Chapter 9 - Microbial Growth Flashcards
Binary Fission
Bacteria and archaea most commonly engage in a process known as binary fission, where a single cell splits into two equally sized cells
Other Less Common forms of Reproduction
Multiple Fission, Budding and production of Spores
Binary Fission Step 1:
Elongation
Elongation
Careful enlargement of the cell membrane and the cell wall, in addition to an increase in cell volume.
Binary Fission Step 2:
DNA Replication
What happens during DNA replication?
Prepares to have two copies of each chromosome, one for each cell
Binary Fission Step 3:
Protein FtsZ initially manifests as a ring in the middle of the elongated cell. Important for the septum to form.
Binary Fission Step 4:
After the nucleoids are segregated to each end of the elongated cell, septum formation is completed, dividing the elongated cell into two equally sized daughter cells.
Closed System/Batch Culture
no food added, no wastes removed
What are the parts of a growth curve for bacteria in a closed system
- the lag phase 2.The exponential or log phase 3. The stationary phase, 4. The death or decline phase.
Generation Time
The amount of time it takes for a population to double
lag phase
Adaption period and adjusting. Length can vary greatly. They synthesize RNA, enzymes, and essential metabolites that might be missing from their new environment. Also adjustment to environment pH, temp and O2
Shortest Lag Period?
Actively growing cells transferred from one type of media into the same type of media, with the same environmental conditions
Longest Lag Period?
Damaged Cells
Exponential/Log Phase
Marked by predictable doublings of the population, where 1 cell become 2 cells, becomes 4, becomes 8 etc. Cells are healthiest during this period.
What is needed for Rapid Growth? What results in slower growth?
Rapid - optimal conditions. (Steeper Curve) Slow - Less than idea conditions.
Log Phase equation?
N=N02^n
N
Final Cell Concentration
N0
Initial Cell Concentration
n
Number of Generations that occurred between the specified period of time
How can we represent generation time
g = t/n, where t is a period of time
Stationary Phase
Population runs out a nutrients, or growth hindered by waste products, or physical space. At this point the number of new cells being produced is equal to the number of cells dying off or growth has entirely ceased, resulting in a flattening out of growth on the growth curve.
What happens to cells during stationary phase?
The new cells that are created are smaller in size. Bacilli can become near spherical in shape. Membrane becomes less fluid. More hydrophobic on outside. Nucleoid condenses and DNA binds with DNA-binding proteins from starved cells (DPS).
oligotrophic
Low Nutrient Environment
secondary metabolites
metabolites produced after active growth, such as antibiotics
Death Phase/Decline Phase
Last phase. Number of cells decreases predictably. Steepness depends on how fast cells lose viability
viable but nonculturable (VBNC)
cells thought to be dead might be revived under specific conditions - important for pathogens
Is 100% cell death likely?
No, as the cells mutate to adapt to their environmental conditions, however harsh.
