World journal of microbiology & biotechnology最新文献

Rare earth elements (REE) are metals in great demand by the overall industry, they are present in most electronic equipment, ceramics and green energy generation. The REE are currently at high risk of supply and have become critical to world development. The increasing demand for REE brings out the necessity to obtain these metals from multiple sources. Chemically centered processes like leaching and resin adsorption have been the predominant techniques to extract REE from primary and secondary sources. These processes are harsh and damaging to the environment due to the use of strong inorganic acids, high temperatures and low regeneration potential. It has become necessary to find ways to obtain these metals without causing environmental harm. Bioprocesses may prove to be a potential solution to the extraction and recovery of REE in a less harmful way. Bioprocesses involve the use of microorganisms to produce acids, chelating substances or to serve as sorbates, allowing for the solubilization and adsorption of metals, respectively. Since these processes utilize microorganisms, they can be seen as renewable and clean, though selectivity and process time may impact effectiveness. In this review the two main bioprocesses: bioleaching and biosorption will be analyzed regarding their mechanisms, process parameters and challenges, a comparison discussing the two is also expressed.

This study investigates the biocalcification potential of Bacillus subtilis ATCC 6633, a ureolytic bacterium, for the biohealing of marble surfaces through calcium carbonate (CaCO₃) precipitation. Comparative experiments were conducted using live and dead bacterial cells on CO₂-pre-treated and untreated marble samples, with calcium chloride and calcium acetate employed as calcium sources, to evaluate their effects on crystal polymorphism and surface modification. The results show that bacterial viability and calcium source jointly influence mineral phase formation, with live cells predominantly promoting the formation of stable calcite and aragonite, whereas dead cells and calcium acetate favor the formation of metastable vaterite. Microstructural and mineralogical analyses using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and atomic force microscopy (AFM) confirmed substantial CaCO₃ deposition on marble surfaces. AFM measurements indicated a reduction in maximum pore depth, defined as the vertical height difference between pore bottoms and the surrounding marble surface, from 35.00 ± 7.07 μm in control samples to 22.50 ± 8.20 μm in biocalcified samples, reflecting partial filling of pores and cracks. In addition, micropores (0.02-0.03 mm) were fully filled, while macropores (3-5 mm) were partially occluded by crystalline deposits. CO₂ pre-treatment enhanced surface carbon availability and promoted more uniform CaCO₃ nucleation, as supported by SEM-EDX and XRD analyses. Overall, these findings indicate that microbially induced carbonate precipitation (MICP), combined with appropriate surface preconditioning and calcium source selection, represents a potential and sustainable strategy for marble conservation and related bio-construction applications.

Press mud is an acidic by-product of sugarcane processing that is commonly discarded, despite containing components with potential agricultural value. This study assessed sugarcane mill press mud through physicochemical, microbiological and enzymatic analyses to evaluate its environmental implications and suitability as a soil amendment. The material was slightly acidic (pH 6.4) and rich in essential nutrients, including potassium (1061.06 ppm), magnesium (624.96 ppm), calcium (461.06 ppm) and phosphorus (513.11 ppm). However, elevated metals such as aluminium (2083.22 ppm), iron (2342.57 ppm), manganese (85.90 ppm), zinc (60.84 ppm), copper (17.70 ppm), lead (3.10 ppm) and chromium (4.18 ppm), together with the detection of the pollutant 2,4-di-tert-butylphenol (2,4-DTBP), suggest the need for proper regulated application to mitigate environmental risks. Microbial profiling across acidic (6.4), neutral (7.0) and alkaline (9.5) conditions revealed diverse bacterial taxa. Acidic conditions yielded Escherichia coli (PQ001953), Bacillus licheniformis (PQ001957) and Moraxella catarrhalis (PQ047632); neutral conditions favored Herbaspirillum seropedicae (PQ008927), Enterococcus faecium (PQ012564) and Micrococcus luteus (PQ012569); while alkaline conditions supported Bacillus subtilis (PQ012572), Listeria ivanovii (PQ060442) and Paracoccus pantotrophus (PQ012574). Notably, E. coli, H. seropedicae and M. luteus exhibited pronounced ligninolytic enzyme activity, indicating a capacity to degrade complex organic substrates. Plant growth trials using mustard (Brassica campestris) demonstrated that a 5:1 soil-to-press-mud ratio significantly enhanced plant growth relative to untreated soil. Collectively, these findings indicate that when applied in controlled quantities, press mud, represents a promising bioresource with valuable ligninolytic and plant growth-promoting microbial communities, while warranting careful oversight due to its contaminant load.

Microbial melanin, a natural pigment produced by diverse bacteria and fungi, has emerged as a sustainable and biotechnologically viable alternative to traditional sources. This review summarizes recent advancements in the field of microbial melanin, focusing on its biosynthetic pathways, production optimization strategies, challenges, and potential applications. It specifically highlights the pivotal roles of omics technologies and genetic engineering in elucidating biosynthetic mechanisms and enhancing yield. We first detail the different types of microbial melanin, along with the synthesis mechanisms and key intermediates of the three main biosynthetic pathways. Subsequently, the latest strategies for increasing yield are summarized, emphasizing cultivation parameters and biotechnological approaches. This review further explores the main analytical techniques for structural characterization and proposes potential applications of emerging technologies. Despite encouraging progress, this review also highlights the ongoing challenges and controversies in this field. Finally, we provide a perspective on future research directions, emphasizing the need to integrate synthetic biology, advanced analytical techniques, and comprehensive safety evaluations to bridge the gap between fundamental research and industrialization. This work aims to provide a comprehensive and critical reference for researchers in this rapidly developing field.

We assessed the fungal diversity and functional profile of two soils collected in contrasting environments: one unimpacted soil, Hennequin Point, King George Island, and the other impacted by whale oil, Whalers Bay, Deception Island, Maritime Antarctica, using metagenomic approaches. Taxonomic assignment revealed a predominance of Ascomycota in both soils. A total of 20 and 23 fungal genera were identified at King George and Deception islands, respectively. The rare genera Thermothielavioides, Pyricularia, Fulvia, and Coccidioides were detected in the Antarctic environment. The highest fungal diversity was observed in the soil of Deception Island. Canonical analysis of King George Island soil displayed higher values of total organic carbon, sulfur, and lead, which may have favored the presence of the genera Puccinia, Lachancea, and Akanthomyces. The soil of Deception Island presented correlations with higher levels of nitrogen, chromium, and iron, with a predominance of genera such as Aspergillus, Trichoderma, and Malassezia. Functional analysis revealed distinct adaptive strategies among the soils. Domains related to translation, gene regulation, and metabolic efficiency were observed for fungi in Hennequin Point soil, King George Island, suggesting resource optimization in a cold, moss-covered environment. In Deception Island soil, fungal redox metabolism, iron acquisition, and the degradation of nitrogen compounds were highlighted, reflecting adaptation to an anthropogenic soil rich in metal oxides. Both soils exhibited functional fungal networks involved in hydrolytic enzymatic pathways that may act in the decomposition of organic compounds. New sequencing must be performed due to the insufficient depth of the data. Our results indicated that the soil from Hennequin Point and Whalers Bay exhibited distinct fungal communities, which can be influenced by environmental and ecological factors such as moss, oil, and heavy metals encountered in pristine and oil-impacted soils resulting from anthropogenic activities over the years.

Leptospirosis, a globally prevalent zoonosis caused by pathogenic and intermediate Leptospira species, poses significant threats to public health and livestock industries. Despite its substantial impact, knowledge gaps persist regarding the prevalence and genetic diversity of Leptospira strains in many regions, including South America. This study aimed to characterize a diverse collection of Leptospira strains isolated from various sources in Colombia to enhance our understanding of the genetic diversity within this genus. Using a tiered approach combining conventional and genomic methods, we genotyped 55 isolates from various sources using 16S rRNA and rpoB gene sequencing, DNA ribotyping, and Multiple-Locus Variable-Number Tandem Repeat Analysis (MLVA). Most isolates were classified into phylogenetic groups containing pathogenic and intermediate strains of L. interrogans and L. wolffii, respectively, which was corroborated by ribotyping and MLVA. Whole-genome sequencing of selected strains revealed distinct genomic characteristics compared to related strains. Pan-genome analysis identified strain-specific genes, primarily hypothetical, while virulence factor analysis distinguished species-specific patterns. Furthermore, CRISPR-Cas system analysis uncovered genetic variations among the isolates. This study provides a framework for understanding Leptospira genetic diversity in Colombia and its potential implications on human and animal health. Our findings highlight the need for improved diagnostic methods and surveillance strategies that encompass both pathogenic and intermediate Leptospira species, which could significantly impact public health policies and veterinary practices in the region.

Aquaculture plays a vital role in ensuring global food security. However, the use of Artemia as crucial live food in the hatchery industry is often limited by cost, availability, and nutritional variability. This study investigated the potential of Purple Non-Sulphur Bacteria isolates, specifically Rhodopseudomonas sp. strain AZR1 and Rhodopseudomonas sp. strain AZW1, isolated from a mangrove ecosystem in Terengganu, Malaysia, as a sustainable feed supplement for Artemia. Following 16 S rRNA gene sequencing, these strains were characterized for growth kinetics, carotenoid production, nutritional composition, and fatty acid profiles to determine the best isolate for use as Artemia feed. Strain AZR1 outperformed strain AZW1, exhibiting higher growth rates (maximum 4.93 g/L dry cell weight vs. 3.9 g/L), better carotenoid production (10.16 mg/g vs. 7.68 mg/g), and enhanced nutritional values (53.17% protein, 7.77% lipid vs. 50.55% protein, 6.76% lipid), with elevated levels of astaxanthin (0.324 µg/mL vs. 0.254 µg/mL) and β-carotene (0.228 µg/mL vs. 0.16 µg/mL). Subsequently, strain AZR1 was evaluated as a diet for Artemia franciscana under both hatchery and small-scale Artemia test conditions, comparing its effects to Baker's yeast (control) and a Palm Kernel Cake by-product (PKC Nutri+). Results revealed that Artemia fed with strain AZR1 displayed significantly improved growth (length 9.6-10.11 mm), enhanced water quality (low ammonium concentrations: 2 mg/L vs. 8 mg/L for both yeast and PKC Nutri+), increased resistance to Vibrio campbellii (91.67% survival after challenge with 10⁸ cells/mL), upregulated expression of immune-related genes (Hsp70, Hsp90, proPO), and superior nutritional profiles (50.96% protein, 6.62% lipid, enhanced carotenoid composition) compared to the other feeds. However, while PKC Nutri + exhibited higher levels of polyunsaturated fatty acids (PUFAs), strain AZR1 presented a safer, healthier, and mycotoxin-free alternative. This study demonstrates the potential of strain AZR1 as a promising candidate for sustainable single-cell protein (SCP) production, and its beneficial effect on Artemia growth performance, nutritional quality, disease resistance, and immune function.

Despite the extensive use of chemical controls in weed management programs, the effect of herbicides on soil microbial communities is inconclusive. In this study, the effects of glufosinate-ammonium (T1) and metsulfuron-methyl (T2) application at the recommended rate (495 g a.i./ha and 15 g a.i./ha) on the soil bacterial communities within an oil palm plantation were investigated using 16 S rRNA gene high-throughput sequencing. Herbicides were applied in the rhizosphere area of oil palms, and soil microbial communities were assessed over multiple time-points, for 9 months. Herbicides did not drastically influence the alpha or beta diversity of the soil bacterial community, but a significant decrease in the Shannon and inverse Simpson diversity indices was observed at 6 months after application (MAA) and recovered at 9 MAA in T2. The relative abundance of selected beneficial soil bacteria strains was stable across both herbicide treatments and sampling times. FAPROTAX functional profile prediction showed minimal influence of herbicides on soil bacterial activity and functions. The complexity and stability of the bacterial network had increased in T1 but were reduced in the rhizosphere soil in T2. Herbicide application was shown to increase the abundance of the bacterial phylum Latescibacterota, which may have the potential to metabolise chemical compounds that could be explored for future bioremediation use. Our results suggested that application of glufosinate-ammonium and metsulfuron-methyl at the recommended rate may not adversely affect soil bacterial communities or their functions in oil palm plantations.

Kluyveromyces marxianus is a fast-growing, food-grade yeast with broad substrate utilization, however, its limited expression tools hinder its synthetic biology applications. Here, we developed single- and dual-gene expression systems based on screened elements, including a promoter pENO and a bidirectional promoter pHTX. These systems enabled stable expression across multiple K. marxianus strains, with expression levels affected by genetic element combinations, carbon source, and culture time. Using the single-gene system with a short intergenic sequence (IGG) for bicistronic expression, the production of leghemoglobin from Vigna angularis (VaHB) reached 30.4 mg/L using galactose as carbon source. In contrast, the dual-gene system achieved 48.4 mg/L of VaHB with the co-expression of HEM1, enhancing heme biosynthesis using glucose as a carbon source. Additionally, Simian Virus 40 (SV40) nuclear localization signals (NLS) directed fluorescent proteins to the nucleus, enabling subcellular targeting. This toolkit supports efficient and context-responsive gene expression in K. marxianus, facilitating its development as a versatile microbial chassis for industrial protein production and synthetic biology applications.