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Srpski arhiv za celokupno lekarstvo
2002, vol. 130, br. 3-4, str. 110-114
jezik rada: srpski
vrsta rada: članak
doi:10.2298/SARH0204110O
Prenos genetskog materijala bakterije Streptococcus pneumoniae procesom transformacije
Univerzitet u Beogradu, Medicinski fakultet, Institut za mikrobiologiju i imunologiju

Sažetak

Streptococcus pneumoniae je jedna od glavnih patogenih bakterija respiracionog sistema, koja najčešće izaziva pneumoniju, zapaljenje srednjeg uva, bakterijemiju i meningitis. Takođe, pneumokok je jedna od najviše proučavanih bakterija. Neka vrlo značajna naučna otkriva učinjena su na eksperimentnom modelu pneumokoka: transformacija; DNK kao nosilac genetskih informacija; uloga kapsule bakterije u rezistenciji na fagocitozu imunogenost polisaharida kapsule; terapijsko delovanje penicilina, kao i mehanizam rezistencije na beta-laktamske antibiotske lekove. S. pneumoniae je jedna od retkih vrsta bakterija koje su prirodno transformabilne i kod kojih je transformacija osnovni način razmene genetskog materijala. Transformacija gena je proces u kome ćelije preuzimaju slobodnu DNK iz okolnog medijuma i inkorporišu je, pri čemu nastaje izmena genotipa, koja se prenosi nasleđem. Potpun proces se može podeliti u nekoliko faza: a) razvoj kompetencije (sposobnost preuzimanja DNK); b) vezivanje DNK; c) transport DNK; i d) integracija DNK u hromozom ćelije primaoca. Determinante kodirane u hromozomu su ograničene na prenos u iste bakterije ili u srodne vrste bakterija. Kao posledica rekombinacije između vrsta nastaju mozaički geni koji se sastoje od naizmeničnih blokova nukleotida, poreklom od donora i primaoca. Ako selekcija deluje na ovom nivou, korisni "mozaici" postaju fiksirani u populaciji bakterija, a mogu se i horizontalno širiti iz jedne u drugu vrstu bakterija. Horizontalni prenos gena i homologa rekombinacija dovodi do stvaranja raznolikosti gena. Kod pneumokoka, rezistencija na beta-laktamske antibiotske lekove nastala je usled sticanja determinanti rezistencije, poput nisko-afinitetnih penicilin-vezujućih proteina procesom horizontalnog prenosa gena od viridansnih streptokoka. Geni koji kodiraju determinante virulencije mogu se prenositi izmenu pneumokoka i srodnih vrsta bakterija. Ova pojava utiče na nastanak vrlo rezistentnih i virulentnih izolata S. pneumoniae. Takođe, izmene gena koji kodiraju sintezu autolizina i dovode do promene serotipa mogu ometati identifikaciju pneumokoka i biti uzrok neuspeha delovanja vakcine.

Ključne reči

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