rifampin and Starvation

Mutation rates in bacteria can vary depending on the genetic target studied and the specific growth conditions of the cells. Here, two different methods were used to determine how rates of mutation to antibiotic resistance, auxotrophy, and prototrophy were influenced by carbon starvation on agar plates. The rate of mutation to rifampin resistance was increased by starvation as measured by fluctuation tests, similar to what has been reported previously for Escherichia coli. In contrast, the rates of mutation to various types of auxotrophy were unaffected or decreased as measured by both fluctuation tests and a repeated-streaking procedure. Similarly, the rates of reversion to prototrophy of his and lac nonsense and missense mutations were unaffected by starvation. Thus, mutation rates of different genetic targets can be affected differently by starvation and we conclude that carbon starvation is not generally mutagenic in Salmonella typhimurium.

Topics: Drug Resistance, Microbial; Galactose; Glucose; Hexoses; Histidine; Lactose; Mutagenesis; Rifampin; Salmonella typhimurium; Starvation

The response of marine Vibrio sp. strain S14 (CCUG 15956) to long-term (48-h) multiple-nutrient starvation (i.e., starvation for glucose, amino acids, ammonium, and phosphate simultaneously) can be described as a three-phase process. The first phase, defined as the stringent control phase, encompasses an accumulation of guanosine 5'-diphosphate 3'-diphosphate (ppGpp) and decreases in RNA and protein synthesis during the first 40 min. In the second phase, there is a temporary increase in the rates of RNA and protein synthesis between 1 and 3 h paralleling a decrease in the ppGpp pool. The third phase includes gradual decline in macromolecular synthesis after 3 h. Using two-dimensional gel electrophoresis of pulse-labeled proteins, a total of 66 proteins were identified as starvation inducible (Sti), temporally expressed throughout the three phases of starvation. The inhibition of protein synthesis during the first phase of starvation partly disrupted the subsequent temporally ordered synthesis of starvation proteins and prevented the expression of some late starvation proteins. It was also found that the early temporal class of starvation proteins, which included the majority of the Sti proteins, was the most essential for long-term survival. Vibrio sp. strain S14 cultures prestarved (1 h) for glucose, amino acids, ammonium, or phosphate as well as cultures exposed (1 h) to CdCl2 exhibited enhanced survival during the subsequent multiple-nutrient starvation in the presence of chloramphenicol or rifampin, while heat or the addition of cyclic AMP or nalidixic acid prior to starvation had no effect. It was demonstrated that amino acid starvation and CdCl2 exposure, which induced the stringent response, were the most effective in conferring enhanced survival. A few Sti proteins were common to all starvation conditions. In addition, the total number of proteins induced by multiple-nutrient starvation significantly exceeded the sum of those induced by starvation for each of the individual nutrients.

Topics: Bacterial Proteins; Chloramphenicol; Electrophoresis, Gel, Two-Dimensional; Energy Metabolism; Guanosine Tetraphosphate; Isoelectric Point; Marine Biology; Molecular Weight; Rifampin; RNA, Bacterial; Starvation; Vibrio

Topics: Amino Acids; Amino Acyl-tRNA Synthetases; Bacterial Proteins; Carbon Isotopes; Escherichia coli; Glucose; Models, Biological; Polyribosomes; Rifampin; RNA, Transfer; Starvation; Tritium; Uracil; Valine

Topics: Amino Acids; Carbon Isotopes; Escherichia coli; Fusidic Acid; Galactosidases; Half-Life; Kinetics; Peptide Biosynthesis; Peptide Chain Elongation, Translational; Peptide Chain Termination, Translational; Propionates; Protein Biosynthesis; Rifampin; RNA, Messenger; Starvation; Transcription, Genetic