Evaluation of morphological changes of Staphylococcus aureus and Escherichia coli induced with the antimicrobial peptide AN5-1

Musical protein: Mapping the time sequence of music onto the spatial architecture of proteins

BACKGROUND AND OBJECTIVE

Music, the ubiquitous language across human cultures, is traditionally considered as a form of art but has been linked to biomolecules in recent years. However, previous efforts have only been addressed on sonification of nucleic acids and proteins to produce so-called life music, the soundscape from the basic building blocks of life. In this study, we attempted to, for the first time, conduct a reverse operation of this process, i.e. conversion of music to protein (CoMtP).

METHODS

A novel notion termed musical protein (MP) -- the protein defined by music -- was proposed and, on this basis, we described a computational strategy to map the time sequence of music onto the spatial architecture of proteins, which considered that each note in the stave of a music (target) can be simply characterized by two acoustical quantities and that each residue in the primary sequence of a protein (hit) was represented by amino acid descriptors.

RESULTS

A simulated annealing (SA) algorithm was applied to iteratively generate the best matched MP hit for a music target and structural bioinformatics was then used to model spatial advanced structure for the resulting MP. We also demonstrated that some small MPs derived from music segments may have potential biological functions, which, for example, can serve as antimicrobial peptides (AMPs) to inhibit clinical bacterial strains with moderate or high antibacterial potency.

CONCLUSIONS

This work may benefit many aspects; for example, it would open a door for the hearing-impaired persons to 'listen' music in a biological vision and could be a mean of exposing students to the concepts of biomolecules at an earlier age through the use of auditory characteristics. The CoMtP would also facilitate the rational design of proteins with biological and medicinal significance.

Synthesis and Antibacterial Analysis of Analogues of the Marine Alkaloid Pseudoceratidine

In an effort to gain more understanding on the structure activity relationship of pseudoceratidine 1, a di-bromo pyrrole spermidine alkaloid derived from the marine sponge Pseudoceratina purpurea that has been shown to exhibit potent biofouling, anti-fungal, antibacterial, and anti-malarial activities, a large series of 65 compounds that incorporated several aspects of structural variation has been synthesised through an efficient, divergent method that allowed for a number of analogues to be generated from common precursors. Subsequently, all analogues were assessed for their antibacterial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. Overall, several compounds exhibited comparable or better activity than that of pseudoceratidine 1, and it was found that this class of compounds is generally more effective against Gram-positive than Gram-negative bacteria. Furthermore, altering several structural features allowed for the establishment of a comprehensive structure activity relationship (SAR), where it was concluded that several structural features are critical for potent anti-bacterial activity, including di-halogenation (preferable bromine, but chlorine is also effective) on the pyrrole ring, two pyrrolic units in the structure and with one or more secondary amines in the chain adjoining these units, with longer chains giving rise to better activities.

Biophysical approaches for exploring lipopeptide-lipid interactions

In recent years, lipopeptides (LPs) have attracted a lot of attention in the pharmaceutical industry due to their broad-spectrum of antimicrobial activity against a variety of pathogens and their unique mode of action. This class of compounds has enormous potential for application as an alternative to conventional antibiotics and for pest control. Understanding how LPs work from a structural and biophysical standpoint through investigating their interaction with cell membranes is crucial for the rational design of these biomolecules. Various analytical techniques have been developed for studying intramolecular interactions with high resolution. However, these tools have been barely exploited in lipopeptide-lipid interactions studies. These biophysical approaches would give precise insight on these interactions. Here, we reviewed these state-of-the-art analytical techniques. Knowledge at this level is indispensable for understanding LPs activity and particularly their potential specificity, which is relevant information for safe application. Additionally, the principle of each analytical technique is presented and the information acquired is discussed. The key challenges, such as the selection of the membrane model are also been briefly reviewed.

The antibacterial activity and modes of LI-F type antimicrobial peptides against Bacillus cereus in vitro

AIMS

LI-Fs are a family of highly potent cyclic lipodepsipeptide antibiotics with a broad antimicrobial spectrum (Gram-positive bacteria and fungi). In this study, LI-F-type antimicrobial peptides (AMP-jsa9) composing of LI-F03a, LI-F03b, LI-F04a, LI-F04b and LI-F05b were isolated from Paenibacillus polymyxa JSA-9. To better understand the antimicrobial mechanism of AMP-jsa9, the potency and action(s) of AMP-jsa9 against Bacillus cereus were examined.

METHODS AND RESULTS

Flow cytometry, confocal laser microscopy, scanning electron microscopy, transmission electron microscopy (TEM) and atomic force microscopy observation, as well as determination of peptidoglycan and cell wall-associated protein and other methods were used. The results indicate that AMP-jsa9 exhibits strong, broad-spectrum antimicrobial activity. Moreover, AMP-jsa9 targets the cell wall and membrane of B. cereus to impair membrane integrity, increase membrane permeability and enhance cytoplasm leakage (e.g. K⁺ , protein, nucleic acid). This leads to bacterial cells with irregular, withered and coarse surfaces. In addition, AMP-jsa9 is also able to bind to DNA and break down B. cereus biofilms.

CONCLUSIONS

In this study, the action mechanism of LI-Fs against B. cereus was clarified in details.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results of this study provide a theoretical basis for utilizing AMP-jsa9 or similar analogues as natural and effective preservatives in the food and feed industries. These efforts could also stimulate research activities interested in understanding the specific effects of other antimicrobial agents.