Microbiology- Ch. 6: Microbial Nutrition and Growth
Describe what the terms colony and biofilm mean
Colony: Aggregation of cells arising from single parent cell Biofilm: Collection of microbes living on a surface in a complex community
Describe the purpose of culture media
Culture Media Majority of prokaryotes have not been grown in culture medium Nutrient broth is common medium Agar is a common addition to many media Complex polysaccharide derived from certain red algae Produces a solid surface for colonial growth Most microbes cannot digest agar
Slant Tube
Culture made on a slanting surface of a medium that has been solidified in a test tube inclined from the perpendicular so as to give a greater area than that of the lumen of the tube
Describe the following terms: inoculum, medium, broths, culture and colony
Inoculum: a substance used for inoculation Medium: A liquid or gelatinous substance containing nutrients in which microorganisms, cells, or tissues are cultivated for scientific purposes Culture: A method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory conditions. Microbial cultures are used to determine the type of organism, its abundance in the sample being tested, or both. Colony: Several individual organisms (especially of the same species) living together in close association. (cell culture) A cluster of identical cells (clones) on the surface of (or within) a solid medium, usually derived from a single parent cell, as in bacterial colony.
Describe what is meant by clinical specimen and possible sources of this specimen
Is a sample of human material, such as feces, saliva, cerebrospinal fluid, or blood that is examined or tested for the presence of microorganisms.
Describe the purpose and function of a chemostat
Is an open system; that is, fresh medium is continuously supplied while an equal amount of old medium (containing microbes) is removed. Its function is to provide a continuous culture for population estimation purposes.
Describe the three ways scientists preserve bacterial cultures
Refrigeration: Best technique for short periods of time (years) Deep-Freezing: Involving freezing the cells from -50 degrees celcius to -95 degrees celcius, and can be restored years later by thawing them and placing them in an appropriate medium.Used for long periods of time (years) Lyophilization: Involves removing water from a frozen culture using an intesnse vaccum. The ice then sublimates (directly becomes a gas) and is removed from cells without permanently damaging cellular structures and chemicals. Used for even longer periods of time (Decades)
Logarithmic Growth
1.) Lag 2.) Log 3.) Stationary 4.) Death The process of the number of bacteria doubling each time binary fission is completed
Agar
A gel-like polysaccharide compound used for culturing microbes; extracted from certain red algae
Describe the difference between: autotrophs, heterotrophs, chemotrophs, and phototrophs
Autotrophs: Make their own food, make organic compounds from CO2 and thius need not acquire carbon from other organic organisms. Heterotrophs: Catabolize reduced organic molecules, such as proteins, carbs, amino acids, and fatty acids that acquire from other organisms. Chemotrophs: Acquire energy from redox reactions involving inorganic and organic chemicals. These reactions can be aerobic, anaerobic or fermentation depending on the final electron acceptor. Phototrophs: Organisms that use light as their energy source.
Explain why scientists have developed special culture techniques outside of the ones already discussed
Because not all organisms can be grown under the culture conditions recently discussed. Animal and Cell Culture. Used when artificial media are inadequate Required for growth of viruses and other obligate intracellular parasite Low-Oxygen Culture. Many organisms prefer intermediate oxygen levels Carbon dioxide incubators mimic the environment of many body tissues Candle jars are a low cost alternative Ideal for the growth of capnophiles — microbes that grow best in high carbon dioxide levels
Describe the difference between facultative anaerobes, aerotolerant anaerobes, and microaerophiles
Facultative: Can grow with or without oxygen, but their ability to use aerobic respiratory pathways enhances their growth near the surface. Aerotolerant: Can grow equally well with or without oxygen; their growth is relatively evenly distributed throughout the medium Microaerophiles: Require oxygen levels of 2% to 10%. Are damaged by the 21% concentration of oxygen in the atmosphere, because the have limited ability to detoxify hydrogen peroxide and superoxide radicals.
Describe the difference between the four phases of bacteria growth in broth
Lag Phase: Cells are adjusting to new environment Log Phase: Bacteria synthesize necessary chemicals for conducting metabolism in their new environment. They then enter a phase of rapid chromosome replication, growth, and reproduction. Stationary Phase: Nutrients are depleted and wastes accumulate, the rate of replication decreases. Death Phase: Population reaches a point at which cells die at a faster rate than they are produced due to a lack of resources.
Nutrient Broth
Liquid medium containing beef extract and peptone
Describe the difference between microbe antagonistic, synergistic and symbiotic relationships
Organisms live in association with different species Antagonistic relationships — a microbe harms another organism Synergistic relationships — members of an association receive benefits that exceed those that would result if each lived by itself Symbiotic relationships — organisms become interdependent and rarely live outside the relationship
Describe two reasons why microorganisms require water
Microbes require water to dissolve enzymes and nutrients Water is important reactant in many metabolic reactions Most cells die in absence of water Some have cell walls that retain water Endospores and cysts cease most metabolic activity Two physical effects of water Osmotic pressure Hydrostatic pressure Osmotic pressure Pressure exerted on a semipermeable membrane by a solution containing solutes that cannot freely cross membrane Hypotonic solutions have lower solute concentrations Cell placed in hypotonic solution swells Hypertonic solutions have greater solute concentrations Cell placed in hypertonic solution shrivels Restricts organisms to certain environments Obligate and facultative halophiles Hydrostatic pressure Water exerts pressure in proportion to its depth Barophiles live under extreme pressure Their membranes and enzymes depend on pressure to maintain their three-dimensional, functional shape
Describe how biofilms form as a result of quorum sensing
Microorganisms respond to the desity of nearby microorganisms. The microbes secrete quorum-sensing molecules that act to communicate number and types of cells among members of the biofilm.
Describe the following terms: pure cultures, CFU, sterile, and aspetic techniques
Pure cultures are composed of cells arising from a single progenitor Colony-forming unit (CFU) Aseptic technique prevents contamination of sterile substances or objects
Explain what growth factors are
Necessary organic chemicals that cannot be synthesized by certain organisms
Identify which atom is the growth-limiting nutrient for many microorganisms and explain why
Nitrogen, because they do not have sufficient nitrogen to rebuild proteins and nucleotides.
Describe the difference between the different ways microbiologists directly estimate the number of bacteria cells
Not Requiring Incubation Microscopic Counts: Counts directly through Microscope Electronic Counts: Coulter Counters: Counts cells as they interrupt electrical current flowing in front of an electric detector. Flow Cytomentry: Light sensitive detector to record changes in light transmission as cells pass through a tube. Direct Methods: Requiring Incubation Serial Dilution and Viable Plate counts: Membrane Filtration: Most Probable Number: (MPN):
Describe what the term nutrient means and what the four most important atoms in a nutrient are.
Nutrients: Chemical and Energy Requirements Most common nutrients contain necessary elements such as carbon, oxygen, nitrogen, and hydrogen Sources of carbon, energy, and electrons Organisms classified into two groups based on source of carbon Autotrophs Heterotrophs Organisms classified into two groups based on source of energy Chemotrophs Phototrophs
Explain why organisms are sensitive to pH changes. Also, describe the difference between neutrophils, acidophiles and alkalinophiles
Organisms are sensitive to changes in acidity H+ and OH- interfere with H bonding Neutrophiles grow best in a narrow range around neutral pH Acidophiles grow best in acidic habitats Many microbes produce acidic waste products that can accumulate and inhibit their growth Alkalinophiles live in alkaline soils and water
Identify which two features allow organisms to be categorized into one of four groups. Also, identify and describe those four groups.
Organisms classified into two groups based on source of carbon Autotrophs Heterotrophs Organisms classified into two groups based on source of energy Chemotrophs Phototrophs
Identify the difference between between organotrophs and lithotrophs
Organisms classified into two groups based on source of electrons Organotrophs — heterotrophs acquire electrons from same organic molecules that provide them carbon Lithotrophs — autrotrophs acquire electrons from inorganic molecules
Describe the difference between obligate aerobes and obligate anaerobes
Oxygen is essential for obligate aerobes Oxygen is deadly for obligate anaerobes
Exponential Growth Pattern
Pattern exhibited by a population which is increasing exponentially (i.e, doubles repeatedly); results in a J-shaped curve showing a brief lag phase, followed by a steep increase in the growth curve
Describe how osmosis can result in swelling and crenation of cells.
Pressure exerted on a semipermeable membrane by a solution containing solutes that cannot freely cross membrane Hypotonic solutions have lower solute concentrations Cell placed in hypotonic solution swells Hypertonic solutions have greater solute concentrations Cell placed in hypertonic solution shrivels Restricts organisms to certain environments Obligate and facultative halophiles
Describe the differences between the general types of culture media
Six types of general culture media Defined media Medium in which the exact chemical composition is known Fastidious organisms require the addition of a large number of growth factors Complex media Exact chemical composition is unknown Contain nutrients released by partial digestion of yeast, beef, soy, or proteins Support growth of wide variety of microorganisms Used to culture organisms with unknown nutritional needs Enrichment media Use of a selective medium to increase the numbers of a chosen microbe to observable levels May require a series of cultures to enrich for the desired microbe Cold enrichment used to enrich a culture with cold-tolerant species Anaerobic media Obligate anaerobes must be cultured in the absence of free oxygen Reducing media contain compounds that combine with free oxygen and remove it from the medium Petri plates are incubated in anaerobic culture vessels Sealable containers that contain reducing chemicals Transport media Used by hospital personnel to ensure clinical specimens are not contaminated and to protect people from infection Rapid transport of samples is important Differential Media Used to detect visible changes in the medium or differences in the appearance of colonies, this helps differentiate among the types of bacteria.
Describe the three things all cells need to conduct metabolism
Sources of carbon, energy, and electrons
Describe the streak-plate method and the pour-plate technique
Streak-Plate method: An inoculum that is spread across the surface of an agar plate plate in a sequential pattern of streaks. Pour-Plate Technique: After an initial sample is diluted through a series of transfers, the final dilutions are mixed with warm agar in petri-plates.
Identify the four types of physical requirements organisms need for growth in addition to chemical nutrients.
Temperature pH Physical Requirements of Water (Osmotic, hydrostatic)
Explain optimum growth temperature and why microorganisms are temperature sensitive. Also, describe the four categories of microorganisms based on temperature requirements
Temperature affects three-dimensional structure of proteins Lipid-containing membranes of cells and organelles are temperature sensitive If too low, membranes become rigid and fragile If too high, membranes become too fluid
Describe purpose and steps of binary fission
The process in which cells grow twice its notmal size and devides in half to produce two daughter cells of equal size and dna molecules. The purpose of binary fission is to increase the number of population. Steps: Cell replicates its chromosome (DNA). Cell elongates. Cell forms a new cytoplasmic membrane and wall (septum) at midline. When the septum is complete the daughter cells separate. The process repeats.
Describe what is meant by generation time
Time required for a bacterial cell to grow and divide, and is dependent of physical and chemical conditions
