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Flashcards in Chapter 5 Deck (83)

What is bacterial growth

Refers to the increase in the number of cells in a population. ex. growth of bacteria in something such as a food or tissue


What is binary fission

Cell division following enlargement of a bacterial cell to twice its starting size. It produces two identical daughter cells, each daughter cell receives a chromosome and sufficient copiues of all other cell constituents to exist as an independent cell


What is generation time

Time required for microbial cells to double in number


What is the septum

The point of division in an elongated cell to two daughter cells. There are changes in the cell wall


What re FTS (Filamentous temperature-sensitive) proteins

The name comes from genetic experiments and they are essential for cell division in prokaryotes. They interact with one another to form the divisome (cell division apparatus)


What are the FTS proteins and what do they do

FtsZ: forms ring around the center of cell, related to tubulin
ZipA: anchor that connects the FtsZ ring to cytoplasmic membrane
FtsA: helps connected FtsZ ring to membrane and also recruits other divisome proteins, related to actin


In bacterial cell division when does the DNA replicate

Before the FtsZ ring forms


What facilitates the location of the FtsZ ring

Min proteins find the middle of the cell


What is the FtsK protein

It mediates the separation of chromosomes to daughter cells, makes sure that each daughter cell gets a chromosome


What recruits the FtsZ ring to the middle of the cell

Min proteins?


What is MreB protein

Major shape determining protein in prokaryotes. FOrms cytoskeleton, spiral-shaped bands around the inside of cell, underneath the cytoplasmic membrane. Not found in coccus bactiera, and localized synthesis of new peptidoglcan to specific locations along the cylinder of a rod-shaped cell during growth


How do cell walls grow in cocci

Cell walls grow in opposite directions outward from the FtsZ ring


How do cell walls grow in rod-shaped cells

Growth occurs at several points along length of the cell


How is new petidoglycan synthesized

Preexisting peptidoglycan needs to be partially severed to allow new synthesis. Beginning at the FtsZ ring, smalle openings in the wall are created by autolysins (enzymes). New cell wall material is added across the opening.


What happens when there is too much autolysin

Too much autolysin activity causes cells to lyse


What are wall bands

The junction between new and old peptidolycan


What is bactoprenol

A carrier molecule that plays major role in export and insertion of peptidoglycan precursors


What is transglycosylase

Enzyme that interacts with bactoprenol and forms sugar backbone. Inserts cell wall precurors into growing points of cell wall and catalyzes a glycosidic bond formation


How does the peptidoglycan process work

First the autolysin activity makes a cleavage in the backbone. Enzyme in the cell will make the precursor MG with pentapeptide and bactoprenol helps flip it up into the cell. Transglycosylase activity stitches that flipped segment into the cell wall


What is transpeptidation

The final step in cell wall synthesis. Forms the peptide cross-links and can be inhibited by the antibiotic penicillin. Defects in cross-links causes growing cells to lyse


Why doesnt penicillin work on non-growing cells

Only growing cells will lyse because penicillin blocks this growth activity, if the cell isnt growing then the peptidoglycan does not become weaken


What does generation time depend on

It depends on growth medium and incubation conditions: temperature, pH, nutrients available. Good conditions allow faster growth


What is Exponential growth

Log phase growth, cell numbers double within a specific time interval over several generations. Increase in cell numbers is a geomtric progression of the number 2


What is the equation for exponential growth

N = final cell number
N0 = initial cell number
n = number of generations during the period of exponential growth


What is the equation for generation time

g = generation time
t = the duration of exponential growth
n = number of generations during the period of exponential growth


What is a batch culture

A closed-system microbial culture of fixed volume. Something in a tube, a closed system where you have a certain amount of nutrients to begin with and a certain number of bacteria in the beginning


What are the 4 phases of a typical growth curve for a closed system

1. Lag Phase
2. Exponential Phase
3. Stationary Phase
4. Death Phase


Describe the lag phase

Interval between when a culture is inoculated and when growth begins. Cells are making enzymes and adjusting to the growth medium and conditions such as temperature


Describe the exponential/log phase

Rapid growth, healthiest state


Describe the stationary phase

The net growth rate of population is zero. Either an essential nutrient is being used up or waste products are accumulating and inhibiting growth, or both


Describe the death phase

The lack of nutrients and build up of waste products leads to net death of cells. Cells begin to die.


What is a continuous culture

An open-system microbial culture of fixed volume. New nutrients are entering and waste products are being removed


What is a chemostat

Most common type of continuous culture. Growth rate and population density of culture can be controlled. Constnatly supplies fresh nutrients nad washes away waste products


What is the dilution rate

Rate at which fresh medium is pumped in and spent medium leaves, determines growth rate. Concentration of a limiting nutrient determines cell density. Rich medium = high cell density. Poor medium = low cell density


What leaves the chemostat

Cells can leave the system, ones that they want to collect and obtain something from them that they are making


What are some limitations of microscopic cell counts

Can't distinguish between live and dead cells without special stains, phase-contrast microscope is required if stain is not used, staining takes time, motile cells need to be immobilized, debris in sample can be mistaken for cells


What is a Petroff-Hausser counting chamber

Allows cells to be counted in squares to determine an average number of cells


What is a flow cytometer

It uses laser beams, fluorescent dyes, and electronics, allows large number of cells to be counted quickly but the machines are relatively expensive.


What are viable cell counts

Measurement of living, reproducing population. After incubation for 1 day, colonies of cells are counted because it is assumed that each colony came form one cell


What are the two main ways to perform plate counts

Spread-plate method and Pour-plate method


To obtain accurate colony numbers samples much be diluted between what two values

Between 30 and 300 colonies per plate


Describe the spread=plate method

Sample is pipptted oto the surface of plate. Sample is spread evenly over surface and incubated. Cells are counted afterwards


Describe the pour-plate method

Sample is pipetted into sterile plate. Sterile medium is then added and mixed well with inoculum. It is allowed to solidify then incubated. Cells are counter afterwards (surface and subsurface colonies)


In what units are viable cell counts reported in

colony forming units CFU


What is the Great Plate Anomaly

Direct microscopic counts of natural samples reveal far more organisms are present than those recoverable on plates


Why does the Great Plate Anomlay exist

Microscopic methods count dead cells whereas viable counts do not. Different organisms may have vastly different requires for growth so a particular medium and incubation conditions are only good for some organisms. And we don't know how to grow all the different kinds of bacteria in the lab


What is the turbidity measurements for microbial growht

Turbidity measurements are an indirect, rapid, and useful method for measuring microbial growth. A spectrophometer is used to measure optical density


What is optical density

Measuring the amount of light that fails to pass through the solution (hits a cell). NOT the light absorbed


What results in higher OD values

More cells due to more light scattering


What is an abiotic factor in the environment

A factor that is not living: temperature, pH, media


What are cardinal temperatures

The minimum, optimum, and maximum teamperatures at which an organism grows


What is the minimum growth temperature

The minimum temperature is the temperature that is so cold the enzyme don't work so growth is unable to take place


What is the optimum growth temperature

The optimum temperature is the temperature at which enzymatic reactions are occurring at the maximal possible rate


What is the maximum growth temperature

The maximum growth temperature si the temperature at which the proteins denature and the enzymes won't work any more


What is a psychrophile

Grows best at cold temperatures (4C)


What is a mesophile

Grows best at normal/room temperature(20C-40C)


What is a thermophile

Grows best at hot temperatures (45C=80C)


What is a hyperthermophile

Grows best at temperatures hotter than that of thermophiles (Above 80C) Inhabit boiling hot springs and seafloor hydrothermal vents that can be in excess of 100C


What are extremophiles

Organisms that have evolved to grow under very hot or very cold conditions


What are psychrotolerants

Organisms that can grow at 0C but have an optimum growth temperature of 20C to 40C


What are the molecular adaptations of psychrophily

Evolution of enzymes and transport proteins taht function optimally in the cold. Cytoplasmic membranes have high UNSATURATED fatty acid contect


Describe membranes with high unsaturated fatty acid content

Unsaturated fatty acids have multiple double bonds, which causes kinks, and results in less-stable hydrophobic interactions and a more fluid membrane


How does microbial life compare growing at different temperatures

Prokaryotes grow at higher temperatures than eukaryotes, organisms with the highest temperature optima are Archaea, and nonphototropic organisms can grow at higher temperatures than phototrophic organisms


Why do nonphototropic organisms grow at higher temperatures than phototrophic organisms

There is much more membrane involved in photosynthesis due to generating the hydrogen charge across the memrbane and generating this charge could be problematic at higher temperatures


What are the molecular adaptations to thermophily

Enzymes and proteins evolved to function optimally at high temperatures. Bacteria have lipids rich in saturated fatty acids and Archaea have lipid monolayer rather than bilyar (more stable and less fluid)


Describe membranes with high saturated fatty acid content

Saturated fatty acids have only single bonds, no kinks, and causes the membrane to be less fluid and more stable


What is an example of a hyperthermophile enzyme used in industry

Taq DNA polymerase is used to automate the repetitive steps in PCR because the enzyme is stable at the near-boiling temperatures required to melt DNA strains (75 C to 80C)


What are neutrophiles

Organisms that grow best between ph 6 and pH 8


What are acidophiles

Organisms that grow best at low pH, acidic environments


What are alkaliphiles

Organisms that grow best at high pH, alkaline environments


What are the osmotic effects of an organism growing in fresh water

In fresh water, the cytoplasm has a higher solute concentration than the surrounding environment, thus water moves into the cell (positive water balance)


What are the osmotic effects of an organism growing in salt water

In salt water, the external solute concentration is higher, then water will flow out of the cell. Can be prevented by the accumulation of high concentration of small molecules (osmolytes) in the cell


What are halotolerants

Organisms that can survive under salty conditions


What are halophiles

Organisms that can't grow in freshwater, require a salty environment to thrive (3% NaCl)


What are extreme halophiles

Organisms that can grow in saturated salty environments


What are osmophiles

Organisms that live in environments high in sugar as the solute (as opposed to salt), can take advantage of the nutrients available


What are xerophiles

Organisms that are able to grow in very dry environments, they put down a thick capsule or slime layer around the cell to keep themselves from drying out between periods of rain


What are aerobes

Organisms that require oxygen to live


What are anaerobes

Organisms that do not require oxygen to live and may be killed by exposure to oxygen


What are faculative organisms

Organisms that can live with or without oxygen


What are aerotolerant anaerobes

Organisms that can tolerate oxygen and grow in its presence even though they cannot use it


What are microaerophiles

Organisms that can use oxygen only when it is present at low levels


When growing anaerobic microorganisms what are reducing agents

Chemicals added to culture media to reduce oxygen