Characterization of Argonaute nucleases from mesophilic bacteria Paenibacillus borealis and Brevibacillus laterosporus

Thermophilic Argonaute proteins (Agos) have been shown to utilize small DNA guides for cleaving complementary DNA in vitro, which shows great potential for nucleic acid detection. In this study, we explored mesophilic Agos for the detection of small molecule by cooperating with allosteric transcription factors (aTFs). Two Agos from mesophilic bacteria, Paenibacillus borealis (PbAgo) and Brevibacillus laterosporus (BlAgo), showed nuclease activity for single-stranded DNA at moderate temperatures (37 °C) by using 5′-phosphorylated and 5′-hydroxylated DNA guides. Both Agos perform programmable cleavage of double-stranded DNA, especially in AT-rich regions of plasmid. Furthermore, we developed a simple and low-cost p-hydroxybenzoic acid detection method based on DNA-guided DNA cleavage of Agos and the allosteric effect of HosA, which expands the potential application of small molecule detection by Agos.

Brevilaterin B from Brevibacillus laterosporus has selective antitumor activity and induces apoptosis in epidermal cancer

Brevibacillus laterosporus, a newly discovered genus, had been shown to be one of the best candidates for producing multiple antimicrobial peptides (AMPs). Herein, we discovered a new bioactivity of Brevilaterin B, an AMP produced by Br. laterosporus S62-9, and investigated the details about its Anticancer. Proliferation, membrane permeability and apoptotic rate were checked using CCK-8 Assay, LDH Assay and Annexin V-FITC/PI Kits. ROS levels and mitochondrial membrane potential were detected using the fluorescent probe DCFH-DA and JC-1. Brevilaterin B exhibited broad anticancer activity in a dose-dependent manner. It selectively inhibited the proliferation of epidermal cancer cell A431 but had no effect on normal cells at 2 µg/mL. Typical morphological characteristics of apoptosis and an apoptotic ratio of 71.0% in A431 were observed after treatment with 2-3 µg/mL of Brevilaterin B. In A431 cells, 21.3% ROS generated and 48.8% reduction in mitochondrial membrane potential further occurred, indicating the main site of action was the mitochondrion. Brevilaterin B secreted by Br. laterosporus S62-9 has potential application as an anticancer medicament, increasing its commercial value. It’s believed to be the first report of the anticancer activity of this type of AMPs.

Transcriptional Analysis of Microcystis aeruginosa Co-Cultured with Algicidal Bacteria Brevibacillus laterosporus

Harmful algal blooms caused huge ecological damage and economic losses around the world. Controlling algal blooms by algicidal bacteria is expected to be an effective biological control method. The current study investigated the molecular mechanism of harmful cyanobacteria disrupted by algicidal bacteria. Microcystis aeruginosa was co-cultured with Brevibacillus laterosporus Bl-zj, and RNA-seq based transcriptomic analysis was performed compared to M. aeruginosa, which was cultivated separately. A total of 1706 differentially expressed genes were identified, which were mainly involved in carbohydrate metabolism, energy metabolism and amino acid metabolism. In the co-cultured group, the expression of genes mainly enriched in photosynthesis and oxidative phosphorylation were significantly inhibited. However, the expression of the genes related to fatty acid synthesis increased. In addition, the expression of the antioxidant enzymes, such as 2-Cys peroxiredoxin, was increased. These results suggested that B. laterosporus could block the electron transport by attacking the PSI system and complex I of M. aeruginosa, affecting the energy acquisition and causing oxidative damage. This further led to the lipid peroxidation of the microalgal cell membrane, resulting in algal death. The transcriptional analysis of algicidal bacteria in the interaction process can be combined to explain the algicidal mechanism in the future.

Biologically Active Extracts from Different Medicinal Plants Tested as Potential Additives against Bee Pathogens

Honey bees (Apis mellifera) perform pollination service for many agricultural crops and contribute to the global economy in agriculture and bee products. However, honey bee health is an ongoing concern, as illustrated by persistent local population decline, caused by some severe bee diseases (e.g., nosemosis, AFB, EFB, chalkbrood). Three natural recipes are in development based on the bioactive compounds of different plants extract (Agastache foeniculum, Artemisia absinthium, Evernia prunastri, Humulus lupulus, Laurus nobilis, Origanum vulgare and Vaccinium myrtillus), characterised by HPLC-PDA. The antimicrobial activity of these recipes was tested in vitro against Paenibacillus larvae, Paenibacillus alvei, Brevibacillus laterosporus, Enterococcus faecalis, Ascosphaera apis and in vivo against Nosema ceranae. A mix of 20% blueberry, 40% absinthium, 10% oakmoss, 10% oregano, 10% Brewers Gold hops, 5% bay laurel and 5% anise hyssop extract showed the strongest antibacterial and antifungal activity. Combing several highly active plant extracts might be an alternative treatment against bee-disease-associated parasites and pathogens, in particular to replace synthetic antibiotics.

Brevibacillin 2V, a Novel Antimicrobial Lipopeptide With an Exceptionally Low Hemolytic Activity

Bacterial non-ribosomally produced peptides (NRPs) form a rich source of antibiotics, including more than 20 of these antibiotics that are used in the clinic, such as penicillin G, colistin, vancomycin, and chloramphenicol. Here we report the identification, purification, and characterization of a novel NRP, i.e., brevibacillin 2V (lipo-tridecapeptide), from Brevibacillus laterosporus DSM 25. Brevibacillin 2V has a strong antimicrobial activity against Gram-positive bacterial pathogens (minimum inhibitory concentration = 2 mg/L), including difficult-to-treat antibiotic-resistant Enterococcus faecium, Enterococcus faecalis, and Staphylococcus aureus. Notably, brevibacillin 2V has a much lower hemolytic activity (HC50 > 128 mg/L) and cytotoxicity (CC50 = 45.49 ± 0.24 mg/L) to eukaryotic cells than previously reported NRPs of the lipo-tridecapeptide family, including other brevibacillins, which makes it a promising candidate for antibiotic development. In addition, our results demonstrate that brevibacillins display a synergistic action with established antibiotics against Gram-negative bacterial pathogens. Probably due to the presence of non-canonical amino acids and D-amino acids, brevibacillin 2V showed good stability in human plasma. Thus, we identified and characterized a novel and promising antimicrobial candidate (brevibacillin 2V) with low hemolytic activity and cytotoxicity, which can be used either on its own or as a template for further total synthesis and modification.