Chapter 9 Flashcards
What kind of reproduction occurs in prokaryotes?
Asexual
How does DNA replication occur before binary fission?
The cell grows and DNA replication starts at a location on the circular chromosome called the origin of replication. Replication continues in both directions until two chromosomes are established.
What is FtsZ?
A protein that directs the cytokinesis and cell division for binary fission.
What is a Z ring?
FtsZ assembles into a Z ring on the cytoplasmic membrane. The Z ring is anchored by FtsZ-binding proteins and defines the division plane between the two daughter cells.
What occurs after the Z ring has defined the division?
Additional proteins required for cell division are added to the Z ring to form the divisome. The divisome activates to produce a peptidoglycan cell wall and build a septum that divides the two daughter cells. The daughter cells are separated by the division septum, where all of the cells’ outer layers must be remodeled to complete division.
What is generation time (doubling time)?
The time it takes for the population to double through one round of binary fission.
What is cultural density?
The number of cells per unit volume.
What are the four phases of the growth curve?
-Lag phase
-Log phase
-Stationary phase
-Death or decline phase
What is the Lag phase?
No increase in number of bacterial cells.
What is the Log phase?
Exponential increase in number of living bacterial cells.
What is the stationary phase?
Plateau in number of living bacterial cells; rate of cell division and death are roughly equal.
What is the death or decline phase?
Exponential decrease in number of living bacterial cells.
What is the intrinsic growth rate?
The generation time under specific growth conditions is genetically determined.
How can cells be counted?
- Direct viable cell count (microscopic or plate)
- Serial dilutions
What are serial dilutions?
The pour plate and spread plate methods are used to plate into or onto, respectively, agar to allow counting of viable cells that give rise to colony-forming units (diluted each time placed on a plate).
What is the most probable number (MPN) method?
A statistical procedure for estimating the number of viable microorganisms in a sample.
What are the indirect methods of counting cells?
Measuring turbidity or measuring dry weight of a culture sample or measuring metabolic activity.
What does turbidity mean?
The cloudiness of a sample of bacteria in a liquid suspension.
What can be used to measure turbidity?
A spectrophotometer which measures how much light can pass through the solution.
What are the other methods of cell division that prokaryotes could use?
Asymmetrical division (budding) or production of spores in aerial filaments or fragmentation (a new cell splits from the parent filament and floats away).
What are biofilms?
Biofilms are complex and dynamic ecosystems that form on a variety of environmental surfaces. Ex. inside mouth
- highly structured communities that provide a selective advantage to their constituent microorganisms
How do environmental conditions influence the overall structure of biofilms?
The form structures to give them an advantage in their select environment.
How is the extracellular matrix related to the biofilm?
Consists of extracellular polymeric substances (EPS) secreted by the organisms in the biofilm which plays a key role in maintaining the integrity and function of the biofilm. The extracellular matrix represents a large fraction of the biofilm, accounting for 50%–90% of the total dry mass.
What is the EPS important for?
Channels in the EPS allow movement of nutrients, waste, and gases throughout the biofilm. This keeps the cells hydrated, preventing desiccation. EPS also shelters organisms in the biofilm from predation by other microbes or cells (e.g., protozoans, white blood cells in the human body).