Archives of Microbiology最新文献

In spite of being dispensable for catalysis, Dpb2, the second largest subunit of leading strand DNA polymerase (Polymerase ε) is essential for cell survival in budding yeast. Dpb2 physically connects polymerase epsilon with the replicative helicase (CMG,Cdc45-Mcm-GINS) by interacting with its Psf1 subunit. Dpb2-Psf1 interaction has been shown to be critical for incorporating polymerase ε into the replisome. Site-directed mutagenesis studies on conserved amino acid residues within the N-terminal domain of Dpb2 led to identification of key amino acid residues involved in interaction with Psf1 subunit of GINS. These amino acid residues are found to be well conserved among Dpb2 orthologues in higher eukaryotes thereby indicating the protein-protein interaction to be evolutionarily conserved. Replicating cells are known to mount a strong replicative stress response and DNA damage response upon exposure to diverse range of stressors. Here, we show that the absence of the N-terminal domain of Dpb2 increases the vulnerability of the budding yeast cells towards the cytotoxic effects of hydroxyurea (HU) and methyl methane sulphonate (MMS). Our results illustrate the importance of N-terminal domain of Dpb2 not only during replisome assembly but also in coordinating stress response in budding yeast. Considering high degree of sequence conservation across eukaryotes, Dpb2 subunit of leading-strand DNA polymerase appears to have important implications in maintenance of genome integrity.

Bdellovibrio bacteriovorus, an obligate predator of Gram-negative bacteria, has emerged as a promising natural antibiotic to combat the escalating threat of antibiotic resistance. Plaque forming units (PFU) counting is commonly used to determine the viable numbers of B. bacteriovorus. However, nearly three-days incubation is always necessary for getting the single, obvious plaques on the double-layer agar plate. This time-consuming procedure greatly impedes the purification and enumeration efficiency of B. bacteriovorus. Until now, no simplified method has been developed to address this issue. In this work, we evaluated the advantages of using fluorescent prey to enhance the visualization of the B. bacteriovorus plaques. Our work reveals that the regular single plaques are easily observed under the enhanced background of fluorescent prey lawn in one and a half days, reducing nearly half of the time consumption in the purification and enumeration of B. bacteriovorus.

Cultured milk products including yogurt, buttermilk, and lassi have made their way into South Asian cuisine for hundreds of years and are extraordinarily beneficial to human health. With a study background on lactic acid bacteria (LAB), these products are scientifically proved to aid in strengthening the immune system, for their anti-mutagenic effects, suitability for those who are lactose intolerant, and for protection against cancer, osteoporosis, and gut disorders. As of now, no scientific attention has been given to the microbial diversity of cultured milk products despite its prominent production and importance in the culture. New emerging approaches for studying the genetic composition and metabolic features of microbial communities, such as metagenomics and metabolomics, will open up important sources of knowledge and be a significant tool for informing conservation. These products are highly valued worldwide in the management of cardiometabolic diseases (CMDs), which encompass hypertension, type 2 diabetes, and obesity. The aim of this article will therefore advocate for the health benefits as well as cultural importance of cultured milk products. Indian fermented milk products, along with their historical development, cultural, and research aspects, thereby, highlighting the potential of this kind of product in promoting global health through functional food application, with a focus on recent advancements in their therapeutic potential and applications.

Antimicrobial resistance (AMR) is an urgent worldwide health concern, requiring the exploration for novel antimicrobial interventions. A Gram-negative bacterium, Chromobacterium violaceum, synthesizes quorum-sensing-regulated violacein pigment, develops resilient biofilms, and is often used for the screening of anti-infective drugs. The aim of this work is to assess the antibacterial and antibiofilm properties of three polyphenols: 1,4-naphthoquinone, caffeic acid, and piperine. The determination of antibacterial activity was conducted by the agar overlay and broth microdilution techniques. Analysis of membrane rupture was conducted by crystal violet uptake and β-galactosidase assay. Inhibition of biofilm was evaluated using a 96-well microtiter plate assay. Biofilm structures were visualized using light, scanning electron microscopy (SEM), and confocal laser scanning electron microscopy (CLSM). Among the phytochemicals, 1,4-naphthoquinone exhibited the highest antibacterial action (25 mm zone of inhibition). The minimum inhibitory concentration of 1,4-naphthoquinone was determined to be 405 µM. Outer and inner membrane permeability was enhanced by 52.01% and 1.28 absorbance, respectively. Violacein production was reduced by 74.85%, and biofilm formation was suppressed by 63.25% at sub-MIC levels (202.5 µM). Microscopic analyses confirmed reduced adhesion on surfaces. Hemolytic activity of 1,4-naphthoquinone showed a concentration-dependent effect, with 32.16% haemolysis at 202.5 µM. Molecular docking revealed significant interactions of 1,4-naphthoquinone with DNA gyrase followed by CviR. These findings highlight 1,4-naphthoquinone’s potent antibacterial efficacy against C. violaceum, proposing its use as a surface coating agent to prevent biofilm formation on medical devices, thereby offering a promising strategy to combat bacterial infections.

Hydrogen (H₂) energy has garnered significant attention due to its numerous advantages. Nonetheless, for future commercialization, it is imperative to screen and identify strains with enhanced H₂-producing capacities. In order to attain a high and consistent production performance, the conversion of biomass sources into H₂ requires careful selection of the most appropriate H₂-producing bacteria. This study aimed to isolate and identify a highly effective H₂ producing bacteria from local sewage sludge and assess its fermentability for H₂ production. The isolate was first identified by means of morphological, phenotypic, biological, and 16 S rRNA investigations. A facultative anaerobe that produces H₂ and is gram-negative was identified as Alcaligenes ammonioxydans strain SRAM. For the purpose of determining whether the isolate could produce H₂ using glucose as the substrate, its fermentability was evaluated in 500 mL serum bottles. This strain demonstrated the ability to produce H₂ from glucose under anaerobic environment, achieving a maximum H₂ yield of 2.9 mol H₂/mol of glucose. The highest rate of H₂ production, 9.261 mmol H₂/ g dry cell weight per hr, was attained at 37 °C and an initial pH of 6.8. This work effectively illustrated the use of a novel locally isolated strain in the biotechnological conversion of glucose to H₂. This strategy offers an effective remedy for the world’s energy instability in addition to addressing environmental issues related to industrial operations.

Deoxynivalenol (DON), a type-B trichothecene mycotoxin, is primarily produced by Fusarium species and widely pollutes wheat and other grains. Enzymatic treatment of DON has been widely studied in recent years. Here, we present the biochemical identification of the DON dehydrogenase from Pelagibacterium sp. SCN 63–126 (Pe DDH). After removing the signal peptide, Pe DDH is effectively expressed in its soluble form. Biochemical identification indicates that the optimal temperature and pH of Pe DDH against DON is 35 ℃ and pH 8.5. Furthermore, Pe DDH is activated significantly in the presence of Ca²⁺, Mg²⁺, and Cu²⁺, and alternatively activated by pyrroloquinoline quinone (PQQ), phenazine methosulfate (PMS), and 2, 6-dichlorophenolindophenol (DCPIP). When PQQ, PMS, and DCPIP are combined, Pe DDH (60 µg/mL) effectively degrads DON (150 µM) in just 5 min, suggesting a synergistic effect of three cofactors on DON degradation. All these results suggest a great potential of Pe DDH in the control of DON contamination.

Systemic mycoses, particularly those caused by Candida albicans, represent a serious global health concern due to rising multidrug resistance and limited treatment options. This study explores the antifungal potential of sodium lignosulfonate (LIG), a natural phenolic compound, as a multitarget therapeutic agent against various virulence proteins of C. albicans and other pathogenic Candida species. The objective of this study was to further evaluate its multiple-targeting/polypharmacological potential with plausible mode of action against C. albicans. At first, LIG was subjected to in-silico analysis to acquire preliminary knowledge about its multiple targeting potential. Subsequently, some biochemical analyses were performed to demonstrate its fungicidal activity. In-vitro analysis (plasma membrane permeation, ROS production, chitin depletion study) was performed to further validate its promising multiple-targeting/polypharmacological potential and revealed its mechanism of action. Homology modeling and docking studies revealed that LIG effectively binds to critical C. albicans proteins, including ERG1, ERG11, FKS1, CHS3, CLB2, and CEK1. The docking scores indicated strong interactions, supporting LIG’s potential to inhibit multiple virulence factors With ROS production we could confirm the involvement of apoptosis. Time-kill assays confirmed the antifungal effect of LIG against C. albicans, C. glabrata, C. tropicalis, and C. parapsilosis. LIG demonstrated a > 3-log10 reduction in CFU/mL, and in combination with fluconazole, it showed synergistic activity, particularly reducing CFU in C. dubliniensis by 2.5-fold compared to fluconazole alone. The chitin depletion assay has reported a decrease in levels of chitin which indicates another aspect of LIG’s mode of action. This study reveals LIG as a potent and persuasive natural antifungal agent that targets multiple proteins of Candida. This revelation might impact the direction of potent antifungal agent development by aiming multiple targets of fungal pathogens simultaneously.

Archaea represents a significant population of up to 10% in soil microbial communities. The role of Archaea in soil is often overlooked mainly due to its unculturability. Among the three domains of life biological nitrogen fixation (BNF) is mainly a trait of Eubacteria and some Archaea. Archaea mediated processes like BNF may become even more important in the face of global Climate change. Although there are reports on nitrogen fixation by Archaea, to best of our knowledge there is no comprehensive report on BNF by Archaea under environmental stresses typical to climate change. Here we report a survey of literature and DNA database to study N₂-fixation among Archaea. A total of 37 Archaea belonging to Methanogens of the phylum Euryarchaeota within the class Methanococcus, Methanomicrobia Methanobacteria, and Methanotrophic ANME2 lineages either contain genes for BNF or are known to fix atmospheric N₂. Archaea were found to have their nif genes arranged as clusters of 6–8 genes in a single operon. The genes code for commonly found Mo-nitrogenase while in some archaea the genes for alternative metal nitrogenases like vnf were also found. The nifHDK gene similarity matrices show that Archaea shared the highest similarity with the nifHDK gene of anaerobic Clostridium beijerinckii. Although there are various theories about the origin of N₂-fixation in Archaea, the most acceptable is the origin of N₂-fixation first in bacteria and its subsequent transfer to Archaea. Since Archaea can survive under extreme environmental conditions their role in BNF should be studied especially in soil under environmental stress.

Salmonella enteritidis is one of the most common pathogens that cause foodborne disease outbreaks and food spoilage, which seriously threatens human health. Bacteriophages have shown broad application prospects in controlling harmful microorganisms during food processing and preservation due to their ability to specifically infect bacteria. In this study, Salmonella enteritidis bacteriophage Salmp-p7 was isolated and characterized from slaughterhouse wastewater. Transmission electron microscopy (TEM) analysis showed that Salmp-p7 belonged to the Siphoviridae family and was active against Salmonella enteritidis and Escherichia coli. Whole genome sequence analysis showed that Salmp-p7 was a lytic bacteriophage with a total length of 60,066 bp of sequence. Salmp-p7 has a short incubation period and a long burst duration, with a burst volume of 55 PFU/cell and a good lysis effect. It can maintain a stable state within the temperature range of 30–60℃ and pH range of 4–12 and has the potential for application in food. In vitro, antimicrobial curves and inhibition of biofilm removal experiments showed that Salmp-p7 could effectively inhibit and eliminate Salmonella enteritidis. The application of Salmp-p7 to the whole liquid of infected eggs resulted in a significant reduction of viable bacteria. And Salmp-p7 has high stability and lytic activity and has the potential to become a new biological control agent for Salmonella enteritidis in eggs.

Orally dissolving films (ODFs) have emerged as a versatile platform that combines convenience, efficacy, and patient compliance. In this study, the cell-free supernatant of the oral probiotic Streptococcus salivarius M18 was incorporated into various biopolymer-based ODF formulations, evaluated for demolding, fragility, and flexibility. The combination of carboxymethyl cellulose, sodium alginate, and glycerol successfully formed stable films. The films were characterized by weight, thickness, pH, and disintegration times. Fourier-transform infrared spectroscopy (FTIR) was used to analyze ODF content and release profiles in simulated saliva. Unique absorption peaks in the cell-free product-incorporated ODF samples confirmed the integration of bacterial proteins, lipids, and nucleic acids into the ODF matrix. The biological activity of the ODF carrying M18 bioactive products was assessed by its inhibitory effect on the growth of Streptococcus mutans, a pathogen linked to dental plaque and cavities. Additionally, the anti-proliferative effect on cancer epithelial cells was demonstrated. This study show that probiotic products can be integrated into bio-based thin films without losing activity, making this delivery platform promising for local and potentially systemic effects.