• Journal of Microbiology and Biotechnology
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• v.25 no.7
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• pp.1007-1014
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• 2015

Plectasin, the first defensin extracted from a fungus (the saprophytic ascomycete Pseudoplectania nigrella), is attractive as a prospective antimicrobial agent. The purpose of this study was to establish a bacterium-based production system and evaluate the antimicrobial activity of the resulting plectasin. A gene encoding plectasin, with the codon preference of Escherichia coli, was optimized based on its amino acid sequence, synthesized using genesplicing with overlap extension PCR, and inserted into the expression vector pGEX-4T-1. The fusion protein was expressed in the soluble fraction of E. coli and purified using glutathione Stransferase affinity chromatography. Plectasin was cleaved from the fusion protein with thrombin and purified by ultrafiltration. The purified plectasin showed strong, concentrationdependent antimicrobial activity against gram-positive bacteria, including antibiotic-resistant bacteria, especially penicillin-resistant Enterococcus faecium. This antimicrobial activity was equal to chemically synthesized plectasin and was maintained over a wide range of pH and temperatures. This soluble recombinant expression system in E. coli is effective for producing plectasin at a relatively lower cost, and higher purity and efficiency than prior systems, and might provide a foundation for developing a large-scale production system. Overall, plectasin shows potential as a novel, high-performance, and safe antibiotic for the treatment of refractory diseases caused by drug-resistant bacterial strains.

• Korean Journal of Food Science and Technology
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• v.54 no.2
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• pp.241-246
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• 2022

Antibiotic resistance is a serious problem to food safety as well as human healthcare. To avoid this, there are several approaches for a new class of antibiotic agents that target only production of virulence factors such as biofilm without bacterial growth defect. The objective of this study was to investigate the antibiofilm activity of tuberostemonine in Staphylococcus aureus. Tuberostemonine significantly reduced the biofilm formation (26.07-47.02%) in the crystal violet assay whereas there were no effect on S. aureus growth. The dispersion in preformed biofilm was also observed by confocal laser scanning microscopy (CLSM). Quantification real-time PCR revealed that the icaA and agrA expression having an important role in biofilm production of S. aureus were strongly affected with tuberostemonine. These results suggest that tuberostemonine has potential for controlling biofilm formation and dispersion by effect on virulence regulation of S. aureus.

• Journal of Animal Science and Technology
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• v.65 no.3
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• pp.479-489
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• 2023

Livestock production depends on the utilization of nutrients, and when this is accomplished, there is accelerated momentum toward growth with a low cost-to-feed ratio. Public concern over the consumption of pork with antibiotic residues in animals fed antibiotic growth promoters (AGP) has paved the way for using other natural additives to antibiotics, such as herbs and their products, probiotics, prebiotics, etc. Numerous feed additives are trending to achieve this goal, and a classic example is vitamins and minerals. Vitamins and minerals represent a relatively small percentage of the diet, but they are critical to animal health, well-being, and performance; both play a well-defined role in metabolism, and their requirements can vary depending on the physiological stage of the animals. At the same time, the absence of these vitamins and minerals in animal feed can impair the growth and development of muscles and bones. Most commercial feeds contain vitamins and trace minerals that meet nutrient requirements recommended by National Research Council and animal feeding standards. However, the potential variability and bioavailability of vitamins and trace elements in animal feeds remain controversial because daily feed intake varies, and vitamins are degraded by transportation, storage, and processing. Accordingly, the requirement for vitamins and minerals may need to be adjusted to reflect increased production levels, yet the information presented on this topic is still limited. Therefore, this review focuses on the role and function of different sources of minerals, the mode of action, the general need for micro and macro minerals in non-ruminant diets, and how they improve animal performance.

• Journal of Microbiology and Biotechnology
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• v.34 no.8
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• pp.1609-1616
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• 2024

The Burkholderia cepacia complex (Bcc) consists of opportunistic pathogens known to cause pneumonia in immunocompromised individuals, especially those with cystic fibrosis. Treating Bcc pneumonia is challenging due to the pathogens' high multidrug resistance. Therefore, inhalation therapy with tobramycin powder, which can achieve high antibiotic concentrations in the lungs, is a promising treatment option. In this study, we investigated potential mechanisms that could compromise the effectiveness of tobramycin therapy. By selecting for B. cenocepacia survivors against tobramycin, we identified three spontaneous mutations that disrupt a gene encoding a key enzyme in the biosynthesis of cobalamin (Vitamin B₁₂). This disruption may affect the production of succinyl-CoA by methylmalonyl-CoA mutase, which requires adenosylcobalamin as a cofactor. The depletion of cellular succinyl-CoA may impact the tricarboxylic acid (TCA) cycle, which becomes metabolically overloaded upon exposure to tobramycin. Consequently, the mutants exhibited significantly reduced reactive oxygen species (ROS) production. Both the wild-type and mutants showed tolerance to tobramycin and various other bactericidal antibiotics under microaerobic conditions. This suggests that compromised ROS-mediated killing, due to the impacted TCA cycle, underlies the mutants' tolerance to bactericidal antibiotics. The importance of ROS-mediated killing and the potential emergence of mutants that evade it through the depletion of cobalamin (Vitamin B₁₂) provide valuable insights for developing strategies to enhance antibiotic treatments of Bcc pneumonia.

• Microbiology and Biotechnology Letters
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• v.49 no.2
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• pp.255-263
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• 2021

In this study, we assessed the technological characteristics and safety of 88 Enterococcus faecium strains isolated from meju; the strains possess the glutamate decarboxylase gene gadA/B involved in γ-aminobutyric acid production. The study was conducted to evaluate the possibility of introducing E. faecium meju isolates as food fermentation starters. We observed that a NaCl concentration of 6% (w/v) facilitated the growth and acid production of all strains. At a NaCl concentration of 7%, 21 strains (24%) exhibited a low growth rate, 72 strains (82%) a weak acid production, and 16 strains (18%) showed no acid production. All strains exhibited protease activity at a NaCl concentration of 4%. At a NaCl concentration of 5%, 86 strains exhibited weak activity, and one strain showed no protease activity. We could not detect any lipase activity in the investigated strains. None of the strains exhibited an acquired antibiotic resistance to the seven antibiotics tested in the present study, namely ampicillin, chloramphenicol, ciprofloxacin, gentamicin, penicillin G, tetracycline, and vancomycin. We could identify the Enterococcus endocarditis antigen gene efaA and the tyrosine decarboxylase gene tdc contributing to tyramine production, in 88 meju isolates. We could not detect the Enterococcus surface protein gene esp, which is specifically possessed by human-originated E. faecium strains, in any of the 88 strains tested in the study.

• Journal of Applied Biological Chemistry
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• v.66
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• pp.258-265
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• 2023

After application of veterinary antibiotics, they may be partially metabolized before they are excreted by feces or urine either as unaltered form or as metabolites. Residual antibiotics enter the adjacent agricultural environments by spraying manure-based compost and liquid fertilizer on farmlands and lead to secondary pollution. The objective of this study was to compare the residual concentrations of 6 veterinary antibiotics by different production stages of liquid fertilizer from livestock manure recycling facilities. The relationship between concentration change of the residual antibiotics and the amount of liquid fertilizer component was also assessed. Pre-treatment showed the recovery of 63.4-106.7% at ppb level and the limit of quantification of 0.009-0.037 ㎍/L.As the result of analyzing the relationship between the residual concentrations of antibiotics and the amount of N component in liquid fertilizer by different production stages, the residual concentrations of antibiotics and N tended to decrease as the stabilization period elapsed during the liquid fertilization process. Average concentrations of sulfamethazine in raw materials, middle and final products of liquid fertilizer were 40.85, 26.17, 3.54 ㎍/L, respectively. Those of chlortetracycline decreased from 2.32 to 1.25 ㎍/L. The other 4 antibiotics also showed a decreasing trend by different production stages of liquid fertilizer. The amount of liquid fertilizer component N decreased from 0.21 to 0.096% by production stages of liquid fertilizer. It is considered that the correlation between residual antibiotic concentrations and N content can be applied as basic data for setting antibiotic reduction indicators.

• Asian-Australasian Journal of Animal Sciences
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• v.23 no.3
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• pp.410-416
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• 2010

Methane emitted from ruminant livestock is regarded as a loss of feed energy and also a contributor to global warming. Methane is synthesized in the rumen as one of the hydrogen sink products that are unavoidable for efficient succession of anaerobic microbial fermentation. Various attempts have been made to reduce methane emission, mainly through rumen microbial manipulation, by the use of agents including chemicals, antibiotics and natural products such as oils, fatty acids and plant extracts. A newer approach is the development of vaccines against methanogenic bacteria. While ionophore antibiotics have been widely used due to their efficacy and affordable prices, the use of alternative natural materials is becoming more attractive due to health concerns regarding antibiotics. An important feature of a natural material that constitutes a possible alternative methane inhibitor is that the material does not reduce feed intake or digestibility but does enhance propionate that is the major hydrogen sink alternative to methane. Some implications of these approaches, as well as an introduction to antibiotic-alternative natural materials and novel approaches, are provided.

• Korean Journal of Animal Reproduction
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• v.19 no.2
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• pp.153-157
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• 1995

These studies were conducted to investigate the microbe control effect of antibiotics treatment in all media used for in vitro fertilization(IVF) embryo production. The bovine oocytes were recovered from follicles(2~5mm) and were cultrued for 22hrs at 38.5$^{\circ}C$ with 5% CO2 incubator. The contamination and development rate in vitro fertilized oocyte was evaluated everyday. The results were summerized as follow ; 1. Control, antibiotic-antimycotic solution(AAS, Gibco) 1%＋gentamycin, and AAS 1%＋kanamycin(Sigma, USA) treatment was contaminated with 72hrs. However Baytril and Kanamycin(Korea) added was not contaminated. 2. The blastocyst formation rate in Baytril supplementated 1, 2 and 3${mu}ell$/ml was 3.73, 1.28 and 0.00%, respectively. 3. The blastocyst formation in kanamycin added concentration of 50, 75 and 100$\mu\textrm{g}$/ml was 13.0, 9.4 and 3.49%, respectively.

• Microbiology and Biotechnology Letters
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• v.32 no.1
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• pp.1-10
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• 2004

Many bacteria monitor their population density and control the expression of specialized gene sets in response to bacterial cell density based on a mechanism referred to as quorum sensing. In all cases, quorum sensing involves the production and detection of extracellular signaling molecules, auto inducers, as which Gram-negative and Gram-positive bacteria use most prevalently acylated homoserine lactones and processed oligo-peptides, respectively. Through quorum-sensing communication circuits, bacteria regulate a diverse array of physiological functions, including virulence, symbiosis, competence, conjugation, antibiotic production, motility, sporulation, and biofilm formation. Many pathogens have evolved quorum-sensing mechanisms to mount population-density-dependent attacks to over-whelm the defense responses of plants, animals, and humans. Since these AHL-mediated signaling mechanisms are widespread and highly conserved in many pathogenic bacteria, the disruption of quorum-sensing system might be an attractive target for novel anti-infective therapy. To control AHL-mediated pathogenicity, several promising strategies to disrupt bacterial quorum sensing have been reported, and several chemicals and enzymes have been also investigated for years. These studies indicate that anti-quorum sensing strategies could be developed as possible alternatives of antibiotics.

• Journal of Microbiology and Biotechnology
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• v.24 no.10
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• pp.1405-1412
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• 2014

Lysozyme is a protein found in egg white, tears, saliva, and other secretions. As a marketable natural alternative to preservatives, lysozyme can act as a natural antibiotic. In this study, we have isolated Bacillus licheniformis TIB320 from soil, which contains a lysozyme gene with various features. We have cloned and expressed the lysozyme in E. coli. The antimicrobial activity of the lysozyme showed that it had a broad antimicrobial spectrum against several standard strains. The lysozyme could maintain efficient activities in a pH range between 3 and 9 and from $20^{\circ}C$ to $60^{\circ}C$, respectively. The lysozyme was resistant to pepsin and trypsin to some extent at $40^{\circ}C$. Production of the lysozyme was optimized by using various expression strategies in B. subtilis WB800. The lysozyme from B. licheniformis TIB320 will be promising as a food or feed additive.