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Optimized Protocol for the Incorporation of FDAA (HADA Labeling) for in situ Labeling of Peptidoglycan
Katharina Peters1, Manuel Pazos1, Michael S VanNieuwenhze2
1Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, NE2 4AX, Newcastle upon Tyne, United Kingdom.
Abstract:
The essential peptidoglycan (PG) layer surrounds the cytoplasmic membrane in nearly all bacteria. It is needed to maintain the shape of the cell and protect it from lysis due to high turgor. Growth of the PG layer is a complex process that involves the activities of PG synthases and hydrolases during elongation and cell division. PG growth sites can be labeled by the recently developed fluorescent D-amino acid (FDAA) probes in a range of different bacteria. FDAAs are incorporated into PG by dd-transpeptidases (Penicillin-binding proteins, PBPs) or, if present, ld-transpeptidase (LDTs). Long-pulse in situ labeling of E. coli cells with the FDAA 7-hydroxycoumarincarbonylamino-D-alanine (HADA) is expected to result in a uniform label at the side wall of cells and enhanced label at cell division sites due to the intense PG synthesis. However, we observed reduced label at mid-cell when labeling E. coli cells with HADA. We reasoned that probe incorporated at cell division sites may be removed by PG hydrolases and modified the labeling protocol to better preserve PG-incorporated HADA for fluorescence microscopy. Here, we report the optimized HADA-labeling protocol by which cells retain an enhanced HADA signal at the division septum.
Insights
Researchers optimized fluorescent D-amino acid (FDAA) labeling in E. coli. This new method enhances visualization of peptidoglycan synthesis at bacterial cell division sites, overcoming previous limitations.
Area of Science:
- Microbiology
- Cell Biology
- Biochemistry
Background:
- The bacterial peptidoglycan (PG) layer is crucial for cell shape and integrity, protecting against osmotic lysis.
- PG synthesis involves a dynamic balance of synthases and hydrolases during cell growth and division.
- Fluorescent D-amino acid (FDAA) probes are used to visualize PG synthesis sites in bacteria.
Purpose of the Study:
- To optimize the labeling protocol for fluorescent D-amino acid (FDAA) 7-hydroxycoumarincarbonylamino-D-alanine (HADA) in E. coli.
- To overcome the observed reduced HADA signal at mid-cell division sites.
- To develop a method for enhanced visualization of peptidoglycan synthesis at bacterial division septa.
Main Methods:
- Utilized in situ long-pulse labeling of E. coli with the FDAA HADA.
- Investigated the cause of reduced HADA signal at cell division sites.
- Modified the HADA labeling protocol to improve preservation of incorporated probe.
Main Results:
- Observed an unexpected reduction in HADA signal at mid-cell division sites in E. coli.
- Identified potential removal of incorporated HADA by peptidoglycan hydrolases.
- Developed an optimized HADA labeling protocol that preserves signal at the division septum.
Conclusions:
- The optimized HADA labeling protocol successfully enhances the visualization of peptidoglycan synthesis at E. coli division sites.
- This improved method allows for better study of the dynamic PG synthesis and turnover at the bacterial cell division septum.
- The findings contribute to understanding bacterial cell wall dynamics and provide a refined tool for microbiological research.
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