Microbiology Chapter 9: Microbe Growth

Binary Fission

• How bacteria cells turn into more bacterial cells

• Not perfectly split division on matter between cells

• Multistep process

- DNA replication

- Formation of division septum

- Cells separate

DNA replication

• First step of the binary fission

• DNA is copied through circular replication

Division septum

• Necessary for the second binary fission

• A membrane wall that divides the cell in half

• Acts as the point of separation

Germination Time

• How long it takes one bacterial cell to become 2

• About 16 minutes to 2 weeks

- Most about 60 minutes

- Escherichia coli is 20 minutes

- Mycobacterium tuberculosis is 15-20 hours

Bacterial Growth Curve

• Measures the growth of bacteria

• Multi-phase process

- Lag phase

- Log phase

- Stationary phase

- Death or decline phase

Lag phase

• First phase of the bacterial growth curve

• The bacteria is new to the environment and isn't increasing or declining in number

• Uses this time to determine necessary enzymes for survival and replication

- Makes them

Log phase

• Second phase of the bacterial growth curve

• Large increase in number of living bacterial cells

- Causes by presence of necessary enzymes

• Cells are most vulnerable to manipulation at this point

Stationary phase

• Third phase of the bacterial growth curve

• Plateau in the number of living and nonliving cells

- Death and replication rate are roughly the same

• Nutrients become scarce and waste builds up

- Sometimes secondary metabolites are made to survive

Death or decline phase

• Fourth phase of the bacterial growth curve

• Exponential decrease in number of living bacterial cells

- Caused by lack of nutrients and buildup of waste

Secondary Metabolites

• Organic compounds produced by bacteria

• Not eventual for growth or reproduction but mediate ecological interactions

• Most needed in stationary phase of bacterial curve

Hemocytometer or Petroff-Hauser Chamber

• Type of direct growth measurement of bacteria cells

Fluorescent staining

• Type of direct growth measurement of bacteria cells

Coulter counter

• Type of direct growth measurement of bacteria cell

Plate counting

• Type of direct growth measurement of bacteria cells

• Done by counting the number of bacterial colonies on an agar plate

- Uses naked eye

Spectrophotometer

• Type of indirect growth measurement of bacteria cells

• Done by shooting light through a sample of bacteria invested liquid medium

- Measures amount of colonies based on light refraction

• Liquid medium is diluted in many steps before being put into the machine

Dry weight

• Type of indirect growth measurement of bacteria cells

Direct Counting

• Method of determining number of colonies in a sample

• Counts the amount of colonies

Direct Counting

• Method of determining number of colonies in a sample

• Counts the amount of byproduct made by colonies and estimates how many are there

Fragmenting

• Alternative form of bacteria growth

• Cells break away

• Used in Actinomyces

Budding

• Alternative form of bacteria growth

• Non-equal cellular material splits off

Biofilms

• Created by large communities of organisms growing together

• Made of extracellular polymeric substance

• Very common

• Very hardy

• Located on airways tissue and teeth enamel

Extracellular Polymeric Substance (EPS)

• A mixture of proteins and polysaccharides that make a gel like substance

Obligate aerobe

• Bacteria classification based on oxygen needs

• Needs oxygen to survive

Obligate anaerobe

• Bacteria classification based on oxygen needs

• Oxygen is toxic to it

Facultative anaerobe

• Bacteria classification based on oxygen needs

• Uses oxygen when available but can survive without it

• Grows better with O2

Aerotolerant

• Bacteria classification based on oxygen needs

• Doesn’t require oxygen but can survive in it’s presence

Microaerophile

• Bacteria classification based on oxygen needs

• Needs oxygen to survive but prefers it under atmospheric levels

Capnophile

• Bacteria classification based on oxygen needs

• Prefers high level of carbon dioxide

Optimum temperature

• The temperature where the bacteria grows the best

Minimum temperature

• The lowest possible temperature that bacteria can grow at

• Doesn’t mean death for all bacteria

Maximum temperature

• The highest possible temperature that bacteria can grow at

• Bacteria dies because proteins denature

Psychrophiles

• Classification of bacteria based off temperature growth ability

• Grows best at cold temperature, 8 - 12 celsius

Mesophiles

• Classification of bacteria based off temperature growth ability

• Grows best at moderate temperature, 31 - 41 celsius

Thermophiles

• Classification of bacteria based off temperature growth ability

• Grows best at hot temperature, 62 - 72 celsius

Hyperthermophiles

• Classification of bacteria based off temperature growth ability

• Grows best at very hot temperature, 90 - 100 celsius

Halophiles

• Bacteria the liked high salt content

Photosynthetic

• An organism that requires light

Nutrient agar (NA)

• Type of basic nutrient agar

Tryptic soy agar (TSA)

• Type of basic nutrient agar

Complex media

• Media that contains more material than just a basic nutrient agar

Selective media

• A bacteria medium

• Some bacteria are inhibited by properties

Differential media

• A bacteria medium

• Designed to distinguish between two organisms based off affinity for properties of the media

Anaerobic jar

• Creates an environment with no O2 in it

Candle Jar

• Creates environment with little O2 and a lot of CO2

Chemostat

• A machine that keeps bacteria in a nutrient rich and limited waist environment

• Measures amounts of waist and nutrients

• Pulls excess waist from environment and adds necessary nutrients

Quorum Sensing

• Communication method bacterial cells use to communicate with each other

• Regulates growth rate and biofilm