Search

Cyanobacteriota , the sole prokaryotes capable of oxygenic photosynthesis (OxyP), occupy a unique and pivotal role in Earth's history. While the notion that OxyP may have originated from Cyanobacteriota is widely accepted, its early evolution remains elusive. Here, by using both metagenomics and metatranscriptomics, we explore 36 metagenome-assembled genomes from hot spring ecosystems, belonging to two deep-branching cyanobacterial orders: Thermostichales and Gloeomargaritales. Functional investigation reveals that Thermostichales encode the crucial thylakoid membrane biogenesis protein, vesicle-inducing protein in plastids 1 (Vipp1). Based on the phylogenetic results, we infer that the evolution of the thylakoid membrane predates the divergence of Thermostichales from other cyanobacterial groups and that Thermostichales may be the most ancient lineage known to date to have inherited this feature from their common ancestor. Apart from OxyP, both lineages are potentially capable of sulfide-driven AnoxyP by linking sulfide oxidation to the photosynthetic electron transport chain. Unexpectedly, this AnoxyP capacity appears to be an acquired feature, as the key gene sqr was horizontally transferred from later-evolved cyanobacterial lineages. The presence of two D1 protein variants in Thermostichales suggests the functional flexibility of photosystems, ensuring their survival in fluctuating redox environments. Furthermore, all MAGs feature streamlined phycobilisomes with a preference for capturing longer-wavelength light, implying a unique evolutionary trajectory. Collectively, these results reveal the photosynthetic flexibility in these early-diverging cyanobacterial lineages, shedding new light on the early evolution of Cyanobacteriota and their photosynthetic processes. [ABSTRACT FROM AUTHOR]

Notably, single-amplified genomes (SAGs) and metagenome-assembled genomes (MAGs) obtained from single-cell genomic and metagenomic approaches, respectively, have become the most effective methods that enable organism-level genomic analysis of complex microbial ecosystems without the need for cultivation, which brings lighttoMDM. Hug et al. used more than 1000 MDM genomes, together with public genomic data,toinferthetreeoflifeanddescribed a hyper-diverse clade of MDM termed the Candidate Phyla Radiation (CPR), subdividing the domain Bacteria [4]. The study of MDM is still in its infancy and further exploration of MDM will continue to provide unanticipated and excitinganswersabouttheevolutionand roles of MDM in nature. This is so-called Microbial Dark Matter (MDM): the enormous diversity of yet-uncultivated microbes that microbiologists can only study by using cultivation-independent techniques. [Extracted from the article]

Aims CD1d is a member of the cluster of differentiation 1 (CD1) family of glycoproteins expressed on the surface of various antigen-presenting cells, which is recognized by natural killer T (NKT) cells. CD1d-dependent NKT cells play an important role in immune-mediated diseases; but the role of these cells in regulating cardiac remodelling remains unknown. Methods and results Cardiac remodelling was induced by angiotensin (Ang) II infusion for 2 weeks. Ang II-induced increase in hypertension, cardiac performance, hypertrophy and fibrosis, inflammatory response, and activation of the NF-kB and TGF-β1/Smad2/3 pathways was significantly aggravated in CD1d knockout (CD1dko) mice compared with wild-type (WT) mice, but these effects were markedly abrogated in WT mice treated with α-galactosylceramide (αGC), a specific activator of NKT cells. Adoptive transfer of CD1dko bone marrow cells to WT mice further confirmed the deleterious effect of CD1dko. Moreover, IL-10 expression was significantly decreased in CD1dko hearts but increased in αGC-treated mice. Co-culture experiments revealed that CD1dko dendritic cells significantly reduced IL-10 mRNA expression from NKT cells. Administration of recombinant murine IL-10 to CD1dko mice improved hypertension, cardiac performance, and adverse cardiac remodelling induced by Ang II, and its cardioprotective effect was possibly associated with activation of STAT3, and inhibition of the TGF-β1 and NF-kB pathways. Conclusion These findings revealed a previously undefined role for CD1d-dependent NKT cells in Ang II-induced cardiac remodelling, hence activation of NKT cells may be a novel therapeutic target for hypertensive cardiac disease. [ABSTRACT FROM AUTHOR]

Menaquinone (MK) is an important component of the electron-transfer system in prokaryotes. One of its precursors, 1,4-dihydroxy-2-naphthoate, can be synthesized from chorismate by the classical MK pathway. Interestingly, in some bacteria, chorismate can also be converted to 1,4-dihydroxy-6-naphthoate by four enzymes encoded by mqnABCD in an alternative futalosine pathway. In this study, six crucial enzymes belonging to these two independent nonhomologous pathways were identified in the predicted proteomes of prokaryotes representing a broad phylogenetic distribution. Although the classical MK pathway was found in 32.1% of the proteomes, more than twice the proportion containing the futalosine pathway, the latter was found in a broader taxonomic range of organisms (18 of 31 phyla). The prokaryotes equipped with the classical MK pathway were almost all aerobic or facultatively anaerobic, but those with the futalosine pathway were not only aerobic or facultatively anaerobic but also anaerobic. Phylogenies of enzymes of the classical MK pathway indicated that its genes in archaea were probably acquired by an ancient horizontal gene transfer from bacterial donors. Therefore, the organization of the futalosine pathway likely predated that of the classical MK pathway in the evolutionary history of prokaryotes. [ABSTRACT FROM AUTHOR]

A xylanase gene (thxyn11A) from the Thermobifida halotolerans strain YIM 90462 was cloned and expressed in Escherichia coli. The open reading frame (ORF) of thxyn11A has 1,008 bp encoding a mature xylanase with a high degree of similarity (80 %) to the xylanase from Nocardiopsis dassonvillei subsp . dassonvillei DSM 43111. This enzyme (Thxyn11A) also possesses a glycosyl hydrolases family 11 (GH11) domain and a high isoelectric point (pI = 9.1). However, Thxyn11A varies from most GH11 xylanases, due to its large molecular mass (34 kDa). Recombinant Thxyn11A demonstrated a strong pH and temperature tolerance with a maximum activity at pH 9.0 and 70 °C. Xylotriose, the end-product of xylan hydrolysis by Thxyn11A, serves as a catalyst for hemicellulose pretreatment in industrial applications and can also function as a food source or supplement for enterobacteria. Due to its attractive biochemical properties, Thxyn11A may have potential value in many commercial applications. [ABSTRACT FROM AUTHOR]

In the present study, the taxonomic position of Bacillus aryabhattai and Bacillus megaterium was evaluated using morphological, biochemical, phylogenomic and genome analysis. The morphological and biochemical of these two species were almost similar with few exceptions. The major fatty acids in B. megaterium DSM 32T and B. aryabhattai 21047T were anteiso-C15:0 and iso-C15:0. In the phylogenomic tree, both species clade together and shared high 16S rRNA gene sequence similarity (99.6%). The average nucleotide identity values between Bacillus aryabhattai and Bacillus megaterium were above the threshold values for bacterial species delineation. Based upon morphological, biochemical, chemotaxonomic and comparative genome analysis, we propose to reclassify Bacillus aryabhattai Shivaji et al. 2009 as a later heterotypic synonym of Bacillus megaterium de Bary 1884 (Approved Lists 1980). [ABSTRACT FROM AUTHOR]