ABSTRACT
We studied the impact of a sublethal concentration of erythromycin on the fitness and proteome of a continuously cultivated population of Escherichia coli. The development of resistance to erythromycin in the population was followed over time by the gradient plate method and minimum inhibitory concentration (MIC) measurements. We measured the growth rate, standardized efficiency of synthesis of radiolabeled proteins, and translation accuracy of the system. The proteome changes were followed over time in two parallel experiments that differed in the presence or absence of erythromycin. A comparison of the proteomes at each time point (43, 68, and 103 h) revealed a group of unique proteins differing in expression. From all 35 proteins differing throughout the cultivation, only three were common to more than one time point. In the final population, a significant proportion of upregulated proteins was localized to the outer or inner cytoplasmic membranes or to the periplasmic space. In a population growing for more than 100 generations in the presence of antibiotic, erythromycin-resistant bacterial clones with improved fitness in comparison to early resistant culture predominated. This phenomenon was accompanied by distinct changes in protein expression during a stepwise, population-based development of erythromycin resistance.
Subject(s)
Anti-Bacterial Agents/pharmacology , Erythromycin/pharmacology , Escherichia coli Proteins/genetics , Escherichia coli/genetics , Gene Expression Regulation, Bacterial , Proteome/genetics , Culture Media , Drug Resistance, Bacterial/genetics , Escherichia coli/drug effects , Escherichia coli/metabolism , Escherichia coli Proteins/metabolism , Genetic Fitness/drug effects , Microbial Sensitivity Tests , Proteome/metabolism , Time FactorsABSTRACT
A two-phase cultivation system was developed which will enable studies of streptomycete differentiation by molecular biological and global techniques such as transcriptomics and proteomics. The system is based on a solid phase formed by glass beads corresponding to particles in soil, clay, or sand natural habitats of streptomycetes. The beads are immersed in a liquid medium that allows easy modification or replacement of nutrients and growth factors as well as radioactive labeling of proteins. Scanning electron microscopy was used to analyze morphological differentiation of streptomycetes on glass beads and two-dimensional protein electrophoresis to demonstrate the potential of the system for analyses of protein synthesis profiles during the developmental program. This system facilitates studies of differentiation including expression and post-translation modifications of streptomycetes proteins, secondary metabolite biosynthesis, and morphological development.
