Detection of antimicrobial compounds produced from bacteria of the intestinal tract of healthy neonates

Postgraduate Thesis uoadl:1316184 401 Read counter

ΠΜΣ Μικροβιακή Βιοτεχνολογία
Library of the School of Science
Deposit date:
Τσάπατου Άννη
Supervisors info:
Αμαλία Δ. Καραγκούνη Καθηγήτρια (Επιβλέπουσα), Γεώργιος Διαλλινάς Αναπλ. Καθηγητής, Δημήτριος Χατζηνικολάου Επίκ. Καθηγητης
Original Title:
Ανίχνευση αντιμικροβιακών ουσιών σε βακτήρια του εντερικού συστήματος υγιών νεογνών
Translated title:
Detection of antimicrobial compounds produced from bacteria of the intestinal tract of healthy neonates
The present study aimed to investigate the production of antimicrobial
compounds, particularly bacteriocins, from bacterial strains isolated from the
faecal microbiota of healthy, full-term neonates.
A total of 50 Lactobacillus spp. strains and 22 Bifidobacterium spp. strains
were tested for the production of antimicrobial compounds by the “agar spot
test” and the “agar well diffusion assay” against 12 Gram – positive indicator
strains. Only one isolate, identified as Lactobacillus gasseri by 16S rDNA
sequence amplification, exhibited antimicrobial activity against Lactobacillus
delbrueckii DSMZ 20081 by both assays. Effect of hydrolytic enzymes, catalase,
pH, temperature and detergents on antibacterial activity were examined. The
antimicrobial peptide from Lactobacillus gasseri had a narrow spectrum of
activity and was extremely stable at pH and temperature ranges. The production
began in early logarithmic phase and maximum activity (12.800 AU/mL) was
reached in early stationary phase. The mode of action was determined to be
probably bacteriolytical against Lactobacillus delbrueckii DSMZ 20081 by
killing kinetics experiments. Further investigation is needed to ascertain the
lytic mechanism.
Finally, purification of the peptide from Lactobacillus gasseri was performed
by ammonium sulfate precipitation and gel filtration chromatography. In order
to determine molecular mass of bacteriocin-like molecule, electrophoresis
assays of protein extracts obtained from chromatography, have taken place. None
of these assays showed accurate results, as it was appeared that bacteriocin is
in complex with other proteinaceous factors. This result indicated the
necessity to develop additional methods of chromatography for bacteriocin
purification and isolation.
Intestinal tract, Antimicrobial compounds, Bacteriocins, Lactobacillus, Bifidobacterium
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