Zaustavljanje staničnog ciklusa u oskudnim uvjetima u bakteriji Escherichia coli

undergraduate thesis

• Title (english): The stringent response and cell cycle arrest in Escherichia coli
• Author: Branimir Berečić
• Mentor: Ivana Ivančić Baće (mentor)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2012, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology

Abstract

Bakterijski "stringent response", uzrokovan nedostatkom hranjivih tvari, potiče gomilanje signalnih nukleotida ppGpp i pppGpp. Stanice divljeg tipa prolaze kroz zastoj ovisan o proteinu RelA nakon što ih se tretira serin hidroksamatom kako bi imale cijeli broj kromosoma u sebi i omjer ishodišta/terminacijskih slijedova 1. Stanje rasta prije nestašice hranjivih tvari određuje broj kromosoma u stanici nakon zastoja staničnog ciklusa; regije kromosoma u kojima se nalaze ishodišta replikacije su razdvojene, ali regije sa terminacijskim slijedovima su sparene. Nukleoidi u takvim "zaustavljenim" bakterijama su nekondenzirani. Ukoliko se stanice tretiraju kloramfenikolom nukleoidi postaju vrlo kondenzirani, a tretiranjem rifampicinom i cefaleksinom kromosomi više nisu spareni kod terminacijskih slijedova. Stvaranje kolonija je inhibirano zbog nakupljanja ppGpp, osim u mutantima ΔseqA i Δdam. Završetak gladovanja dovodi do vrlo brze reorganizacije nukleoida, razdvajanja kromosoma i dovršavanja replikacije. Osim nakupljanja ppGpp, metilacija DNA i vezanje SeqA su čimbenici potrebni za pokretanje potpunog zastoja u stanici, čime se utjecalo na inicijaciju replikacije i segregaciju kromosoma.

Abstract (english)

The bacterial stringent response, triggered by nutritional deprivation, causes an accumulation of the signaling nucleotides ppGpp and pppGpp. Wild type cells undergo a RelA-dependent arrest after treatment with serin hydroxamage in order to contain an integer number of chromosomes and a replication origin/terminus ratio of 1. The growth rate prior to starvation determines the number of chromosomes after arrest; chromosomal regions corresponding to the origins of replication are segregated, while the termination regions remain colocalized. Nucleoids of these arrested cells are decondensed. If treated with chloramphenicol, they become highly condensed, and treatment with rifampicin and cephalexin causes the chromosomes to segregate at their termination regions. Colony formation is inhibited due to ppGpp accumulation, except in ΔseqA and Δdam mutants. Release from starvation causes rapid nucleoid reorganization, chromosome segregation and replication resumption. Accumulation of nucleotid ppGpp, DNA methilation and SeqA binding are all factors which contribute to initiating complete cell cycle arrest, which in turn affects replication initiation and chromosome segregation.

• Keywords: bakterijski odgovor u oskudnim uvjetima; Escherichia coli
• Keywords (english): bacterial stringent response; Escherichia coli
• Language: croatian
• URN:NBN: urn:nbn:hr:217:389620
• Study programme: Title: Ecology; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) biologije (sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) biologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2018-04-12 11:13:56