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2 types of cell activity
Growth and reproduction
2 types of metabolic reactions
Catabolic and Anabolic
Catabolic
Breakdown of larger molecules Produces smaller molecules Releases energy Examples: Breaking down starch into simple sugars Breaking down simple sugars into CO2 and H2O
Anabolic
Building of larger molecules Uses smaller molecules Requires energy Examples: Joining amino acids into proteins Linking carbs + amino acids into cells walls
Macronutrient
Chemicals needed in large amounts for building macromolecules Structural components Enzymes
Macronutrients needed by bacteria
Carbon Hydrogen Nitrogen Oxygen Phosphorus Sulfur **OCHNPS
Why are macronutrients needed?
To build structural components and macromolecules in the cell
Micronutrients
Metals; structural components of enzymes *Critical to cell function
Growth factors
Organic compounds required in trace amounts Form part of enzymes Include vitamins, amino acids, purines, pyrimidines Most microbes can synthesize these
Cellular energy
Powers the anabolic reactions in cells In the form of electrons Given off when chemical nutrients are broken down
Photosynthetic organisms
Obtain some of their energy from sunlight
Energy stored in cells
Electrons are never loose in the cytoplasm Captured and stored in ATP (chemical 'battery') ATP donates or accepts electrons
Generation time
The time it takes a microbial cell to divide The population doubles Always measured under ideal conditions Varies among microbial species (e. coli-17 min; treponema pallidum - 33 hrs) Most bacteria range from 1-3 hrs Varies with growth conditions Nutrition available in their environ…
Growth curve - Lag Phase
1 hr - several days Period of adjustment to new environmental conditions No cell division!! (Population does not increase) Bacteria adapting to new environment Phase of intense metabolic activity Energy spent on anabolic activities Making new enzymes needed to use nutrients in new e…
Growth curve - Log or Exponential Phase
Cell division begins Generation time becomes constant Period of rapid growth with a big increase in population Cells are very susceptible to adverse environmental factors
Growth curve - Stationary Phase
Population stabilizes and growth rate slows down; NOT a dormant period Number of new cells = number of dying cells Cell size is smaller Nutrients becoming scarce Waste products accumulate and become toxic pH becoming acidic Oxygen decreasing
Growth curve - Death (decline) Phase
Population begins to decline Number of dying cells exceeds number of new cells Cells die at logarithmic rate Population will eventually die off
Influences on microbial growth
Temperature Oxygen pH Water
Temperature
Different organisms grow at different temperatures Temperature affects enzyme rates Growth is slower below optimum temperature
3 groups based on optimal growth temperature
Psychrophile Mesophile Thermophile
Psychrophile
"Cold-loving" Found in polar regions and ocean depths Membranes have unique fatty acids that are fluid at low temperatures No medical importance; don't grow at our body temperature Can grow in refrigerator and spoil food
Mesophile
"Middle loving" Most of the organisms we will study Pathogens!!
Thermophile
"Heat-loving" Found in hot springs and compost heaps Not medically important; don't grow at our temperature Food spoilage organisms; withstand pasteurization, canning process
How do high and low temperature affect cells?
Two targets: Membranes - solidify, no movement in or out (thermal lysis - collapse membrane) Proteins (especially enzymes) - as you add heat, speeds it up, until max is reached
3 types of Oxygen requirements
Aerobic Anaerobic Aerotolerant
Aerobic
Obligate - grow at surface Oxygen is essential Found on skin and dust 2. Facultative - grow with or without oxygen Found in large intestine 3. Microaerophiles - require less oxygen than in the atmosphere Found in mouth; Sexually transmitted organisms
Anearobic
Oxygen harms them Found in colon
Aerotolerant
Indifferent to oxygen Found in respiratory tract
pH range in microbial growth
Intracellular pH remains neutral Most around pH of 7.0 with a range of 3 pH units
Function of water in microbial cells
Acts as a solvent and a reactant A medium for chemical reactions inside the cell
Bacterial DNA
Bacteria have one large chromosome Single strand of DNA in double helix Floats free in cytoplasm Packed very tightly Single largest molecule in microbial cell Configured in closed loops
Description and size of Plasmids
Not all bacteria have plasmids! Like chromosomes, but MUCH smaller Less than 2% its size About 5-100 genes
Advantages of Plasmids to cells
All cells are able to live without them Plasmids can encode a product that might aid the cell Antibiotic resistance Toxin (poison) production
Mutation
Change in a base sequence of the DNA molecule (usually a small change)
2 types of mutation
Insertion of something that was not in the parent strand Deletion of information that was in the parent strand
Rates of mutation
DNA mutations occur regularly in nature If change is beneficial, altered cells will flourish and outgrow other cells Rate once every billion base pair replications
2 causes of mutation
Spontaneous Mutagen
Spontaneous
Simple mistake of nature that occurs during cell replication (replication error)
Mutagen
Agents which interfere with DNA replication Increase the mutation rate 10-1,000 times Mutagens can cause insertion and deletion errors High energy radiation Benzopyrene Nitrosamines
Genetic Recombination
Transfer of genetic information between bacteria
Mechanisms of Genetic Recombination
Acquired from environment (transformation) Exchanged between bacteria (conjugation) Transfered from viruses (transduction)
Transformation
DNA is absorbed directly from the environment by live bacteria Donor cell dies and disintegrates DNA released into environment and degrades Live component bacterium takes up a fragment Same species or very similar species Fragments contain a few genes Occurs everywhere; in your inte…
Conjugation
Transfer of DNA between 2 living bacteria One organism is a donor and transfers DNA to another organism Transfer chromosome or plasmid through pilus Usually donate part; rarely entire chromosome Occurs among closely related species Common method for transfer of antibiotic resistance …
Process of conjugation
Pilus of donor contacts recipient and pulls it close Channel forms (conjugate bridge) through which the genetic material passes Takes about 90 minutes
Transduction
Virus transfers bacterial DNA Bacteria get viral infections, shuts down, and uses resources to manufacture virus particles. Sometimes there are mistakes during viral replication Abnormal virus can infect a bacterium Antibiotic resistance is NOT transferred this way; amount of genetic …

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