International Microbiology最新文献

Protease enzymes are widely used in industrial applications, often requiring resistance to alkaline and high-temperature conditions while maintaining activity in organic solvents. Discovering thermotolerant proteases from thermophilic organisms is crucial for such applications. This study aimed to identify a novel thermotolerant protease among 201 thermophilic strains isolated from hot springs in Aydın province. Geobacillus thermoleovorans HBB208 was identified as the most efficient protease producer, exhibiting a 3.1 (D/d) ratio on skim milk agar. The protease purified via ammonium sulfate precipitation, hydrophobic interaction, and ion-exchange chromatography, resulting in a 70.2-fold purification. SDS-PAGE and zymogram analyses confirmed the molecular weight of approximately 33.5 kDa and proteolytic activity. The enzyme showed optimal activity at pH 8.0 and 70 °C, and retained 50% activity after 30 min at 87.3 °C in the presence of 10 mM Ca²⁺, indicating remarkable thermostability. Kinetic analysis using casein as substrate yielded a K_m of 0.11 ± 0.01 mM, k_cat 27.4 ± 0.77, and 2.4 × 10⁵ k_cat/K_m. The enzyme was stable in the presence of various organic solvents and detergents and displayed broad substrate specificity. These findings suggest that HBB208pro metalloprotease enzyme is a promising candidate for biotechnological and industrial applications requiring extreme operational conditions.

This study investigated the potential of native arbuscular mycorrhizal fungi (AMF) isolated from organic cassava fields as a biofertilizer, assessing their effects on cassava growth both alone and in combination with plant growth-promoting bacteria (PGPB). AMF spores were isolated from the rhizospheric soil of organic cassava field soils in northeastern Thailand and grouped into two consortia based on spore size: A45 and A75. Molecular identification revealed that both consortia were dominated by the genera Claroideoglomus and Entrophospora, with Paraglomus additionally present in the A45 consortium. An outdoor pot experiment demonstrated that AMF inoculation significantly enhanced cassava growth compared to the uninoculated control, highlighting the potential of these locally adapted strains. Utilization of diverse AMF consortia showed better outcomes in cassava growth enhancement resulted from various abilities of AMF inside. However, the addition of the compatible PGPB strains (Pantoea dispersa and Serratia marcescens) did not further enhance plant growth. These findings emphasize the potential of locally adapted AMF consortia as effective biofertilizers for cassava and underscore the need for targeted evaluation of microbial interactions in sustainable agriculture.

Carotenoids are essential natural pigments, and ZISO plays a pivotal role in their biosynthesis. This study compares ZISO enzyme activity in Dunaliella salina and Dunaliella bardawil to evaluate their efficiency in synthesizing 9,9'-di-cis-ζ-carotene. Bacterial strains lacking ZISO (ΔDsZISO, ΔDbZISO) and ZDS (ΔDsZDS, ΔDbZDS) were constructed, and HPLC analysis revealed the accumulation of 9,9'-di-cis-ζ-carotene in ΔDbZDS but not in ΔDsZDS, suggesting that DbZISO exhibits higher activity. Molecular docking and kinetic simulations further indicate that DbZISO forms a more stable complex with 9,9',15-tri-cis-ζ-carotene, with a binding energy lower than that of DsZISO, where the affinity between DbZISO and the substrate is - 13.09 kcal/mol, and the affinity between DsZISO and the substrate is - 12.13 kcal/mol. These results demonstrate that DbZISO is more efficient than DsZISO in catalyzing the isomerization of carotenoid intermediates. This study provides mechanistic insights into ZISO-mediated carotenoid biosynthesis and establishes a foundation for metabolic engineering aimed at enhancing carotenoid production.

This study was conducted in response to the growing need for alternative microbial control strategies in the face of escalating antibiotic resistance, aiming to evaluate the antibacterial and antibiofilm potential of postbiotic components derived from Akkermansia muciniphila. Focusing on Enterococcus faecalis, a Gram-positive, biofilm-forming opportunistic pathogen, the effects of cell-free supernatant were analyzed in vitro on both planktonic growth and biofilm structures. The supernatant significantly suppressed planktonic proliferation, while biofilm assays revealed over 50% inhibition of biofilm formation and up to 40% disruption of preformed biofilms. These effects, confirmed via crystal violet staining, indicate that the supernatant possesses both preventive and curative antibiofilm properties. While the immunomodulatory and barrier-enhancing roles of A. muciniphila have been increasingly documented in the literature, this study provides direct experimental evidence of its antibiofilm efficacy, offering a novel perspective on its therapeutic scope. The findings suggest that postbiotics from A. muciniphila act not only through inhibition of bacterial growth but also by targeting biofilm-associated resistance mechanisms. Thus, A. muciniphila supernatant emerges as a promising and innovative candidate for next-generation antimicrobial and antibiofilm strategies, particularly for managing infections involving drug-resistant biofilm-forming pathogens.

This study establishes a scalable, GRAS-compliant bioprocess for hyaluronic acid (HA) production using Bacillus paralicheniformis PV154040.1, a novel strain isolated from local garden soil and identified via ribotyping. Through the systematic optimization of submerged fermentation conditions, M4 medium (5% glucose, 5% lactose, 1.5% tryptone, and 0.5% yeast extract) was identified as the most productive formulation. The optimal culture parameters were determined to be pH 6.5, a 72-hour incubation at 37 °C, and a 1.0 ml inoculum volume. A key finding was the significant enhancement in HA recovery using a cetyltrimethylammonium bromide (CTAB)-ethanol extraction method, which yielded 374.21 µg/ml, doubling the yield obtained with conventional ethanol precipitation (188.33 µg/ml; *p* ≤ 0.05). The identity of the biopolymer as HA was confirmed by Ultraviolet-Visible (UV/Vis) spectrophotometry, which showed characteristic absorbance, and FTIR analysis, which revealed functional peaks corresponding to glycosidic linkages (834.92 cm⁻¹), proteoglycan sugar rings (998.92 cm⁻¹), amide II (1617.66 cm⁻¹), and hydroxyl groups (3257.69 cm⁻¹). This work presents the first report of HA production by B. paralicheniformis, introducing a safe, efficient, and sustainable microbial platform as a promising potential alternative to traditional animal-derived or pathogenic sources for biomedical and cosmetic applications.

Storing biochar in soil is an effective method for improving the soil environment and reducing atmospheric greenhouse gases. Some strains of Bacillus species have been utilized as plant growth-promoting bacteria or biological control agents against plant diseases and pests. By colonizing biochar with beneficial bacteria, highly functional biochar that contributes to increased crop yields can be developed. In this study, we investigated the survival of type strains of eight Bacillus species (Bacillus amyloliquefaciens, B. licheniformis, B. nakamurai, B. pumilus, B. siamensis, B. subtilis, B. thuringiensis, and B. velezensis) in rice husk biochar, based on the sporulation state of vegetative cells or endospores. The bacterial density in the biochar significantly reduced when inoculated with a high concentration of vegetative cells, whereas it remained high when inoculated with a high concentration of spores. When water-washed biochar was inoculated with a high concentration of vegetative cells, survival significantly improved compared to that when unwashed biochar was inoculated. When a high concentration of vegetative cells was inoculated into the biochar water extract (biochar: water = 1:10), the bacterial densities of most species, except B. nakamurai and B. licheniformis, were significantly lower than those in alkali-sterilized water at pH 10.2 (same pH as biochar) and normal sterilized water (pH 6.7). These results suggest that the survival of Bacillus vegetative cells in biochar is inhibited by water-soluble inhibitors contained in the biochar rather than by alkaline conditions. When endospores were inoculated onto unwashed biochar, all strains maintained high viability for at least 12 weeks.

Antibiotic resistance and virulence factor of Helicobacter pylori pose formidable challenge towards eradication of this pathogen. Heterogeneity of H. pylori cagPAI is essential in the emergence of antibiotic resistance. The objective of this study was to investigate the correlation between antibiotic resistance and cagPAI variability among H. pylori strains in multiethnic Malaysian patients. H. pylori antibiotic susceptibility profile to six antibiotic classes was determined using E-test and the presence of each cagPAI gene was determined using polymerase chain reaction (PCR). The highest resistance was observed against metronidazole (58.6%, 34/58), followed by clarithromycin (36.2%, 21/58), and levofloxacin (25.9%, 15/58); all strains were susceptible to amoxicillin, tetracycline and rifampicin. Clarithromycin-resistance in H. pylori was significantly higher among elderly patients (> 50 years old) (P = 0.040). Isolates harboring complete cagT4SS genes exhibited significantly higher resistance to antibiotic treatments, primarily towards a single antibiotic (P = 0.043). Resistance to a single antibiotic was significantly higher in East Asian strains (P = 0.027), of which majority of the infected patients were Chinese. Among the resistant isolates, 20.9% (9/43) exhibited multi-drug resistance (MDR), demonstrating resistance to metronidazole, clarithromycin, and levofloxacin concurrently. Female patients were notably at higher risk of being infected with MDR-H. pylori (P = 0.022) than males. Our findings offer insights into the association between variability of cagPAI and antibiotic resistance in H. pylori, of which further research is warranted to elucidate the mechanisms underlying cagPAI heterogeneity and antibiotic resistance in H. pylori for effective therapeutic strategies.

Exopolysaccharides (EPSs) synthesized by thermophilic bacteria are natural biopolymers, that have recently garnered attention due to their potential applications in areas such as pharmaceuticals and biomedicine. In this study, EPSs produced by five distinct thermophilic bacterial isolates from hot springs in Turkey were purified using ion exchange and gel chromatography, and the larvicidal and cytotoxic effects of these EPSs were examined. While Geobacillus thermodenitrificans HBB111 produced the highest quantity (650.9 mg mL^-1) of EPS, the protein content of crude EPS samples ranged from 0.3 to 1.5%. EPS111 and EPS261 showed the most effective larvicidal action, eliminating 72% and 62.7% of Ae. albopictus larvae after 48 h, respectively. Among the purified samples, EPS111 exhibited the most significant effect on the proliferation of PC3 cells, resulting in a 68% inhibition (IC₅₀ of 0.23 mg mL^-1) followed by EPS106 in 55% (IC₅₀ of 0.45 mg mL^-1). According to our study's results, thermophilic EPSs show promise because of their insecticidal and anticancer properties.

Strain HM32M-2 ^T, an aerobic, catalase-positive, oxidase-positive, and Gram-stain-negative bacterium, was isolated from a sandy sediment sample collected from Qinzhou Gulf in Guangxi Zhuang Autonomous Region, China. Strain HM32M-2 ^T grew at 15-37 °C (optimum, 30 °C), at pH 5.5-9.5 (optimum, pH 8.5), and with 1.0-12.0% (w/v) NaCl (optimum, 3.0%). Strain HM32M-2 ^T exhibited the highest 16S rRNA gene sequence similarity with Sedimentitalea nanhaiensis NH52F^T (98.4%). Phylogenetic analyses based on 16S rRNA gene sequences and whole-genome sequences showed that strain HM32M-2 ^T formed a distinct lineage with Sedimentitalea nanhaiensis NH52F^T. The draft genome of strain HM32M-2 ^T was 3.40 Mbp in size and its DNA G + C content was 63.6%. Comparative genome analysis revealed that average nucleotide identity and digital DNA-DNA hybridization among strain HM32M-2 ^T and other Sedimentitalea species were below cut-off levels of 95-96% and 70%, respectively. Chemotaxonomic analyses indicated that strain HM32M-2 ^T contained Q-10 as the respiratory quinone, C_18:1ω7c as the major cellular fatty acid, and diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, one unidentified aminolipid, and one unidentified lipid as the major polar lipids. Strain HM32M-2 ^T had a typical chemical composition of fatty acids, polar lipids, and quinones for Sedimentitalea species, but could be distinguished from known species of the genus Sedimentitalea. On the basis of the polyphasic evidence, strain HM32M-2 ^T should be classified as a novel species of the genus Sedimentitalea, for which the name Sedimentitalea sediminis sp. nov. is proposed. The type strain is HM32M-2 ^T (= MCCC 1K08873^T = KCTC 8272 ^T).

Due to the variety of applications for nanomaterials (NMs) and ultrafine solids, their amounts released into the environment is constantly increasing, and their impact on ecosystems and organisms has led to remarkable problems. However, extensive studies on the effects of dispersed ultrafine inorganic metal oxides on algal growth at cellular and genomic levels still need to be performed. We assessed the potential toxicity of two commercial ultrafine inorganic metal oxides, silicon dioxide (SiO₂) and zinc oxide (ZnO), using the single-celled green microalgae Chlamydomonas sp. strain GO1 as a eukaryotic model. The cell response to commercial inorganic oxides was evaluated at physiological, biochemical, and molecular levels. An estimation of population growth inhibition levels was made. After 72 h of exposure, the IC₅₀ of SiO₂ and ZnO were 14.50 ± 2.98 mg/L and 56.80 ± 8.3 mg/L, respectively. Genotoxic effects of the studied materials were evaluated by acridine orange staining method and showed DNA fragmentation and morphological changes, including cell shrinkage and chromatin condensation on microalgae cells treated with both oxide materials. In addition, generated cytotoxic effects were evaluated. An inhibition of microalgae growth and a decrease in cell viability were observed. Antioxidant defense mechanisms, including enzymatic and non-enzymatic, were activated in response to materials exposure. We have also proven an overexpression of genes involved in carbohydrate biosynthesis and apoptosis. Infrared investigation suggested surface chemical interaction between algal cells and commercial ultrafine inorganic oxides.