Ch 5 Flashcards
Peptidoglycan
Sting mesh like material found only in bacteria interconnected glycan chains form a large sheet
Alternating series of subunits form glycan chains
N acetylmuramic acid NAM
N acetylglucusamine NAG
Tetrapeptide chain string of four amino acids links glycan chains
Gram positive cells have peptide Interbridge between tetra peptide chains
Bacteria growth
Increases in number not in cells size
Bacteria grow by dividing via binary fission
Exponential growth
Generation time
Time required for a cell to divide/double
Can be thought of as how long it takes to double
Varies for each microorganism
Principles of bacteria
Binary fission leads to exponential growth
2^n
Bacteria growth in nature
Planktonic: single cells
Biofilms: bacterial communities
Polysaccharide encased communities
Form slime
Adhere to surface
Benefits of biofilms bacteria
Share nutrients
Shelter bacteria from harmful factors like our immune system and medications
Cells sense changes each other adjust to surroundings
Synthesize compounds useful for growth
To humans, it can beneficial to us through bioremediation
Bacteria grows as biofilms
Is polysaccharide encased communities
Can act as a shelter cells are more protected
Bacteria growth in nature
Prokaryotes regularly grow in close association
Many different species
Interactions can be cooperative: can fostered growth of species otherwise unable to survive
Interactions can be competitive:some synthesize toxic compounds to inhibit competitors
Biofilms have important implications
70% of human infections are caused by biofilms. Industrial concerns:accumulations in pipes/drains
Biofilms benefits to bacteria
Share nutrients via channels
Shelter bacteria from harm (immune systems, antibiotics)
Inoculate
Introduce microbes into a medium
Culture
Microbes growing in or on medium
Pure culture
Microbes from one species/strain
Culture medium
Nutrients for microbial growth
Agar
Solid form of media
Look for isolated colonies
Broth
Liquid form of media
Look for tubidity= cloudiness of the culture
The growth curve
Bacteria are inoculated into a medium in lab. You see a bacterial growth curve.
Growth curves can show the growth of bacteria overtime
Growth curve are represented logarithmically
Four main phases of the growth curve
Lagged face, log face, stationary face, death face
Lag face
Little bacteria, division, as bacteria, adjust to new, medium, high metabolism, or metabolically active cells
Log phase
Exponential growth increase in bacteria population high cell division
Stationary phase
Rate of bacteria, growth/division equals rate of bacterial death
Death phase
High death of bacteria, due to lack of nutrients and toxic by products
Requirements for a microbial growth
Prokaryotes inhibit nearly all environment
Some live comfortable in habitats favored by humans
Extremophiles
Harsh environment prokaryotes:most are archaea
Environmental requirements for microbial growth
Temperature PH osmotic, pressure and oxygen
Nutritional requirements for microbial growth
Carbon, nitrogen, sulfur, and phosphorus, and trace elements
Psychrotrophs/pyschrophiles
Cold, loving loving optimal temperature equals 10 c
Cause food spoilage in the refrigerator
Mesophiles
Moderate temperature loving optimal temperature equals 37C
Thermophiles
Heat loving optimal temperature equals 60 c
Hyperthermophiles
Superheat, loving optimal, temperature 95C
PH
Most bacteria grow within a pH of 6.5 and 7.5.
Neutrophils ph 6-8
Acidophilus ph<5.5
Alkaliphiles ph>8.5
Osmotic pressure water availability
Isotonic solution equals no net movement of water particles. The cell membrane is attached to cell wall.
Hypertonic solution equals water particles move out of the cell, the cell membrane, it shrinks and detaches from cell wall
Hypotonic solution water particles move into the cell cell wall, counteracts osmotic pressure to prevent swelling and lysis
Hypertonic environment
The cell wall of the bacteria usually protects itself to keep it from bursting
High salt environments
Plasmolysis
Cell lose water take and shrink up and die the fluid moves out of the cell
Facultative halophiles
Tolerate high osmotic pressure so they are not killed by salt
Obligate aerobes
Require oxygen for respiration and have enzymes to help with oxygen toxic by products, such as catalase and super oxide dismutase
Obligate anaerobes
Killed by oxygen, only girl with no oxygen
Facultative anaerobes
Grow by anaerobic respiration, when oxygen is present but grow via fermentation or anaerobic respiration when oxygen is not available
Aerotolerant anaerobes
Tolerate oxygen, but cannot use oxygen
Microaerophilles
Require low, oxygen concentration
Bacteria require major elements, and trace elements needed for growth
Carbon, part of all macromolecules of cells is a major energy source
Heterotrophs
organic carbon sources most microbes need food
Autotrophs
Use of CO2 and inorganic carbon source
Photo synthetic microbes
Nitrogen
Component of proteins
Component of DNA,RNA and ATP
Phosphorus
Component of DNA,RNA and ATP
Found a phospholipid cell membranes
Sulfur
Found in amino acids, thiamine, and biotin
Most bacteria, decompose proteins for the sulfur source
Trace elements
Inorganic elements required and very small amounts, such as iron, zinc, copper, potassium, magnesium calcium cobalt manganese these are usually enzyme cofactors
Hundreds of types of my growth media available
Some medically, important microbes, and most environmental ones have not been grown in lab
MacConkey agar media
A type of selective and differential media
MacConkey agar is a selective media used to isolate Graham negative bacteria from a culture contains a die and bile salts that inhibit the growth of gram-positive bacteria
It is also a differential media because it contains lactose in a pH indicator
Selective media
Contains ingredient, that inhibit the growth of certain species while allowing the growth of other species
Differential media
Contain a substance that specific microbes change in a recognizable way
MacConkey agar. Is a differential media because it contains lactose.
Material that ferment lactose produce lactic acid
The acid turn the pH indicator, pink red
colonies that ferment lactose and pure pink red
Colonies, that don’t ferment lactose a colorless
LB agar plate
Nonselective culture media
Use for bacterial cultures
Nutrient, rich Knigge used to grow enteric, intestinal species of bacteria
Will gro, a lot of different species of a
Commonly used for E. coli
Contains proteins, used salt and agar
Direct cell counts
Total numbers living plus dead
Message to detect and measure microbial growth, : viable plate count
Count the number of cells capable of multiplying
Colony equals colony forming units CSU
Take 1 mL of your samples
Dilute the sample through a series of dilutions called serial dilution
As you dilute, the number of bacteria progressively decreases
Play some sample for me to solution into an agar plate to grow
Incubate the plates
Count the bacterial colonies in each plate in the various solutions to determine the number of valuable bacteria in the original 1 mL sample 
Play Tacones
Single soul gives rise to one colony 30-300 as ideal 
Membrane filtration
Concentrates microbes by filtration
Filter is incubated, on appropriate, agar, medium
Measuring biomass
Optical density turbidity is proportional to concentration of cells 1OD=5x10^8 cells/ml measure with spectrophotometer absorbents at 600 nm 
