Bacteriocins are a heterogeneous group of ribosomally synthesised antimicrobial peptides with the ability to kill closely related (narrow spectrum), or a diverse range of (broad spectrum), microorganisms [1]. They are classified into three major classes based on their structural and physicochemical properties: class I bacteriocins, class II bacteriocins, and class III bacteriocins. These antibacterials inhibit the growth of target organisms by functioning primarily on the cell envelope and by affecting gene expression and protein production within cells. These molecules have antimicrobial activity against pathogenic and deteriorating bacteria, which justifies their biotechnological potential. The use of bacteriocins has been reported for the following: food preservation, diverse therapeutic purposes such as treatment of peptic ulcer, spermicidal agent, and woman care, anticancerous agent, veterinary use, skincare, and oral care, and also for plant growth promotion in agriculture among others [2].
The genus Geobacillus comprises bacteria that are Gram-positive, thermophilic spore-formers, which are found in a variety of environments from hot-springs, cool soils, to food manufacturing plants, including dairy manufacturing plants [3]. Geobacillus has historically been associated with spoilage of canned food. However, in recent years it has become the subject of much attention due its biotechnological potential. One aspect of this genus that has not been fully explored or realized is its use as a source of novel forms of the ribosomally synthesized antimicrobial peptides known as bacteriocins [4]. Bacteriocins from thermophilic bacteria have the potential to be used in various industries that maintain higher temperatures, since thermophilic bacteria proteins are usually thermostable.
Geobacillus stearothermophilus 15, isolated from oilfield located in Lithuania, produces two bacteriocins geobacillin 26 (Geo26) and geobacillin 19 (Geo19). Since Geo26 have already been purified, heterologously expressed in Escherichia coli and characterized, the aim of our study is to clone, perform heterologous expression of recombinant novel Geo19 bacteriocin in E.coli and to characterize it. This bacteriocin can be assigned to class II, it has similarity to already characterized bacteriocin SDP. Native Geo19 is active against thermophilic bacteria, which often survive high temperatures during heat treatment of food and could therefore be widely applied in the food industry.