Journal of Basic Microbiology最新文献

The emergence of multidrug-resistant pathogens has significantly reduced the efficacy of current antimicrobial treatments against bacterial and fungal infections. To combat this challenge, the exploration of novel antimicrobial sources or the development of synthetic antibiotics is imperative. Microbes have emerged as promising natural reservoirs for antimicrobial compounds, with slime molds garnering attention due to their unique bioactive metabolites in recent years. Some of these metabolites demonstrate potent antibiotic properties. This study investigates the inhibitory effects of slime mold extracts on pathogenic bacteria, attributing this activity primarily to symbiotic bacteria associated with the slime molds rather than to the slime mold cells themselves. Furthermore, we demonstrate that this antibacterial effect can be horizontally transferred through bacterial ingestion, enabling recipient slime molds to exhibit antibacterial properties upon extraction. Importantly, slime molds selectively acquire bacteria from their environment to enhance their antibacterial characteristics, a process that appears non-random and persists through sexual cycles. These findings underscore slime molds as valuable reservoirs of antimicrobial agents. Nevertheless, it remains critical to ascertain whether these antimicrobial agents originate solely from symbiotic bacteria or result from complex interactions between these bacteria and their slime mold hosts. Understanding the mechanisms behind this antimicrobial activity not only expands our knowledge of host-microbe interactions but also provides new avenues for bioprospecting novel antibiotics. Investigating how slime molds selectively acquire and retain beneficial bacteria may offer insights into microbial symbiosis that could be leveraged for antimicrobial discovery, potentially addressing the urgent need for alternative treatments against resistant pathogens.

Drought-tolerant multifunctional soil bacteria can increase drought tolerance mechanisms in plants. Here, rhizobacteria CRB-4 and SPGPR-11 were isolated and their single and co-inoculation effect was evaluated in drought-stressed tomato plants. Isolates were selected based on their preliminary polyethylene glycol (PEG) screening, and plant growth-promoting properties. Increasing water stress adversely affected growth and physiological attributes of tomato plant. However, plant growth-promoting bacteria (PGPB), particularly their combined inoculation, alleviated drought stress. For instance, CRB-4, SPGPR-11 and their co-inoculation significantly increased root biomass (33.3, 37.5% and 45.4%), total chlorophyll (17.5, 15.6% and 19.2%) and carotenoid content (20, 30.4% and 48.3%) in 3%-PEG-stressed tomatoes. Similarly, co-inoculation of 3%-PEG-treated plants with PGP isolates resulted in a significant increase in Fv/Fm (50%), Fv'/Fm' (29.4%), PS-II (44.4%), Pq (40%), NPQ (40%), and effective electron transfer rate (37.5%). Furthermore, under 5%-PEG stress, CRB-4, SPGPR-11, and their co-inoculation enhanced drought stress resilience in tomato by improving leaf gas exchange attributes. Combined inoculation significantly enhanced gs (19%), Ci (31.2%), transpiration rate (41%), water vapor deficit (38.7%), iWUE (33.7%), and photosynthetic rate (33.3%) in 5%-PEG-stressed tomatoes. Among the treatments, co-inoculations significantly enhanced the antioxidant defense responses in drought-stressed tomatoes. Concurrently, qRT-PCR analysis revealed a significant upregulation in ROS scavenging genes, SOD, CAT, APX, GR, and POD, by 6.53, 14.08, 11.72, 10.12, and 5.95-fold, respectively, in drought-stressed plants co-inoculated with bacterial strains. This study concludes that PGP isolates CRB-4 and SPGPR-11, alone or in combination, offer an effective, eco-friendly solution for improving drought resilience in tomatoes.

Metal contamination represents a critical environmental challenge, adversely impacting ecosystems and human health. Microorganisms, including fungi, have developed diverse mechanisms to tolerate and resist metal-induced stress, making them valuables for bioremediation. This study evaluates the metal tolerance of Absidia glauca, Penicillium bilaiae, and Trichoderma viridescens using minimum inhibitory concentration (MIC) assay and the alternative minimum profile change concentration (MPCC) approach via MALDI-TOF MS. MIC assay revealed species-specific tolerances to copper, zinc, and cadmium. A. glauca showed the highest tolerance to copper and cadmium (75 and 9 mg L⁻¹), producing a dry biomass of 0.03 and 0.04 g, respectively. While P. bilaiae exhibited the highest tolerance to zinc (75 mg L⁻¹) producing a dry biomass of 0.06 g. MALDI-TOF MS provided rapid proteomic information on fungal responses to metals, showing changes in the protein profile as the metal concentration increased. We performed a comparative analysis between the values obtained in the MIC and MPCC, giving a positive correlation in the results of both techniques for Cu, Zn, and Cd (r = 1.00; 0.87 and 0.99 respectively, p < 0.05). In conclusion, MALDI-TOF MS has proven to be an effective method for analyzing fungal proteomic responses to metal exposure, providing more detailed molecular insights than traditional MIC assays. Future studies should investigate the mechanisms underlying metal resistance, particularly focus on the regulation of specific proteins.

DeaD or CsdA (cold-shock DEAD box protein A), is an ATP-dependent RNA helicase, a major cold-shock protein that plays key roles in translation initiation, ribosome biogenesis, and mRNA decay at low temperatures in bacteria. The DeaD homolog of Escherichia coli is ubiquitously present in eukaryotes, archaea, and bacteria. DeaD has been extensively studied at the protein level in E. coli. However, the complex mechanism of deaD gene regulation is yet to be deciphered. To study deaD gene regulation, we engineered a promoter-less reporter plasmid vector which contains an ORF of green fluorescence protein (GFP) without a promoter region. We performed sequential, incremental, zone-wise cloning of DNA fragments of the upstream region of the deaD ORF and analyzed GFP expression in our promoter-less plasmid vector to identify the promoter region. We found out the promoter around 800 nucleotides upstream of deaD ORF, which was further confirmed by its In Vivo deletion in the E. coli genome. We observed the expression of the deaD gene might also occur from the immediate upstream of the nlpI and pnp gene, revealing the phenomenon of an operon system. Interestingly, we found the short ORF of the gene yrbN overlaps with the ORF of deaD but not in the frame. Subsequently, Multiple Sequence Alignment profiles showed that not only the promoter and the unusually long 5'UTR region but the whole genetic arrangement of the deaD gene, including the overlapping phenomenon of ORF of the yrbN gene, is conserved in Gamma-proteobacteria indicating a conserved gene expression pattern.

Microorganisms have developed sophisticated mechanisms to invade the host and evade the host's immune surveillance while exploiting the host's resources for their establishment through co-evolution. Many pathogens employ specialized protein secretion systems to transport virulence factors from the bacterial cytosol into host cells. These bacterial protein secretion systems can generally be categorized into different classes based on their structures, functions, and specificity. Notably, some pathogens have evolved proteins that mimic specific eukaryotic cell proteins, enabling them to manipulate host cellular pathways. This phenomenon is known as molecular mimicry. These proteins either closely resemble eukaryotic proteins or possess domains typically found in eukaryotes but generally absent in prokaryotes. This mimicry allows pathogens to interfere with host functions and facilitate their survival and proliferation within the host. Here, we review the fundamental characteristics of these secretion pathways, delve into the remarkable diversity of effector proteins, and explore the molecular mechanisms by which different pathogens rewire cellular pathways. Additionally, we discuss recent findings on strategies to counteract pathogen mimicry and the insights gained for the discovery of new antimicrobials.

In the present study, sunlight-mediated Carboxymethyl cellulose silver nanoparticles (CMC-AgNPs) have been synthesized as a carrier for serratiopeptidase immobilization. Morphological behavior of CMC-AgNPs, crystallinity and functional group identification were evaluated using scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy, respectively. The prepared nanoparticles (NPs) were also subjected to zeta potential, which disclosed the zeta potential value of about—36.06 mV, suggesting their negative charge surface, good stability and polydispersity. SRP was immobilized on synthesized NPs through covalent adsorption using glutaraldehyde as a crosslinker. Immobilized (CMC/Ag-SRP) exhibited 80.95% immobilization efficiency and 79.73% immobilization yield, respectively. Remarkably greater relative activities at broader temperature and pH ranges were attained by SRP after immobilization in comparison to its free counterpart. The K_m value was significantly higher for immobilized enzyme, whereas V_max value was conspicuously lower, indicating that less enzyme was sufficient to achieve maximum velocity. The greater zone of inhibition was displayed by immobilized CMC-AgNPs than that of native NPs against both gram-positive Listeria monocytogenes (12 ± 0.05 mm) and gram-negative Escherichia coli (22 ± 0.12 mm). The bigger zone on casein agar plates for immobilized NPs confirms enhanced caseinolytic activity in comparison to starting materials. In Vitro anti-inflammatory assessment of CMC/Ag-SRP presented more potency than the native NPs, which was comparable to the standard drug. Reusability data demonstrated 50% of initial activity was retained after seven successive cycles. Thereby, it is concluded that incorporation of serratiopeptidase onto CMC-AgNPs presented enhanced effects at lower concentrations with improved anti-inflammatory activity.