquely sustained methane-reducing effect. A metagenomics-guided screening and in vitro validation identified Komagataeibacter intermedius SLAM-NK6B as a key strain underlying the methane-reducing effect of kombucha. The genome of SLAM-NK6B encodes biosynthetic gene clusters for cellulose, malate, citrate, and methanobactin-metabolites that can modulate the rumen microbiota. SLAM-NK6B supplementation reduced methanogen abundance by 53.32 % and increased hydrogen pressure, shifting microbial metabolism. Excluding acetate, VFA production increased significantly, with propionate levels elevated by 15.39-43.81 %. Metagenomic data further indicated activation of alternative hydrogen sink pathways, including citrate-to-propionate and malate-to-propionate conversions. This study proposes a novel microbial metabolic strategy for methane mitigation, enabling both methane reduction and enhanced fermentation efficiency. Such metabolic guidance of the rumen microbiome offers a sustainable approach to low-emission ruminant production.

Pseudogymnoascus destructans Transcriptional Response to Chronic Copper Stress

Copper (Cu) is an essential metal micronutrient, and a fungal pathogen's ability to thrive in diverse niches across a broad range of bioavailable copper levels is vital for host colonization and fungal propagation. Recent transcriptomic studies have implied that trace metal acquisition is important for the propagation of the white nose syndrome (WNS) causing fungus, Pseudogymnoascus destructans, on bat hosts. This report characterizes the P. destructans transcriptional response to Cu-withholding and Cu-overload stress. We identify 583 differently expressed genes (DEGs) that respond to Cu-withholding stress and 667 DEGs that respond to Cu-overload stress. We find that the P. destructans Cu-transporter genes CTR1a and CTR1b, as well as two homologs to Cryptococcus neoformans Cbi1/BIM1 VC83_03095 (BLP2) and VC83_07867 (BLP3), are highly regulated by Cu-withholding stress. We identify a cluster of genes, VC83_01834 - VC83_01838, that are regulated by copper bioavailability, which we identify as the Cu-Responsive gene Cluster (CRC). We find that chronic exposure to elevated copper levels leads to an increase in genes associated with DNA repair and DNA replication fidelity. A comparison of our transcriptomic datasets with P. destructans at WNS fungal infection sites reveals several putative fungal virulence factors that respond to environmental copper stress.

Pseudogymnoascus destructans transcriptional response to chronic copper stress

Copper (Cu) is an essential metal micronutrient, and a fungal pathogens' ability to thrive in diverse niches across a broad range of bioavailable copper levels is vital for host-colonization and fungal-propagation. Recent transcriptomic studies have implemented that trace metal acquisition is important for the propagation of the white nose syndrome (WNS) causing fungus, Pseudogymnoascus destructans , on bat hosts. This report characterizes the P. destructans transcriptional response to Cu-withholding and Cu-overload stress. We identify 583 differently expressed genes (DEGs) that respond to Cu-withholding stress and 667 DEGs that respond to Cu-overload stress. We find that the P. destructans Cu-transporter genes CTR 1a and CTR1 b, as well as two homologs to Cryptococcus neoformans Cbi1/BIM1 VC83_03095 (BLP2) and VC83_07867 (BLP3) are highly regulated by Cu-withholding stress. We identify a cluster of genes, VC83_01834 - VC83_01837, that are regulated by copper bioavailability, which we identify as the Cu Responsive gene Cluster (CRC). We find that chronic exposure to elevated copper levels leads to an increase in genes associated with DNA repair and DNA replication fidelity. A comparison of our transcriptomic data sets with P. destructans at WNS fungal infection sites reveals several putative fungal virulence factors that respond to environmental copper stress.

Copper-chelating natural products

Bacteria and fungi produce natural products that coordinate copper for a variety of functions. Many copper-binding natural products function as copper-chelating metallophores, or chalkophores, that scavenge copper from the environment to meet cellular needs. By contrast, some compounds sequester toxic levels of environmental copper to protect the producing microorganism. These copper-binding compounds often have antimicrobial activities as well. In recent years, a number of new copper-coordinating natural products have been reported, including both ribosomally and non-ribosomally synthesized molecules. There have also been significant advances in understanding the biosynthesis of these and previously known copper chelators, leading to the discovery of new enzyme families. This review summarizes the recently discovered copper-binding natural products, their biosynthetic pathways, and their functions. By highlighting key biosynthetic enzymes, we hope to inspire the discovery of new copper-coordinating natural products that may be used as therapeutics and antimicrobial agents.