Chapter 6: Bacterial Growth

Define bacterial growth?

- This is the increase in number of cells, not cell size.

- It is measured at the population level.

Define growth rate?

This is the measure of the number of cells in a population over time.

Define binary fission?

This is where one parent cell divides and forms two offspring cells.

Ture or False: Most bacteria reproduce by binary fission.

True

Define Generation time?

- This is the time required for a cell to divide.

- between 20 minutes to 24 hours in different species.

Define Bacterial Growth Curve?

- This is showing the change in growth rate over time.

- Phases:

1. Lag phase,

2.Log Phase,

3.Stationary Phase

4.Death Phase

- X axis: Time

- Y axis: Number of microbes (log scale)

Describe the Lag phase of the Bacterial Growth Curve?

Bacteria are preparing their cell machinery for growth.

Describe the Log phase of the Bacterial Growth Curve?

Growth approximates an exponential curve (straight line, on a logarithmic scale).

Describe the Stationary Phase of the Bacterial Growth Curve?

- # of division

=

# of death

- Cells stop growing and shut down their growth machinery while turning on stress responses to help retain viability

Describe the Death Phase of the Bacterial Growth Curve?

- # of deaths

>

# of divisions

- Cells begin to die at an exponential rate.

Define Batch Bacterial Culture?

This is a closed system where you start with a set amount of resources and let it run its course

Define Continuous Bacterial Culture?

This is designed to maintain a steady state of exponential growth by constantly adding and removing equal amounts of culture media.

- Ex: humans with digestion/waste

What are the chemical requirements for bacterial growth?

- essential elements

- trace elements

- organic growth factors

What are the essential elements used for bacterial growth?

Carbon, Nitrogen, Sulfur, and Phosphorus

Explain Carbon as an essential element?

It is a structural backbone of organic molecules

Explain Nitrogen as an essential element?

It is a component of proteins, DNA, and ATP

Explain Sulfur as an essential element?

It is used in amino acids, thiamine, and biotin

Explain Phosphorus as an essential element?

Used in DNA, RNA, and ATP

Explain Trace Elements?

- these are inorganic elements required in small amounts

- usually as enzyme cofactors

- includes iron, copper, molybdenum, and zinc

Explain Growth Factors as a chemical requirement for bacterial growth ?

- these are organic compounds obtained from the environment

- includes: vitamins, amino acids, purines, and pyrimidines

- bacteria CANNOT grow without them

What are the physical requirements for bacterial growth?

- temperature

- barometric pressure

- pH

- Osmotic pressure

- Oxygen

Describe Psychrophile?

- This microorganism can grow at temperatures minimum as 0° C (freezing) but their maximum growth temperature is around 20° C.

- Ex: in fridge and grows in less than 37 degrees Celsius.

Describe Mesophiles?

- This kind of microorganism live in moderate temperature conditions such as the human body around 37 degrees in centigrade.

- minimum: 13 degrees C

- maximum: 45 degrees C

Describe Thermophiles?

This microorganism like warm/hot environments.

- minimum: 40 degrees C

- Maximum: 70 degrees C

- Ex: deep sea hydrothermal vents, hot springs, compost piles

Describe Hyperthermophiles?

This kind of microorganism thrives in extremely hot environments.

- minimum: 63 degrees C

- Maximum: 110 degrees C

- Ex: deep sea hydrothermal vents, hot springs, volcanic areas

What does not kill bacteria but rather stops them from growing?

Cold temperatures

Describe Barophiles?

This microbe survives at very high barometric pressures.

- Ex: Mariana Trench, Average Depth of the ocean, average height of land, mount everest

What is Barometric pressure?

This is also known as atmospheric pressure

Describe Halophiles?

These microorganisms survive with 30% concentration of salt.

Define osmotic pressure?

This is the amount of force needed to prevent solvent flow across a semipermeable membrane

Hypertonic environments

( higher concentration of solutes than inside the cell) cause..... due to high osmotic pressure?

Plasmolysis

Define plasmolysis?

This process in which cells lose water when they are placed in a hypertonic solution

Define Extreme or obligate halophiles?

These microorganisms require high osmotic pressure (high salt)

Define Facultative halophiles?

These microorganisms tolerate high osmotic pressure such as our skins sweat.

Explain how pH and osmotic pressure affects microbial growth?

These things significantly impact microbial growth by influencing the cell's internal environment and its ability to function properly

Describe Acidophiles?

- these contain more H+ ions > OH- ions

- range on PH scale: 0-5

Describe Neutrophiles?

- usually in human pathogens/

microbes

- pH scale: 6-8

Describe Alkaliphiles?

- basic

- there are more OH- ions than H+ ions

- pH scale: 9-14

Describe how microbes are classified on the basis of oxygen requirements?

Classified into these categories:

- obligate aerobes

- obligate anaerobes

- facilitative anaerobes

- aerotolerant anaerobes

- microaerophiles

Describe Obligate aerobes?

- They DO use oxygen to generate ATP.

- They DO have enzymes that break ROS.

Describe Obligate anaerobes?

- They DONT use oxygen to generate ATP

- They DONT have enzymes that break ROS

Describe Facilitative anaerobes?

- They DO use oxygen to generate ATP, but can also be an aerobe.

- They DO have enzymes that break ROS

Describe Aerotolerant anaerobes?

- They DONT use oxygen to generate ATP.

- They DO have enzymes that break ROS

Describe Microaerophiles?

- They DO use oxygen to generate ATP

- They DO have enzymes that break ROS, but less of them.

Define Reactive Oxygen Species (ROS)?

This is a group of unstable molecules that contain oxygen and are highly reactive

True or False: To survive in the presence of oxygen organisms developed enzymes (peroxisomes) that neutralizes ROS.

True

What percent of earth's atmosphere is oxygen?

21%

Describe the process of biofilm formation?

1.) Cellular flagella attach to the monolayer

2.) Microcolonies form

3.) Cells produce

exopolysaccharides (EPSs)

4.) Biofilm matures

5.) The biofilm dissolves and cells disperse

Function of biofilms?

Is to shelter bacteria from harmful environmental factors.

Define Biofilm?

This is when bacteria grow in specialized, surface attached communities, and communicate cell-to-cell by quorum sensing

- Ex: in digestive system and clogged pipes

Function of endospores?

This is to ensure the survival of the bacteria during periods of environmental stress by allowing them to remain dormant and resistant to harsh conditions until favorable conditions return

Function of sporulation?

This is to ensure survival in harsh or unfavorable environmental conditions.

Function of germination?

formation of vegetative cell from endospore

Describe the process of sporulation?

production of endospores

What kills endospores?

Autoclaves