Jan-Fang Cheng

A hybrid gene cluster, mfq, predicted to govern the biosynthesis of both meroterpenoids and phenaziterpenes, was cloned from the genome of Streptomyces sp. S4.7 and introduced into the heterologous host Streptomyces coelicolor M1154. The biosynthesis of the meroterpenoids marfuraquinocins C and D, previously isolated from Streptomyces niveus SCSIO 3406, as well as a new congener, marfuraquinocin E, which exhibited antibacterial activity, was activated upon overexpression of the regulatory protein MfqF. However, production of neither phenaziterpenes nor phenazines was detected. The structure of marfuraquinocin E was elucidated, revealing the attachment of a terpene moiety at C-2, in contrast to C-6 as seen in the known congeners A-D. Using the CRISPR/Cas9 system, several genes in the mfq cluster were inactivated, confirming the role of MfqW as a prenyltransferase specific to the meroterpenoid pathway. Both gene overexpression and further knockouts provided the first insights into the complex regulation of this hybrid gene cluster. To restore the presumably deficient phenazine biosynthetic pathway, a gene encoding a PhzF homologue from another gene cluster in S4.7 was heterologously expressed alongside the mfq cluster, leading to the production of 1,6-phenazine dicarboxylic acid upon MfqF overexpression. This work lays the foundation for elucidating the complete biosynthetic pathway of marfuraquinocins and its potential coregulation with that of phenazines.

Fervidibacter sacchari is an aerobic hyperthermophile belonging to the phylum Armatimonadota that degrades a variety of polysaccharides. Its genome encodes 117 enzymes with one or more annotated glycoside hydrolase (GH) domain, but the roles of these putative GHs in polysaccharide catabolism are poorly defined. Here, we describe one F. sacchari enzyme encoding a GH10 domain, Fsa02490Xyn, that was previously shown to be active on Miscanthus, oat β‐glucan, and beech‐wood xylan, with optimal activity at 90–100 °C. We show that Fsa02490Xyn is also active on birch‐wood xylan and gellan gum. The pH range on beech‐wood xylan was 4.5 to 9.5 (pH_opt 7.0–8.0). Fsa024940Xyn had a K_m of 2.375 mm, V_max of 1250 μm·min⁻¹, and k_cat/K_m of 1.259 × 10⁴ s⁻¹·m⁻¹ when using a para‐nitrophenyl‐𝛽‐xylobioside assay. A phylogenetic analysis of GH10 family enzymes revealed a large clade of enzymes from diverse members of the class Fervidibacteria, including Fsa02490Xyn and a second enzyme from F. sacchari, with apparent horizontal gene transfer within Fervidibacteria and between Fervidibacteria and thermophilic Bacillota. This study establishes Fsa02490Xyn as a hyperthermophilic GH10 enzyme with endo‐β‐1,4‐xylanase activity and identifies a large clade of homologous GH10 enzymes within the class Fervidibacteria. Impact statement: The depolymerization of xylan at high temperatures is important because this process limits the degradation of polysaccharides in nature and the synthesis of biofuels from plant wastes. Our study is also important because F. sacchari is one of only a few cultivated members of the Armatimonadota, which are polysaccharide‐degradation specialists.

Heme has a critical role in the chemical framework of the cell as an essential protein cofactor and signaling molecule that controls diverse processes and molecular interactions. Using a phylogenomics-based approach and complementary structural techniques, we identify a family of dimeric hemoproteins comprising a domain of unknown function DUF2470. The heme iron is axially coordinated by two zinc-bound histidine residues, forming a distinct two-fold symmetric zinc-histidine-iron-histidine-zinc site. Together with structure-guided in vitro and in vivo experiments, we further demonstrate the existence of a functional link between heme binding by Dri1 (Domain related to iron 1, formerly ssr1698) and post-translational regulation of succinate dehydrogenase in the cyanobacterium Synechocystis, suggesting an iron-dependent regulatory link between photosynthesis and respiration. Given the ubiquity of proteins containing homologous domains and connections to heme metabolism across eukaryotes and prokaryotes, we propose that DRI (Domain Related to Iron; formerly DUF2470) functions at the molecular level as a heme-dependent regulatory domain.

CRISPR–Cas systems defend prokaryotic cells from invasive DNA of viruses, plasmids and other mobile genetic elements. Here, we show using metagenomics, metatranscriptomics and single-cell genomics that CRISPR systems of widespread, uncultivated archaea can also target chromosomal DNA of archaeal episymbionts of the DPANN superphylum. Using meta-omics datasets from Crystal Geyser and Horonobe Underground Research Laboratory, we find that CRISPR spacers of the hosts Candidatus Altiarchaeum crystalense and Ca. A. horonobense, respectively, match putative essential genes in their episymbionts’ genomes of the genus Ca. Huberiarchaeum and that some of these spacers are expressed in situ. Metabolic interaction modelling also reveals complementation between host–episymbiont systems, on the basis of which we propose that episymbionts are either parasitic or mutualistic depending on the genotype of the host. By expanding our analysis to 7,012 archaeal genomes, we suggest that CRISPR–Cas targeting of genomes associated with symbiotic archaea evolved independently in various archaeal lineages.

The rapid design and assembly of synthetic DNA constructs have become a crucial component of biological engineering projects via iterative design–build–test–learn cycles. In this perspective, we provide an overview of the workflows used to generate the thousands of constructs and libraries produced each year at the U.S. Department of Energy Joint Genome Institute. Particular attention is paid to describing pipelines, tools used, types of scientific projects enabled by the platform and challenges faced in further scaling output.