growth phase transitions

Examples of growth phase transitions in the following topics:

• Regulation of Sigma Factor Activity

  • Often times, sigma factor expression or activity is dependent on specific growth phase transitions of the organism.
  • If transcription of genes involved in growth is necessary, the sigma factors will be translated to allow for transcription initiation to occur.

• Generation Time

  • In autecological studies, bacterial growth in batch culture can be modeled with four different phases: lag phase, exponential or log phase, stationary phase, and death phase .
  • During lag phase, bacteria adapt themselves to growth conditions.
  • During this phase of the bacterial growth cycle, synthesis of RNA, enzymes, and other molecules occurs.
  • The exponential phase (sometimes called the log phase or the logarithmic phase) is a period characterized by cell doubling.
  • The phases of growth are labelled on top.

• Enrichment and Isolation

  • During lag phase, bacteria adapt themselves to growth conditions.
  • During the lag phase of the bacterial growth cycle, synthesis of RNA, enzymes and other molecules occurs.
  • In comparison to batch culture, bacteria are maintained in exponential growth phase, and the growth rate of the bacteria is known.
  • Bacterial growth in batch culture can be modeled with four different phases: lag phase (A), exponential or log phase (B), stationary phase (C), and death phase (D).
  • List the growth phases of microrganisms and the different types of growth media available to culture them

• Growth Rate and Temperature

  • Bacterial growth is the division of one bacterium into two daughter cells in a process called binary fission.
  • When Escherichia coli is exposed to a temperature drop from 37 to 10 degrees Celsius, a four to five hour lag phase occurs and then growth is resumed at a reduced rate.
  • During the lag phase, the expression of around 13 proteins, which contain cold shock domains is increased two- to ten-fold.
  • Bacterial growth in batch culture can be modeled with four different phases: (A) the lag phase, when the population stays roughly the same; (B) the exponential, or log, phase, when the population grows at an increasing rate; (C) the stationary phase, when population growth stagnates; and (D) the death phase, when bacteria begin to die off and the population decreases in size.
  • Describe how the growth of bacteria is affected by temperature and how bacterial growth can be measured

• Limitation of Microbial Growth by Nutrient Supply

  • Nutrients are necessary for microbial growth and play a vital role in the proper cultivation of microorganisms in the laboratory and for proper growth in their natural environments.
  • The limiting factor or limiting nutrient effects and controls growth.
  • When all nutrients and parameters are ideal and constant during the growth phase, this is regarded as a steady state: all requirements are present and microorganisms thrive.
  • In industrial microbiology this concept is critical, as microbial growth and production is dictated by proper cellular growth and metabolism.
  • Describe the role of nutrients in microbial growth and their culture in the lab

• Intermediates Produced During the Calvin Cycle

  • In organisms that require carbon fixation, the Calvin cycle is a means to obtain energy and necessary components for growth.
  • The Calvin cycle can be divided into three major phases which include: Phase 1: carbon fixation; Phase 2: reduction; and Phase 3: regeneration of ribulose .
  • Once 3-PGA is formed, one of two molecules formed continues into the reduction phase (phase 2).
  • This energy is necessary for cellular growth and metabolic processes.
  • Outline the function of the intermediates produced in the major phases of the Calvin Cycle

• Units of Measurement for Microbes

  • Microbial growth is an important measure in understanding microbes.
  • Microbial growth is the division of one microbe into two daughter cells in a process called binary fission.
  • Since there are limits on space, food, and other factors, actual growth never matches actual measured growth.
  • This chart shows the logarithmic growth of bacteria.
  • The phases of growth are labelled on top.

• Measurements of Microbial Mass

  • Bacterial growth follows three phases: the lag phase, the log phase, and the stationary phase.
  • The measurement of an exponential bacterial growth curve in a batch culture was traditionally a part of the training of all microbiologists; the basic means requires bacterial enumeration (cell counting) by direct and individual (microscopic, flow cytometry), direct and bulk (biomass), indirect and individual (colony counting), or indirect and bulk (most probable number, turbidity , nutrient uptake) methods.
  • This has made spectrophotometry the methods of choice for quick measurements of bacterial growth and related applications.

• Primary and Secondary Metabolites

  • Bacterial metabolism can be classified into three major categories: the kind of energy used for growth, the carbon source, and the electron donors used for growth.
  • Primary metabolites are involved in growth, development, and reproduction of the organism.
  • Primary metabolites are typically formed during the growth phase as a result of energy metabolism, and are deemed essential for proper growth.
  • Secondary metabolites do not play a role in growth, development, and reproduction like primary metabolites do, and are typically formed during the end or near the stationary phase of growth.

• Regulation of Sigma Factor Translation

  • Sigma factors are groups of proteins that regulate transcription and therefore function in house-keeping, metabolic, and regulation of growth processes in bacteria.
  • In E. coli, the RpoS is the regulator of growth phase genes, specifically in the stationary phase.