Journal of microbiology and biotechnology最新文献

A novel Gram-negative bacterial strain, 20NA77.7^T, was isolated from fresh water of the Nakdong River. Strain 20NA77.7^T shared the highest similarity with Flavobacterium indicum GPTSA100-9^T (97.91%) and Flavobacterium urocaniciphilum DSM 27078^T (96.24%) in the 16S rRNA gene sequence. The digital DNA-DNA hybridization and average nucleotide identity values for strain 20NA77.7^T with Flavobacterium species were below 20.8% and 77.33%, respectively. The major fatty acids of strain 20NA77.7^T were identified as iso-C_15:0, iso-C_16:0, iso-C_15:1 G, anteiso-C_15:0, iso-C_15:0 3OH, and iso-C_16:0 3OH. Strain 20NA77.7^T contained phosphatidylethanolamine, one unidentified aminolipid, and three unidentified lipids as polar lipids and menaquinone-6 as menaquinone. The polyphasic evidence supports the classification of strain 20NA77.7^T as a novel species belonging to the genus Flavobacterium, for which the name Flavobacterium nakdongensis is proposed. The type strain is 20NA77.7^T (= KCTC 102000^T = LMG 33137^T).

Natural products, especially isoprenoids have many industrial applications, including medicine, fragrances, food additives, personal care and cosmetics, colorants, and even advanced biofuels. Recent advancements in metabolic engineering with synthetic biology and systems biology have drawn increased interest in microbial-based isoprenoid production. In order to engineer microorganisms to produce a large amount of value-added isoprenoids, great efforts have been made by employing various strategies from synthetic biology and systems biology. We also have engineered E. coli to produce various isoprenoids by targeting and engineering the isoprenoid biosynthetic pathways, methylerythritol phosphate (MEP), and mevalonate (MVA) pathways. Here, we introduced new combinations of the MVA pathway in E. coli with genes from biosafety level 1 (BSL 1) organisms. The reconstituted MVA pathway constructs (pSCS) are not only preferred to the living modified organism (LMO) regulation, but they also improved carotenoid production. In addition, the pSCS constructs resulted in enhanced lycopene production and cell-specific productivity compared to the previous MVA pathway combination (pSNA) in fed-batch fermentation. The pSCS constructs would not only bring an increase in isoprenoid production in E. coli, but they could be an efficient system to be applied for the industrial production of isoprenoids with industry-preferred genetic combinations.

Pigments find widespread application in the fields of food, medicine, textiles, and cosmetics. At present, synthetic colorants dominate the global pigment market. However, the environmental and health hazards associated with synthetic colorants have spurred extensive research on eco-friendly and safe alternatives. Natural pigments are particularly intriguing for meeting consumer demands and sustainable development, as they not only exhibit various vibrant color shades without discernible toxic side effects but also offer additional healthful features such as antibacterial, antioxidant, anticancer, and antiviral properties compared with their synthetic counterparts. Among natural sources, bacterial strains share distinct advantages for large-scale pigment production because of their intrinsic robustness of cellular metabolic systems. This review comprehensively outlines the bacterial sources, extraction and purification methods, structural characteristics, biological activities, and potential applications of typical pigments, including but not limited to violacein, indigoidine, melanin, carotenoids, prodigiosin, and rhodopsin. Additionally, it underscores the primary obstacles to the development and production of bacterial pigments for commercial applications, discussing feasible strategies for overcoming production bottlenecks. This work also provides valuable insights for the scientific and rational advancement of bacterial pigment development.

Hypertonic saline (HTS) resuscitation can enhance immune responses against various pathogens, however, the effect of HTS on brucellosis is yet to be defined. In this study, we found that HTS inhibited Brucella infection in mice by augmenting Th1 immunity. HTS treatment enhanced the serum cytokines production and the expression of nitric oxide synthase (NOS2) and nuclear factor kappa B (NF-ĸB) p50 and p65, crucial anti-Brucella effectors in splenocytes. In addition, HTS treatment also inhibited the phosphorylation of MAPK signaling, accompanied by the down-regulation of the autophagy marker LC3B-II. Due to directing an appropriate immune response, HTS treatment substantially decreased bacterial burden in spleen and liver tissues. In summary, corroborating previous studies showing the antimicrobial effects of HTS, our findings indicate that HTS treatment triggers a protective immune response against Brucella infection. Additionally, these results provide promising evidence of the immunomodulatory role of HTS in controlling bacterial infections.

There is increasing interest in utilizing senolytics to selectively remove senescent cells from intestinal tissues, with the aim of maintaining a healthy gut environment during aging. This strategy underscores the potential of senolytics to enhance gut health by delaying intestinal aging and positively modulating gut microbiota. Certain plant-based phytochemicals have demonstrated promising senolytic effects. Beyond their ability to eliminate senescent cells, these compounds also exhibit antioxidant and anti-inflammatory properties, reducing oxidative stress and inflammation-key drivers of age-related diseases. By selectively removing senescent cells from the intestine, senolytic phytochemicals contribute to an improved intestinal inflammatory environment and promote the growth of a diverse microbial community. Ultimately, the dietary intake of these senolytic phytochemicals aids in maintaining a healthier intestinal microenvironment by targeting and clearing aged enterocytes.

Rhodobacter sphaeroides is a strain capable of both photoautotrophic and chemoautotrophic growth, with various metabolic pathways that make it highly suitable for converting carbon dioxide into high value-added products. However, its low transformation efficiency has posed challenges for genetic and metabolic engineering of this strain. In this study, we aimed to increase the transformation efficiency of R. sphaeroides by deleting the rshI gene coding for an endogenous DNA restriction enzyme that inhibits. We evaluated the effects of growth conditions for making electrocompetent cells and optimized electroporation parameters to be a cuvette width of 0.1 cm, an electric field strength of 30 kV/cm, a resistance of 200 Ω, and a plasmid DNA amount of 0.5 μg, followed by a 24-h recovery period. As a result, we observed over 7,000 transformants per μg of DNA under the optimized electroporation conditions using the R. sphaeroides ΔrshI strain, which is approximately 10 times higher than that of wild-type R. sphaeroides under standard bacterial electroporation conditions. These findings are expected to enhance the application of R. sphaeroides in various industrial fields in the future.

Gamma herpesviruses, including Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV), are key contributors to the development of various cancers through their ability to manipulate host cellular pathways. This review explores the intricate ways these viruses rewire host metabolic pathways to sustain viral persistence and promote tumorigenesis. We look into how EBV and KSHV induce glycolytic reprogramming, alter mitochondrial function, and remodel nucleotide and amino acid metabolism, highlighting the crucial role of lipid metabolism in these oncogenic processes. By understanding these metabolic alterations, which confer proliferative and survival advantages to the virus-infected cells, we can identify potential therapeutic targets and develop innovative treatment strategies for gamma herpesvirus-associated malignancies. Ultimately, this review underscores the critical role of metabolic reprogramming in gamma herpesvirus oncogenesis and its implications for precision medicine in combating virus-driven cancers.

Aquaculture products, such as clams, scallops, and oysters, are major vectors of fecal-derived pathogens. Male-specific and somatic coliphages are strongly correlated with human noroviruses, the major enteric viruses worldwide. Geographic information system with local land-use patterns can also provide valuable information for tracking sources of fecal-derived pathogens. We examined distributions of four fecal indicator microorganisms, i.e., male-specific and somatic coliphage, total coliform, and Escherichia coli (E. coli) in three river and seawater sampling sites located on the coast of Gomso Bay in the Republic of Korea during the sampling period (from March 2015 to January 2016). Geospatial analyses of fecal indicators and correlations between environmental parameters and fecal indicators or among fecal indicators were also performed. Overall, river water samples showed highest concentrations of both types of coliphage in summer (July 2015). High concentrations of both total coliform and E. coli were detected in river water during the period from July to September 2015. High concentrations of all fecal indicators were found at site GL02, located in the innermost part of Gomso Bay, which has high-density agriculture and residential areas. Environmental factors related to precipitation-cumulative precipitation on and from 3 days before the sampling day (Prep-0 and Prep-3, respectively)-and salinity were strongly correlated with the concentrations of all fecal indicators. The present results suggest that investigations of multiple fecal indicators with systemic geospatial information are necessary for precisely tracking fecal contaminations of aquaculture products.

With the recent stringent criteria for antibiotic susceptibility in probiotics, the presence of antibiotic resistance genes and plasmids associated with their transfer has become a limiting factor in the approval of probiotics. The need to remove genes related to antibiotic resistance and virulence through plasmid curing for the authorization of probiotics is increasing. In this study, we investigated the curing efficiency of ethidium bromide, acridine orange, and novobiocin at different concentrations and durations in five strains of plasmid-bearing lactic acid bacteria and examined the curing characteristics in each strain. Limosibacillus reuteri and Lacticaseibacillus paracasei exhibited curing efficiencies ranging from 5% to 44% following treatment with ethidium bromide (10-50 μg/ml) for 24-72 h, while Lactobacillus gasseri showed the highest efficiency at 14% following treatment with 10 μg/ml novobiocin for 24 h. Lactiplantibacillus plantarum, which harbors two or more plasmids, demonstrated curing efficiencies ranging from 1% to 8% after an additional 72-h treatment of partially cured strains with 10 μg/ml novobiocin. Plasmid curing in strains with larger plasmids exhibited lower efficiencies and required longer durations. In strains harboring two or more plasmids, a relatively low curing efficiency with a single treatment and a high frequency of false positives, wherein recovery occurred after curing, were observed. Although certain strains exhibited altered susceptibilities to specific antibiotics after curing, these outcomes could not be attributed to the loss of antibiotic resistance genes. Furthermore, the genomic data from the cured strains revealed minimal changes throughout the genome that did not lead to gene mutations.

Protein solubility and purification challenges often hinder the large-scale production of valuable proteins like brazzein, a potent sweet protein with significant health benefits and commercial potential. This study introduces two novel tools to overcome protein expression and purification bottlenecks: a gnd_v2 fusion tag and an engineered Tobacco Etch Virus (TEV) protease. The gnd_v2 tag, derived from 6-phosphogluconate dehydrogenase, was engineered to improve the soluble expression of brazzein. This tag increased brazzein's solubility by four times compared to the wild-type gnd tag, marking a significant advancement in efficient brazzein production. To address the challenge of cleaving the fusion tag, we engineered a TEV protease variant with high efficiency, particularly at the glutamine residue at brazzein's P1' site - a known difficulty for wild-type TEV proteases. We achieved streamlined production of pure, functional brazzein by integrating this tailored protease cleavage with an ultrafiltration-based purification protocol. Notably, the purified brazzein demonstrated a sweetness potency approximately 2500 times that of sucrose, highlighting its potential as a high-intensity natural sweetener. While this study focused on brazzein, the gnd_v2 tag shows promise for enhancing the solubility of other challenging proteins. More broadly, this work presents a versatile toolset for the scalable production of diverse functional proteins, with significant implications for industrial applications in food and pharmaceutical domains.