Fungal biofilm is a microbial community composed of fungal cells and extracellular polymeric substances (EPS). In recent years, fungal biofilms have played an increasingly important role in many fields. However, there are few studies on fungal biofilms and their related applications and development are still far from enough. Therefore, this review summarizes the composition and function of EPS in fungal biofilms, and improves and refines the formation process of fungal biofilms according to the latest viewpoints. Moreover, based on the study of Saccharomyces cerevisiae and Candida albicans, this review summarizes the gene regulation network of fungal biofilm synthesis, which is crucial for systematically understanding the molecular mechanism of fungal biofilm formation. It is of great significance to further develop effective methods at the molecular level to control harmful biofilms or enhance and regulate the formation of beneficial biofilms. Finally, the quorum sensing factors and mixed biofilms formed by fungi in the current research of fungal biofilms are summarized. These results will help to deepen the understanding of the formation process and internal regulation mechanism of fungal biofilm, provide reference for the study of EPS composition and structure, formation, regulation, group behavior and mixed biofilm formation of other fungal biofilms, and provide strategies and theoretical basis for the control, development and utilization of fungal biofilms.

Background: Marine microbes are a large and diverse group, which are exposed to a wide variety of pressure, temperature, salinity, nutrient availability and other environmental conditions. They provide a huge potential source of novel enzymes with unique properties that may be useful in industry and biotechnology. To explore the lipolytic genetic resources in the South China Sea, 23 sediment samples were collected in the depth < 100 m marine areas. Results: A metagenomic library of South China Sea sediments assemblage in plasmid vector containing about 194 Mb of community DNA was prepared. Screening of a part of the unamplified library resulted in isolation of 15 unique lipolytic clones with the ability to hydrolyze tributyrin. A positive recombinant clone (pNLE1), containing a novel esterase (Est_p1), was successfully expressed in E. coli and purified. In a series of assays, Est_p1 displayed maximal activity at pH 8.57, 40°C, with ρ-Nitrophenyl butyrate (C₄) as substrate. Compared to other metagenomic esterases, Est_p1 played a notable role in specificity for substrate C₄ (k _cat/K _m value 11,500 S^-1m M^-1) and showed no inhibited by phenylmethylsulfonyl fluoride, suggested that the substrate binding pocket was suitable for substrate C₄ and the serine active-site residue was buried at the bottom of substrate binding pocket which sheltered by a lid structure. Conclusions: Esterase, which specificity towards short chain fatty acids, especially butanoic acid, is commercially available as potent flavoring tools. According the outstanding activity and specificity for substrate C₄, Est_p1 has potential application in flavor industries requiring hydrolysis of short chain esters.

Root-associated microorganisms, particularly plant growth-promoting rhizobacteria (PGPR) from the Bacillus genus, play a crucial role in enhancing crop yield and health. In this study, a Bacillus strain was isolated from the rhizosphere soil of maize and identified as Bacillus velezensis D103. The primary objective of this research was to evaluate the potential of D103 as a PGPR. Laboratory tests demonstrated that D103 is capable of nitrogen fixation, inorganic phosphorus solubilization, potassium solubilization, and the synthesis of indole-3-acetic acid, ammonia, siderophores, amylase, protease, cellulase, β-1,3-glucanase, and 1-aminocyclopropane-1-carboxylate deaminase. Additionally, D103 exhibited swimming and swarming motility, biofilm formation, and an antagonistic activity against pathogenic fungi. Genome mining identified genes associated with growth promotion and biocontrol activities. In a hydroponics experiment, maize plants treated with a D103 suspension at a cell density of 10 ³ CFU·mL ⁻¹ resulted in the most pronounced showed significant growth stimulation, with shoot length and total root length increasing by 43% and 148%, respectively. These results support the potential of D103 as an effective PGPR for promoting maize crop growth. IMPORTANCE: In this study, we assessed the capacity of D103 to promote plant growth and examined the effects of hydroponic experiments inoculated with this strain on the growth of maize seedlings. We sequenced and analyzed the complete genome of D103, identifying several genes and gene clusters associated with plant growth promotion and resistance to pathogenic fungi, thus revealing the plant growth-promoting mechanisms of this strain. The isolation and characterization of new strains with beneficial traits are essential for expanding microbial resources available for biofertilizer production. Collectively, these findings highlight the promising potential of Bacillus velezensis D103 as a biofertilizer for agricultural applications.

Plant growth-promoting rhizobacteria (PGPR) can produce hormone-like substances, promote plant nutrient uptake, enhance plant resistance, inhibit the growth of pathogenic bacteria, and induce plant resistance to biotic and abiotic stresses. Bacillus is one of the most studied genera that promote plant root development. Since its discovery in 2009, B. aryabhattai has shown promising properties such as promoting plant growth and improving crop yield. However, the mechanisms of B. aryabhattai promoting plant growth remain to be investigated. In this study, the chromosome of B. aryabhattai strain LAD and five plasmids within the cell were sequenced and annotated. The genome, with a length of 5,194,589 bp and 38.12% GC content, contains 5,288 putative protein-coding genes, 39 rRNA, and 112 tRNA. The length of the five plasmids ranged from 116,519 to 212,484 bp, and a total of 810 putative protein-coding genes, 4 rRNA, and 32 tRNA were predicted in the plasmids. Functional annotation of the predicted genes revealed numerous genes associated with indole-3 acetic acid (IAA) and exopolysaccharides (EPSs) biosynthesis, membrane transport, nitrogen cycle metabolism, signal transduction, cell mobility, stress response, and antibiotic resistance on the genome which benefits the plants. Genes of carbohydrate-active enzymes were detected in both the genome and plasmids suggesting that LAD has the capacity of synthesizing saccharides and utilizing organic materials like root exudates. LAD can utilize different carbon sources of varied carbon chain length, i.e., methanol, acetate, glycerol, glucose, sucrose, and starch for growth and temperature adaptation suggesting a high versatility of LAD for thriving in fluctuating environments. LAD produced the most EPSs with sucrose as sole carbon source, and high concentration of IAA was produced when the maize plant was cultivated with LAD, which may enhance plant growth. LAD significantly stimulated the development of the maize root. The genome-based information and experimental evidence demonstrated that LAD with diverse metabolic capabilities and positive interactions with plants has tremendous potential for adaptation to the dynamic soil environments and promoting plant growth.

Increasing salinity undermines soil fertility and imposes great threats to soil ecosystem productivity and ecological sustainability. Microbes with the ability to adapt to environmental adversity have gained increasing attention for maintenance and restoration of the salt-affected soil ecosystem structure and functioning; however, the characterization of microbial communities in saline–sodic soils remains limited. This study characterized the bacterial community composition and diversity in saline–sodic soils along a latitude gradient across Northeast China, aiming to reveal the mechanism of physicochemical and geographic characteristics shaping the soil bacterial communities. Our results showed that the bacterial community composition and diversity were significantly impacted by soil pH, electrical conductivity, Na⁺, K⁺, Cl⁻, and CO₃²⁻. Significant differences in bacterial diversity were revealed along the latitude gradient, and the soil factors accounted for 58.58% of the total variations in bacterial community composition. Proteobacteria, Actinobacteria, Gemmatimonadetes, Chloroflexi, and Bacteroidetes were dominant across all samples. Actinobacteria and Gemmatimonadetes were significantly enriched in high soil sodicity and salinity, while Acidobacteria and Proteobacteria were suppressed by high pH and salt stress in the saline–sodic soils. Increase in soil pH and salinity significantly decreased bacterial species richness and diversity. Community composition analysis indicated that bacterial taxonomic groups (e.g., Bacillus, Egicoccus, Truepera, Halomonas, and Nitrolancea) that may adapt well to high salinity were greatly enriched in the examined soils. The findings collectively evidenced that bacterial community composition and diversity in a broad biographic scale were determined by niche-based environmental characteristics and biotic interactions. The profiling of the soil bacterial communities along the latitude gradient will also provide a basis for a better understanding of the salt-affected soil ecosystem functioning and restoration of these soil ecosystems.