MALDI-TOF analysis of a novel extremophile peptide purified from Halarchaeum acidiphilum ASDL78 with antiarchaeal and antibacterial activities

Halocins, natural antimicrobials of Archaea: Exotic or special or both?

Haloarchaea are adapted to survive under extreme saline conditions by accumulating osmolytes and salts to counteract the high osmotic pressure in their habitats. As a consequence, their proteins have evolved to remain active, or even most active, at very high ionic strength. Halocins are proteinaceous antimicrobial substances that are ribosomally-synthesized by haloarchaea and they provide the producers an advantage in the competition for nutrients and ecological niches. These antimicrobials are stable at high temperature, elevated salt concentrations, and alkaline pH conditions. These properties have endowed them with great potential in diverse biotechnological applications, which involve extreme processing conditions (such as high salt concentrations, high pressure, or high temperatures). They kill target cells by inhibition of Na⁺/H⁺ antiporter in the membrane or modification/disruption of the cell membrane leading to cell lysis. In general, the taxonomy of haloarchaea and their typical phenotypic and genotypic characteristics are well studied; however, information regarding their halocins, especially aspects related to genetics, biosynthetic pathways, mechanism of action, and structure-function relationship is very limited. A few studies have demonstrated the potential applications of halocins in the preservation of salted food products and brine-cured hides in leather industries, protecting the myocardium from ischemia and reperfusion injury, as well as from life-threatening diseases such as cardiac arrest and cancers. In recent years, genome mining has been an essential tool to decipher the genetic basis of halocin biosynthesis. Nevertheless, this is likely the tip of the iceberg as genome analyses have revealed many putative halocins in databases waiting for further investigation. Identification and characterization of this source of halocins may lead to antimicrobials for future therapeutics and/or food preservation. Hence, the present review analyzes different aspects of halocins such as biosynthesis, mechanism of action against target cells, and potential biotechnological applications.

Expression regulation of chitin-binding protein and metal-binding peptide in new Bacillus velezensis: MALDI-TOF MS/MS analysis

Metallothionein and metal-binding peptides are small cysteine-rich proteins produced by different organisms in stress conditions. In this study, the metal-binding peptide was detected in extracellular proteins of a new Bacillus velezensis strain, isolated from metal contaminated soil, and grown on the lead-enriched medium, for the first time. The presence of sulfide peptide was assayed by two simple tests (lead sulfide and Ellman's reagent test) for preliminary, and subsequently confirmed using polyacrylamide gel electrophoresis at media with different lead concentrations that the low-molecular-weight protein fragments (≈10 kDa) were observed while none were detected in the medium containing sodium chloride or calcium salt. The amino acids of the observed fragments were analyzed by matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF MS/MS). Also, the metal adsorption was confirmed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) by staining with chromium solution. The results showed that the putative sulfide peptide is metallothionein, which is induced in stress conditions. It was interesting that in all SDS profiles, one protein fragment (≈18 kDa) was inhibited in lead-enriched media. The data from MALDI-TOF MS/MS analysis showed that this fraction was a chitin-binding protein whose production was regulated by metal contamination. It is anticipated that these two proteins regulate the toxicity of lead.

Novel Chronic Wound Healing by Anti-biofilm Peptides and Protease

Chronic wounds have made a challenge in medical healthcare due to their biofilm infections, which reduce the penetrance of the antibacterial agents in the injury site. In infected wounds, the most common bacterial strains are Staphylococcus aureus and Pseudomonas aeruginosa. Biofilm disruption in chronic wounds is crucial in wound healing. Due to their broad-spectrum antibacterial properties and fewer side effects, anti-biofilm peptides, especially bacteriocins, are promising in the healing of chronic wounds by biofilm destruction. This study reviews the effects of antimicrobial and anti-biofilm agents, including bacteriocins and protease enzymes as a novel approach, on wound healing, along with analyzing the molecular docking between a bacterial protease and biofilm components. Among a large number of anti-biofilm bacteriocins identified up to now, seven types have been registered in the antimicrobial peptides (AMPs) database. Although it is believed that bacterial proteases are harmful in wound healing, it has recently been demonstrated that these proteases like the human serine protease, in combination with AMPs, can improve wound healing by biofilm destruction. In this work, docking results between metalloprotease from Paenibacillus polymyxa and proteins of S. aureus and P. aeruginosa involved in biofilm production, showed that this bacterial protease could efficiently interact with biofilm components. Infected wound healing is an important challenge in clinical trials due to biofilm production by bacterial pathogens. Therefore, simultaneous use of proteases or anti-biofilm peptides with antimicrobial agents could be a promising method for chronic wound healing.