Šiame darbe tirtas gramteigiamųjų ir gramneigiamųjų bakterijų atsakas į natyvaus ir katalitiškai neaktyvaus lizocimo bei jo 9 aminorūgščių katijoninio peptido sukeltus ląstelės apvalkalo pažeidimus. Panaudojant potenciometrinius metodus, buvo nustatyta, kad šie junginiai sukelia viduląstelinio K+ ištekėjimą iš L. lactis, B. subtilis ir P. aeruginosa ląstelių ir dalinę jų citoplazminės membranos depoliarizaciją, tačiau natyvus, kaitintas lizocimas ir 9a peptidas skirtingai veikia L. lactis apvalkalėlio laidumą. Peptidas bei kaitintas lizocimas sukelia staigesnį K+ jonų ištekėjimą ir membranos įtampos sumažėjimą nei natyvus lizocimas. Peptido sukeliamas K+ jonų ištekėjimas yra grįžtamas. Taip pat buvo įvertintas įvairių mutantinių L. lactis padermių jautrumas lizocimui. Pastebėta, kad kuo padermė atsparesnė lizocimui, tuo vėliau prasideda K+ jonų ištekėjimas iš šios padermės ląstelių. Pasitelkus DNR mikrogardelių metodą, buvo tiriamas lizocimo bei peptido poveikis L. lactis MG1363 bei ΔoppA ląstelių genų raiškos pokyčiams. Nustatyta, jog peptidu ir lizocimu veiktose ląstelėse iššaukiama dvikomponentės valdymo sistemos CesSR raiška ir sukeliamas nuo SpxB priklausomas ląstelių atsparumas lizocimui. Gauti rezultatai rodo, jog lizocimas ir 9a peptidas sukelia kiek skirtingus L. lactis transkriptomo pokyčius: lizocimas savitai skatina nuo N-deacetilazės priklausomo atsparumo mechanizmo įsijungimą, taip pat skiriasi OpuA sistemą koduojančių genų raiška. / We used potenciometric measurments to investigate the response of Gram-positive and Gram-negative bacteria to cell envelope stress, caused by native and heat-inactivated lysozyme and lysozyme-derived 9 amino acid peptide. It was found that these antimicrobial compounds induce leakage of K+ outside the cells of L. lactis, B. subtilis and P. aeruginosa and cause partial depolarization of bacterial cytoplasmic membrane. We observed different response of L. lactis cells to these compounds – peptide and heat-inactivated lysozyme cause more rapid efflux of K+ ions than native lysozyme. Peptide has a reversible effect on K+ leakage. Sensitivity of different mutant strains of L. lactis to lysozyme was studied. It was shown that more resistant the strain is, the later the leakage of K+ ions is induced by lysozyme. To investigate the genome-wide response of L. lactis MG1363 and ΔoppA strains to lysozyme and 9 a.a. peptide, changes of gene expression after challenging cells with these antimicrobial compounds were analysed using DNA microarrays. It was estimated, that lysozyme and lysozyme-derived 9a.a. peptide induce CesSR system and SpxB-mediated response. It was also shown that L. lactis response to 9a.a. peptide and lysozyme differs. Lysozyme specifically induces PgdA-mediated resistance mechanism. Changes of expression of OpuA system in lysozyme and peptide treated cells are also different.

Work size - 60 pages, including 35 pictures, 1 table. List of literature - 44 sources. The beginning of the work -2004 09 01, the end of the work - 2006 05 15. Purpose of work: To explore, what influence the additive lysozyme on technological properties of milk which are important in manufacture of fermental cheeses and sour - milk products has. In work presents the analysis of lysozyme influence on the technological properties of. The results show that lysozyme prevent to develop of undesirable microorganisms and positively influences on the quality of fermented milks. It was established that the additive of lysozyme prolongs the duration of the bactericidal phase. The investigation of the rennet formation time has shown that the clothing of the milk in samples with lysozyme formed 12 - 15  faster as in compared with the control sample without lysozyme. Besides, it is established, that the additive of lysozyme intensifies the process removal of the whey. The research investigation show that in samples with lysozyme, whey distinguish in smaller optical density as compared with control samples. The development of lactic bacteria during fermentation process was examined too. It was found that lysozyme influence on this process is very insignificant. It was established that the additive of lysozyme insignificant reduces viscosity and acidity of fermented milk gels.