ΠΜΣ Μικροβιακή ΒιοτεχνολογίαLibrary of the School of Science
Καθηγήτρια ΕΚΠΑ Αμαλία Καραγκούνη Κύρτσου
Διερεύνηση της παραγωγής αντιμικροβιακών ενώσεων/βακτηριοσινών από οξυγαλακτικά βακτήρια έναντι παθογόνων μικροοργανισμών που εμπλέκονται στη στοματική υγεία
In the present study 237 lactic acid bacteria (LAB), isolated from traditional
Greek dairy products, were screened for potential antimicrobial activity
against 10 oral pathogens ("target" strains) which are associated to the
inflammatory diseases of dental decay and periodontitis.
The oral pathogens included 3 Gram¬- strains: Aggregatibacter
actinomycetemcomitans DSM 11123, Fusobacterium nucleatum subsp. vincentii DSM
19507T και Porphyromonas gingivalis DSM 20709T while the rest were Gram+
streptococci. The lactic acid bacteria were tested for antimicrobial potential
after their growth in Skim Milk, MRS and M17.
The antimicrobial activity was tested with the Well Diffusion Assay method
(WDA). No antimicrobial activity was observed against Gram¬- pathogens.
Against the Gram+, Cell Free Culture Supernatant (CFCS) of S. macedonicus
ACA-DC 198 (grown on Skim Milk), demonstrated an inhibitory effect on the
growth of S. gordonii LMG 14518, S. oralis LMG 14532T and S. sanguinis DSM
20068, while CFCS of L. fermentum ACA-DC 179 (grown on MRS) and L. plantarum
ACA-DC 269 (Grown on Skim Milk) only against S. oralis LMG 14532T. Producer
strains’ culture supernatants were treated with ammonium sulfate and a 10-fold
concentration was achieved. In all cases antimicrobial activity of the CFCS
(10X) was completely lost after proteinase K treatment, suggesting the
proteinaceous nature of the molecules.
The thermostability of the antimicrobial compounds was tested at autoclaving
temperature (121ο C for 15min). The bacteriocin-like inhibitory substances
(BLIS) produced by L. fermentum ACA-DC 179, L. plantarum ACA-DC269 and S.
macedonicus ACA-DC 198 against S. oralis LMG 14532T were heat labile, whereas
the BLIS produced by S. macedonicus ACA-DC 198 against S. gordonii LMG 14518
and S. sanguinis DSM 20068 was heat stable.
Further studies were carried out on the susceptibility of the target cells to
the BLIS, in the different growth phases: acceleration phase, exponential phase
and stationary phase. All target strains appeared to be sensitive during the
acceleration phase of growth. A remarkable reduction between 2 and 3
logarithmic cycles was observed after 2h treatment of all target strains with
the concentrated (10Χ) supernatant of S. macedonicus ACA-DC 198. No effect was
observed after treatment with the 10Χ CFCS supernatants of L. fermentum ACA-DC
179 and L. plantarum ACA-DC269 with S. oralis LMG 14532T.
Fourier transform infrared spectroscopy was used in order to determine the mode
of action of the heat labile and heat stable bacteriocins produced by S.
macedonicus ACA-DC 198 against S. oralis LMG 14532Τ and S. sanguinis DSM 20068,
respectively. The second derivative of the original spectra revealed changes in
spectral regions corresponding toi absorptions of major cellular components
like polysaccharides of the cell wall, fatty acids of the cell membrane and
proteins. Principal component analysis of the second derivative-transformed
spectra provided evidence for major changes in the cellular composition, due to
treatment with the CFCSs of S. macedonicus ACA-DC 198.
Lactic acid bacteria, Antimicrobial compounds, Bacteriocins, Dental decay, Periodontitis
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