Antibacterial activity of novel peptide derived from Cry1Ab16 toxin and development of LbL films for foodborne pathogens control

More than just an insect killer: The non-insecticidal activities of Bacillus thuringiensis with biotechnological potential

Bacillus thuringiensis (Bt) is known for the biological control of important insect pests, but scientific advances have revealed several interesting characteristics, in addition to this classical function as a bioinsecticide. To investigate the current knowledge about these non-insecticidal activities, a systematic research on primary data in the scientific literature was conducted on alternative functions of Bt with biotechnological potential. Out of a total of 140 articles selected, 15 non-insecticidal Bt activities were found. Publications related to this topic are available since 1971, and different metadata were reported, such as biomolecules and genes involved in Bt performances in non-insecticidal bioactivities. A total of 11 Bt activities with different effect measures (response variables) were identified, with an average of 48 distinct Bt strains evaluated per activity. Approximately 81.2% of all identified experiments/tests deal with the direct effects of Bt on target cells/organisms, with 36.3% of the strains within these studies tested for antibacterial action; of all microbial targets tested, 92.8% are bacteria, which led to 75.2% of the experimental conditions for all direct activities being performed in vitro. Regarding indirect Bt activities, 67.6% of these studies reported tritrophic Bt-plant-pathogen interactions. Bioremediation also appears as a relevant Bt activity being investigated in-depth. Alternative Bt activities offer innovative ways of developing biotechnology for different areas of anthropic interest; hence, we also focus on the possibility of finding multifunctional strains of Bt, as this may be advantageous from a bioeconomic point of view. Our findings are discussed in terms of research trends, aspects, details and depth of the current knowledge on alternative non-insecticidal Bt traits. We also discuss the potential application of this science for useful technological developments, aiming at solving issues related to human health, sustainable agriculture and environmental preservation/restoration.

Research Progress on New Environmentally Friendly Antifouling Coatings in Marine Settings: A Review

Any equipment submerged in the ocean will have its surface attacked by fouling organisms, which can cause serious damage. Traditional antifouling coatings contain heavy metal ions, which also have a detrimental effect on the marine ecological environment and cannot fulfill the needs of practical applications. As the awareness of environmental protection is increasing, new environmentally friendly and broad-spectrum antifouling coatings have become the current research hotspot in the field of marine antifouling. This review briefly outlines the formation process of biofouling and the fouling mechanism. Then, it describes the research progress of new environmentally friendly antifouling coatings in recent years, including fouling release antifouling coatings, photocatalytic antifouling coatings and natural antifouling agents derived from biomimetic strategies, micro/nanostructured antifouling materials and hydrogel antifouling coatings. Highlights include the mechanism of action of antimicrobial peptides and the means of preparation of modified surfaces. This category of antifouling materials has broad-spectrum antimicrobial activity and environmental friendliness and is expected to be a new type of marine antifouling coating with desirable antifouling functions. Finally, the future research directions of antifouling coatings are prospected, which are intended to provide a reference for the development of efficient, broad-spectrum and green marine antifouling coatings.

Effects of adding poly-histidine tag on stability, antimicrobial activity and safety of recombinant buforin I expressed in periplasmic space of Escherichia coli

The lack of cost-effective methods for producing antimicrobial peptides has made it impossible to use their high potential as a new and powerful class of antimicrobial agents. In recent years, extensive research has been conducted to decrease the cost of recombinant proteins production through microorganisms, transgenic animals, and plants. Well-known genetic and physiological characteristics, short-term proliferation, and ease of manipulation make E. coli expression system a valuable host for recombinant proteins production. Expression in periplasmic space is recommended to reduce the inherently destructive behavior of antimicrobial peptides against the expressing microorganism and to decline susceptibility to proteolytic degradation. In this study, a pET-based expression system was used to express buforin I at E. coli periplasmic space, and its antimicrobial, hemolytic, and cell toxicity activities as well as structural stability were evaluated. The hemolysis activity and cytotoxicity of His-tagged buforin I were negligible and its antimicrobial activity did not show a significant difference compared to synthetic buforin I. In addition, in silico investigating of stability of native and His-tagged buforin I showed that RMSF, RMSD and Rg curves had followed a similar trend during 150 ns simulation. Furthermore, evaluating the modelled structures, FTIR and X-ray methods of both peptides indicated an insignificant structural difference. It was concluded that the recombinant buforin I could be a viable alternative to some currently used antibiotics by successfully expressing it in the pET-based expression system.

Efficacy of natural antimicrobial peptides versus peptidomimetic analogues: a systematic review

Aims: This systematic review was carried out to determine whether synthetic peptidomimetics exhibit significant advantages over antimicrobial peptides in terms of in vitro potency. Structural features - molecular weight, charge and length - were examined for correlations with activity. Methods: Original research articles reporting minimum inhibitory concentration  values against Escherichia coli, indexed until 31 December 2020, were searched in PubMed/ScienceDirect/Google Scholar and evaluated using mixed-effects models. Results: In vitro antimicrobial activity of peptidomimetics resembled that of antimicrobial peptides. Net charge significantly affected minimum inhibitory concentration values (p < 0.001) with a trend of 4.6% decrease for increments in charge by +1. Conclusion: AMPs and antibacterial peptidomimetics exhibit similar potencies, providing an opportunity to exploit the advantageous stability and bioavailability typically associated with peptidomimetics.

Antibacterial, conductive, and osteocompatible polyorganophosphazene microscaffolds for the repair of infectious calvarial defect

Many osteoconductive and osteoinductive scaffolds have been developed for promoting bone regeneration; however, failures would occur in osteogenesis when the defect area is significantly infected while the biomaterials have no antibacterial performances. Herein, a kind of multipurpose PATGP@PDA + Ag microspheres was prepared via emulsion method by using a conductive aniline tetramer (AT) substituted polyphosphazene (PATGP), followed by polydopamine (PDA) modification and silver nanoparticles (AgNPs) loading. The PATGP@PDA + Ag microspheres demonstrated a strong antibacterial activity against Staphylococcus aureus both in vitro and in vivo, while showing no cytotoxicity at an optimized AgNPs loading amount. Due to the electron-donor structure of the AT moieties, the PATGP@PDA + Ag microspheres displayed antioxidant capacities to scavenge reactive oxygen species (ROS). Due to their phosphorus-rich feature, the PATGP@PDA + Ag microspheres favored the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). As controls, nonconductive microspheres (PAGP@PDA, PAGP@PDA + Ag) were prepared similarly by using poly[(ethylalanine)(ethylglycyl)]phosphazene (PAGP). By co-implanting these microspheres with S. aureus into rat calvarial defects, among them, it was determined that the PATGP@PDA + Ag microspheres achieved the most abundant neo-bone formation, benefiting from their antibacterial, antioxidant and osteogenic activities. These results revealed that AgNPs loaded scaffolds made of conductive polyphosphazenes were promising for the regeneration of infected bone defects.

Evaluation of Antimicrobial Activity of Buforin I and Nisin and Synergistic Effect of the Combination of them as a Novel Antimicrobial Preservative

One of the most effective methods for increasing the antimicrobial activity of a substance is to combine it with one or more other antimicrobial agents. The aim of the present study was to evaluate the antimicrobial effect of buforin I and nisin alone and investigate the synergistic action of these compounds against the most important food spoilage microorganisms in clouding B. subtilis, S. epidermidis, L. innocua, E. coli, S. Enteritidis, A. oryzae, R. glutinis and G. candidum. The results of MIC and MBC/MFC examinations showed that buforin I had higher antimicrobial activity than nisin on all the microbial strains used in this study (p≤0.5). E.coli was the most resistant to both antimicrobial agents, while Listeria innocua and Staphylococcus epidermidis were the most sensitive to nisin and buforin I, respectively. The results of synergistic interaction between buforin I and nisin indicated that the combination of buforin I and nisin on B. subtilis, S. epidermidis and A. oryzae showed synergistic effect, while it had no effect on S. Enteritidis and Geotrichum candidum. The combination of buforin I and nisin showed partial synergistic effect on Listeria innocua, Escherichia coli, Rhodotorula glutinis. Assessment of viability of the microorganisms under the antimicrobial agents alone and in combination with each other at MICs and FICs indicated that use of these antimicrobial agents in combination enhances antimicrobial activity at lower concentrations of both agents. The present study investigated the antimicrobial properties of buforin I against food spoilage microorganisms for the first time and suggests that its use alone or in combination with nisin may provide a clear horizon for the application of antimicrobial peptides as natural preservatives. Thus, the combination of antimicrobial peptides and traditional antimicrobial food preservative could be a promising option for the prevention of contamination, spoilage, and infestation of food and beverage products.

Two novel cationic antifungal peptides isolated from Bacillus pumilus HN-10 and their inhibitory activity against Trichothecium roseum

Public concern for food safety and environmental issues and the increase in fungicide-resistant pathogen have enhanced the interest in developing alternative methods to fungicides to control postharvest fruit decay. In this study, a bacterial strain isolated from stale potato vermicelli was identified as Bacillus pumilus HN-10 based on morphological characteristics and 16S rRNA gene sequence analysis. Furthermore, two novel cationic antifungal peptides named P-1 and P-2 were purified from B. pumilus HN-10 using macroporous adsorbent resin AB-8, Sephadex G-100 chromatography, and reversed-phase high-performance liquid chromatography. The primary structure of P-1 and P-2, which were proved to be novel antifungal peptides by BLAST search in NCBI database, was PLSSPATLNSR and GGSGGGSSGGSIGGR with a molecular weight of 1142.28 and 1149.14 Da, respectively, as indicated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Both P-1 and P-2 exhibited strong antifungal activity against Trichothecium roseum with minimum inhibitory concentrations starting from 1 μg/mL. The two novel antifungal peptides were stable below 80 °C for 2 h, but lost their activity in 15 min at 121 °C. In addition, they were resistant to the proteolytic action of pepsin, trypsin, and papain, and stable within a wide range of pH (2.0-12.0). These results showed that P-1 and P-2 are novel cationic antifungal peptides with specific activity against T. roseum.