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Gram-Positive Bacteria


Ongoing research into bacteria and how it spreads has led to the identification of an enzyme that plays a critical role in its growth. A team at the Centre for Cellular and Molecular Biology (CCMB) have been studying E. coli for the past decade in an effort to learn more about how cell walls develop during bacterial growth and division. This is important for food safety professionals because once the mechanism is better understood, it may be possible to develop technologies that inhibit it.


The Importance of the Cell Wall

Bacterial cells are enclosed by peptidoglycan, which is a polymer composed of sugars and amino acids. These substances are cross-linked to form a mesh-like layer that protects the contents of the cell from external environmental factors and also plays a role in maintaining the internal pressure of the cell. The mesh enclosure is permeable to small molecules that contribute to the cell’s health, while preventing larger, potentially toxic molecules from entering. When the wall of a cell is compromised, death follows shortly, which is why cellular walls are the topic of such intense study.


How Bacteria Grow

Bacteria are living organisms that continue to grow and multiply when a sufficient supply of nutrients is available. A single cell reproduces by splitting into two, those two become four, and so on. Cell walls expand and grow when hydrolyzing enzymes cleave the mesh-like layer to allow new material to be introduced without compromising the wall itself. This cleaving happens at links between amino acid residues on neighboring peptide chains.

The research team at CCMB have discovered a particular enzyme, MepK, that is instrumental in breaking down the amino acid residues in a class of cross-links known as mDAP. This is an important mechanism because if there is a possibility of preventing or interrupting it, there may be a possibility of curbing the growth of bacteria. Gaining a better understanding of this mechanism could lead to new ways to prevent bacterial contamination in food processing facilities, healthcare environments, and educational spaces.


The Relevance to Gram-Positive Bacteria

Although E. coli is an example of gram-negative bacteria, the lessons learned can also potentially be applied to gram-positive bacteria. This is especially true for bacteria that have the particular types of cross-links studied in this research, including Clostridia and M. tuberculosis, because bacteria with a lot of mDAP cross-links will rely heavily on MepK enzymes for cell growth. mDAP crosslinks account for only about 10 percent of all cross-link types in gram-negative bacteria, which is what was used in this study. However, in gram-negative bacteria, such as Mycobacteria and Clostridia, mDAP cross-links make up to 80 percent of the link types in the peptidoglycan mesh, which indicates that MepK enzymes play a significant role in their growth.


Research Leads to Practical Solutions

This research could eventually lead to new products and methods for preventing the growth of gram-negative and gram-positive bacteria in food processing environments. In the meantime, FSQA managers must rely on proven approaches for keeping bacteria at bay and addressing contamination when it happens. Because bacteria can grow at such a rapid rate, it is important to continually remove any bacteria that are present and to avoid creating the types of environments in which they thrive. This includes daily sanitation and ongoing cleaning to remove waste products and residues that contribute to bacterial growth on food preparation surfaces. Decon7 in particular has been formulated to remove E. coli and is safe for use on food surfaces with a potable water rinse afterwards. 

Although FSQA managers don’t necessarily need to understand the molecular science behind cellular growth, they do need to be aware of the latest technologies for facility sanitation. To learn more about the steps you can take to prevent an outbreak in your facility, download and read The Busy FSQA Manager’s Guide to Proactive Plant Sanitation.