Purification, Characterization and Bactericidal Action of Lysozyme, Isolated from Bacillus subtillis BSN314: A Disintegrating Effect of Lysozyme on Gram-Positive and Gram-Negative Bacteria

Combinatorial therapeutic enzymes to combat multidrug resistance in bacteria

AIMS

Antibiotic resistance including multidrug resistance (MDR) is a negative symbol to the human health system because it loses the capability to treat infections. Unfortunately, the available antibiotics do not show an effective therapeutic response against bacterial infections. In the situation of global antibiotic unresponsiveness, enzymatic therapy especially in combinatorial form seems an effective approach to control bacterial infection and combat resistance. The article is important because it focuses on combinatorial enzymatic therapy that has multiple properties (effective antibacterial performances, antibiofilm capacity, immunomodulators, targeted actions, synergistic actions, multiple targeting, and resistance-proof properties) and can address antibiotic resistance effectively.

MATERIALS AND METHODS

We searched the related topics with Pubmed, Scopus, and Google Scholar databases and finally 73 relevant papers were reviewed in detail and cited in this article.

KEY FINDINGS

Discusses properties of combinatorial therapeutic enzymes made it an accomplished means over antibiotic therapy. This article discusses the need for combinatorial enzymatic therapy against bacterial infection, its distinguished features, and properties with multi-mechanistic antibacterial action. It discussed the European Medicine Agency and Food and Drug Administration-approved therapeutic enzymes (antibacterial and antibiofilm).

SIGNIFICANCE

This article provided the possible combination of the enzyme that may be used as an antibacterial agent along with limitations and future scope of combinatorial antibacterial enzymatic agents. This article could draw the attention of researchers to combinatorial therapeutic enzymatic molecules as effective and futuristic therapy to overcome the problem of multiple antibiotic resistance in bacteria.

Whole-cell biocatalysis for ε-poly-l-lysine production by a food-grade recombinant Bacillus subtilis

ε-Poly-l-lysine (ε-PL), a natural food preservative with various advantages, is primarily produced by Streptomyces. It has attracted considerable attentions for the outstanding antibacterial activity, safety, heat stability, water solubility and other remarkable properties. In this study, a food-grade recombinant Bacillus subtilis was constructed for the biocatalysis of ε-PL. Firstly, the d-alanine racemase gene (alrA) was deleted from the genome of Bacillus subtilis 168 to construct an auxotrophic B. subtilis 168 (alrA-). Based on the shuttle plasmid pMA5, a food-grade plasmid pMA5a was constructed by replacing the genes of kanamycin resistance (Kanr) and ampicillin resistance (Ampr) with alrA and the gene encoding α-peptide of β-galactosidase (lacZα), respectively. Subsequently, codon-optimized ε-PL synthase gene (pls) and P-pls were ligated into pMA5a and transformed in E. coli DH5α and expressed in B. subtilis 168 (alrA-). Finally, the whole-cell biocatalysis conditions for ε-PL production by B. subtilis 168 (alrA-)/pMA5a-pls were optimized, and the optimal conditions were 30°C, pH 4, l-lysine concentration of 0.6 g/L, bacterial concentration of 15 % (w/v) and a catalytic time of 7 h. The ε-PL production reached a maximum of 0.33 ± 0.03 g/L. The product was verified to be ε-PL by HPLC and tricine-SDS-PAGE. The information obtained in this study shows critical reference for the food-grade heterologous expression of ε-PL.

Antibacterial activity of lysozyme after association with carboxymethyl konjac glucomannan

The unique high isoelectric point of lysozyme (LYZ) restricts its application in composite antibacterial coating due to the unfavorable liability to electrostatic interaction with other components. In this work, the antibacterial activity of a dispersible LYZ-carboxymethyl konjac glucomannan (CMKGM) polyelectrolyte complex was evaluated. Kinetic analysis revealed that, compared with free LYZ, the complexed enzyme exhibited decreased affinity (Km) but markedly increased Vmax against Micrococcus lysodeikticus, and QCM and dynamic light scattering analysis confirmed that the complex could bind with the substrate but in a much lower ratio. The complexation with CMKGM did not alter the antibacterial spectrum of LYZ, and the complex exerted antibacterial function by delaying the logarithmic growth phase and impairing the cell integrity of Staphylococcus aureus. Since the LYZ-CMKGM complex is dispersible in water and could be assembled easily, it has great potential as an edible coating in food preservation.

Characterization of Antimicrobial Activities of Bifidobacterium lactis BB-12 and Their Inhibitory Effect Against Some Foodborne Pathogens

Bifidobacterium animalis subsp. lactis BB-12, a probiotic, has shown potential to promote health benefits and control pathogens. This study aimed to investigate the effectiveness of BB-12 and its cell-free supernatant (CFS) in inhibiting the growth of Listeria monocytogenes and Salmonella enterica serovar Typhimurium. To assess the antimicrobial activity of BB-12, agar well diffusion, disk diffusion, and minimum inhibitory concentration (MIC) tests were conducted. The bicinchoninic acid (BCA) assay was performed to measure the protein concentration in CFS. The study's results indicated that the BB-12 strain inhibited the pathogens' growth. The disk diffusion test using BB-12 showed inhibitory results ranging from 11 to 14 mm for both bacteria. The agar well diffusion test reported the zone of inhibition ranging from 11.6 to 16 mm for both bacteria. The MIC test was conducted as a confirmatory test, which demonstrated the highest inhibitory zone using 2 McFarland (6 × 108 CFU/mL) concentrations of probiotics on L. monocytogenes (44.98%) and S. Typhimurium (66.41%). The disk diffusion test revealed that the probiotic CFS had a significant inhibitory impact on S. Typhimurium with a 16.6 mm zone of inhibition. The BCA test findings indicated that the 24- and 48-h CFSs exhibited inhibitory properties against infections. Notably, the 24-h CFS, including a protein level of 78.47 μg/mL, demonstrated a more pronounced inhibitory impact on both pathogens. The findings highlight that utilizing the BB-12 strain and its CFS can serve as a viable approach to battle infections, enhancing food safety and public health.

Screening of cellulose-degrading bacteria and optimization of cellulase production from Bacillus cereus A49 through response surface methodology

Cellulose-degrading microorganisms hold immense significance in utilizing cellulose resources efficiently. The screening of natural cellulase bacteria and the optimization of fermentation conditions are the hot spots of research. This study meticulously screened cellulose-degrading bacteria from mixed soil samples adopting a multi-step approach, encompassing preliminary culture medium screening, Congo red medium-based re-screening, and quantification of cellulase activity across various strains. Particularly, three robust cellulase-producing strains were identified: A24 (MT740356.1 Brevibacillus borstelensis), A49 (MT740358.1 Bacillus cereus), and A61 (MT740357.1 Paenibacillus sp.). For subsequent cultivation experiments, the growth curves of the three obtained isolates were monitored diligently. Additionally, optimal CMCase production conditions were determined, keeping CMCase activity as a key metric, through a series of single-factor experiments: agitation speed, cultivation temperature, unit medium concentration, and inoculum volume. Maximum CMCase production was observed at 150 rpm/37 °C, doubling the unit medium addition, and a 5 mL inoculation volume. Further optimization was conducted using the selected isolate A49 employing response surface methodology. The software model recommended a 2.21fold unit medium addition, 36.11 °C temperature, and 4.91 mL inoculant volume for optimal CMCase production. Consequently, three parallel experiments were conducted based on predicted conditions consistently yielding an average CMCase production activity of 15.63 U/mL, closely aligning with the predicted value of 16.41 U/mL. These findings validated the reliability of the model and demonstrated the effectiveness of optimized CMCase production conditions for isolate A49.

Engineering strategies and challenges of endolysin as an antibacterial agent against Gram-negative bacteria

Bacteriophage endolysin is a novel antibacterial agent that has attracted much attention in the prevention and control of drug-resistant bacteria due to its unique mechanism of hydrolysing peptidoglycans. Although endolysin exhibits excellent bactericidal effects on Gram-positive bacteria, the presence of the outer membrane of Gram-negative bacteria makes it difficult to lyse them extracellularly, thus limiting their application field. To enhance the extracellular activity of endolysin and facilitate its crossing through the outer membrane of Gram-negative bacteria, researchers have adopted physical, chemical, and molecular methods. This review summarizes the characterization of endolysin targeting Gram-negative bacteria, strategies for endolysin modification, and the challenges and future of engineering endolysin against Gram-negative bacteria in clinical applications, to promote the application of endolysin in the prevention and control of Gram-negative bacteria.

Expression of BSN314 lysozyme genes in Escherichia coli BL21: a study to demonstrate microbicidal and disintegarting potential of the cloned lysozyme

This study is an extension of our previous studies in which the lysozyme was isolated and purified from Bacillus subtilis BSN314 (Naveed et al., 2022; Naveed et al., 2023). In this study, the lysozyme genes were cloned into the E. coli BL21. For the expression of lysozyme in E. coli BL21, two target genes, Lyz-1 and Lyz-2, were ligated into the modified vector pET28a to generate pET28a-Lyz1 and pET28a-Lyz2, respectively. To increase the production rate of the enzyme, 0.5-mM concentration of IPTG was added to the culture media and incubated at 37 °C and 220 rpm for 24 h. Lyz1 was identified as N-acetylmuramoyl-L-alanine amidase and Lyz2 as D-alanyl-D-alanine carboxypeptidase. They were purified by multi-step methodology (ammonium sulfate, precipitation, dialysis, and ultrafiltration), and antimicrobial activity was determined. For Lyz1, the lowest MIC/MBC (0.25 μg/mL; with highest ZOI = 22 mm) were recorded against Micrococcus luteus, whereas the highest MIC/MBC with lowest ZOI were measured against Salmonella typhimurium (2.50 μg /mL; with ZOI = 10 mm). As compared with Aspergillus oryzae (MIC/MFC; 3.00 μg/mL), a higher concentration of lysozyme was required to control the growth of Saccharomyces cerevisiae (MIC/MFC; 50 μg/mL). Atomic force microscopy (AFM) was used to analyze the disintegrating effect of Lyz1 on the cells of selected Gram-positive bacteria, Gram-negative bacteria, and yeast. The AFM results showed that, as compared to Gram-negative bacteria, a lower concentration of lysozyme (Lyz1) was required to disintegrate the cell of Gram-positive bacteria.

Biofilm-Inhibitory Activity of Wild Mushroom Extracts against Pathogenic Bacteria

Objective

This study aims to investigate the bacterial biofilm-inhibitory effect of mushroom extracts.

Methods

Mushrooms were collected from Arabuko-Sokoke and Kakamega forests and identified using morphological and molecular approaches. Auricularia auricula-judae, Microporus xanthopus, Termitomyces umkowaani, Trametes elegans, and Trametes versicolor were extracted by chloroform, 70% ethanol, and hot water. Extracts were tested against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus (ATCC25923). Data were analyzed using SPSS ver. 20.0.

Results

Chloroform, 70% ethanol, and hot water extracts of A. auricula-judae (50 μg/mL) showed statistically significant antibiofilm activities against P. aeruginosa, E. coli, and S. aureus (p ≤ 0.05). M. xanthopus extracts (250 μg/mL) revealed significantly significant antibiofilm activities against each test bacterium (p ≤ 0.05). All extracts of T. umkowaani (250 μg/mL) exhibited statistically significant antibiofilm activities against S. aureus only (p ≤ 0.05). Chloroform extract of T. elegans (250 μg/mL) showed the best antibiofilm activity (69.75 ± 0.01%) against S. aureus. All T. versicolor extracts (250 μg/mL) indicated the best antibiofilm activities against S. aureus.

Conclusions

Being the first study of its kind to be conducted in Kenya, it added a novel concept to the body of knowledge already known about medical biotechnology research. It offers a fresh understanding of the various varieties of mushrooms found in Kenya, their potential biological function in the production of drugs, particularly those that combat drug resistance, and perhaps even a peek at their bioactive elements. Wild mushrooms, a hidden gem, might help to reopen the pipeline of new antibiotics that have been on the decline. However, further research is required to determine the potential mechanism(s) of action of the extracts that are in charge of the apparent antibiofilm activity.

Administration of probiotics affects Artemia franciscana metanauplii intestinal ultrastructure and offers resistance against a Photobacterium damselae ssp. piscicida induced oxidative stress response

The effects of Photobacterium damselae ssp. piscicida (Phdp) on immune responses and intestinal ultrastructure of Artemia franciscana following infection and their amelioration by the probiotic bacteria Bacillus subtilis, Lactobacillus plantarum and Lactococcus lactis were evaluated. Pathogen growth inhibition in coculture with each probiotic and its virulence against Artemia were confirmed with an LC50 of 105 CFU mL-1. Phdp administration to Artemia at sublethal levels resulted in depletion of superoxide dismutase, glutathione reductase, glutathione transferase and phenoloxidase activities, extensive lipid peroxidation and reduced survival. Following a combined administration of each probiotic and the pathogen, enzyme activities and survival were significantly higher, while lipid peroxidation was reduced, compared to the infected group with no probiotic treatment (P < 0.05). The transmission electron microscopy study revealed that pathogen infection resulted in disarranged and fragmented microvilli, formation of empty or pathogen containing cytoplasmic vacuoles and damaged mitochondria. In the probiotic-treated and Phdp-infected series, intestinal cells showed normal appearance, except for the presence of pathogen-containing vacuoles and highly ordered but laterally stacked microvilli. The results of the present study indicate that Phdp induces cell death through an oxidative stress response and probiotics enhance Artemia immune responses to protect it against the Phdp induced damage.

Detection of non-ribosomal and polyketide biosynthetic genes in bacteria from green mud crab Scylla serrata gut microbiome and their antagonistic activities

Multi-modular enzyme complexes known as non-ribosomal peptide synthetases (NRPSs) and polyketide synthetases (PKSs) have been widely reported in bacteria that produce secondary bioactive metabolites such as non-ribosomal peptides (NRPs) and polyketides (PKs), respectively. These NRPS/PKS pathways contribute to synthesizing several antibiotics, such as vancomycin, rifamycin, and bleomycin, which are vital in human medicine. The present study aimed to isolate gut-associated bacteria from mud crab Scylla serrata, and detect NRPS and PKS gene clusters associated with it. This study included 36 bacterial isolates from five mud crab gut samples. Biosynthetic gene clusters (NRPS and PKS), were detected by PCR using degenerative primers specific to these genes. Three isolates (FKP2-4, FKP4-1, and FKP2-16) were positive for NRPS and two for PKS (FKP2-4 and FKP4-1) genes. The isolates were subjected to 16S rRNA gene amplification and sequenced. In silico analysis of the sequences using the Basic Local Alignment Search Tool (BLAST) identified the isolates FKP2-4, FKP4-1, and FKP2-16 as Acinetobacter variabilis, Vagococcus fluvialis, and Staphylococcus arlettae, respectively, after comparing with the existing sequences available in the National Center for Biotechnology Information (NCBI) database. Compared to the control, it was observed that these isolates exhibited intriguing antagonistic activities against Escherichia coli and Staphylococcus aureus. However, these isolates failed to show significant activity against Candida albicans. Exopolysaccharide production by the isolated organisms was tested using Zobell marine agar (ZMA) with 5% sucrose, but none of the colonies were mucoid or slimy.

Nutritional composition assessment and antimicrobial activity of Catostylus perezi, jellyfish blooms along the coast of Pakistan: an awareness to avoid food neophobia in Pakistan

This study highlighted the nutritional importance of Catostylus perezi (an edible jellyfish) in Pakistan; a society where a large proportion of the population suffers from malnutrition, while C. perezi, a blessing of the sea, is wasted or exported. In the present study, the amino acid and fatty acid profiles of the oral arms and umbrella of C. perezi were determined by HPLC. The total amino acid concentration (ΣAA) in the oral arms was 151.19 mg/100g, while in the umbrella it was 100.17 mg/100g. The ratio of total essential amino acids to total non-essential amino acids (TEAA/TNEAA) was 0.72 in the oral arms, while it was 0.70 in the umbrella. Higher amount of ω-3 with lower ratio of ω-6/ω-3 in oral arms (0.52), rather umbrella (ω-6/ω-3 ratio; 0.62). The antimicrobial activity, MIC, MBC, and MFC of the whole body of the edible jellyfish were determined. On the basis of polarity, different solvents were used, e.g. water, methanol, dichloromethane, chloroform, and n-hexane. Among all the extracts, the water extract gave the highest ZOI against C. xerosis (29 mm), while the n-hexane extract gave the lowest ZOI against S. aureus (MRSA) ATCC 33591 (8.20 mm). The water extract of C. perezi had high potential against C. xerosis with the highest AMI and PAI (1.53 and 153, respectively), while the same extract had the highest TAI against E. coli (81.43 mL/g). For fungi/yeast, the methanolic extract had the highest ZOI (29.70 mm) against S. cerevisiae and the lowest MIC/MFC (2.40 µg/mL) against the same pathogen. The n-Hexane extract gave the lowest ZOI (11.10 mm) against P. variotii and the highest MIC/MFC (31.60 µg/mL) against Penicillium sp. Atomic force microscopy (AFM) was used to analyse the disintegrating effect of the extracts (with the highest antimicrobial effect) on the cells of selected Gram-positive, Gram-negative and yeast species. The amino acid and fatty acid profiles and antimicrobial assessment showed that C. perezi has great nutritional importance, so the use of C. perezi as food is highly recommended for the Pakistani community.