Novel activity evaluation and subsequent partial purification of antimicrobial peptides produced by Bacillus subtilis LFB112

Microbial lipopeptides: their pharmaceutical and biotechnological potential, applications, and way forward

As lead molecules, cyclic lipopeptides with antibacterial, antifungal, and antiviral properties have garnered a lot of attention in recent years. Because of their potential, cyclic lipopeptides have earned recognition as a significant class of antimicrobial compounds with applications in pharmacology and biotechnology. These lipopeptides, often with biosurfactant properties, are amphiphilic, consisting of a hydrophilic moiety, like a carboxyl group, peptide backbone, or carbohydrates, and a hydrophobic moiety, mostly a fatty acid. Besides, several lipopeptides also have cationic groups that play an important role in biological activities. Antimicrobial lipopeptides can be considered as possible substitutes for antibiotics that are conventional to address the current drug-resistant issues as pharmaceutical industries modify the parent antibiotic molecules to render them more effective against antibiotic-resistant bacteria and fungi, leading to the development of more resistant microbial strains. Bacillus species produce lipopeptides, which are secondary metabolites that are amphiphilic and are typically synthesized by non-ribosomal peptide synthetases (NRPSs). They have been identified as potential biocontrol agents as they exhibit a broad spectrum of antimicrobial activity. A further benefit of lipopeptides is that they can be produced and purified biotechnologically or biochemically in a sustainable manner using readily available, affordable, renewable sources without harming the environment. In this review, we discuss the biochemical and functional characterization of antifungal lipopeptides, as well as their various modes of action, method of production and purification (in brief), and potential applications as novel antibiotic agents.

Whole-genome sequencing and antimicrobial potential of bacteria isolated from Polish honey

The aim of this study was the whole-genome analysis and assessment of the antimicrobial potential of bacterial isolates from honey harvested in one geographical location-the north of Poland. In total, 132 strains were derived from three honey samples, and the antimicrobial activity of CFAM (cell-free after-culture medium) was used as a criterion for strain selection and detailed genomic investigation. Two of the tested isolates (SZA14 and SZA16) were classified as Bacillus paralicheniformis, and one isolate (SZB3) as Bacillus subtilis based on their ANI and phylogenetic analysis relatedness. The isolates SZA14 and SZA16 were harvested from the same honey sample with a nucleotide identity of 98.96%. All three isolates have been found to be potential producers of different antimicrobial compounds. The secondary metabolite genome mining pipeline (antiSMASH) identified 14 gene cluster coding for non-ribosomal peptide synthetases (NRPs), polyketide synthases (PKSs), and ribosomally synthesized and post-translationally modified peptides (RiPPs) that are potential sources of novel antibacterials. The BAGEL4 analysis revealed the presence of nine putative gene clusters of interest in the isolates SZA14 and SZA16 (including the presence of six similar clusters present in both isolates, coding for the production of enterocin Nkr-5-3B, haloduracin-alpha, sonorensin, bottromycin, comX2, and lasso peptide), and four in B. subtilis isolate SZB3 (competence factor, sporulation-killing factor, subtilosin A, and sactipeptides). The outcomes of this study confirm that honey-derived Bacillus spp. strains can be considered potential producers of a broad spectrum of antimicrobial agents. KEY POINTS: • Bacteria of the genus Bacillus are an important component of honey microbiota. • Honey-derived Bacillus spp. strains are potential producers of new antimicrobials.

Isolation and characterization of Bacillus sp. GFP-2, a novel Bacillus strain with antimicrobial activities, from Whitespotted bamboo shark intestine

The abuse of antibiotics and following rapidly increasing of antibiotic-resistant pathogens is the serious threat to our society. Natural products from microorganism are regarded as the important substitution antimicrobial agents of antibiotics. We isolated a new strain, Bacillus sp. GFP-2, from the Chiloscyllium plagiosum (Whitespotted bamboo shark) intestine, which showed great inhibitory effects on the growth of both Gram-positive and Gram-negative bacteria. Additionally, the growth of salmon was effectively promoted when fed with inactivated strain GFP-2 as the inhibition agent of pathogenic bacteria. The genes encoding antimicrobial peptides like LCI, YFGAP and hGAPDH and gene clusters for secondary metabolites and bacteriocins, such as difficidin, bacillibactin, bacilysin, surfactin, butirosin, macrolactin, bacillaene, fengycin, lanthipeptides and LCI, were predicted in the genome of Bacillus sp. GFP-2, which might be expressed and contribute to the antimicrobial activities of this strain. The gene encoding β-1,3-1,4-glucanase was successfully cloned from the genome and this protein was detected in the culture supernatant of Bacillus sp. GFP-2 by the antibody produced in rabbit immunized with the recombinant β-1,3-1,4-glucanase, indicating that this strain could express β-1,3-1,4-glucanase, which might partially contribute to its antimicrobial activities. This study can enhance a better understanding of the mechanism of antimicrobial activities in genus Bacillus and provide a useful material for the biotechnology study in antimicrobial agent development.

Production and characterization of a new antibacterial peptide obtained from Aeribacillus pallidus SAT4

A novel thermophilic bacterial strain of the genus Aeribacillus was isolated from Thar Dessert Pakistan. This strain showed significant antibacterial activity against Micrococcus luteus, Staphylococcus aureus, and Pseudomonasaeruginosa. The strain coded as 'SAT4' resembled with Aeribacillus pallidus in the morphological, biochemical and molecular tests. The production of antibacterial metabolites by SAT4 was optimized. These active metabolites were precipitated by 50% ammonium sulphate and purified through sephadex G-75 gel permeation chromatography and reverse phase HPLC. The molecular weight of 37 kDa was examined by SDS-PAGE. The structural elucidation of the purified product was studied by FTIR, 1H and 13C NMR. The X-ray diffractions study showed that the crystals belonged to the primitive orthorhombic lattice (a = 12.137, b = 13.421, c = 14.097 Å) and 3D structure (proposed name: Aeritracin) was determined. This new peptide antibacterial molecule can get a position in pharmaceutical and biotechnological industrial research.

Antimicrobial peptides of the genus Bacillus: a new era for antibiotics

The rapid onset of resistance reduces the efficacy of most conventional antimicrobial drugs and is a general cause of concern for human well-being. Thus, there is great demand for a continuous supply of novel antibiotics to combat this problem. Bacteria-derived antimicrobial peptides (AMPs) have long been used as food preservatives; moreover, prior to the development of conventional antibiotics, these AMPs served as an efficient source of antibiotics. Recently, peptides produced by members of the genus Bacillus were shown to have a broad spectrum of antimicrobial activity against pathogenic microbes. Bacillus-derived AMPs can be synthesized both ribosomally and nonribosomally and can be classified according to peptide biosynthesis, structure, and molecular weight. The precise mechanism of action of these AMPs is not yet clear; however, one proposed mechanism is that these AMPs kill bacteria by forming channels in and (or) disrupting the bacterial cell wall. Bacillus-derived AMPs have potential in the pharmaceutical industry, as well as the food and agricultural sectors. Here, we focus on Bacillus-derived AMPs as a novel alternative approach to antibacterial drug development. We also provide an overview of the biosynthesis, mechanisms of action, applications, and effectiveness of different AMPs produced by members of the Bacillus genus, including several recently identified novel AMPs.

Microbial symbionts of honeybees: a promising tool to improve honeybee health

Among pollinators, honeybees are the most important ones and exert the essential key ecosystem service of pollination for many crops, fruit and wild plants. Indeed, several crops are strictly dependent on honeybee pollination. Since few decades, honeybees are facing large-scale losses worldwide, the causes of which are found in the interaction of several biotic and abiotic factors, such as the use of pesticides, the habitat loss, the spread of pathogens and parasites and the occurrence of climate changes. Insect symbionts are emerging as a potential tool to protect beneficial insects, ameliorating the innate immune homeostasis and contributing to the general insect wellbeing. A review about the microbial symbionts associated to honeybees is here presented. The importance of the honeybee microbial commensals for the maintenance and improvement of honeybee health is discussed. Several stressors like infestations of Varroa mites and the use of pesticides can contribute to the occurrence of dysbiosis phenomena, resulting in a perturbation of the microbiocenosis established in the honeybee body.