Ch. 6 Microbial Growth (lecture exam 2)
At what temperature do you denature protein?
Maximum (very high) growth
How do most bacteria reproduce?
Most bacteria reproduce asexually by dividing in two, a process called binary fission. These two new cells grow and then each divides to form two new cells, resulting in a total of four cells with identical DNA from a single parent cell.
Why did molecular oxygen kill many primitive oxygen?
O2 levels rose and many obligate/strict anaerobes were killed. Toxic properties of atmospheric oxygen: highly reactive, toxic. Oxidizes membranes, enzymes.
Chemoheterotroph
Organic compound/ molecules are source of energy & carbon source e.g. *Non-photosynthetic bacteria, protozoa, fungi, and animals
What is the carbon source for Chemoheterotrophs?
Organic compounds (hetero-)
What are "growth factors"?
Required organic compounds which cannot be synthesized by a microbe are growth factors. e.g. amino acids, purines/ pyrimidines
What pathogen has high salt tolerance and is heat stable to produce enterotoxins?
Staphylococcus aureus (Staph- food poisoning)
In which phase are endospores present?
Stationary & Death Phase
In which phase does one see false gram-negative reactions?
Stationary & Death Phase
In which phase represents "carrying capacity" of the environment?
Stationary Phase
Example of Alkalinophile
Vibrio cholerae pH 9
Additional protective substances: (ROI's)
Vitamin C, E which provide electrons to reduce toxic forms of oxygen
How did Earth's atmosphere become oxygenated?
When oxygenic photosynthesis first evolved ( ~2.5 bya) with primitive cyanobacteria, O2 levels rose and many obligate/strict anaerobes were killed.
Microbial Growth Curve of four phases:
1. Lag Phase 2. Log (exponential) Phase 3. Stationary Phase 4. Death (decline) Phase
Describe production of "ROI's" (Reactive Oxygen Intermediates) in 1ST STEP
1. singlet oxygen: Molecular oxygen with electrons boosted to higher energy state -protective carotenoids in photosynthetic organisms
What are the protective enzymes that evolved from Aerobic environments?
1. superoxide dismutase "SOD" 2.catalase/ peroxide
Describe production of "ROI's" (Reactive Oxygen Intermediates) in 2ND STEP
2. superoxide anions, (free radicals) -protective superoxide dismutase "SOD" 2 O2- + 2H+ -> SOD-> H2O2 +O2
Describe production of "ROI's" (Reactive Oxygen Intermediates) in 3RD STEP
3. Peroxide anion O2 2- : from hydrogen peroxide; antimicrobial -protective catalase or peroxidase catalase reaction: H2O2 + NADH + H+ -> 2 H2O + NAD+
What are problems with exponential growth of microbial populations? number of cells doubles per unit time
= number of cells doubles per unit time ****note:Very hard to graph on arithmetic graph paper
Example of Acidophile
A bacterium that grows below pH 4 e.g. lactic acid bacteria -Helicobacter pylori: bicarbonate and urease
What are "fastidious pathogens"?
A fastidious organism is any organism that has a complex nutritional requirement. In other words, a fastidious organism will only grow when specific nutrients are included in its diet: *vitamins *amino acids *purantines
Which enzymes evolved/protected microbes from toxic ROI's?
Aerobic organisms evolved enzymes for protection; a. superoxide dismutase 2O2.- + 2H+-superoxide dismutase--> O2 + H2O2 b. catalase/peroxidase: 2H2O2--catalase-->O2 + 2H2O
Facultative Anaerobe
An organism that can grow with or without molecular oxygen (O2). e.g. E. coli
Obligate/strict Anaerobe
An organism that does not use molecular oxygen (O2) and is killed in the presence of oxygen (O2). e.g. Clostridium
Aerotolerant Anaerobe
An organism that does not use molecular oxygen (O2) but is not affected by its presence. e.g. Streptococcus
Example of Psychrophile
An organism that grows best about 15*C and does not grow above 20*C; a cold-loving microbe e.g. algae Chlamydomonas nivalis Sierra Nevadas
Example of Mesophile
An organism that grows best between about 10*C and 50*C; a moderate-temperature-loving microbe
Example of Halophile
An organism that requires a high salt concentration for growth
Obligate/strict Aerobe
An organism that requires molecular oxygen (O2) to live. e.g. Pseudomonas
Example of Thermophile
An organism whose optimum growth temperature is between 50*C and 60*C; a heat loving microbe
What is the carbon source for Photoautotrophs?
Carbion dioxide (auto-)
What is the energy source for Chemoheterotrophs?
Chemical compounds (chemo-)
For all cellular pathogens that invade other organisms, what is their source of food?
Chemoheterotrophs *kingdom animalia *kingdom fungi *some animal-like protozoa
Which phase do cells adapt to new environment, transporting nutrients into cell, synthesizing organic molecules?
Lag Phase
What is the energy source for Photoautotrophs?
Light (photo-)
In which phase are cells most sensitive to antibiotics, disinfectants, etc?
Log (exponential) Phase
In which phase could one calculate doubling/generation time?
Log (exponential) Phase
In which phase do cells divide at the highest rate possible given environment conditions?
Log (exponential) Phase
What is the best phase to perform gram stains?
Log (exponential) Phase
Why is it so difficult to kill bacterial pathogens living in biofilms in patients?
because phagocytes can't reach them , anitbodies can't reach them, and antibiotics have a hard time diffusing down to the deeper layers , bacterium in the deeper layers of biofilm are often in stationary phase of growth & are naturally more resistant
What temperature do you have the best growth of microbes?
optimum growth
How does Campylobacter survive on raw poultry?
presume it's covered in fecal residue by a biolfilm forming at an intermediate level of the poultry and grows best on reduce oxygen atmosphere
Problems with Listeria monocytogenes under Psychrophile conditions
raw unpasteurized milk affect moms barring child which cause miscarriage & neonatal sepsis & meningitis that leads to death of baby. Also HIV patients are sepstable to Listeria as well =(
Example of Obligate/strict Aerobe
some bacteria, algae, most fungi/protozoa
The atmosphere of primitive Earth
the atmosphere was anaerobic, it lacked free molecular oxygen. -The first cells to evolve were obligate anaerobes and use fermentation to generate energy.
Photoautotroph
use light as energy source. e.g. *oxygenic photosynthetic cyanobacteria, algae, plants *anoxygenic photosynthetic bacteria that have bacteria chloriphyll a *purple & green sulfur bacteria *
How does salt and sugar used in preserving foods inhibit growth of microbes?
use of salt/sugar to create a hyperosmotic environment -practical applications: salting or adding sugar to foods to increase osmotic pressure of environment. Causes dehydration of microbes, plasmolysis. No growth/death of microbes, preserves food. (also honey used in infected wounds...)
What kind of paper do you use to graph exponential growth microbial?
use semi-log paper
Example of growth factor
vitamins: small organic molecules which make up all/part of enzyme cofactors Enterococcus faecalis requires 8 vitamins. Leuconostoc cirovorum requires all 20 amino acids, many purine/pyrimidines and 10 vitamins . - E. coli has no organic growth factor requirements. -other growth factors: heme required by Haemophilus influenzae, cholesterol by some Mycoplasma
Alcohol fermentation
dentures protein
Reactive Oxygen Intermediates include:
formed in Aerobic environments= molecular oxygen interacts with molecular molecules and get the following products: Superoxide anion/radical= O2 which damages the cytoplasmic membrane, protein, nucleic acid H2 O2 Hydrogen peroxide
How does lactic acid & alcohol produced during fermentation prevent the growth of spoilage microbes?
in absence of refrigeration (when pH7 drops to pH4)
What is lactic acid fermentation?
inhibit spoilage microbes in absence of refrigeration, brings down the pH from 7 down to pH 4
What is Camplybacter?
leading cause of foodborne illness -fecal oral transmission -forms biofilm -including birds/poultry
Example of Neutrophile
most human pathogens
