Characterization and Synergistic Antimicrobial Evaluation of Lipopeptides from Bacillus amyloliquefaciens Isolated from Oil-Contaminated Soil

Production of biosurfactant by salt-resistant Bacillus in lead-supplemented media: application and toxicity

A group of biosurfactants are lipopeptides that are produced by some microorganisms, especially Bacillus strains. They are new bioactive agents with anticancer, antibacterial, antifungal, and antiviral activities. Also, they are used in sanitation industries. In this study, a lead-resistant strain of Bacillus halotolerans was isolated for lipopeptide production. This isolate exhibited metal resistance (lead, calcium, chromium, nickel, copper, manganese, and mercury), salt tolerance (12%), and antimicrobial activities against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Saccharomyces cerevisiae. The production of lipopeptide was optimized, concentrated, and then extracted from the polyacrylamide gel in a simple way for the first time. The nature of the purified lipopeptide was determined by FTIR, GC/MS, and HPLC analyses. The purified lipopeptide indicated significant antioxidant properties (90.38% at a concentration of 0.8 mg ml-1). Also, it had anticancer activity by apoptosis (flow cytometry analysis) in MCF-7 cells, while it had no cytotoxicity on HEK-293 normal cells. Therefore, Bacillus halotolerans lipopeptide has the potential to be used as an antioxidant, antimicrobial, or anticancer agent in the medical and food industries.

Multifarious Plant Probiotic Features of Bacillus sp. W11 Isolated from Vermicast and Its Promises for Biocontrol Activity Against Phytopathogens

Organic agricultural practice using vermisources is considered as one of the common sustainable strategies in agriculture. Apart from their nutrient content, beneficial microbes associated with natural vermicast serve as an efficient bioinoculant for improving agricultural productivity. Hence, studies on the identification of suitable microbial inoculants with multi-trait plant beneficial properties from these hotspots are highly promising as an ecofriendly substitute against harmful chemical fertilizers. The current study has been designed to isolate bacterial strains with various plant probiotic and biocontrol properties against various fungal phytopathogens. Among the various bacteria obtained in the study, the isolate W11 was found to have remarkable inhibitory activity against a broad range of phytopathogens like Fusarium oxysporum, Pythium myriotylum, and Rhizoctonia solani, in addition to its multiple plant growth-promoting properties. The W11 was further identified as Bacillus sp. by 16S rDNA sequence-based analysis. The W11 treatment was also found to enhance the plant growth parameters of Vigna unguiculata. In addition, the priming of Bacillus sp. W11 on potato tuber has confirmed to protect it from Fusarium wilt caused by Fusarium oxysporum. This highlights the possible protective effect of W11 during the post-harvest storage of potatoes. Also, the metabolite analysis of W11 extract by LC-QTOF-MS/MS analysis has revealed the presence of lipopeptide surfactin derivatives with m/z of 1008, 1022, and 1036 (M + H)⁺. All the results obtained in the study thus indicate the remarkable agricultural promises of Bacillus sp. W11 isolated from vermicast. Even though vermicast has been studied for its beneficial agricultural applications, the isolation of plant beneficial bacteria from it and detailed characterization of its beneficial effects make the study important.

Isolation and purification of antibacterial lipopeptides from Bacillus velezensis YA215 isolated from sea mangroves

The increasing burden and health risks of antimicrobial resistance (AMR) pose a great threat to society overall. Lipopeptides exhibit great potential as novel and safe alternatives to traditional antibiotics. In this study, the strain YA215, which was isolated from the mangrove area in Beibu Gulf, Guangxi, China, was identified as Bacillus velezensis. Then, YA215 lipopeptide extracts (YA215LE) from B. velezensis was found to exhibit a wide spectrum of antibacterial and antifungal activities. Additionally, YA215LE was identified and found to contain three groups of lipopeptides (surfactin, iturin, and fengycin). Furthermore, one separation fraction (BVYA1) with significant antibacterial activity was obtained. Additionally, liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis of BVYA1 showed three molecular ion peaks ([M + H]⁺: m/z 980.62; 994.66; 1008.66) corresponding to conventional surfactin homologs. By MS/MS analysis, BVYA1 was identified as sufactin with the precise amino acid sequence Glu-Leu/Ile-Leu-Val-Asp-Leu-Leu/Ile and hydroxyl fatty acids with 11-13 carbons. [M + H]⁺ at m/z 980.62 was detected for the first time in B. velezensis, which demonstrates that the strain corresponds to a new surfactin variant. In particular, BVYA1 showed antibacterial activity with the minimum inhibitory concentration (MIC) values of 7.5-15 μg/ml. Finally, the preliminary mechanism of inhibiting E. coli treated with BVYA1 showed that BVYA1 effectively permeabilized the cytoplasmic membrane and disrupted the morphology of targeted bacterial cells. In conclusion, this study suggests that the YA215LE from B. velezensis YA215 might be a potential candidate for a bactericide.

Biological Control of Acinetobacter baumannii: In Vitro and In Vivo Activity, Limitations, and Combination Therapies

The survival, proliferation, and epidemic spread of Acinetobacter baumannii (A. baumannii) in hospital settings is associated with several characteristics, including resistance to many commercially available antibiotics as well as the expression of multiple virulence mechanisms. This severely limits therapeutic options, with increased mortality and morbidity rates recorded worldwide. The World Health Organisation, thus, recognises A. baumannii as one of the critical pathogens that need to be prioritised for the development of new antibiotics or treatment. The current review will thus provide a brief overview of the antibiotic resistance and virulence mechanisms associated with A. baumannii’s “persist and resist strategy”. Thereafter, the potential of biological control agents including secondary metabolites such as biosurfactants [lipopeptides (surfactin and serrawettin) and glycolipids (rhamnolipid)] as well as predatory bacteria (Bdellovibrio bacteriovorus) and bacteriophages to directly target A. baumannii, will be discussed in terms of their in vitro and in vivo activity. In addition, limitations and corresponding mitigations strategies will be outlined, including curtailing resistance development using combination therapies, product stabilisation, and large-scale (up-scaling) production.

Lipopeptide Biosurfactants from Bacillus spp.: Types, Production, Biological Activities, and Applications in Food

Biosurfactants are a functionally and structurally heterogeneous group of biomolecules produced by multiple filamentous fungi, yeast, and bacteria, and characterized by their distinct surface and emulsifying ability. The genus Bacillus is well studied for biosurfactant production as it produces various types of lipopeptides, for example, lichenysins, bacillomycin, fengycins, and surfactins. Bacillus lipopeptides possess a broad spectrum of biological activities such as antimicrobial, antitumor, immunosuppressant, and antidiabetic, in addition to their use in skincare. Moreover, Bacillus lipopeptides are also involved in various food products to increase the antimicrobial, surfactant, and emulsification impact. From the previously published articles, it can be concluded that biosurfactants have strong potential to be used in food, healthcare, and agriculture. In this review article, we discuss the versatile functions of lipopeptide Bacillus species with particular emphasis on the biological activities and their applications in food.

Simultaneous Production of Antibacterial Protein and Lipopeptides in Bacillus tequilensis, Detected by MALDI-TOF and GC Mass Analyses

As antibiotic resistance is nowadays one of the important challenges, efforts are crucial for the discovery of novel antibacterial drugs. This study aimed to evaluate antimicrobial/anticancerous activities of halophilic bacilli from the human microbiota. A spore-forming halotolerant bacterium with antibacterial effect against Staphylococcus aureus was isolated from healthy human feces. The antibacterial protein components of the extracted supernatant were identified by SDS-PAGE and zymography. The MALDI-TOF, GC mass, and FTIR analyses were used for peptide and lipopeptide identification, respectively. The stability, toxicity, and anticancerous effects were investigated using MTT and Flow cytometry methods. According to the molecular analysis, the strain was identified as Bacillus tequilensis and showed potential probiotic properties, such as bile and acid resistance, as well as eukaryotic cell uptake. SDS-PAGE and zymography showed that 15 and 10-kDa fragments had antibacterial effects. The MALDI-TOF mass analysis indicated that the 15-kDa fragment was L1 ribosomal protein, which was the first report of the RpL1 in bacilli. GC-mass and FTIR analyses confirmed the lipopeptide nature of the 10-kDa fragment. Both the extracted fractions (precipitation or "P" and chloroform or "C" fractions) were stable at < 100 °C for 10 min, and their antibacterial effects were preserved for more than 6 months. Despite its non-toxicity, the P fraction had anticancer activities against MCF7 cells. The anticancer and antibacterial properties of B. tequilensis, along with its non-toxicity and stability, have made it a potential candidate for studying the beneficial probiotic properties for humans and drug production.

Production optimization, stability and oil emulsifying potential of biosurfactants from selected bacteria isolated from oil-contaminated sites

Oil pollution is of increasing concern for environmental safety and the use of microbial surfactants in oil remediation has become inevitable for their efficacy and ecofriendly nature. In this work, biosurfactants of bacteria isolated from oil-contaminated soil have been characterized. Four potent biosurfactant-producing strains (SD4, SD11, SD12 and SD13) were selected from 27 isolates based on drop collapse assay and emulsification index, and identified as species belonging to Bacillus, Burkholderia, Providencia and Klebsiella, revealed from their 16S rRNA gene-based analysis. Detailed morphological and biochemical characteristics of each selected isolate were determined. Their growth conditions for maximum biosurfactant production were optimized and found quite similar among the four isolates with a pH of 3.0 and temperature 37°C after 6 or 7 days of growth on kerosene. The biosurfactants of SD4, SD11 and SD12 appeared to be glycolipids and that of SD13 a lipopeptide. Emulsification activity of most of the biosurfactants was stable at low and high temperatures (4-100°C), a wide range of pH (2-10) and salt concentrations (2-7% NaCl). Each biosurfactant showed antimicrobial activity against two or more pathogenic bacteria. The biosurfactants were well-capable of emulsifying kerosene, diesel and soya bean, and could efficiently degrade diesel.

Dereplication of antimicrobial biosurfactants from marine bacteria using molecular networking

Biosurfactants are amphiphilic surface-active molecules of microbial origin principally produced by hydrocarbon-degrading bacteria; in addition to the bioremediation properties, they can also present antimicrobial activity. The present study highlights the chemical characterization and the antimicrobial activities of biosurfactants produced by deep-sea marine bacteria from the genera Halomonas, Bacillus, Streptomyces, and Pseudomonas. The biosurfactants were extracted and chemically characterized through Chromatography TLC, FT-IR, LC/ESI-MS/MS, and a metabolic analysis was done through molecular networking. Six biosurfactants were identified by dereplication tools from GNPS and some surfactin isoforms were identified by molecular networking. The half-maximal inhibitory concentration (IC50) of biosurfactant from Halomonas sp. INV PRT125 (7.27 mg L-1) and Halomonas sp. INV PRT124 (8.92 mg L-1) were most effective against the pathogenic yeast Candida albicans ATCC 10231. For Methicillin-resistant Staphylococcus aureus ATCC 43300, the biosurfactant from Bacillus sp. INV FIR48 was the most effective with IC50 values of 25.65 mg L-1 and 21.54 mg L-1 for C. albicans, without hemolytic effect (< 1%), and non-ecotoxic effect in brine shrimp larvae (Artemia franciscana), with values under 150 mg L-1, being a biosurfactant promising for further study. The extreme environments as deep-sea can be an important source for the isolation of new biosurfactants-producing microorganisms with environmental and pharmaceutical use.

In vitro identification of antimicrobial hemolytic lipopeptide from halotolerant Bacillus by Zymogram, FTIR, and GC mass analysis

OBJECTIVES

The multi-drug resistant bacteria and clinical infections are some of the biggest global concerns, so new drugs are needed. Antimicrobial peptides and lipopeptides are new bioactive agents with great potential that can become a new strategy for clinical applications.

MATERIALS AND METHODS

Some Bacillus strains were isolated based on hemolytic antimicrobial production from the soil. The extracellular proteins were extracted by acidic precipitation and chloroform/methanol method and analyzed by SDS-PAGE electrophoresis and stained with Sudan black. The black fragment was purified and characterized by FTIR, GC/MS, and HPLC analysis to demonstrate the presence of lipids and proteins. The anti-microbial ability and stability of the purified lipopeptide were assayed by the Kirby-Bauer method. Also, it was examined for metal removal.

RESULTS

A new Bacillus halotolerans strain SCM 034 with hemolytic antimicrobial production was isolated. According to GC/MS (detecting C16, C17) and HPLC (detecting leucine, glutamic acid, valine, arginine, glycine, and aspartic acid) data, the black fragment was lipopeptide. Polyacrylamide hydrogel containing lipopeptide and gel purified lipopeptide showed anti-microbial activities against S. aureus and S. cerevisiae that were stable for a few months. Also, the lipopeptide was useful for cation removal and decreased cobalt, nickel, and calcium by 10.81 %, 24.39 %, and 34 %, respectively.

CONCLUSION

Production of antibacterial lipopeptide hemolysin from this strain is reported for the first time and according to the results, lipopeptides have unique properties with biomedical and pharmaceutical applications. Also, polyacrylamide hydrogel lipopeptide is a promising candidate for wound healing.

In-Vitro Antibacterial and Anti-Inflammatory Effects of Surfactin-Loaded Nanoparticles for Periodontitis Treatment

Periodontitis is an inflammatory disease associated with biofilm formation and gingival recession. The practice of nanotechnology in the clinical field is increased overtime due to its potential advantages in drug delivery applications. Nanoparticles can deliver drugs into the targeted area with high efficiency and cause less damages to the tissues. In this study, we investigated the antibacterial and anti-inflammatory properties of surfactin-loaded κ-carrageenan oligosaccharides linked cellulose nanofibers (CO-CNF) nanoparticles. Three types of surfactin-loaded nanoparticles were prepared based on the increasing concentration of surfactin such as 50SNPs (50 mg surfactin-loaded CO-CNF nanoparticles), 100SNPs (100 mg surfactin-loaded CO-CNF nanoparticles), and 200SNPs (200 mg surfactin-loaded CO-CNF nanoparticles). The results showed that the nanoparticles inhibited the growth of Fusobacterium nucleatum and Pseudomonas aeruginosa. The reduction in biofilm formation and metabolic activity of the bacteria were confirmed by crystal violet and MTT assay, respectively. Besides, an increase in oxidative stress was also observed in bacteria. Furthermore, anti-inflammatory effects of surfactin-loaded CO-CNF nanoparticles was observed in lipopolysaccharide (LPS)-stimulated human gingival fibroblast (HGF) cells. A decrease in the production of reactive oxygen species (ROS), transcription factor, and cytokines were observed in the presence of nanoparticles. Collectively, these observations supported the use of surfactin-loaded CO-CNF as a potential candidate for periodontitis management.

Isolation and Characterization of Fengycins Produced by Bacillus amyloliquefaciens JFL21 and Its Broad-Spectrum Antimicrobial Potential Against Multidrug-Resistant Foodborne Pathogens

The continuing emergence and development of pathogenic microorganisms that are resistant to antibiotics constitute an increasing global concern, and the effort in new antimicrobials discovery will remain relevant until a lasting solution is found. A new bacterial strain, designated JFL21, was isolated from seafood and identified as B. amyloliquefaciens. The antimicrobial substance produced by B. amyloliquefaciens JFL21 showed low toxicity to most probiotics but exhibited strong antimicrobial activities against multidrug-resistant foodborne pathogens. The partially purified antimicrobial substance, Anti-JFL21, was characterized to be a multiple lipopeptides mixture comprising the families of surfactin, fengycin, and iturin. Compared with commercially available polymyxin B and Nisin, Anti-JFL21 not only could exhibit a wider and stronger antibacterial activity toward Gram-positive pathogens but also inhibit the growth of a majority of fungal pathogens. After further separation through gel filtration chromatography (GFC), the family of surfactin, fengycin, and iturin were obtained, respectively. The results of the antimicrobial test pointed out that only fengycin family presented marked antimicrobial properties against the indicators of L. monocytogenes, A. hydrophila, and C. gloeosporioides, which demonstrated that fengycins might play a major role in the antibacterial and antifungal activity of Anti-JFL21. Additionally, the current study also showed that the fengycins produced by B. amyloliquefaciens JFL21 not only maintained stable anti-Listeria activity over a broad pH and temperature range, but also remained active after treatment with ultraviolet sterilization, chemical reagents, and proteolytic enzymes. Therefore, the results of this study suggest the new strain and its antimicrobials are potentially useful in food preservation for the biological control of the multidrug-resistant foodborne pathogens.

The use of low-cost brewery waste product for the production of surfactin as a natural microbial biocide

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For the first time Bacillus subtilis was able to grow in a culture medium containing Brewery waste (Trub) and produced surfactin.

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Surfactin showed bactericidal effect against Pseudomonas aeruginosa.

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P. aeruginosa biofilm was inhibited (79.8%) when co-incubated with surfactin.

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Surfactin showed anti-adhesive activity on polystyrene surfaces.

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P. aeruginosa biofilm was disrupted (44.9%) when treated with surfactin (700 μg/mL).

Surfactin has potential as next generation antibiofilm agent to combat antimicrobial resistance against emerging pathogens. However, the widespread industrial applications of surfactin is hampered by its high production cost. In this work, surfactin was produced from Bacillus subtilis using a low-cost brewery waste as a carbon source. The strain produced 210.11 mg L−1 after 28 h. The antimicrobial activity was observed against all tested strains, achieving complete inhibition for Pseudomonas aeruginosa, at 500 μg mL−1. A growth log reduction of 3.91 was achieved for P. aeruginosa while, Staphylococcus aureus and Staphylococcus epidermidis showed between 1 and 2 log reductions. In the anti-biofilm assays against P. aeruginosa, the co-incubation, anti-adhesive and disruption showed inhibition, where the greatest inhibition was observed in the co-incubation assay (79.80%). This study provides evidence that surfactin produced from a low-cost substrate can be a promising biocide due to its antimicrobial and anti-biofilm abilities against pathogens.

Selection of sponge-associated bacteria with high potential for the production of antibacterial compounds

The potential of sponge-associated bacteria for the biosynthesis of natural products with antibacterial activity was evaluated. In a preliminary screening 108 of 835 axenic isolates showed antibacterial activity. Active isolates were identified by 16S rRNA gene sequencing and selection of the most promising strains was done in a championship like approach, which can be done in every lab and field station without expensive equipment. In a competition assay, strains that inhibited most of the other strains were selected. In a second round, the strongest competitors from each host sponge competed against each other. To rule out that the best competitors selected in that way represent similar strains with the same metabolic profile, BOX PCR experiments were performed, and extracts of these strains were analysed using metabolic fingerprinting. This proved that the strains are different and have various metabolic profiles, even though belonging to the same genus, i.e. Bacillus. Furthermore, it was shown that co-culture experiments triggered the production of compounds with antibiotic activity, i.e. surfactins and macrolactin A. Since many members of the genus Bacillus possess the genetic equipment for the biosynthesis of these compounds, a potential synergism was analysed, showing synergistic effects between C14-surfactin and macrolactin A against methicillin-resistant Staphylococcus aureus (MRSA).