Evidence has shown that gut microbiome plays a role in modulating the development of diseases beyond the gastrointestinal tract, including skin disorders such as psoriasis. The gut–skin axis refers to the bidirectional relationship between the gut microbiome and skin health. This is regulated through several mechanisms such as inflammatory mediators and the immune system. Dysregulation of microbiota has been seen in numerous inflammatory skin conditions such as atopic dermatitis, rosacea, and psoriasis. Understanding how gut microbiome are involved in regulating skin health may lead to development of novel therapies for these skin disorders through microbiome modulation, in particularly psoriasis. In this review, we will compare the microbiota between psoriasis patients and healthy control, explain the concept of gut–skin axis and the effects of gut dysbiosis on skin physiology. We will also review the current evidence on modulating gut microbiome using probiotics in psoriasis.

While most bacteria are unicellular microbes they communicate with each other and with their environments to adapt their behaviors. Quorum sensing (QS) is one of the best-studied cell-cell communication modes. QS signaling is not restricted to bacterial cell-to-cell communication - it also allows communication between bacteria and their eukaryotic hosts. The diffusible signal factor (DSF) family represents an intriguing type of QS signal with multiple roles found in diverse Gram-negative bacteria. Over the last decade, extensive progress has been made in understanding DSF-mediated communication among bacteria, fungi, insects, plants, and zebrafish. This review provides an update on these new developments with the aim of building a more comprehensive picture of DSF-mediated intraspecies, interspecies, and inter-kingdom communication.

Actinobacteria constitute prolific sources of novel and vital bioactive metabolites for pharmaceutical utilization. In recent years, research has focused on exploring actinobacteria that thrive in extreme conditions to unearth their beneficial bioactive compounds for natural product drug discovery. Natural products have a significant role in resolving public health issues such as antibiotic resistance and cancer. The breakthrough of new technologies has overcome the difficulties in sampling and culturing extremophiles, leading to the outpouring of more studies on actinobacteria from extreme environments. This review focuses on the diversity and bioactive potentials/medically relevant biomolecules of extremophilic actinobacteria found from various unique and extreme niches. Actinobacteria possess an excellent capability to produce various enzymes and secondary metabolites to combat harsh conditions. In particular, a few strains have displayed substantial antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), shedding light on the development of MRSA-sensitive antibiotics. Several strains exhibited other prominent bioactivities such as antifungal, anti-HIV, anticancer, and anti-inflammation. By providing an overview of the recently found extremophilic actinobacteria and their important metabolites, we hope to enhance the understanding of their potential for the medical world.

Summary: The diffusible factor synthase XanB2 , originally identified in Xanthomonas campestris pv. campestris (Xcc), is highly conserved across a wide range of bacterial species, but its substrate and catalytic mechanism have not yet been investigated. Here, we show that XanB2 is a unique bifunctional chorismatase that hydrolyses chorismate, the end‐product of the shikimate pathway, to produce 3‐hydroxybenzoic acid (3‐HBA) and 4‐HBA. 3‐HBA and 4‐HBA are respectively associated with the yellow pigment xanthomonadin biosynthesis and antioxidant activity in Xcc. We further demonstrate that XanB2 is a structurally novel enzyme with three putative domains. It catalyses 3‐HBA and 4‐HBA biosynthesis via a unique mechanism with the C‐terminal YjgF‐like domain conferring activity for 3‐HBA biosynthesis and the N‐terminal FGFG motif‐containing domain responsible for 4‐HBA biosynthesis. Furthermore, we show that Xcc produces coenzyme Q8 (CoQ8) via a new biosynthetic pathway independent of the key chorismate‐pyruvate lyase UbiC. XanB2 is the alternative source of 4‐HBA for CoQ8 biosynthesis. The similar CoQ8 biosynthetic pathway, xanthomonadin biosynthetic gene cluster and XanB2 homologues are well conserved in the bacterial species within Xanthomonas, Xylella, Xylophilus, Pseudoxanthomonas, Rhodanobacter, Frateuria, Herminiimonas and Variovorax, suggesting that XanB2 may be a conserved metabolic link between the shikimate pathway, ubiquinone and xanthomonadin biosynthetic pathways in diverse bacteria.

Background: Our previously published reports have described an effective biocontrol agent namedPseudomonassp. M18 as its 16S rDNA sequence and several regulator genes share homologous sequences with those ofP. aeruginosa, but there are several unusual phenotypic features. This study aims to explore its strain specific genomic features and gene expression patterns at different temperatures.Results: The complete M18 genome is composed of a single chromosome of 6,327,754 base pairs containing 5684 open reading frames. Seven genomic islands, including two novel prophages and five specific non-phage islands were identified besides the conservedP. aeruginosacore genome. Each prophage contains a putative chitinase coding gene, and the prophage II contains acapBgene encoding a putative cold stress protein. The non-phage genomic islands contain genes responsible for pyoluteorin biosynthesis, environmental substance degradation and type I and III restriction-modification systems. Compared with otherP. aeruginosastrains, the fewest number (3) of insertion sequences and the most number (3) of clustered regularly interspaced short palindromic repeats in M18 genome may contribute to the relative genome stability. Although the M18 genome is most closely related to that ofP. aeruginosastrain LESB58, the strain M18 is more susceptible to several antimicrobial agents and easier to be erased in a mouse acute lung infection model than the strain LESB58. The whole M18 transcriptomic analysis indicated that 10.6% of the expressed genes are temperature-dependent, with 22 genes up-regulated at 28°C in three non-phage genomic islands and one prophage but none at 37°C.Conclusions: TheP. aeruginosastrain M18 has evolved its specific genomic structures and temperature dependent expression patterns to meet the requirement of its fitness and competitiveness under selective pressures imposed on the strain in rhizosphere niche.