International Microbiology最新文献

Foodborne infections in humans are one of the major concerns of the food industries, especially for minimally processed foods (MPF). Thereby, the packaging industry applies free chlorine in the sanitization process, ensuring the elimination of any fecal coliforms or pathogenic microorganisms. However, free chlorine's propensity to react with organic matter, forming toxic compounds such as trihalomethanes and haloacetic acid. Therefore, the present work aimed to synthesize a novel organic biomaterial as an alternative to free chlorine. Chitosan microparticles were produced, with Pimpinella anisum (anise) essential oil immobilized in the biopolymer matrix (MPsQTO). The characterization of this biomaterial was done through GC-MS/MS, FT-IR, and SEM. Antimicrobial assays proved that the MPsQTO presented antibacterial activity for Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, and Bacillus subtilis at 300 µL mL^-1 of concentration. The fluorescence microscope also showed the MPsQTO targets the cytoplasmatic membrane, which is responsible for cell death in the first minutes of contact. Studies with the mutant B. subtilis (amy::pspac-ftsZ-gfpmut1) and the Saccharomyces cerevisiae D7 also proved that the biomaterial did not affect the genetic material and did not have any mutagenic/carcinogenic effect on the cells. The sanitization assays with pumpkin MPF proved that the MPsQTO is more effective than free chlorine, increasing the shelf-life of the MPF. Consequently, the novel biomaterial proposed in this work is a promising alternative to traditional chemical sanitizers.

Antimicrobial peptides (AMPs) are a family of short defense proteins that are naturally produced by all organisms and have great potential as effective substitutes for small-molecule antibiotics. The present study aims to excavate AMPs from sea cucumbers and achieve their heterologous expression in prokaryotic Escherichia coli. Using MytC as a probe, a cysteine-stabilized peptide SCAK33 with broad-spectrum antimicrobial activity was discovered from the proteome of Apostichopus japonicas. The SCAK33 showed inhibitory effects on both gram positive and gram negative bacteria with MICs of 3-28 μM, and without significant hemolysis activity in rat blood erythrocyte. Especially, it exhibited good antimicrobial activity against Bacillus megaterium, B. subtilis, and Vibrio parahaemolyticus with the MIC of 3, 7, and 7 μM, respectively. After observation by scanning electronic microscopy (SEM) and confocal laser scanning microscope (CLSM), it was found that the cell membrane of bacteria was severely damaged. Furthermore, the recombinant SCAK33 (reSCAK33) was heterologously expressed by fusion with SUMO tag in E. coli BL21(DE3), and the protein yield reached 70 mg/L. The research will supplement the existing quantity of sea cucumber AMPs and provide data support for rapid mining and biological preparation of sea cucumber AMPs.

A series of known diterpenoids from Isodon serra (Maxim.) Hara exhibited antibacterial activities against Staphylococcus aureus and even methicillin-resistant S. aureus (MRSA). Among these diterpenoids, hebeirubescensin K (7), effusanin E (8), and nodosin (9) showed the optimal minimum inhibitory concentration (MIC) values ranging from 3.12 to 6.25 μg/mL against tested MRSA strains, and they also inhibited bacterial proliferation, biofilm formation, and key gene expressions related to adhesion and virulence of MRSA. In vivo experiments also demonstrated the antibacterial abilities of 7-9 as topical drugs and promoted wound healing caused by a MSRA infection. It is the first time that the anti-S. aureus and MRSA activities of diterpenoids from I. serra has been systematically reported. These current findings provide insight into the anti-MRSA mechanism of diterpenoids from I. serra; indicating these compounds may be used as antimicrobial agents and contribute to the development as well as application of I. serra in phytomedicine for MRSA infections.

Dendrobium officinale Kimura et Migo has long been utilized in traditional Chinese medicine and other Asian cultures for its medicinal properties. One of the key bioactive compounds found in D. officinale is D. officinale polysaccharides (DOPs). Recent studies have indicated that the rhizosphere microbiome can influence the accumulation of bioactive compounds in medicinal plants. Our findings revealed that the bacterial phylum Bacteroidetes played a significant role in shaping the ecological stability of the rhizosphere bacteria associated with D. officinale. Additionally, Pandoraea may have the potential to enhance the production of polysaccharides in D. officinale. Overall, this research contributes to our understanding of the intricate relationship between the rhizosphere microbiome and the accumulation of bioactive compounds in D. officinale. It highlights the potential of specific bacterial taxa, such as Pandoraea, in promoting the production of polysaccharides, thus further establishing the medicinal value of this plant. Our results provide insights for further development of specific fertilizers for medicinal plants.

The main objective of this study was to assess cellulolytic probiotic strains from traditional fermented beverages such as palm wine in order to supplement the animal feed and strengthen the gut health of the animal for better digestibility and absorption. In the present study, different types of microbes were isolated from traditionally prepared palm wine and analyzed for their probiotic nature. For any microbe to be probiotic in nature, it has to sustain the harsh conditions of the human gastrointestinal tract such as acid tolerance, bile tolerance at the lower range of pH, and other properties like auto aggregation test, cell surface hydrophobicity test with non-polar hydrocarbons for evaluating its capabilities to adhere to the intestinal cells and antimicrobial nature against pathogens. Bacillus mycoides strain PR04 and Bacillus subtilis strain PR21 were found to be resistant to acid and bile in simulated artificial gastrointestinal tract model, found to be than 55% hydrophobic with xylene and n-hexadecane and also showed antimicrobial activity greater towards pathogenic strains like Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, and Salmonella typhimurium respectively. The cellulolytic activity of the isolates PR04 and PR21 was evaluated in (0.2–2) % CMC (carboxymethyl cellulose) plate. Bacillus mycoides PR04 and Bacillus subtilis PR21 could degrade carboxymethyl cellulose, filter paper, and sugarcane bagasse. The degradation of sugarcane bagasse was confirmed by Scanning electron microscopy and filter paper degradation after 4 days of incubation at 37 °C. Cellulase gene of the identified Bacillus sp. strains was amplified by primers CF5′-ACAGGATCCGATGAAAACGGTCAATTTCTATTTT-3′ and CR5′-ACTCTCGAGATTGGGTTCTGTTCCCAAT-3′. This study proposes potential probiotic Bacillus mycoides PR04 (Accession no. OR625070) and Bacillus subtilis PR21 (Accession no. OR625072) in the application as an animal feed additive to assist in its digestibility and encourage the gut health.

The broad-spectrum antibacterial capabilities of fatty acids (FAs) and their reduced propensity to promote resistance have rendered as a promising substitute for conventional antibiotics. The structural significance of fatty acid production with the other lipids is a major energy source, and signal transduction has drawn a great deal of research attention to these biomolecules. Saturated and monounsaturated fatty acids reduce virulence by preventing harmful opportunistic bacteria like Pseudomonas aeruginosa and Chromobacterium violaceum from activating their quorum sensing (QS) systems. In this finding, the fatty acids capric acid, caprylic acid, and monoelaidin were selected to evaluate their anti-QS activity against the C. violaceum and P. aeruginosa. At the minimum inhibitory concentration (MIC) and sub-MIC concentration of the three fatty acids, the virulence factor production of both the bacteria was quantified. The virulence factors like EPS, biofilm quantification and visualization, and motility assays were inhibited in the dose-dependent manner (MIC and sub-MIC) for both the organisms whereas this pattern was followed in the pyocyanin, pyoverdine, rhamnolipid, protease of P. aeruginosa and the violacein, and chitinase of C. violaceum. In all these biochemical assays, the capric acid could effectively reduce the production and further validated at gene expression level by RT-qPCR. The study on the gene expression for all these virulence factors reveals that the capric acid inhibited the growth of both the organisms in a higher fold than the caprylic and monoelaidin. The in silico approach of structural validation for the binding of ligands with the proteins in the QS circuit was studied by molecular docking in Schrodinger software. The Las I and Las R in P. aeruginosa and the CviR of C. violaceum protein structures were docked with the selected three fatty acids. The capric acid binds to the pocket with the highest binding score of all the proteins than the caprylic and monoelaidin fatty acids. Thus, capric acid proves to be the therapeutic biomolecule for the anti-QS activity of opportunistic bacteria.

Graphical Abstract

Background

Coagulase-negative staphylococci (CoNS) are evolving as major reservoirs and vectors of unusual and critical antimicrobial resistance (AMR) mechanisms.

Materials and methods

In this study, the genomic characterization of 26 multidrug-resistant (MDR)-CoNS (S. borealis, S. saprophyticus, S. sciuri, S. hominis, S. epidermidis, S. pasteuri, S. hyicus, S. simulans, S. haemolyticus, and S. arlettae) previously obtained from the nasal cavity of healthy nestling storks, humans who had no contact with animals, pigs, and pig farmers, as well as dogs and dog owners from Spain was performed. High-quality draft genomes obtained by Illumina sequencing technology were used to determine their resistome, virulome, mobile genetic elements, and CRISPR-Cas types.

The relatedness of three CoNS species with publicly available genomes was assessed by core-genome single nucleotide polymorphisms (SNPs).

Results

AMR genes to all classes of antibiotics in staphylococci were detected including unusual ones (mecC, ermT, and cfr), of which their corresponding genetic organizations were analyzed. About 96.1% of the MDR-CoNS strains harbored diverse adherence or immune evasion genes. Remarkably, one enterotoxin-C and -L-carrying S. epidermidis-ST595 strain from a nestling stork was detected. Moreover, various plasmid bound-biocide resistance genes (qacACGJ) were identified in 34.6% of the MDR-CoNS. Two genes that encode for cadmium and zinc resistance (cadD, czrC) were found, of which czrC predominated (42.3%). Complete CRISPR-Cas system was detected in 19.2% of the CoNS strains, of which cas-1, -2, and -9 predominated, especially in 75% of the S. borealis strains. The phylogenetic analysis identified clusters of related S. epidermidis lineages with those of other countries (SNP < 100). Also, highly related S. borealis isolates (SNP < 10) from pigs was confirmed for the first time in Spain.

Conclusion

These findings showed that various ecological niches harbor CoNS that presented MDR phenotypes mediated by multiple AMR genes carried by mobile genetic elements with relatively low frequency of intact CRISPR-Cas systems. Furthermore, the transmission of some CoNS species in humans and animals is strongly suggested.

Free-living amoebae infections are on the rise while the prognosis remains poor. Current therapies are ineffective, and there is a need for novel effective drugs which can target Naegleria, Balamuthia, and Acanthamoeba species. In this study, we determined the effects of a nano-formulation based on flavonoid patuletin-loaded gallic acid functionalized zinc oxide nanoparticles (PA-GA-ZnO) against Acanthamoeba, Balamuthia, and Naegleria trophozoites. Characterization of the nano-formulation was accomplished utilizing analytical tools, namely Fourier-transform infrared spectroscopy, drug entrapment efficiency, polydispersity index, dimensions, and surface morphologies. Anti-amoebic effects were investigated using amoebicidal assay, cytopathogenicity assay, and cytotoxicity of the nano-formulation on human cells. The findings revealed that nano-formulation (PA-GA-ZnO) displayed significant anti-amoebic properties and augmented effects of patuletin alone against all three brain-eating amoebae. When tested alone, patuletin nano-formulations showed minimal toxicity effects against human cells. In summary, the nano-formulations evaluated herein depicts efficacy versus Acanthamoeba, Balamuthia, and Naegleria. Nonetheless, future studies are needed to comprehend the molecular mechanisms of patuletin nano-formulations versus free-living amoebae pathogens, in addition to animal studies to determine their potential value for clinical applications.

Obligate endosymbiont bacteria associated with insects are naturally providing their hosts with essential nutrients such as vitamins and amino acids and biological services including protection from pathogens. In this study, we aimed to investigate the presence of Wolbachia infection among males and females of the parasitic apricot seed wasp (ASW) Eurytoma samsonowi Vassiliev (Vassiliev Petrograd 11: 1-15, 1915) (Hymenoptera: Eurytomidae), a very harmful pest of apricot (Prunus armeniaca), in the oasis of Gafsa, Southern-West of Tunisia. The detection of Wolbachia infection was assessed based on the amplification of the Wolbachia surface protein (wsp) gene and a multilocus sequence typing (MLST) as a universal genotyping tool for Wolbachia involving the analyses of genes gatB, coxA, hcpA, fbpA, and ftsz. Confirming the screening results, Wolbachia was detected in the natural apricot wasp for the first time, with a significant difference between males (5%) and females (59%) based on wsp gene. All Wolbachia strains identified in E. samsonowi were clustered among supergroups B of Wolbachia.

Thermophilic bacteria able to produce exopolysaccharides (EPSs) have become attractive in recent years. EPSs synthesized by thermophiles are worth investigating due to their unexplored structural and biological properties. In this study, EPSs from thermophilic, Gram-positive bacterial isolates were purified and tested for their biological activities. A total of one hundred seven thermophilic bacteria were screened for their ability to produce exopolysaccharides. Nine isolates belonging to Geobacillus, Parageobacillus, Aeribacillus, and Anoxybacillus genera with highest EPS production were chosen, and purified EPSs (20, 61, 74, 76, 78, 89, 106, 134, and 261) were used for biological activity studies. EPS yields of selected thermophilic bacteria ranged between 117 and 419 mg/L. Among the tested EPSs, 61, 106, and 261 showed antibacterial effect against E. faecalis JH2-2 at a final concentration of 1.5 mg/mL. EPS samples had significant antioxidant capacity, especially EPS 134, with the highest DPPH radical scavenging activity of 100% at a concentration of 5 mg/mL and the strongest reducing power. EPS 20 showed the highest lipid peroxidation inhibition effect at a rate of 31%. EPSs displayed weak alpha-amylase inhibition activity when compared with standard acarbose. The prebiotic indices of EPSs 20, 61, 76, 89, 134, and 261 were found to be higher than that of inulin, a representative prebiotic carbohydrate for all tested lactic acid bacteria in the study. All examined EPSs inhibited the biofilms formed by various bacteria depending on the test strain. Results indicated that thermophilic EPSs had remarkable antioxidant, prebiotic, and antibiofilm activities. Therefore, EPSs characterized in this study may have technological applications in health and food fields.