The Antimicrobial Peptides of the Bacillus Species

Antimicrobial peptides (AMPs) produced by Bacillus species are a fascinating and diverse group of molecules that have garnered significant attention in the fields of microbiology, biotechnology, and medicine. Bacillus species are renowned for their ability to synthesize a wide range of antimicrobial peptides, which serve various functions, including defense against competing microorganisms, protection against environmental stressors, and potential applications in biotechnology and healthcare. In this article, we will explore the various antimicrobial peptides produced by Bacillus species, their mechanisms of action, and their potential applications. Please note these have been well reviewed by Puan et al., (2023).

1. Bacitracin

Bacitracin is one of the most well-known antimicrobial peptides produced by Bacillus species, particularly by Bacillus subtilis. This peptide is a cyclic polypeptide antibiotic, a macrocyclic dodecapeptide to be more precise and is used clinically as a topical antibiotic ointment. Bacitracin primarily targets Gram-positive bacteria by interfering with cell wall synthesis. It inhibits the dephosphorylation of the lipid carrier molecule that transports peptidoglycan precursors, ultimately leading to cell wall disruption.

Bacitracin’s clinical use highlights its potency as an antimicrobial agent. This particular AMP is the subject of intense interest in terms of its production by fermentation by Bacillus licheniformis. (Wu et al., 2019a).

2. Subtilin

Subtilin is another prominent antimicrobial peptide produced by Bacillus subtilis. It belongs to the class of lantibiotics, which are post-translationally modified peptides with potent antibacterial activity. Subtilin is active against Gram-positive bacteria and functions by forming pores in the target cell membrane, leading to cell lysis. It has been explored for various applications, including food preservation and as a potential natural alternative to chemical preservatives in the food industry.

3. Surfactin

Surfactin is a well-known lipopeptide produced by various Bacillus species, including Bacillus subtilis. While it is primarily recognized for its surface-active properties, it also possesses antimicrobial activity. Surfactin disrupts microbial cell membranes by forming micelles, which solubilize membrane lipids and proteins, leading to cell lysis. Surfactin has applications in bioremediation, cosmetics, and the pharmaceutical industry, and it has shown potential as an antimicrobial agent in agricultural settings.

4. Fengycin

Fengycin is another lipopeptide produced by Bacillus species, with Bacillus subtilis being a common producer. It exhibits antifungal activity and has been studied for its potential as a biocontrol agent against plant-pathogenic fungi. Fengycin disrupts fungal cell membranes, leading to leakage of cellular contents and ultimately fungal cell death. Its use in agriculture represents a sustainable and eco-friendly approach to combat fungal diseases.

5. Iturin

Iturin is a cyclic lipopeptide with antimicrobial properties produced by various Bacillus species. Iturin has antifungal activity and is particularly effective against a wide range of plant-pathogenic fungi. Its mechanism of action involves perturbing fungal cell membranes and interfering with membrane-bound proteins. Iturin has garnered interest in agriculture for its potential to protect crops from fungal diseases.

6. Cerein

Cerein is a bacteriocin produced by Bacillus cereus. Bacteriocins are a class of antimicrobial peptides produced by bacteria to inhibit the growth of closely related bacterial strains. Cerein targets other Bacillus species and exhibits antibacterial activity. It functions by forming pores in the target cell membrane, leading to cell lysis. Cerein’s production by B. cereus represents a competitive advantage in the microbial world.

7. Amylocyclicin

Amylocyclicin is a cyclic peptide produced by Bacillus amyloliquefaciens. It has demonstrated antimicrobial activity against various pathogenic bacteria, including Staphylococcus aureus. Amylocyclicin works by disrupting bacterial cell membranes. This peptide has potential applications in the development of new antibiotics.

8. Plantazolicin

Plantazolicin is an antimicrobial peptide produced by Bacillus subtilis. It has a unique mode of action, as it inhibits the biosynthesis of phospholipids in the target cell membrane. This leads to changes in membrane integrity and, ultimately, cell death. Plantazolicin’s novel mechanism of action makes it an intriguing candidate for the development of antimicrobial agents.

9. Thiopeptins

Thiopeptins are a group of thiopeptide antibiotics produced by Bacillus species, including Bacillus thiooxidans. Thiopeptins have broad-spectrum antimicrobial activity against both Gram-positive and Gram-negative bacteria. They function by interfering with bacterial protein synthesis, specifically targeting the ribosome. Thiopeptins have garnered attention for their potential as antibiotics.

10. TasA

TasA is a proteinaceous matrix produced by Bacillus subtilis that plays a role in biofilm formation. While it is not a traditional antimicrobial peptide, the formation of robust biofilms by Bacillus species can serve as a defense mechanism against competing microorganisms and environmental stressors. TasA contributes to the structural integrity of these biofilms and indirectly influences the microbial community’s composition.

The diverse array of antimicrobial peptides produced by Bacillus species reflects their adaptability and versatility in coping with environmental challenges and competing microorganisms. These peptides have evolved to target a wide range of microorganisms, including bacteria, fungi, and some Gram-negative pathogens, making them valuable resources for various applications.

In addition to their natural roles in microbial competition and ecological fitness, Bacillus-derived antimicrobial peptides have garnered attention for their potential applications in various fields, including agriculture, biotechnology, and medicine:

1. Agriculture: Many Bacillus-derived antimicrobial peptides are being explored for their potential use in agriculture. These peptides can serve as biocontrol agents, protecting crops from pathogens such as fungi and bacteria. By offering an eco-friendly alternative to chemical pesticides, they contribute to sustainable agriculture.

2. Food Preservation: Some Bacillus-derived antimicrobial peptides have been investigated for their use in food preservation. These peptides can inhibit the growth of foodborne pathogens and spoilage microorganisms, extending the shelf life of perishable products. This application aligns with the growing demand for natural and safe food preservatives.

3. Antibiotic Development: Bacillus-derived antimicrobial peptides hold promise for the development of novel antibiotics. With the rise of antibiotic-resistant pathogens, there is a pressing need for new antimicrobial agents. These peptides, which have diverse mechanisms of action, offer potential solutions to combat drug-resistant bacteria.

4. Bioremediation: Surfactin and other lipopeptides produced by Bacillus species have applications in bioremediation. These peptides can aid in the cleanup of environmental pollutants by enhancing the solubilization and degradation of hydrophobic compounds, such as oil.

5. Biotechnology: Bacillus-derived antimicrobial peptides, especially those with surfactant properties, are used in various biotechnological processes. For instance, surfactin can improve the efficiency of microbial fermentation and enhance the production of biofuels, enzymes, and other bioproducts.

6. Medicine: Some Bacillus-derived peptides have potential applications in medicine. They are being explored for their antimicrobial properties, wound healing properties, and immunomodulatory effects. Additionally, they may serve as adjuvants in vaccine development, enhancing the immune response to pathogens.

In conclusion, Bacillus species produce a wide range of antimicrobial peptides with diverse mechanisms of action, allowing them to target various microorganisms. These peptides serve as essential defense mechanisms for the bacteria in their natural environments and have significant potential for applications in agriculture, biotechnology, and medicine. As the need for effective and sustainable antimicrobial agents continues to grow, Bacillus-derived antimicrobial peptides offer innovative solutions to address these challenges and contribute to various fields, from biotechnology to public health. Further research and development in this area will likely uncover new and exciting opportunities for the use of these peptides in the future.

References

Puan, S.L., Erriah, P., Baharudin, M.M.Aa. et al. (2023) Antimicrobial peptides from Bacillus spp. and strategies to enhance their yield. Appl Microbiol Biotechnol 107, pp. 5569–5593 (Article).

Wu F, Cai D, Li L, Li Y, Yang H, Li J, Ma X, Chen S (2019a) Modular metabolic engineering of lysine supply for enhanced production of bacitracin in Bacillus licheniformis. Appl Microbiol Biotechnol 103:8799–8812 (Article) . 

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