Applications
Direct visualization of the cell wall structures provides insights into bacterial morphology and their growth dynamics. It also improves our ability to study bacterial pathogenesis and their infection pathways. D-amino acid (DAA)-based probes enable specific, efficient cell wall labeling and, more importantly, are eco-friendly compared to antibiotic-based probes.
D-amino acid (DAA)-based probes incorporate into bacterial cell wall through the activity of the cell wall synthesis enzymes. Namely, their incorporation indicates the cell wall synthesis activity spatiotemporally. We can thus visualize when and where the new cell wall is made in vivo by applying DAA probe labeling and microscopy.
The activities of bacterial cell wall synthesis and degradation are highly dynamic and carefully controlled by bacteria. Degraded cell wall fragments are not only a valuable resource for re-building the wall during their life cycle but also key materials for bacterial infection. The DAA-probe-labeled cell wall fragments are, therefore, powerful tools to study such a reconstruction process as well as cell-to-cell interaction during infection.
The incorporation of D-amino acid (DAA)-based probes into the bacterial cell wall is conducted by the activities of the cell wall synthesis enzymes. With a given labeling time, the higher the cell wall growth activity is, the stronger the labeling intensity is (more probe incorporation). Thus, DAA-probe labeling enables quantification of cell wall growth activity and comparisons.
The incorporation of D-amino acid (DAA)-based probes, such as FDAAs, into the bacterial cell wall (peptidoglycan) is conducted by the cell wall synthesis enzymes. Down- and up-regulation of the synthesis enzymes affects the probe incorporation. Therefore, quantifying FDAA labeling intensity provides information about the roles of enzymes involved in the cell wall synthesis and/or remodeling processes.
The level of FDAA incorporation into bacterial peptidoglycan is dependent upon the cell wall growth activity. Therefore, FDAA labeling provides a new approach to quantitatively evaluate the anti-cell wall growth activity of antibiotics. This can be done by co-incubating bacterial cells with the probes and the target antibiotics for a given time, and then quantify the reduction of the probe labeling intensity. This provides an efficient and reliable method to study antibiotic effects and their antibacterial mechanism.
Antibiotics lose their ability of killing bacteria when drug resistance is built in the cells. Since DAA probes are capable of quantifying the anti-cell wall growth activity of antibiotics, they are powerful tools to quantify the resistance ability of bacteria toward those antibiotics. This provides information about where the resistance strains spread out from, and how strong their resistance abilities are, which helps scientists/doctors to track and prevent the occurrence of resistant bacterial strains.
The ability of D-amino acid (DAA)-based probes to quantify the anti-cell wall growth of antibiotics makes them great tools to identify antibiotic candidates. High-throughput screening of natural products is still the most dominant way to discover new antibiotics. DAA probes labeling provide a reliable and efficient method to identify compounds that inhibit bacterial cell wall growth.
The incorporation of D-amino acid (DAA)-based probes into bacterial cell wall occurs in vitro when isolated transpeptidases (the main cell wall synthase) and synthetic substrates are present. This allows us to study the interactions between the enzymes and/or antibiotics and/or the cell wall substrates in molecular levels. The information can provides new insights into the cell wall synthesis and antibiotic inhibition mechanisms.