Microbiology Chapter 4 Flashcards
What are three general reasons to grow microbes in culture?
Medical significance, nutritional uses, industrial uses.
What is German physician Robert Koch famous for?
Studied disease causing bacteria; Nobel prize. Helped understand cholera epidemic in India. Developed methods of cultivating bacteria.
__________ is the time it takes for the population of bacteria to double.
Generation Time
Generation time varies among what two conditions?
Species and environmental conditions.
________ is defined as an increase in the number of cells in a population.
Microbial Growth
How do the growing conditions in nature differ from the growing conditions in the laboratory?
Nature has changing/complex conditions.
What is the name for polymer-encased communities that bacteria grow in?
Biofilm
What are examples of biofilm in our daily lives?
Slippery rocks in stream.
Slimy gunk in sink drains,
Scum in toilet bowl.
Dental plaque.
Describe the formation and structure of biofilm.
Free cells adhere to surface and multiply. Release polymers to which cells attach and grow. Extra polymeric substances (EPS) give slimy appearance. Nutrients and wastes pass through characteristic channels, cells communicate via chemical signals.
What are two helpful aspects of biofilms?
Bioremediation and Wastewater Treatment
What are some negative implications of biofilms?
Most infections involve biofilms, as they are often resistant to immune system and antibiotics. Accumulations in drains and pipes are most resistant to disinfectants. Leads to decay/disease (from dental plaque).
What is the term for a population of cells derived from a single cell that allows the study of a single species?
Pure Culture
What percent of microorganisms can be cultured?
1%
What technique is used to obtain pure culture?
Aseptic Technique
Behavior of microbes is dependent on _______.
Environment/where they are grown.
(Nature vs. Laboratory)
In the laboratory, how are cells grown?
Grown in or on culture medium. Contains nutrients dissolved in water. Can be liquid broth or solid gel.
With correct conditions in laboratory, single cell will multiply to form what?
Colony (Approximately 1 million cells easily visible).
What ingredient is used to solidify medium?
Agar
What are the benefits of using agar to solidify medium?
Few microbes can degrade it. Not destroyed by high temperatures and can be sterilized.
What is a closed system?
Culture in which nutrients are not added, nor are wastes removed.
Characteristic ______ seen in closed broth culture.
Growth Curve
Describe the lag phase of bacterial growth.
Number of cells does not increase. Cells begin synthesizing enzymes required for growth. Delay depends on conditions.
Describe the exponential phase of bacterial growth.
Cells divide at constant rate. Generation time measured. Most sensitive to antibiotics.
What are two byproducts of the exponential growth phase?
Primary metabolites such as amino acids.
Secondary metabolites such as antibiotics are produced as nutrients are depleted and wastes accumulate.
Describe the stationary phase of bacterial growth.
Nutrient levels too low to sustain growth. Growth rate = death rate. Continue to produce secondary metabolites.
Describe the death phase of bacterial growth.
Total number of viable cells decreases. Cells die at constant rate. Exponential, but usually much slower than cell growth.
Describe the phase of prolonged decline of bacterial growth.
Some fraction may survive. Adapted to tolerate worsened conditions.
Describe how cell growth can vary in the middle of the colony vs. on the edge.
Edge has little competition for oxygen and nutrients. Center has depleted oxygen and nutrients, and accumulation of potentially toxic wastes. Can be in different growth phases (edge can be in exponential growth while center is in death phase).
What are the four major factors that affect microbial growth?
Temperature, atmosphere, pH, and water availability.
What is the name for the type of bacteria that live in harsh environments? What domain are they from?
Extremophiles. Archaea.
Temperature range and significance for Psychrophiles.
5 to 15 degrees Celsius. Found in Arctic and Antarctic regions.
Temperature range and significance of Psychrotrophs.
15 to 30 degrees Celsius. Important in spoilage of refrigerated foods.
Temperature range and significance of Mesophiles.
25 to 45 degrees Celsius. Pathogens thrive in 35 to 40 degrees Celsius.
Temperature range and significance of Thermophiles.
45 to 70 degrees Celsius. Common in hot springs and compost heaps.
Temperature range and significance of Hyperthermophiles.
70 degrees Celsius or greater. Usually archaeal, found in hydrothermal vents.
How do thermophiles remain stable under high temperatures?
Proteins of thermophiles resist denaturing. Stability comes from amino acid sequence.
How does refrigeration slow spoilage of food?
Limits growth of otherwise fast growing Mesophiles. Psychrophiles and psychrotrophs can still grow, but slowly.
T/F: Freezing preserves food and is effective at killing microbes.
False, freezing is not effective at killing microbes.
Describe the oxygen requirements of obligate aerobes.
Require O2.
Describe the oxygen requirements of facultative aerobes.
Use O2, but don’t require it.
Describe the oxygen requirements of obligate anaerobes.
Cannot use O2.
Describe the oxygen requirements of microaerophiles.
Require small amounts of O2 only.
Describe the oxygen requirements of aerotolerant anaerobes.
Obligate fermenters (can grow in O2, but they don’t use it).
What is a Reactive Oxygen Species (ROS)? What are the two byproducts and why are they dangerous? How do organisms protect against this?
Harmful by-products of using O2 in aerobic respiration. Superoxide and hydrogen peroxide. Damaging to cellular components, cells must have protective mechanisms (produce enzyme superoxide dimutase that inactivates superoxide, also produce catalase).
What is the one group that does not have protective mechanisms against the harmful byproducts of aerobic respiration?
Obligate anaerobes
What group does not produce catalase?
Aerotolerant anaerobes
How do bacteria respond to changes in environment?
Pump out protons if in acidic environment. Bring in protons if in basic environment.
What bacterial group grows optimally at pH below 5.5?
Acidophiles
What bacterial group grows optimally at pH above 8.5?
Alkaliphiles
Most microbes are _______ and have an optimum pH range of 5 to 8.
Neutrophiles
What two ingredients make water unavailable to cells, hence their use in food preservation?
Dissolved salts and sugars.
What is the name for the type of bacteria that does not require high salt concentrations, but can withstand them?
Halotolerant
What is the name for the type of bacteria that requires high salt concentrations?
Halophiles
What are the (10) major nutritional elements for microbial growth?
Carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, magnesium, calcium, and iron.
What are the (5) trace nutritional elements for microbial growth?
Cobalt, zinc, copper, molybdenum, and manganese.
What process converts inorganic carbon to organic carbon?
Carbon Fixation
_________ use organic carbon vs. ________ use inorganic carbon.
Heterotrophs; Autotrophs
What process converts N2 gas to ammonia then incorporating it into organic compounds? (converts it into a usable form for plants)
Nitrogen Fixation
Nitrogen is required in bacteria for ______ and _____.
Nucleic acids and amino acids.
What two nutrients are often limiting for bacteria?
Phosphorus and Iron.
What are organic molecules that an organism cannot synthesize, as they must be present in the environment?
Growth Factors
________ obtain energy from sunlight. List 3 examples.
Phototrophs. Plants, algae, photosynthetic bacteria.
_______ obtain energy from chemicals. List examples.
Chemotrophs. Animal cells, fungi, many types of prokaryotes.
What are the three most common sources of chemical energy for cells?
Sugar, amino acids, and fatty acids.
Some prokaryotes extract energy from ________, such as hydrogen sulfide and hydrogen gas.
Inorganic Compounds
T/F: Direct cell count counts both living and dead cells.
True
Viable cell counts refer to _______?
Cells capable of multiplying
