Synergistic increase in coproporphyrin III biosynthesis by mitochondrial compartmentalization in engineered Saccharomyces cerevisiae.

Coproporphyrin III (CP III), a natural porphyrin derivative, has extensive applications in the biomedical and material industries. S. cerevisiae has previously been engineered to highly accumulate the CP III precursor 5-aminolevulinic acid (ALA) through the C4 pathway. In this study, a combination of cytoplasmic metabolic engineering and mitochondrial compartmentalization was used to enhance CP III production in S. cerevisiae. By integrating pathway genes into the chromosome, the CP III titer gradually increased to 32.5 ± 0.5 mg/L in shake flask cultivation. Nevertheless, increasing the copy number of pathway genes did not consistently enhance CP III synthesis. Hence, the partial synthesis pathway was compartmentalized in mitochondria to evaluate its effectiveness in increasing CP III production. Subsequently, by superimposing the mitochondrial compartmentalization strategy on cytoplasmic metabolic engineered strains, the CP III titer was increased to 64.3 ± 1.9 mg/L. Furthermore, augmenting antioxidant pathway genes to reduce reactive oxygen species (ROS) levels effectively improved the growth of engineered strains, resulting in a further increase in the CP III titer to 82.9 ± 1.4 mg/L. Fed-batch fermentations in a 5 L bioreactor achieved a titer of 402.8 ± 9.3 mg/L for CP III. This study provides a new perspective on engineered yeast for the microbial production of porphyrins.

De novo transcriptome analysis identifies RpMYB1 as an activator of anthocyanin biosynthesis in Rehmannia piasezkii.

Rehmannia piasezkii is a kind of medicinal plants, of the Orobanchaceae family, and well known for its large pink or purple corolla. However, no research on the molecular mechanism of flower color formation in R. piasezkii has been conducted so far. In this study, we investigated the transcriptome of root, stem, leaf and corollas of R. piasezkii using transcriptome sequencing technology and assembled 144,582 unigenes. A total of 58 anthocyanin biosynthetic genes were identified in the R. piasezkii transcriptome, fourteen of which were highly correlated with anthocyanin content, especially RpF3H2, RpDFR2, RpANS1, RpANS2 and RpUFGT. Totally, 35 MYB genes with FPKM values greater than 5 were identified in the R. piasezkii transcriptome, including an R2R3 MYB transcriptional factor RpMYB1, which belongs to subgroup 6 of the R2R3 MYB family. Agrobacterium-mediated transient expression of Nicotiana benthamiana revealed that overexpression of RpMYB1 could activate the expression of structural genes in anthocyanin synthesis pathway and promote the accumulation of anthocyanins in N. benthamiana leaves, indicating that RpMYB1 is a positive regulator of anthocyanin synthesis. Furthermore, combined transient overexpression of RpMYB1 with RpANS1, RpMYB1+RpANS1 with other structural genes all could further enhance the accumulation of anthocyanins in N. benthamiana leaves. Permanent overexpression of RpMYB1 in R. glutinosa promoted anthocyanin accumulation and expression levels of RgCHS, RgF3H, RgDFR and RgANS. Further evidence from dual-luciferase assay suggested that RpMYB1 could bind to the promoter of RpDFR2 and hence activating its expression. These findings provide insight into the molecular regulation in anthocyanin biosynthesis in R. piasezkii and provide valuable genetic resources for the genetic improvement of flower color.

Efficient genome engineering in Mycolicibacterium neoaurum using Cas9 from Streptococcus thermophilus.

Non-pathogenic mycobacteria, including Mycolicibacterium neoaurum, can directly utilize phytosterols for large-scale industrial production of steroid medicine intermediates due to their natural steroid metabolism pathway. The targeted genetic modification of M. neoaurum is conducive to the selection of high-yield engineering bacteria with high-value-added product, such as Pregnadien-20-carboxylic acid (PDC), which is an important precursor for synthesizing some corticosteroids. Based on heterologous type II CRISPR/sth1Cas9 system, a simple strategy was developed to genetic engineer M. neoaurum genome. Here, a customizable plasmid tool pMSC9 was constructed from pMV261 with integration of sth1Cas9 protein and corresponding sgRNA scaffold. Subsequently, the pMSC9 was inserted with spacer sequences corresponding to different targeted genes, generating editing plasmids, and then transformed into M. neoaurum. As a result, the targeted genes were introduced with DNA double stand breaks (DSBs) by CRISPR/sth1Cas9 system and then repaired by innate non-homologous end-joining (NHEJ) mechanism. Finally, editing plasmids were cured from correctly edited M. neoaurum mutants by means of no resistance cultivation, and the resulting mutant deleting the one target gene was used as the host to which another target gene could be deleted via the same process. This study demonstrated that the CRISPR/sth1Cas9 tool allowed M. neoaurum strains to be rapidly edited. And the editing mode of CRISPR/sth1Cas9 system indicated that this tool was an important supplement to the gene editing toolbox of M. neoaurum.

[Gene cloning and functional analysis of an iridoid oxidase gene in Rehmannia glutinosa].

Rehmannia glutinosa is one of the commonly used Chinese herbal medicines, which has activities of heat-clearing,blood-cooling, Yin-nourishing, and body fluid-promoting. Iridoid glycosides are the main bioactive in R. glutinosa. Iridoid oxidase is a key rate-limiting enzyme in the biosynthetic pathway of iridoid glycosides. In this study, an iridoid oxidase gene Rg IO was screened based on the transcriptome data, followed by bioinformatics analysis, expression characteristic detection, and subcellular localization analysis. The results show that the coding region of Rg IO is 1 536 bp, with 511 amino acids encoded, and the molecular weight is about 58 258. 01. The protein sequence of Rg IO contains the conserved domains and motifs of cytochrome P450 oxidases. Rg IO has the highest sequence identities with its ortholog proteins in Striga asiatica, Striga hermonthica, and Centranthera grandiflora and has good sequence identities(77. 28%) with Catharanthus roseus Cr IO. Rg IO shows specific expression in the leaf of R. glutinosa. In response to MeJA induction, the expression of MeJA in leaves and roots after treatment increases by 3. 15 and 1. 3 times at 3 h and 6 h,respectively. The result of subcellular localization shows that Rg IO is distributed in the endoplasmic reticulum. Agrobacterium-mediated transient expression of Rg IO gene in leaves of R. glutinosa makes the content of catalpol increase by 0. 82 times compared with the transient expression of the empty vector. This study provides a key target gene for the molecular regulation and biosynthesis of catalpol in R. glutinosa and lays a foundation for revealing the complete biosynthetic pathway of catalpol.

Multidimensional engineering of Saccharomyces cerevisiae for the efficient production of heme by exploring the cytotoxicity and tolerance of heme.

Heme has attracted considerable attention due to its indispensable biological roles and applications in healthcare and artificial foods. The development and utilization of edible microorganisms instead of animals to produce heme is the most promising method to promote the large-scale industrial production and safe application of heme. However, the cytotoxicity of heme severely restricts its efficient synthesis by microorganisms, and the cytotoxic mechanism is not fully understood. In this study, the effect of heme toxicity on Saccharomyces cerevisiae was evaluated by enhancing its synthesis using metabolic engineering. The results showed that the accumulation of heme after the disruption of heme homeostasis caused serious impairments in cell growth and metabolism, as demonstrated by significantly poor growth, mitochondrial damage, cell deformations, and chapped cell surfaces, and these features which were further associated with substantially elevated reactive oxygen species (ROS) levels within the cell (mainly H2O2 and superoxide anion radicals). To improve cellular tolerance to heme, 5 rounds of laboratory evolution were performed, increasing heme production by 7.3-fold and 4.2-fold in terms of the titer (38.9 mg/L) and specific production capacity (1.4 mg/L/OD600), respectively. Based on comparative transcriptomic analyses, 32 genes were identified as candidates that can be modified to enhance heme production by more than 20% in S. cerevisiae. The combined overexpression of 5 genes (SPS22, REE1, PHO84, HEM4 and CLB2) was shown to be an optimal method to enhance heme production. Therefore, a strain with enhanced heme tolerance and ROS quenching ability (R5-M) was developed that could generate 380.5 mg/L heme with a productivity of 4.2 mg/L/h in fed-batch fermentation, with S. cerevisiae strains being the highest producers reported to date. These findings highlight the importance of improving heme tolerance for the microbial production of heme and provide a solution for efficient heme production by engineered yeasts.

Engineering non-conventional yeast Rhodotorula toruloides for ergothioneine production.

BACKGROUND: Ergothioneine (EGT) is a distinctive sulfur-containing histidine derivative, which has been recognized as a high-value antioxidant and cytoprotectant, and has a wide range of applications in food, medical, and cosmetic fields. Currently, microbial fermentation is a promising method to produce EGT as its advantages of green environmental protection, mild fermentation condition, and low production cost. However, due to the low-efficiency biosynthetic process in numerous cell factories, it is still a challenge to realize the industrial biopreparation of EGT. The non-conventional yeast Rhodotorula toruloides is considered as a potential candidate for EGT production, thanks to its safety for animals and natural ability to synthesize EGT. Nevertheless, its synthesis efficiency of EGT deserves further improvement. RESULTS: In this study, out of five target wild-type R. toruloides strains, R. toruloides 2.1389 (RT1389) was found to accumulate the highest EGT production, which could reach 79.0 mg/L at the shake flask level on the 7th day. To achieve iterative genome editing in strain RT1389, CRISPR-assisted Cre recombination (CACR) method was established. Based on it, an EGT-overproducing strain RT1389-2 was constructed by integrating an additional copy of EGT biosynthetic core genes RtEGT1 and RtEGT2 into the genome, the EGT titer of which was 1.5-fold increase over RT1389. As the supply of S-adenosylmethionine was identified as a key factor determining EGT production in strain RT1389, subsequently, a series of gene modifications including S-adenosylmethionine rebalancing were integrated into the strain RT1389-2, and the resulting mutants were rapidly screened according to their EGT production titers with a high-throughput screening method based on ergothionase. As a result, an engineered strain named as RT1389-3 was selected with a production titer of 267.4 mg/L EGT after 168 h in a 50 mL modified fermentation medium. CONCLUSIONS: This study characterized the EGT production capacity of these engineered strains, and demonstrated that CACR and high-throughput screening method allowed rapid engineering of R. toruloides mutants with improved EGT production. Furthermore, this study provided an engineered RT1389-3 strain with remarkable EGT production performance, which had potential industrial application prospects.

Unveiling the role of novel carbohydrate-binding modules in laminarin interaction of multimodular proteins from marine Bacteroidota during phytoplankton blooms.

Laminarin, a ß(1,3)-glucan, serves as a storage polysaccharide in marine microalgae such as diatoms. Its abundance, water solubility and simple structure make it an appealing substrate for marine bacteria. Consequently, many marine bacteria have evolved strategies to scavenge and decompose laminarin, employing carbohydrate-binding modules (CBMs) as crucial components. In this study, we characterized two previously unassigned domains as laminarin-binding CBMs in multimodular proteins from the marine bacterium Christiangramia forsetii KT0803T, thereby introducing the new laminarin-binding CBM families CBM102 and CBM103. We identified four CBM102s in a surface glycan-binding protein (SGBP) and a single CBM103 linked to a glycoside hydrolase module from family 16 (GH16_3). Our analysis revealed that both modular proteins have an elongated shape, with GH16_3 exhibiting greater flexibility than SGBP. This flexibility may aid in the recognition and/or degradation of laminarin, while the constraints in SGBP could facilitate the docking of laminarin onto the bacterial surface. Exploration of bacterial metagenome-assembled genomes (MAGs) from phytoplankton blooms in the North Sea showed that both laminarin-binding CBM families are widespread among marine Bacteroidota. The high protein abundance of CBM102- and CBM103-containing proteins during phytoplankton blooms further emphasizes their significance in marine laminarin utilization.

Marine particle microbiomes during a spring diatom bloom contain active sulfate-reducing bacteria.

Phytoplankton blooms fuel marine food webs with labile dissolved carbon and also lead to the formation of particulate organic matter composed of living and dead algal cells. These particles contribute to carbon sequestration and are sites of intense algal-bacterial interactions, providing diverse niches for microbes to thrive. We analyzed 16S and 18S ribosomal RNA gene amplicon sequences obtained from 51 time points and metaproteomes from 3 time points during a spring phytoplankton bloom in a shallow location (6-10 m depth) in the North Sea. Particulate fractions larger than 10 µm diameter were collected at near daily intervals between early March and late May in 2018. Network analysis identified two major modules representing bacteria co-occurring with diatoms and with dinoflagellates, respectively. The diatom network module included known sulfate-reducing Desulfobacterota as well as potentially sulfur-oxidizing Ectothiorhodospiraceae. Metaproteome analyses confirmed presence of key enzymes involved in dissimilatory sulfate reduction, a process known to occur in sinking particles at greater depths and in sediments. Our results indicate the presence of sufficiently anoxic niches in the particle fraction of an active phytoplankton bloom to sustain sulfate reduction, and an important role of benthic-pelagic coupling for microbiomes in shallow environments. Our findings may have implications for the understanding of algal-bacterial interactions and carbon export during blooms in shallow-water coastal areas.

Particle-attached bacteria act as gatekeepers in the decomposition of complex phytoplankton polysaccharides.

BACKGROUND: Marine microalgae (phytoplankton) mediate almost half of the worldwide photosynthetic carbon dioxide fixation and therefore play a pivotal role in global carbon cycling, most prominently during massive phytoplankton blooms. Phytoplankton biomass consists of considerable proportions of polysaccharides, substantial parts of which are rapidly remineralized by heterotrophic bacteria. We analyzed the diversity, activity, and functional potential of such polysaccharide-degrading bacteria in different size fractions during a diverse spring phytoplankton bloom at Helgoland Roads (southern North Sea) at high temporal resolution using microscopic, physicochemical, biodiversity, metagenome, and metaproteome analyses. RESULTS: Prominent active 0.2-3 µm free-living clades comprised Aurantivirga, "Formosa", Cd. Prosiliicoccus, NS4, NS5, Amylibacter, Planktomarina, SAR11 Ia, SAR92, and SAR86, whereas BD1-7, Stappiaceae, Nitrincolaceae, Methylophagaceae, Sulfitobacter, NS9, Polaribacter, Lentimonas, CL500-3, Algibacter, and Glaciecola dominated 3-10 µm and > 10 µm particles. Particle-attached bacteria were more diverse and exhibited more dynamic adaptive shifts over time in terms of taxonomic composition and repertoires of encoded polysaccharide-targeting enzymes. In total, 305 species-level metagenome-assembled genomes were obtained, including 152 particle-attached bacteria, 100 of which were novel for the sampling site with 76 representing new species. Compared to free-living bacteria, they featured on average larger metagenome-assembled genomes with higher proportions of polysaccharide utilization loci. The latter were predicted to target a broader spectrum of polysaccharide substrates, ranging from readily soluble, simple structured storage polysaccharides (e.g., laminarin, α-glucans) to less soluble, complex structural, or secreted polysaccharides (e.g., xylans, cellulose, pectins). In particular, the potential to target poorly soluble or complex polysaccharides was more widespread among abundant and active particle-attached bacteria. CONCLUSIONS: Particle-attached bacteria represented only 1% of all bloom-associated bacteria, yet our data suggest that many abundant active clades played a pivotal gatekeeping role in the solubilization and subsequent degradation of numerous important classes of algal glycans. The high diversity of polysaccharide niches among the most active particle-attached clades therefore is a determining factor for the proportion of algal polysaccharides that can be rapidly remineralized during generally short-lived phytoplankton bloom events. Video Abstract.

CRISPR/Cas9-based toolkit for rapid marker recycling and combinatorial libraries in Komagataella phaffii.

Komagataella phaffii, a nonconventional yeast, is increasingly attractive to researchers owing to its posttranslational modification ability, strict methanol regulatory mechanism, and lack of Crabtree effect. Although CRISPR-based gene editing systems have been established in K. phaffii, there are still some inadequacies compared to the model organism Saccharomyces cerevisiae. In this study, a redesigned gRNA plasmid carrying red and green fluorescent proteins facilitated plasmid construction and marker recycling, respectively, making marker recycling more convenient and reliable. Subsequently, based on the knockdown of Ku70 and DNA ligase IV, we experimented with integrating multiple DNA fragments at a single locus. A 26.5-kb-long DNA fragment divided into 11 expression cassettes for lycopene synthesis could be successfully integrated into a single locus at one time with a success rate of 57%. A 27-kb-long DNA fragment could also be precisely knocked out with a 50% positive rate in K. phaffii by introducing two DSBs simultaneously. Finally, to explore the feasibility of rapidly balancing the expression intensity of multiple genes in a metabolic pathway, a yeast combinatorial library was successfully constructed in K. phaffii using lycopene as an indicator, and an optimal combination of the metabolic pathway was identified by screening, with a yield titer of up to 182.73 mg/L in shake flask fermentation. KEY POINTS: • Rapid marker recycling based on the visualization of a green fluorescent protein • One-step multifragment integration and large fragment knockout in the genome • A random assembly of multiple DNA elements to create yeast libraries in K. phaffii.

Dual-vacancies modulation of 1T/2H heterostructured MoS2-CdS nanoflowers via radiolytic radical chemistry for efficient photocatalytic H2 evolution.

Precise defect engineering of photocatalysts is highly demanding but remains a challenge. Here, we developed a facile and controllable γ-ray radiation strategy to assemble dual-vacancies confined MoS2-CdS-γ nanocomposite photocatalyst. We showed the solvated electron induced homogeneous growth of defects-rich CdS nanoparticles, while the symbiotic •OH radicals etched flower-like 1T/2H MoS2 substrate surfaces. The optimal MoS2-CdS-γ exhibited a H2 evolution rate of up to 37.80 mmol/h/g under visible light irradiation, which was 36.7 times higher than that of bare CdS-γ, and far superior to those synthesized by hydrothermal method. The microscopic characterizations and theoretical calculations revealed the formation of such unprecedented dual-sulfur-vacancies ensured the tight interfacial contact for fast charge separation. Besides, the existence of 1T-MoS2 phase further improved the conductivity and strengthened the adsorption interaction with H+ intermediate. Therefore, the radiolytic radical chemistry offered a facile, ambient and effective synthetic strategy to improve the catalytic performances of photocatalytic materials.

Co-augmentation of a transport gene mfsT1 in Mycolicibacterium neoaurum with genome engineering to enhance ergothioneine production.

Ergothioneine (EGT) is a rare thiohistidine derivative with exceptional antioxidant properties. The blood level of EGT is considered highly reliable predictors for cardiovascular diseases and mortality, yet animals lack the ability to synthesize this compound. Free plasmids have been previously used to overexpress genes involved in the EGT biosynthetic pathway of Mycolicibacterium neoaurum. Here, we tentatively introduced a putative transporter gene mfsT1 into high-copy plasmids and sharply increased the ratio of extracellular EGT concentration from 18.7% to 44.9%. Subsequently, an additional copy of egtABCDE, hisG, and mfsT1 was inserted into the genome with a site-specific genomic integration tool of M. neoaurum, leading a 2.7 times increase in EGT production. Co-enhancing the S-adenosyl-L-methionine regeneration pathway, or alternatively, the integration of three copies of egtABCDE, hisG and mfsT1 into the genome further increased the total EGT yield by 16.1% (64.6 mg/L) and 21.7% (67.7 mg/L), respectively. After 168-h cultivation, the highest titer reached 85.9 mg/L in the latter strain with three inserted copies. This study provided a solid foundation for genome engineering to increase the production of EGT in M. neoaurum.

Pharmacologically significant constituents collectively responsible for anti-sepsis action of XueBiJing, a Chinese herb-based intravenous formulation.

Sepsis, a life-threatening health issue, lacks effective medicine targeting the septic response. In China, treatment combining the intravenous herbal medicine XueBiJing with conventional procedures reduces the 28-day mortality of critically ill patients by modulating septic response. In this study, we identified the combined active constituents that are responsible for the XueBiJing's anti-sepsis action. Sepsis was induced in rats by cecal ligation and puncture (CLP). The compounds were identified based on their systemic exposure levels and anti-sepsis activities in CLP rats that were given an intravenous bolus dose of XueBiJing. Furthermore, the identified compounds in combination were assessed, by comparing with XueBiJing, for levels of primary therapeutic outcome, pharmacokinetic equivalence, and pharmacokinetic compatibility. We showed that a total of 12 XueBiJing compounds, unchanged or metabolized, circulated with significant systemic exposure in CLP rats that received XueBiJing. Among these compounds, hydroxysafflor yellow A, paeoniflorin, oxypaeoniflorin, albiflorin, senkyunolide I, and tanshinol displayed significant anti-sepsis activities, which involved regulating immune responses, inhibiting excessive inflammation, modulating hemostasis, and improving organ function. A combination of the six compounds, with the same respective doses as in XueBiJing, displayed percentage survival and systemic exposure in CLP rats similar to those by XueBiJing. Both the combination and XueBiJing showed high degrees of pharmacokinetic compatibility regarding interactions among the six active compounds and influences of other circulating XueBiJing compounds. The identification of XueBiJing's pharmacologically significant constituents supports the medicine's anti-sepsis use and provides insights into a polypharmacology-based approach to develop medicines for effective sepsis management.

Preparation of potential organic fertilizer rich in γ-polyglutamic acid via microbial fermentation using brewer's spent grain as basic substrate.

Brewer's spent grain (BSG) is a main byproduct of the beer industry. BSG is rich in a variety of nutrients, and the search for its effective, high-value utilization is ongoing. Environmental probiotic factor γ-PGA was produced by fermenting Bacillus subtilis with BSG substrate and the fermenting grain components were analyzed. The γ-PGA yield reached 31.58 ± 0.21 g/kg of BSG. Gas chromatography-mass spectrometry and non-targeted metabolomics analyses revealed 73 new volatile substances in the fermenting grains. Furthermore, 2,376 metabolites were upregulated after fermentation and several components were beneficial for plant growth and development (such as ectoine, acetyl eugenol, L-phenylalanine, niacin, isoprene, pantothenic acid, dopamine, glycine, proline, jasmonic acid, etc). These results show that it is possible to synthesize adequate amounts of γ-PGA for use as a functional fertilizer.

Establishment of an Efficient Expression and Regulation System in Streptomyces for Economical and High-Level Production of the Natural Blue Pigment Indigoidine.

Indigoidine, as a kind of natural blue pigment, is widely used in textiles, food, and pharmaceuticals and is mainly synthesized from l-glutamine via a condensation reaction by indigoidine synthetases, most of which originates from Streptomyces species. However, due to the complex metabolic switches of Streptomyces, most of the researchers choose to overexpress indigoidine synthetases in the heterologous host to achieve high-level production of indigoidine. Considering the advantages of low-cost culture medium and simple culture conditions during the large-scale culture of Streptomyces, here, an updated regulation system derived from the Streptomyces self-sustaining system, constructed in our previous study, was established for the highly efficient production of indigoidine in Streptomyces lividans TK24. The updated system was constructed via promoter mining and σhrdB expression optimization, and this system was applied to precisely and continuously regulate the expression of indigoidine synthetase IndC derived from Streptomyces albus J1704. Finally, the engineered strain was cultured with cheap industrial glycerol as a supplementary carbon source, and 14.3 and 46.27 g/L indigoidine could be achieved in a flask and a 4 L fermentor, respectively, reaching the highest level of microbial synthesis of indigoidine. This study will lay a foundation for the industrial application of Streptomyces cell factories to produce indigoidine.

Maydistacins A-G, Terpestacin-type Sesterterpenoids with Anti-inflammatory Activity from the Phytopathogenic Fungus Bipolaris maydis.

Seven undescribed terpestacin-type sesterterpenoids, maydistacins A-G (1-7), along with two known congeners (8 and 9), were isolated from the phytopathogenic fungus Bipolaris maydis collected from the leaves of Hypericum longistylum. The structures of 1-7 were elucidated based on extensive spectroscopic analysis, chemical methods, NMR calculations with DP4+ probability analysis, and comparison of experimental and calculated electronic circular dichroism (ECD) calculations. In vitro anti-inflammatory effects of these compounds were tested in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Compound 1 exhibited inhibition of the production of nitric oxide in LPS-induced macrophages, with an IC50 value of 19 ± 2 µM. A dexamethasone control displayed an IC50 value of 6.7 ± 0.6 µM. Compound 1 is the first terpestacin-type sesterterpenoid reported to display anti-inflammatory activity and may provide a novel chemical scaffold for the discovery of new anti-inflammatory drugs.

Diagnostic value of cerebrospinal fluid Neutrophil Gelatinase-Associated Lipocalin for differentiation of bacterial meningitis from tuberculous meningitis or cryptococcal meningitis: a prospective cohort study.

BACKGROUND: The early differential diagnosis between bacterial meningitis (BM) and tuberculous meningitis (TBM) or cryptococcal meningitis (CM) remains a significant clinical challenge. Neutrophil Gelatinase-Associated Lipocalin (NGAL) has been reported as a novel inflammatory biomarker in the early stages of infection. This study aimed to investigate whether cerebrospinal fluid (CSF) NGAL can serve as a potential biomarker for distinguishing between BM and TBM or CM. METHODS: We prospectively enrolled the patients with suspected CNS infections at admission and divided them into three case groups: BM (n = 67), TBM (n = 55), CM (n = 51), and an age- and sex-matched hospitalized control (HC, n = 58). Detected the CSF NGAL and assessed its diagnostic accuracy in distinguishing between BM and TBM or CM. Additionally, longitudinally measured the CSF NGAL levels in patients with BM to evaluate its potential as a monitoring tool for antibacterial treatment. RESULTS: The concentration of CSF NGAL in BM was significantly higher than in TBM, CM, and HC (all P < 0.05), while the serum NGAL did not show significant differences among the three case groups. The ROC analysis demonstrated that CSF NGAL presented a good diagnostic performance with an AUC of 0.834 (0.770-0.886) and at the optimal cutoff value of 74.27 ng/mL with 70.15% sensitivity and 77.36% specificity for discriminating BM with TBM and CM. Additionally, the CSF NGAL in the convalescent period of BM was significantly lower than in the acute period (P < 0.05). CONCLUSIONS: CSF NGAL may serve as a potential biomarker for distinguishing between acute BM and TBM or CM. Additionally, it holds clinical significance in monitoring the effectiveness of antibiotic therapy for BM.

Unravelling and engineering an operon involved in the side-chain degradation of sterols in Mycolicibacterium neoaurum for the production of steroid synthons.

BACKGROUND: Harnessing engineered Mycolicibacteria to convert cheap phytosterols into valuable steroid synthons is a basic way in the industry for the production of steroid hormones. Thus, C-19 and C-22 steroids are the two main types of commercial synthons and the products of C17 side chain degradation of phytosterols. During the conversion process of sterols, C-19 and C-22 steroids are often produced together, although one may be the main product and the other a minor byproduct. This is a major drawback of the engineered Mycolicibacteria for industrial application, which could be attributed to the co-existence of androstene-4-ene-3,17-dione (AD) and 22-hydroxy-23,24-bisnorchol-4-ene-3-one (HBC) sub-pathways in the degradation of the sterol C17 side chain. Since the key mechanism underlying the HBC sub-pathway has not yet been clarified, the above shortcoming has not been resolved so far. RESULTS: The key gene involved in the putative HBC sub-pathway was excavated from the genome of M. neoaurum by comparative genomic analysis. Interestingly, an aldolase- encoding gene, atf1, was identified to be responsible for the first reaction of the HBC sub-pathway, and it exists as a conserved operon along with a DUF35-type gene chsH4, a reductase gene chsE6, and a transcriptional regulation gene kstR3 in the genome. Subsequently, atf1 and chsH4 were identified as the key genes involved in the HBC sub-pathway. Therefore, an updated strategy was proposed to develop engineered C-19 or C-22 steroid-producing strains by simultaneously modifying the AD and HBC sub-pathways. Taking the development of 4-HBC and 9-OHAD-producing strains as examples, the improved 4-HBC-producing strain achieved a 20.7 g/L production titer with a 92.5% molar yield and a 56.4% reduction in byproducts, and the improved 9-OHAD producing strain achieved a 19.87 g/L production titer with a 94.6% molar yield and a 43.7% reduction in byproduct production. CONCLUSIONS: The excellent performances of these strains demonstrated that the primary operon involved in the HBC sub-pathway improves the industrial strains in the conversion of phytosterols to steroid synthons.

Short-chain fatty acids (SCFAs) as potential resuscitation factors that promote the isolation and culture of uncultured bacteria in marine sediments.

Many marine bacteria are difficult to culture because they are dormant, rare or found in low-abundances. Enrichment culturing has been widely tested as an important strategy to isolate rare or dormant microbes. However, many more mechanisms remain uncertain. Here, based on 16S rRNA gene high-throughput sequencing and metabolomics technology, it was found that the short-chain fatty acids (SCFAs) in metabolites were significantly correlated with uncultured bacterial groups during enrichment cultures. A pure culture analysis showed that the addition of SCFAs to media also resulted in high efficiency for the isolation of uncultured strains from marine sediments. As a result, 238 strains belonging to 10 phyla, 26 families and 82 species were successfully isolated. Some uncultured rare taxa within Chlorobi and Kiritimatiellaeota were successfully cultured. Amongst the newly isolated uncultured microbes, most genomes, e.g. bacteria, possess SCFA oxidative degradation genes, and these features might aid these microbes in better adapting to the culture media. A further resuscitation analysis of a viable but non-culturable (VBNC) Marinilabiliales strain verified that the addition of SCFAs could break the dormancy of Marinilabiliales in 5 days, and the growth curve test showed that the SCFAs could shorten the lag phase and increase the growth rate. Overall, this study provides new insights into SCFAs, which were first studied as resuscitation factors in uncultured marine bacteria. Thus, this study can help improve the utilisation and excavation of marine microbial resources, especially for the most-wanted or key players. Supplementary Information: The online version contains supplementary material available at 10.1007/s42995-023-00187-w.

Polyketides with Anti-Inflammatory Activity from Trichoderma koningiopsis, a Rhizosphere Fungus from the Medicinal Plant Polygonum paleaceum.

Twelve new fungal polyketides, koningiopisins I-P (1-8) and trichoketides C-F (9-12), together with six known congeners (13-18), were isolated from Trichoderma koningiopsis, a rhizosphere fungus obtained from the medicinal plant Polygonum paleaceum. Their structures and absolute configurations were established by spectroscopic analysis, single-crystal X-ray diffraction, the modified Mosher's method, chemical derivatization, the octant rule, and 13C NMR and ECD calculations. Compounds 1-5 are tricyclic polyketides possessing an octahydrochromene framework with a 6,8-dioxabicyclo[3.2.1]octane core. Compounds 7 and 8 contain a unique ketone carbonyl group at C-7 and differ from other members of this group of compounds with the ketone carbonyl group at C-1. Compounds 1, 2, and 13 showed inhibitory activity on LPS-induced BV-2 cells on NO production with IC50 values of 14 ± 1, 3.0 ± 0.5, and 8.9 ± 2.7 µM, respectively.