DEFINITION AND HISTORY
Bacteriocins are bacterial ribosomally synthesized peptides or proteins with antimicrobial activity. As ribosomally synthesised peptides, bacteriocins are encoded by a plasmid- or chromosome-borne structural gene which is often clustered with genes coding for immunity protein(s) and dedicated transport. Bacteriocins are proteinaceous toxins produced as a tiny molecule by bacteria to inhibit the growth of similar or closely related bacterial strain(s) produced by a wide array of bacteria. They are typically considered to be narrow spectrum antibiotics, though this has been debated (Farkas-Himsley H, 1980). They are phenomenologically analogous to yeast and paramecium killing factors, and are structurally, functionally, and ecologically diverse.
Bacteriocins were first discovered by A. Gratia in 1925 (Gratia A, 1925). He was involved in the process of searching for ways to kill bacteria, which also resulted in the development of antibiotics and the discovery of bacteriophage, all within a span of a few years. He called his first discovery a colicine because it killed E. coli (Gratia JP, October 2000). Most of the colicins are relatively large proteins (up to 80 kDa) that kill very closely related bacteria 67 upon binding to the inner membrane or other cytosolic targets (Cascales et al., 2007).
Bacteriocins differ from most therapeutic antibiotics in being proteinaceous agents that are rapidly digested by proteases in the human digestive tract. Bacteriocins are proteins or complex proteins which are biologically active with antimicrobial action against other bacteria. They are produced by bacteria and are normally not termed antibiotics in order to avoid confusion and concern with therapeutic antibiotics, which can potentially illicit allergic reactions in humans and other medical problems (Deraz et al, 2005).
Bacteriocin production could be considered as an advantage for food and feed producers since, in sufficient amounts, these peptides can kill or inhibit pathogenic bacteria that compete for the same ecological niche or nutrient pool. This role is supported by the fact that many bacteriocins have a narrow host range, and is likely to be most effective against related bacteria with nutritive demands for the same scarce resources (Deegan et al, 2006).
TABLE OF CONTENTS
Table of Contents
1.0 DEFINITION AND HISTORY
Naming and Classification of Bacteriocins
2.0 Bacteriocins of Gram-negative bacteria
Bacteriocins of Gram-positive bacteria
Bacteriocins of Archaea
Bacteriocins of marine bacteria
Class I – Lantibiotics
Class II: Non lantibiotics
Class III: Large heat labile
Bacteriocins produced by lactic acid bacteria
3.0 CHAPTER THREE
Isolation and Purification
Applications in food preservation