Lag Phase Is a Distinct Growth Phase That Prepares Bacteria for Exponential Growth and Involves Transient Metal Accumulation

Abstract

Lag phase represents the earliest and most poorly understood stage of the bacterial growth cycle. We developed a reproducible experimental system and conducted functional genomic and physiological analyses of a 2-h lag phase in Salmonella enterica serovar Typhimurium. Adaptation began within 4 min of inoculation into fresh LB medium with the transient expression of genes involved in phosphate uptake. The main lag-phase transcriptional program initiated at 20 min with the upregulation of 945 genes encoding processes such as transcription, translation, iron-sulfur protein assembly, nucleotide metabolism, LPS biosynthesis, and aerobic respiration. ChIP-chip revealed that RNA polymerase was not "poised" upstream of the bacterial genes that are rapidly induced at the beginning of lag phase, suggesting a mechanism that involves de novo partitioning of RNA polymerase to transcribe 522 bacterial genes within 4 min of leaving stationary phase. We used inductively coupled plasma mass spectrometry (ICP-MS) to discover that iron, calcium, and manganese are accumulated by S. Typhimurium during lag phase, while levels of cobalt, nickel, and sodium showed distinct growth-phase-specific patterns. The high concentration of iron during lag phase was associated with transient sensitivity to oxidative stress. The study of lag phase promises to identify the physiological and regulatory processes responsible for adaptation to new environments.

Antimicrobial activity of zinc oxide (ZnO) nanoparticle againstKlebsiella pneumoniae

“…In the case of untreated cells, the bacterial replication goes to stationary phase after 7 h of incubation. During the lag phase, cellular metabolism is accelerated, resulting in rapid biosynthesis of cellular macromolecules, primarily enzymes (Rolfe et al, 2012). In this study on the treatment with ZnO Nps, cells showed moderate increase in size, thereby limiting cellular metabolism and biosynthesis.…”

Isobaric Tags for Relative and Absolute Quantitation Proteomics Analysis of Gene Regulation by SprC in Staphylococcus Aureus

“…Therefore, it is necessary to identify comprehensive gene networks modulated by SprC. Bacterial growth is most active in logarithmic phase that is involved with DNA synthesis, coupling with transcription and translation and synthesizing indispensable biological macromolecules [23]. In the present study, we chose the late exponential growth phase bacteria (cultured for 6 h) for analysis of proteomics, because SprC reached the maximum amount at this period compared with early and middle exponential growth phases (Figure 1).…”

Effects of medium-chain fatty acids on the structure and immune response of IPEC-J2 cells

“…Figure 2 shows the lag time for both strains. Lag time is the initial period in the life of a bacterial population when cells are adjusting to a new environment before starting exponential growth (Rolfe et al 2012). Interestingly, only very minor differences in lag time were observed for C8 and C10 up to 5 mM MCFAs for both strains.…”