Journal of Basic Microbiology最新文献

Cover illustration:

A segment of the Methanococcus maripaludis gene containing simple sequence repeats (SSR) is shown with corresponding amino acid repeats (Leu: orange, Glu: pink). Rainbowcolored protein models (blue: N-terminal, red: C-terminal) highlight SSR-induced structural rearrangements, including loop refolding that enhances compactness and alters the N-terminal catalytic domain. The SSR region, positioned near the N-terminal, suggests a potential role in mediating local contacts and structural modulation.

(Image: Pragya Anand, Department of Biotechnology, Babasaheb Bhimrao Ambedkar University, Lucknow, India)

Mycobacteriophage Mcgavigan could be a promising candidate for use as a preventative agent against infections with Mycobacterium avium subsp. paratuberculosis. Bioinformatic analysis of the Mcgavigan genome revealed the presence of an operon containing a "Bxb1-like" repressor. The operon may have been acquired by the phage through horizontal gene transfer with a Bxb1-like mycobacteriophage in its evolutionary past. We sought to investigate the function of the acquired repressor as a potential regulator of lysogeny or as a source of heterotypic superinfection immunity. Recombineering with CRISPR counter-selection was employed to achieve a clean deletion of the Bxb1-like repressor from Mcgavigan's genome. Integrase was also deleted as a means of creating a lytic-only phage for comparison purposes and the elimination of lysogeny with this edit was confirmed. To test phenotypic changes which resulted from these deletions, several parameters such as burst size, latency period, and killing efficiency were measured for each knockout mutant and lysogeny was tested. The integrase deletion mutant had complete lysogeny abolishment and performed similarly to wild-type phage on all measured parameters. The deletion of the Bxb1-like repressor did not affect the lysogenic capability of the phage. Whereas Mcgavigan lysogens are typically immune to superinfection from Terelak, a mycobacteriophage related to Bxb1, lysogens created from Mcgavigan with the Bxb1-like repressor deletion were completely resensitized to heterotypic superinfection by Terelak. This suggested that this repressor was acquired by Mcgavigan through horizontal gene transfer for the purposes of superinfection immunity against cluster A1 mycobacteriophages and was not used for maintenance of lysogeny.

Microalgae are emerging as a valuable resource of bioenergy, value-added products, and contribute significantly to carbon sequestration. However, the diversity of endogenous algae in countries like India and their bioprospecting potential is not yet fully explored. During this study, microalgae from the freshwater of Aligarh, India, were isolated, identified using 18S rRNA, ITS and 16S rRNA gene sequences, and screened using GC-MS analysis for their potential use as biofuel. Two isolated strains were identified as members of the genus Chlorella based on ribosomal gene sequences, cell, and colony morphologies. When detected using GC-MS analysis, the strain was found to produce significant quantities of phytol, pentadecanone, and other compounds typically found in algal oil. The influence of silver nanoparticles (~32 nm) and TiO₂ nanoparticles (~23 nm) on the cell integrity of algae was checked using direct microscopy and CSLM analysis after staining with propidium iodide and Syto9. It was found that with 50, 100, and 200 µg/mL of Ag-NPs, the population of intact cells decreased by 20%, 51%, and 79%, as seen under a light microscope, while TiO₂-NPs were less toxic to the cells, decreasing population only by 0%, 12%, and 35%, respectively. When checked using Scanning Laser Microscope after growing with 100 and 200 µg/mL of Ag-NPs and TiO₂-NPs, the population of dead cells increased to 59% and 93%, and 16% and 46%, respectively. These results show that the isolated strains can serve as a source of bioenergy, and nanomaterials can promote cell lysis for downstream processes.

Casuarina equisetifolia, a key species in subtropical coastal shelterbelts, faces serious challenges in sustainable plantation management due to continuous planting obstacles. This study explores how AHL-mediated quorum sensing (QS) influences these obstacles by regulating microbial dynamics in the rhizosphere of continuously planted C. equisetifolia. Results show that with increasing generations of continuous planting, the abundance of QS bacteria-especially pathogenic strains-significantly increased, with notable shifts in community composition. The number of QS isolates rose from 32 (FCP) to 68 (SCP) and 81 (TCP), with Enterobacteriaceae being the most abundant. Among 10 identified QS species, Pantoea ananatis showed the highest AHL activity, while Burkholderia lata had the lowest. Short-chain AHL (C4-HSL and C6-HSL) were most common, with P. ananatis producing the highest diversity and concentration. Pathogenicity tests indicated that seven QS bacteria damaged roots and inhibited water uptake, leading to wilting. In contrast, three Burkholderia species were non-pathogenic. Meanwhile, the abundance of quorum quenching (QQ) bacteria decreased significantly across planting generations (94, 70, to 63), and key QQ strains like Bacillus spp. showed no pathogenicity. These findings suggest that continuous planting enriches pathogenic AHL-mediated QS bacteria while reducing beneficial QQ populations, altering microbial community structure and exacerbating replant issues. This study offers important theoretical insights into the mechanisms behind continuous planting obstacles in C. equisetifolia.

Arbuscular mycorrhizal fungi (AMF) significantly impact on the growth, nutritional intake, and secondary metabolite synthesis of essential oil-producing plants by forming crucial symbiotic relationships with their roots. Recent research findings that demonstrate the diverse functions of AMF in improving the amount and chemical makeup of essential oils are compiled in this article. In sustainable agriculture, particularly in organic farming systems that utilize minimal synthetic inputs, AMF and medicinal herbs have demonstrated a positive relationship. AMF also supports ecological stability by promoting biodiversity and enhancing soil structure. The molecular and pharmacological mechanisms underlying these plant-fungal interactions are still not fully known, however. This study highlights the need for further research into the mechanisms of action of AMF, the development of effective inoculation methods, and the evaluation of novel herb-fungus combinations. It also reveals present research gaps. These revelations will open the door to more environmentally friendly farming methods and the efficient use of AMF in the manufacture of essential oils. AMF and medicinal plants have a promising interaction in sustainable agriculture, especially in organic farming systems that employ fewer synthetic inputs. Additionally, AMF improves soil structure and encourages biodiversity, both of which support ecological stability.

Antimony (Sb) contamination threatens food security by lowering crop yields, reducing nutritional quality, and harming agroecosystems, underscoring the need for sustainable and eco-friendly strategies to alleviate heavy metal stress. Here arbuscular mycorrhizal fungi (AMF) role to mitigate Sb-induced stress in maize, was examined. AMF-inoculated and non-inoculated plants were grown under control and Sb stress conditions for 10 weeks, and growth, nutrient uptake, metabolic profiles, antioxidant capacity, and antimicrobial activity were assessed. Sb exposure markedly suppressed maize performance, reducing fresh and dry biomass by 66% and 65%, respectively, while also impairing the growth-promoting effects commonly associated with AMF. However, AMF inoculation significantly alleviated Sb toxicity, enhancing fresh biomass by 43% and dry biomass by 40%. The recovery was linked to improved nutrient uptake and the accumulation of primary metabolites, which promoted physiological adjustments. Moreover, AMF-inoculated plants under Sb stress showed enriched bioactive metabolites, leading to stronger antimicrobial activity and a 65% increase in antioxidant capacity. Collectively, these findings demonstrate that AMF enhance maize resilience to Sb stress by promoting growth, nutritional quality, and bioactive properties. This study demonstrates that AMF offer a sustainable strategy to enhance crop resilience and biofortification in contaminated environments.

The study of the biofilm mechanical stability is important in the fields of biomedical and environmental engineering. In this paper, we present an innovative simplified bilayer model, which is obtained based on a simplification of the complex four-layer model. We simplify the model and reduce the computational complexity by ignoring the top layer of the biofilm and treating the middle layer and the substrate layer as a spring system connected in series. In finite element analysis, we used a simplified two-layer model to simulate the bending behavior of biofilm wrinkles and found the influence of elastic modulus ratio (Ef/Es) and biofilm thickness (h) on biofilm wrinkles and critical stress ( $\epsilon$ ). We simulated the wrinkle morphology changes of biofilm in regions II and III on three low, medium, and high agar substrates, and compared the simulated wrinkle wavelengths with experimental data for verification, providing a new perspective for understanding the mechanical behavior of biofilms.

Polyhydroxybutyrate (PHB) is a natural polyester synthesized and stored intracellularly as cytoplasmic granules, serving as a carbon and energy reserve in certain bacteria. These granules are surrounded by a variety of proteins, including those directly involved in PHB metabolism—both in its synthesis and degradation—as well as a group of non-enzymatic proteins known as phasins, which constitute the major protein component of the PHB granule. Although phasins lack enzymatic activity, some, such as PhbP1 in Azotobacter vinelandii, significantly influence granule size and number, while others have been shown to modulate enzymes involved in PHB synthesis or degradation in PHB-producing bacteria. This study aimed to elucidate the roles of phasins PhbP2 and PhbP3 in PHB metabolism in A. vinelandii. Our findings indicate that PhbP3 belongs to a novel family of phasin proteins and demonstrate that, although PhbP2 and PhbP3 do not contribute to granule structure, they are involved in PHB degradation. Gene inactivation of phbP2 and phbP3 led to a decrease in PHB depolymerase activity. Additionally, SDS-PAGE analysis revealed alterations in the relative abundance of some granule-associated proteins in the mutants, suggesting that PhbP2 and PhbP3 may play a role in stabilizing proteins on the PHB granule surface.

Malate synthase (MS), the second key enzyme in the glyoxylate cycle, catalyzes the condensation of acetyl-CoA and glyoxylate to produce malate and CoA. Phylogenetic analysis reveals four MS subgroups: MSA, MST, MSG, and MSH. Sequence alignment shows that MSA, MSG, and MSH share similar structures and active sites, while MST exhibits extremely low identity with the other three subtypes. Herein, we report the cloning, expression, and detailed characterization of MS isoforms from Acinetobacter baumannii (AbMSG), Pseudomonas aeruginosa (PaMSG), Escherichia coli (EcMSA), and Sulfolobus acidocaldarius (SaMST). AbMSG, PaMSG, and EcMSA are mesophilic, with optimum temperatures of 40°C, 32°C, and 32°C, respectively. SaMST is thermophilic, with maximal activity at 60°C, and uniquely prefers Mn²⁺, in contrast to the Mg²⁺ dependence of AbMSG, PaMSG, and EcMSA. Despite similar catalytic efficiencies for acetyl-CoA, the isoforms show pronounced differences in glyoxylate turnover. Strikingly, cis-aconitate completely inhibits MS activity, indicating this metabolite and its analogs as potential scaffolds for MS-targeted antibacterial strategies, given the pivotal role of the glyoxylate cycle in bacterial virulence.