Cell division that produces new (daughter) cells and increase the total cell population
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What percentage of bacteria species can be cultured in the laboratory?
1%
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What happens when nutritional requirements are met?
A microbe will enlarge in size and eventually divide
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Bacterial growth
Increase in number of cells
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How is bacteria grown in the laboratory?
Usually grown as pure, single-species cultures
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How do bacteria live in nature?
Intermingle and lives side by side with arches and eukaryotes
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escherichia coli
a species of bacterium normally present in intestinal tract of humans and other animals; sometimes pathogenic- converts from a motile bacillus shape to a filaments non-motile form during urinary tract infections
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Biofilm formation
Occurs when free-floating (planktonic) bacteria adhere to a surface
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Places for biofilm
Indwelling devices (catheters, heart valves)
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Binary Fission
Occurs in most prokaryotes; involves dividing a single cell into two cells; asexual process
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Process of binary fission
1. Before dividing, cell elongates and the chromosome is replicated 2. Parent cell begins to pinch off at the middle 3. Partition (septum) in the center becomes complete 4. Creates 2 genetically identical daughter cells
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Generation Time
Time required for a cell to divides (20 minutes to 24 hours)- time diverse. Depends on the species and conditions
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Doubles the number of cells each generation
Binary fission
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What impacts how fast a microbial population increases?
The nutrient available
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Generation time for E.coli
20 minutes
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Generation time for Mycobacterium Tuberculosis
15-20 hours
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Calculation for generation time
Generation times (in minutes)= Growth time (in minutes)/number of generations
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As bacteria divide by binary fission what do they exhibit?
Exponential growth
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Number of growth phases for bacteria
4 growth phases when cultured using a closed pure batch system
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Bacteria growth phases detected
By counting the number of viable cells
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Phase one: lag phase
Delay that occurs while cells adjust to their new environment
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Endospores occur
Bacteria in a starving environment get endospores
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Phase two: Log phase (endospores)
Period of rapid exponential growth
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Phase three: Stationary phase
Nutrients are depleted, waste accumulates- population growth rate levels off
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Phase Four: Death phase
Critical point of waste buildup and decrease nutrients, the cells begin to die; rate of cell death is exponential; small number of the cells survive by adapting to the waste and by feeding off dead cells
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Low temperature
Decrease enzymatic reactions
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Increased temperature
Speeds up enzymatic reactions; can increase growth rate
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High temperatures
Denature cell proteins (kills cell)
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Thermophile
Grow around 40C-75C; associated with compost piles and hot springs
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Psychrophile
Cold- thrive between- 20C and 10C
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Mesophile
Grow best around 10C-50C; associated with most pathogens
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Maximum temperature
Highest temperature supports growth
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Minimum temperature
Lowest temperature that supports growth
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Optimal temperature
Temperature where cellular growth is highest
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Human pathogen
Would be a mesophile
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Psychrotrophs
Grow at about 0-30C; associated with food borne illness
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Extreme thermophiles
Arches- grow around 65C-120C
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Extremes in pressure
High temperature environments
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Barophiles
Can withstand the high-pressure environment of the deep sea
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Acidophilus (acidic environment)
Grow at pH 1 or less to pH 5 Live in areas such as sulfur hot springs and volcanic vents Often maintain a fairly neutral cytoplasmic pH Proton pumps export excess protons from the cytoplasm to raise pH
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Neutralophiles
Grow best in a pH range of 5-8 Make up the majority of microorganisms
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Alkaliphiles
Grown in the basic pH range of 9-11 Associated with side lakes
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Halophiles
Thrives in high-salt environments Tolerate up to 35% Associated with the Dead Sea and the Great Salt Lake of Utah
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Facultative halophiles
Tolerate higher salt but may not grow well Example: staphylococcus aureus
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Bacterial cytoplasm
80% water
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Normal cells
Undergo plasmolysis
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Must overcome the osmotic stress of a higher-salt environment- keep high concentrations of organic materials and ions in their cytoplasm
Halophiles
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Low oxygen levels
Beneath the soil or within silt deposits in lakes and oceans- most pathogens thrive in low-oxygen environments within the host
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Inside the cell, some of the oxygen is converted
Reactive oxygen species (ROS)
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Reactive oxygen species (ROS)
Superoxide ions (o2-) Hydrogen peroxide (H2O2)- Can rapidly damage proteins and DNA
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superoxide dismutase
Converts reactive superoxide ions to hydrogen peroxide
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Catalase
Converts the hydrogen peroxide to water and oxygen
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Obligate aerobes
Absolute dependence on 02 fro cellular processes
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Microaerophiles
Use only small amounts of o2 Live in low 02 settings
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Facultative anaerobes
Grow with and without 02 Switch between using 02 and fermentation
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Anaerobes
Do not use o2 in their metabolic processes
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Aerotolerant anaerobes
Tolerate o2 but don’t use it Have way to deactivate ROS Detoxify the reactive oxygen species won’t use the oxygen
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Obligate anaerobes
Do not use 02 in their metabolism Can’t eliminate ROS Tend to die in aerobic environments
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Bordetella pertusis (whooping cough)
Obligate aerobe
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Mycobacterium tuberculosis
Facultative anaerobe
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Mycoplasma pneumoniae
Obligate aerobe
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Staphylococcus aureus (Staph infection)
Facultative anaerobe
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Propionibacterium acnes
Aerotolerant anearobe
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Helicobacter pylori (ulcers)
Microaerophile
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Borrelia burgdorferi (Lyme disease)
Microaerophile
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Treponema pallidum (syphillis)
Microaerophile
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yersinia pestis (plague)
Facultative anaerobe
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Clostridium difficile
Obligate anaerobe
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Salmonella species
Facultative anaerobe
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90% of cell dry weight
Carbon, hydrogen, nongaseous oxygen and nitrogen
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Other elements of essential nutrients
Sulfur, phosphorus, potassium, sodium, calcium, magnesium, chlorine; various metal ions (copper, zinc, iron)
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Essential nutrients
Required to build new cells Found in the organic and inorganic compounds of a microbe’s environment
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Macronutrients
Needed in large amounts (carbon)
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Micronutrients
Needed in very small amounts (iron)
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Heterotrophs
Require an external source of organic carbon ( sugar lipids, proteins)
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Autotrophs
Do not require an external source of organic carbon- used carbon fixation to convert inorganic carbon into organic carbon
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Growth factors
The necessary substances that a cell can’t make on it’s own
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fastidious
having complicated nutritional requirements; especially growing only in special artificial cultures- need multiple growth factors
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Growing fastidious microbes in labs
Amino acids, vitamins, and/or nitrogenous bases must be supplied in the growth medium
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Phototrophs
Organisms that use light energy
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Chemotrophs
Organisms that break down chemical compounds for energy
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Photoautotrophs
Inorganic (usually CO2), Cyanobacteria found in freshwater environments
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Photoheterotroph
Organic; heliobacillus mobilis found in rice paddy fields
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Chemoautotroph
Inorganic (usually CO2); Thiobacillus denitrificans found in soil, mud, and freshwater and marine sediments
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Chemoheterotroph
Organic; escherichia coli a common inhabitant of mammalian intestines
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Decontamination
Removes or reduces microbial populations to render an object safe for handling
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Sterilization
Eliminates all bacteria, viruses, and endospores (required for drugs, objects used for medical procedures and for lab medial and glassware)
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Disinfection
Reduces microbial numbers (use for cosmetics, foods, surfaces, and external medical equipment
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Physical methods to control microbial growth
Temperature changes (heat/cold) Radiation Filtration
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Refrigeration and freezing
(4c and 0c) Slows food spoilage In the lab, used to preserve specimen isolates and increase the shelf life of media Refrigeration preserves clinical samples
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Heat
Used to achieve either sterilization or decontamination
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Decimal reduction time (DRT or D value)
Times in minutes it takes to kill 90% of a given microbial population at a set temperature Associated with disinfection
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Thermal death time
Shortest period of time at a certain temperature needed to kill all microbes in a sample
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Thermal death point
Minimum temperature needed to kill all microbes in a sample within 10 minutes
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Autoclave
A machine that applies steam heat along with pressure to sterilize- used for microbiological media and assorted medical or lab equipment
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Autoclave settings
Most substance are steel within 20 minutes using standard autoclave settings -pressure of 15 pounds per square inch -steam heat at 121C (294F)
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Boiling
-Way to reduce microbial numbers -Municipalities often issues a “boil water advisory” when drinking water is contaminated -boiling water for 5 minutes eliminates most pathogenic bacteria, protozoans, and viruses -endospores can withstand hours of boiling therefore it is not an efficient sterilization method
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Pasteurization
Used to eliminate pathogens -application of moderate heat (below the liquids boiling point) -eliminates pathogens and reduces harmless microbes that cause milk spoilage
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Dry heat
Incineration or hot-air ovens can also be for sterilization or disinfection Examples of dry heat sterilization -heating an inoculation loop to red hot in a Bunsen burner flame -incinerating waste -placing an object at 170c (338F) for 2 hours in a dry heat oven achieves sterilization
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Radiation
-High-energy waves -Radiation can serve as a disinfection or sterilization tool depending on the protocol -Radiation is either ionizing or non-ionizing