Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
Metagenomics and advances in molecular biology methods have enhanced knowledge of microbial evolution, metabolism, functions, their interactions with other organisms and their environment. The ability to persist and adapt to changes in their environment is a common lifestyle of 1 % of the known culturable bacteria. Studies in the variety of species have identified an incredible diversity of bacterial lifespan. The holy grail of molecular biology is to understand the integrated genetic and metabolic patterns of prokaryotic organisms like the enteric bacterium Escherichia coli. The usual description of E. coli life cycle comprises four phases: lag, logarithmic, stationary, and death phase, omitting their persistence and evolution during prolonged stationary phase. During prolonged stationary/starvation period, in batch bacterial culture, selected mutants with increased fitness express growth advantage in stationary phase (GASP), which enables them to grow and displace the parent cells as the majority population. The analyses of growth competition of Gram-negative and/or Gram-positive mixed bacterial cultures showed that GASP phenomenon can result in four GASP phenotypes: strong, moderate, weak or abortive. Bacterial stress responses to starvation include functions that can increase genetic variability and produce transient mutator state, which is important for adaptive evolution.Metagenomika i suvremene metode molekularne biologije omogućili su razumijevanje evolucije, metabolizma i funkcije mikroorganizama te njihovih interakcija s drugim organizmima u okolišu. Otpornost i prilagodba na promjene u okolišu uobičajeni su za 1 % poznatih bakterija što se mogu uzgajati u laboratoriju. Istraživanjem različitih bakterijskih vrsta uočena je njihova velika raznolikost. Escherichia coli je „sveti gral“ molekularne biologije u razumijevanju genetike i metaboličkih modela. Životni se ciklus E. coli sastoji od četiri faze: lag, logaritamske, stacionarne i faze odumiranja, zanemarujući bakterijsku postojanost i evoluciju tijekom produljene stacionarne faze. U šaržnoj bakterijskoj kulturi, tijekom produljene stacionarne faze ili vremena izgladnjivanja, preživjele stanice mutanata brže rastu (engl. growth advantage in stationary phase - GASP), pa prerastaju i zamjenjuju većinu roditeljskih stanica. Analiza kompetitivnoga rasta Gram-pozitivnih i/ili Gram-negativnih bakterija, tijekom produljene stacionarne faze u mješovitim kulturama, pokazala je postojanje četiriju GASP fenotipova: jaki, umjereni, slabi i nerazvijeni. Bakterijski odgovor na izgladnjivanje obuhvaća stanične funkcije koje mogu povećati genetičku raznolikost i stvarati mutator stanice bitne za adaptivnu evoluciju bakterija
