World journal of microbiology & biotechnology最新文献

Astaxanthin is a bioactive natural pigment with antioxidant properties. It has extensive applications within the industrial sector as well as in human and animal health. Mucor circinelloides is a zygomycete fungus that accumulates β-carotene as the main carotenoid compound. M. circinelloides is a well-known model organism among Mucorales for studying carotenogenesis in fungi, which makes it a promising candidate for the biotechnological production of carotenoids. In this study, β-carotene hydroxylase (crtR-B) and ketolase (bkt) genes (codon-optimized) were coexpressed from Haematococcus pluvialis in M. circinelloides using two potent promoters gpd1 and zrt1 respectively to generate an astaxanthin-producing biofactory. Following 72 h of cultivation, the recombinant M. circinelloides Mc-57 obtained in this study produced 135 ± 8 µg/g of astaxanthin. This is the highest reported amount in M. circinelloides to date. The mRNA levels of crtR-B and bkt in Mc-57 were assayed using RT-qPCR. These levels showed a 5.7-fold increase at 72 h and a 5.5-fold increase at 24 h, respectively, compared to the control strain. This demonstrated the successful overexpression of both genes, which correlated with the production of astaxanthin in the Mc-57. Moreover, the addition of glutamate (2 g/L) and mevalonate (15 mM) resulted in an increase in astaxanthin production in the recombinant strain. The results showed that the combined addition of these metabolic precursors resulted in 281 ± 20 µg/g of astaxanthin, which is 2.08-fold higher than the control medium (135 ± 8 µg/g). The addition of metabolic precursors also positively impacted the biomass growth of Mc-57, reaching 11.2 ± 0.57 g/L compared to 9.1 ± 0.23 g/L (control medium). The study successfully addressed the challenge of balancing the accumulation of astaxanthin with biomass growth, which has been regarded as common bottleneck in the metabolic engineering of microbial cells. The development of a recombinant fungal strain of M. circinelloides not only increased astaxanthin content. Additionally, it provided a foundation for further improvement of the biotechnological production of astaxanthin in M. circinelloides.

Oil, mineral processing and environmental restoration can be dangerous processes. Attempts are often made to apply microorganisms to reduce the risks, but the adaptability of terrestrial organisms is often weak. Although genetically engineered strains can improve their environmental adaptability through targeted modification, there are problems such as metabolite accumulation, poor plasmid stability and potential pathogenicity. Screening of extremophiles from the natural environment has become an inevitable choice. The special environment in the deep sea (high pressure, low temperature, low nutrition, high salinity) is a natural place for extremophiles to grow and survive, thus screening of extremophiles from the deep sea is conducive to the green and sustainable development of industry. In this paper, the application status and problems of genetically engineered strains are reviewed based on the microorganisms needed for extreme industry. This paper focuses on the application status and advantages of deep-sea microorganisms. It is found that their advantages are strong adaptability, stable gene, friendly environment, simple and convenient technology (compared with genetic engineering), which has a broad industry processes application prospect. This review broadens the scope of microbial applications.

Salmonella Typhimurium (STM), a zoonotic pathogen, can adjust its metabolic pathway according to the variations in the partial pressure of atmospheric oxygen and nitrate via fumarate nitrate reductase regulator (Fnr) and NarL, the response regulator for nitrate reductase. Both Fnr and NarL have been individually reported to be the contributors of virulent phenotypes of STM. Hypoxia along with nitrate-rich environment are prevalent in macrophages and the Salmonella-induced inflammatory lumen of the host's large intestine activates both fnr and narL genes. In this study, the double (fnr and narL) knockout STM showed a synergistic reduction in the swimming (62%), swarming (84%) and biofilm density (86%) phenotypes anaerobically in association with its significant aerobic attenuation. The intracellular replication of the double mutant was reduced by 2.3 logs in chicken monocyte-derived macrophages. Furthermore, the competitive index of the double mutant in liver and spleen was found to be 0.3 and 0.44 respectively at 120 h post-infection (PI) in mice. Surprisingly, no double mutant could be recovered from the infected mouse liver 3 days PI. Histopathological findings showed moderate infiltration of mononuclear cells in the large intestine of mice infected with double mutant, but severe infiltration was seen with the wild-type strain.

Coal, a sedimentary rock harbours a complex microbial community that plays a significant role in its formation and characteristics. However, coal metagenome sequencing and studies were less, limiting our understanding of this complex ecosystem. This study aimed to reconstruct high-quality metagenome-assembled genomes (MAGs) from the coal sample collected in the Neyveli mine to explore the unrevealed diversity of the coal microbiome. Using Illumina sequencing, we obtained high-quality raw reads in FASTQ format. Subsequently, de novo assembly and binning with metaWRAP software facilitated the reconstruction of coal MAGs. Quality assessment using CheckM identified 10 High-Quality MAGs (HQ MAGs), 7 medium-quality MAGs (MQ MAGs), and 6 low-quality MAGs (LQ MAGs). Further analysis using GTDB-Tk revealed four HQ MAGs as known species like Dermacoccus abyssi, Sphingomonas aquatilis, Acinetobacter baumannii, and Burkholderia cenocepacia. The remaining six HQ MAGs were classified as Comamonas, Arthrobacter, Noviherbaspirillum, Acidovorax, Oxalicibacterium, and Bordetella and designated as novel genomes by the validation of digital DNA-DNA hybridization (dDDH). Phylogenetic analysis and further pangenome analysis across the phylogenetic groups revealed a similar pattern with a high proportion of cloud genes. We further analysed the functional potential of these MAGs and closely related genomes using COG. The comparative functional genomics revealed that novel genomes are highly versatile, potentially reflecting adaptations to the coal environment. BlastKOALA was used to conduct a detailed analysis of the metabolic pathways associated with the MAGs. This study highlights the comparative genomic analysis of novel coal genomes with their closely related genomes to understand the evolutionary relationships and functional properties.

Ganoderma lucidum, known as the "mushroom of immortality," is a white rot fungus renowned for its medicinal properties, attributed to its bioactive compounds. Although species with similar morphological traits to G. lucidum are found across the globe, precise identification is made possible through DNA barcoding and molecular phylogenetic analysis. Global cultivation and wild harvesting of G. lucidum are both done in response to the growing market needs. Artificial cultivation is typically performed on sawdust, but other woody substrates and the wood log method are also employed. This cultivation leverages the fungus's ecological role in converting industrial and agricultural solid wastes into biomass, thereby producing functional food and potential pharmaceutical sources. The review consolidates research on various aspects of, including cultivation methods (sawdust, agricultural waste, wood logs, and submerged fermentation), and the current global market conditions.

In recent years, reducing the concentration of carbon dioxide in the atmosphere has become an important issue. Microalgae have a higher photosynthetic efficiency and growth rate than higher plants; thus, biological carbon dioxide fixation using microalgae is attracting particular attention as an efficient carbon dioxide fixation method. However, under dilute atmospheric conditions, microalgae exhibit lower growth rates and reduced carbon dioxide fixation efficiency. In recent years, technology that can efficiently fix carbon dioxide, even in the atmosphere, using a microalgae co-culture system that co-cultivates microalgae and heterotrophic microorganisms has attracted attention. In such a co-culture system, it is believed that a mutualistic relationship is established between microorganisms through the exchange of various compounds. This review focuses on the application of a co-culture system of microalgae and heterotrophic microorganisms for bioproduction and wastewater treatment. In addition, research to elucidate the mutualistic relationships in microalgal co-culture systems using analytical methods that have been widely used in recent years, such as next-generation sequencing technology, is also discussed. In the future, it is expected that the use of microalgae co-culture systems will expand on an industrial scale through the development of key technologies, such as efficient genetic modification techniques for microalgae and their heterotrophic microorganism partners, large-scale cultivation facilities that can efficiently cultivate microalgae, and stable control techniques for co-culture systems using advanced technology.

Macrofungi (or mushrooms) are essential for agriculture, food, and ecology. Although research on the growth and development of macrofungi (GDM) can provide insights into their biological characteristics and metabolite synthesis mechanisms, further exploration is needed for a systematic and visual analysis of the current research progress on GDM. To comprehensively understand the research status and development trend of GDM, a total of 545 scientific literature related to GDM in the Web of Science Core Collection database from 2008 to 2024 were searched and selected as research objects. The general information (publication year, country, institution, and cited journal) and the specific information (co-authorship, keyword co-occurrence, and references with strong citation bursts) were mined and visualized in detail based on CiteSpace software. These analyses demonstrated that related research is still fashionable, and China is dominant and influential in this field. More frequent and in-depth cooperation among authors, institutions and regions is conducive to promoting the research on GDM. Additionally, the quantity and cluster analyses of keywords and references demonstrated that medicinal/edible macrofungi and sustainable development (e.g. mushroom substrate reuse) may be research hotspots and will remain popular in the coming years. This research aims to supply researchers with up-to-date knowledge and cutting-edge issues related to GDM by providing a visually appealing representations on quantitative GDM studies.

Flagella is a well-known bacterial structure crucial for motility, which also plays pivotal roles in pathogenesis. Arcobacter butzleri, an enteropathogen, possesses a distinctive polar flagellum whose functional aspects remain largely unexplored. Upon investigating the factors influencing A. butzleri motility, we uncovered that environmental conditions like temperature, oxygen levels, and nutrient availability play a significant role. Furthermore, compounds that are found in human gut, such as short-chain fatty acids, mucins and bile salts, have a role in modulating the motility, and in turn, the pathogenicity of A. butzleri. Further investigation demonstrated that A. butzleri ΔflaA mutant showed a reduction in motility with a close to null average velocity, as well as a reduction on biofilm formation. In addition, compared with the wild-type, the ΔflaA mutant showed a decreased ability to invade Caco-2 cells and to adhere to mucins. Taken together, our findings support the role of environmental conditions and gut host associated compounds influencing key physiological aspects of the gastrointestinal pathogen A. butzleri, such as motility, and support the role of the flagellum on bacterial virulence.

Bacteriocin is a kind of natural substance that can effectively inhibit bacteria, but its production usually limited by environment. Co-culture is a strategy to stimulate bacteriocin production. Bifidocin A produced by Bifidobacterium animalis BB04, is a novel bacteriocin with a broad-spectrum antimicrobial active of foodborne bacteria. In order to enhance bifidocin A production, bacteriocin-inducing strains were screened firstly in co-cultivation. Then, the molecular mechanism of co-cultural induction was investigated by transcriptomic and proteomic analysis. Finally, the key inducing metabolites were identified by using targeted metabolomic technology. The results showed that Wickerhamomyces anomalus Y-5 in co-cultivation could significantly enhance bifidocin A production, with a 3.00-fold increase compared to mono-culture. The induction may not depend on direct contact with cells and may instead be attributed to be continuous exposure to inducing substances at specific concentration. In co-cultivation, W. anomalus Y-5 up-regulated Hxk2 and Tap42 to activate Glucose-cAMP and Tor and HOG-MAPK pathway, stimulated the expression of the retrograde gene, produced glutamine and glycerol to maintain activity. During this process, glutamine, inosine, guanosine, adenine, uracil, fumaric acid and pyruvic acid produced by W. anomalus Y-5 could induce the synthesis of bifidocin A. In conclusion, W. anomalus Y-5 in co-cultivation induced the synthesis of bifidocin A by regulating various signaling pathways to produce inducing substances. These findings establish a foundation for high-efficient synthesis of bifidocin A and provide a new perspective into the industrial production of bacteriocin.

The phenolic antioxidant 2,6-Di-tert-butyl-p-cresol (BHT) has been detected in various environments and is considered a potential threat to aquatic organisms. Algal-bacterial interactions are crucial for maintaining ecosystem balance and elemental cycling, but their response to BHT remains to be investigated. This study analyzed the physiological and biochemical responses of the microalga Isochrysis galbana and the changes of associated bacterial communities under different concentrations of BHT stress. Results showed that the biomass of I. galbana exhibited a decreasing trend with increasing BHT concentrations up to 40 mg/L. The reduction in chlorophyll, carotenoid, and soluble protein content of microalgal cells was also observed under BHT stress. The production of malondialdehyde and the activities of superoxide dismutase, peroxidase, and catalase were further determined. Scanning electron microscopy analysis revealed that BHT caused surface rupture of the algal cells and loss of intracellular nutrients. Proteomic analysis demonstrated the upregulation of photosynthesis and citric acid cycle pathways as a response to BHT stress. Additionally, BHT significantly increased the relative abundance of specific bacteria in the phycosphere, including Marivita, Halomonas, Marinobacter, and Alteromonas. Further experiments confirmed that these bacteria had the ability to utilize BHT as the sole carbon resource for growth, and genes related to the degradation of phenolic compounds were detected through pangenome analysis.