MICRO BIO CH.9 Dr. Brookins TCC southeast

Microbial growth

refers to population growth rather than growth of individual cells

Binary fission

asexual method of bacterial cell division in which a cell replicates its DNA and divides into two equal daughter cells through septum formation and cell separation

Snapping division

a variation of cell division in some bacteria where cells remain attached at an angle after division due to an asymmetric splitting of the cell wall

Budding (bacterial reproduction)

asymmetrical cell division in which a smaller daughter cell forms as a bulb pulling away from the parent cell such as in the marine bacterium Hyphomicrobium

Exponential growth

pattern of bacterial growth in which each division doubles the number of cells; for example 0 generations produces 1 cell 1 generation produces 2 cells 2 generations produce 4 cells and 3 generations produce 8 cells

Lag phase

first phase of a bacterial growth curve in which bacteria are preparing their cell machinery for growth

Log phase (exponential phase)

phase of a bacterial growth curve in which growth approximates an exponential curve appearing as a straight line on a logarithmic scale

Stationary phase

phase of a bacterial growth curve in which cells stop growing and shut down their growth machinery while turning on stress responses to help retain viability

Death phase

phase of a bacterial growth curve in which cells begin to die at an exponential rate

Generation time (doubling time)

the time it takes for a population of bacteria to double in number

Escherichia coli generation time

approximately 20 minutes

Mycobacterium tuberculosis generation time

approximately 18 hours

Mycobacterium leprae generation time

approximately 14 days

Petroff-Hauser counter

device useful for counting both eukaryotic and prokaryotic cells directly under a microscope but does not indicate whether a cell is dead or alive

Trypan blue

dye used to help distinguish live cells from dead cells during counting

Spread plate technique

viable counting method used to determine the number of live bacteria in a sample

Pour plate technique

viable counting method used to determine the number of live bacteria in a sample

Plate count

method of determining bacterial numbers by counting colonies ideally between 30 and 300 on a plate

CFU/mL

colony forming units per milliliter of sample calculated as the number of colonies multiplied by the dilution factor

Biofilm

community of sessile bacteria that develop an extracellular matrix enabling them to attach to each other and to surfaces as opposed to free-floating planktonic bacteria

Sessile bacteria

bacteria that are attached to a surface as part of a biofilm

Planktonic bacteria

free-floating bacteria not attached to a surface

Quorum sensing

process by which cells in a biofilm communicate and coordinate actions such as gene expression based on population density

Reactive oxygen species (ROS)

toxic byproducts of oxygen metabolism that may damage DNA proteins and lipids

Oxidative stress

cellular damage caused by reactive oxygen species

Superoxide dismutase (SOD)

enzyme that helps cells cope with oxidative stress

Catalase

enzyme that breaks down hydrogen peroxide into water and oxygen

Peroxidase

enzyme that helps break down peroxides as part of coping with oxidative stress

Reductase

enzyme that helps cells cope with oxidative stress

Obligate aerobe

organism that requires oxygen for growth

Obligate anaerobe

organism that cannot grow in the presence of oxygen because it lacks enzymes to resist reactive oxygen species

Facultative anaerobe

organism that can grow with or without oxygen

Aerotolerant anaerobe

organism that does not use oxygen for growth but can survive in its presence

Microaerophile

organism that requires only small amounts of oxygen for growth

Pseudomonas aeruginosa

obligate aerobe widespread in nature that is an opportunistic pathogen producing pyocyanin; commonly infects the lungs of cystic fibrosis patients causes ear infections and burns; biofilm formation protects it from phagocytosis and treatment can be difficult due to drug resistance

Streptococcus pyogenes

aerotolerant anaerobe that causes common infections including pharyngitis (strep throat) scarlet fever pyoderma erysipelas streptococcal toxic shock syndrome necrotizing fasciitis rheumatic fever and glomerulonephritis

Strep throat

disease caused by Streptococcus pyogenes and other organisms; transmitted through upper respiratory tract secretions and droplets causing tonsil and pharynx inflammation with red swollen purulent exudate hemorrhagic patches high fever and lymphadenopathy; possible complications include rheumatic fever glomerulonephritis and otitis media

Acidophile

organism that grows optimally below pH 3

Neutralophile

organism that grows optimally between pH 5 and pH 8

Alkaliphile (alkalinophile)

organism that grows optimally above pH 9

Helicobacter pylori

bacterium that causes many gastric ulcers; copes with acidic conditions using the enzyme urease which converts urea into ammonia and carbon dioxide to neutralize stomach acid; diagnosed using the ammonium breath test

Alkalinophile coping mechanisms

include maintaining an acidic cytoplasm and using pH resistant enzymes

Vibrio cholerae (cholera)

etiologic agent of cholera; transmitted by the fecal-oral route causing sudden-onset dysentery with rice water stools leading to severe dehydration electrolyte imbalance and shock with high mortality if untreated; treated with supportive care and antibiotics; a toxoid vaccine exists but is not very effective

Halobacterium salinarum

archaeon that is an alkalophile found in saline soda lakes

Spirulina

coiled filamentous cyanobacterium that is an alkalophile growing in the alkaline environment of Lake Magadi and gives flamingos their pink color when ingested

Hyperthermophile

organism that grows above 80 degrees Celsius (176 degrees Fahrenheit)

Thermophile

organism that grows between 50 and 80 degrees Celsius (122 to 176 degrees Fahrenheit)

Mesophile

organism that grows between 15 and 45 degrees Celsius (59 to 113 degrees Fahrenheit)

Psychrophile

organism that grows below 15 degrees Celsius (59 degrees Fahrenheit)

Thermus aquaticus

hyperthermophile first isolated at Yellowstone National Park

Chlamydomonas nivalis

example of a psychrophile

Halophile

organism that grows in high salt concentrations greater than 2 molar NaCl

Strict anaerobe (environmental classification)

organism that grows only in the absence of oxygen

Barophile (piezophile)

organism that grows at high pressure greater than 380 atmospheres

Barotolerant organism

organism that grows between 10 and 500 atmospheres of pressure

Extremophile

organism adapted to grow under extreme environmental conditions such as extreme temperature pH salinity or pressure

Osmolarity

measure of solute concentration in a solution that affects the movement of water across a cell membrane

Osmosis

movement of water across a selectively permeable membrane

Isotonic solution

solution in which water concentration is equal inside and outside the cell so rates of diffusion are equal in both directions representing a dynamic equilibrium

Hypotonic solution (microbial)

solution in which there is a net diffusion of water into the cell; in cells with a cell wall this causes the protoplast to swell and press against the wall producing a turgid cell while in cells without a cell wall this can cause lysis if no mechanism exists to remove the excess water

Turgid

term describing a walled cell that has swollen tightly against its cell wall due to water uptake in a hypotonic solution

Hypertonic solution (microbial)

solution in which there is a net diffusion of water out of the cell; in cells with a cell wall this causes the cell membrane to shrink away from the wall in a process called plasmolysis while in cells without a cell wall this causes the cell to shrink and become distorted in a process called crenation

Plasmolysis

shrinking of the cell membrane away from the cell wall due to water loss in a hypertonic environment

Crenation

shrinking and distortion of a cell without a cell wall when placed in a hypertonic environment

Extreme (obligate) halophile

organism that requires very high salt concentrations for growth

Facultative halophile (osmotolerant)

organism that can grow in high salt concentrations but does not require them

Aquaporin

channel protein through which water molecules move across the cell membrane

Staphylococcus aureus

etiologic agent of staphylococcal diseases including MRSA strains; transmitted as part of normal flora; virulence factors include leukocidins coagulase beta-hemolysins dermonecrotic exotoxin and hyaluronidase; disease categories include noninvasive food poisoning cutaneous wound infections and abscesses and scalded skin syndrome as well as systemic diseases such as sepsis abscesses in internal organs toxic shock syndrome bacteremia endocarditis pneumonia and osteomyelitis

Impetigo

skin infection caused by Staphylococcus Streptococcus and Corynebacterium species; virulence factor hyaluronidase; transmitted through direct or indirect contact breaks in the skin or insect bites and is highly contagious through scratching; disease progresses from pustule to rupture to spreading ulcer to crusty lesion; complications include sepsis and internal abscesses