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Bakterije vrste C. jejuni so najpogostejše povzročiteljice kampilobakterioze ter gastroenteritisov pri človeku. Za svoje razmnoževanje in rast potrebujejo optimalne pogoje, zato so znani kot zelo zahtevni in občutljivi mikroorganizmi. Sposobnost tvorbe biofilmov jim omogoča večjo odpornost na protimikrobne učinkovine ter s tem lažje preživetje. Nadzor bakterij v odporni obliki biofilmov zahteva uporabo še večjih koncentracij antibiotikov. Problem naraščajoče odpornosti bakterij zato zahteva vpeljavo novih alternativnih strategij za nadzor nad odpornimi sevi in odpornimi oblikami biofilma. Ena od alternativnih strategij je uporaba protimikrobnih učinkovin naravnega izvora in sicer v njihovih sub-inhibitornih koncentracijah. V teh koncentracijah učinkovine ne vplivajo na rast, ampak na druge lastnosti bakterij in tako ne povzročajo razvoja odpornosti. Namen naloge je bil: (i) predstaviti različne učinkovine naravnega izvora in njihovo dokazano delovanje na inhibicijo tvorbe in redukcijo nastalega biofilma bakterij C. jejuni, (ii) opisati mehanizme delovanja na različnih celičnih nivojih C. jejuni ter (iii) primerjati tarčno delovanje antibiotikov in učinkovin naravnega izvora pri bakterijah C. jejuni. V zaključku naloge smo opisali modulacijo genov oz- proteinov, ključnih za nastanek biofilma ter vključene v mehanizme gibljivosti, adhezije in medcelične komunikacije, v celicah tretiranimi z učinkovinami naravnega izvora. Na ta način smo dokazali tarčne mehanizme delovanja protimikrobnih učinkovin naravnega izvora na C. jejuni. Bacteria of the species C. jejuni are the most common causative agents of campylobacteriosis and gastroenteritis in humans. They require optimal conditions for their replication and growth, which is why they are known to be very fastidious and sensitive microorganisms. The ability to form biofilms makes them more resistant to antimicrobial agents and thus more survivable. To control bacteria in the resistant form of biofilms require the use of even higher concentrations of antibiotics. Therefore increasing bacterial resistance requires the introduction of new alternative strategies to combat resistant strains and resistant forms of biofilms. One of these alternative strategies is the use of antimicrobial agents of natural origin at their subinhibitory concentrations. At these concentrations, the agents do not affect the growth but other properties of the bacteria and thus do not lead to development of resistance. The purpose of this thesis was: (i) to present different compounds of natural origin and to demonstrate their ability to inhibit biofilm formation or reduce the formed biofilm of C.jejuni, (ii) to describe the mechanisms of action at different cellular levels of C. jejuni, and (iii) to compare the target effect of antibiotics and compounds of natural origin on C. jejuni. At the end, we described the modulation of genes or proteins crucial for biofilm formation and their involvement in the mechanisms of motility, adhesion and intercellular communication, in cultures treated with natural antimicrobial agents. In this way, we have explained the target mechanisms of action of antimicrobial agents of natural origin in C. jejuni cells.