Microbial growth
Cell division that produces new (daughter) cells and increase the total cell population
What percentage of bacteria species can be cultured in the laboratory?
1%
What happens when nutritional requirements are met?
A microbe will enlarge in size and eventually divide
Bacterial growth
Increase in number of cells
How is bacteria grown in the laboratory?
Usually grown as pure, single-species cultures
How do bacteria live in nature?
Intermingle and lives side by side with arches and eukaryotes
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
Biofilm formation
Occurs when free-floating (planktonic) bacteria adhere to a surface
Places for biofilm
Indwelling devices (catheters, heart valves)
Binary Fission
Occurs in most prokaryotes; involves dividing a single cell into two cells; asexual process
Process of binary fission
Before dividing, cell elongates and the chromosome is replicated
Parent cell begins to pinch off at the middle
Partition (septum) in the center becomes complete
Creates 2 genetically identical daughter cells
Generation Time
Time required for a cell to divides (20 minutes to 24 hours)- time diverse. Depends on the species and conditions
Doubles the number of cells each generation
Binary fission
What impacts how fast a microbial population increases?
The nutrient available
Generation time for E.coli
20 minutes
Generation time for Mycobacterium Tuberculosis
15-20 hours
Calculation for generation time
Generation times (in minutes)= Growth time (in minutes)/number of generations
As bacteria divide by binary fission what do they exhibit?
Exponential growth
Number of growth phases for bacteria
4 growth phases when cultured using a closed pure batch system
Bacteria growth phases detected
By counting the number of viable cells
Phase one: lag phase
Delay that occurs while cells adjust to their new environment
Endospores occur
Bacteria in a starving environment get endospores
Phase two: Log phase (endospores)
Period of rapid exponential growth
Phase three: Stationary phase
Nutrients are depleted, waste accumulates- population growth rate levels off
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
Low temperature
Decrease enzymatic reactions
Increased temperature
Speeds up enzymatic reactions; can increase growth rate
High temperatures
Denature cell proteins (kills cell)
Thermophile
Grow around 40C-75C; associated with compost piles and hot springs
Psychrophile
Cold- thrive between- 20C and 10C
Mesophile
Grow best around 10C-50C; associated with most pathogens
Maximum temperature
Highest temperature supports growth
Minimum temperature
Lowest temperature that supports growth
Optimal temperature
Temperature where cellular growth is highest
Human pathogen
Would be a mesophile
Psychrotrophs
Grow at about 0-30C; associated with food borne illness
Extreme thermophiles
Arches- grow around 65C-120C
Extremes in pressure
High temperature environments
Barophiles
Can withstand the high-pressure environment of the deep sea
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
Neutralophiles
Grow best in a pH range of 5-8 Make up the majority of microorganisms
Alkaliphiles
Grown in the basic pH range of 9-11 Associated with side lakes
Halophiles
Thrives in high-salt environments Tolerate up to 35% Associated with the Dead Sea and the Great Salt Lake of Utah
Facultative halophiles
Tolerate higher salt but may not grow well Example: staphylococcus aureus
Bacterial cytoplasm
80% water
Normal cells
Undergo plasmolysis
Must overcome the osmotic stress of a higher-salt environment- keep high concentrations of organic materials and ions in their cytoplasm
Halophiles
Low oxygen levels
Beneath the soil or within silt deposits in lakes and oceans- most pathogens thrive in low-oxygen environments within the host
Inside the cell, some of the oxygen is converted
Reactive oxygen species (ROS)
Reactive oxygen species (ROS)
Superoxide ions (o2-) Hydrogen peroxide (H2O2)- Can rapidly damage proteins and DNA
superoxide dismutase
Converts reactive superoxide ions to hydrogen peroxide
Catalase
Converts the hydrogen peroxide to water and oxygen
Obligate aerobes
Absolute dependence on 02 fro cellular processes
Microaerophiles
Use only small amounts of o2 Live in low 02 settings
Facultative anaerobes
Grow with and without 02 Switch between using 02 and fermentation
Anaerobes
Do not use o2 in their metabolic processes
Aerotolerant anaerobes
Tolerate o2 but don’t use it Have way to deactivate ROS Detoxify the reactive oxygen species won’t use the oxygen
Obligate anaerobes
Do not use 02 in their metabolism Can’t eliminate ROS Tend to die in aerobic environments
Bordetella pertusis (whooping cough)
Obligate aerobe
Mycobacterium tuberculosis
Facultative anaerobe
Mycoplasma pneumoniae
Obligate aerobe
Staphylococcus aureus (Staph infection)
Facultative anaerobe
Propionibacterium acnes
Aerotolerant anearobe
Helicobacter pylori (ulcers)
Microaerophile
Borrelia burgdorferi (Lyme disease)
Microaerophile
Treponema pallidum (syphillis)
Microaerophile
yersinia pestis (plague)
Facultative anaerobe
Clostridium difficile
Obligate anaerobe
Salmonella species
Facultative anaerobe
90% of cell dry weight
Carbon, hydrogen, nongaseous oxygen and nitrogen
Other elements of essential nutrients
Sulfur, phosphorus, potassium, sodium, calcium, magnesium, chlorine; various metal ions (copper, zinc, iron)
Essential nutrients
Required to build new cells Found in the organic and inorganic compounds of a microbe’s environment
Macronutrients
Needed in large amounts (carbon)
Micronutrients
Needed in very small amounts (iron)
Heterotrophs
Require an external source of organic carbon ( sugar lipids, proteins)
Autotrophs
Do not require an external source of organic carbon- used carbon fixation to convert inorganic carbon into organic carbon
Growth factors
The necessary substances that a cell can’t make on it’s own
fastidious
having complicated nutritional requirements; especially growing only in special artificial cultures- need multiple growth factors
Growing fastidious microbes in labs
Amino acids, vitamins, and/or nitrogenous bases must be supplied in the growth medium
Phototrophs
Organisms that use light energy
Chemotrophs
Organisms that break down chemical compounds for energy
Photoautotrophs
Inorganic (usually CO2), Cyanobacteria found in freshwater environments
Photoheterotroph
Organic; heliobacillus mobilis found in rice paddy fields
Chemoautotroph
Inorganic (usually CO2); Thiobacillus denitrificans found in soil, mud, and freshwater and marine sediments
Studied by 83 People