Microbiology Chapter 6

Microbial growth

an increase in a population of microbes rather than an increase in size of an individual

Colony

-an aggregation of cells arising from a single cell

-super concentrated mound of bacteria

Biofilm

collection of microbes living on a surface in a complex community

Growth requirements

use a variety of nutrients for their energy needs and to build organic molecules and cellular structures (CHON)

Photoautotrophs (for sure know this)

-their energy source is light

-their carbon source is carbon dioxide

Chemoautotrophs

-energy source is chemical compounds

-carbon source is carbon dioxide

Photoheterotrophs

-energy source is light

-carbon source is organic compounds

Chemoheterotrophs

-energy source is chemical compunds

-carbon source is organic compounds

auto-

carbon source= carbon dioxide

Photo-

energy source= light

chemo-

energy source= chemical compounds

hetero-

carbon source= organic compound

breaking down from other living things

oxygen for obligate aerobes

essential

oxygen for obligate anaerobes

deadly/toxic

Why is oxygen toxic to obligate anaerobes?

-neither gaseous O2 nor oxygen covalently bound in compounds is poisonous

-forms of oxygen that are toxic are highly reactive & oxidizing agents

-oxidations cause irreparable damage to proteins and lipids

How do you combat toxic O2?

consume antioxidants to prevent unnecessary redox reactions from occurring

Aerobes

undergo aerobic respiration

anaerobes

do not use aerobic metabolism

facultative anaerobes

can maintain life via fermentation or anaerobic respiration or by aerobic respiration (prefers aerobic conditions, facilitates in anaerobic)

aerotolerant anaerobes

do not use aerobic metabolism but have some enzymes that detoxify oxygen’s poisonous forms (prefer anaerobic)

Microaerophiles

-aerobes that require oxygen levels from 2 to 10% and have a limited ability to detoxify hydrogen peroxide & superoxide radicals

-tolerate small amounts of oxygen

What element do animo acids need?

nitrogen

What are nitrogen atoms needed for?

proteins and nucleotides

Why can’t we use nitrogen straight from air?

nitrogen gas has triple bond that is very hard to break

Nitrogen fixation

reduction of nitrogen gas to ammonia

Where do humans get nitrogen from?

plants consumed or animals that eat plants consumed

Phosphorus

a component of phospholipid membranes, DNA, RNA, ATP, and some proteins

Sulfur

-a component of sulfur-containing amino acids

-disulfide bonds critical to tertiary structure of proteins, & in vitamins

Trace elements

-only required in small amounts

-usually found in sufficient quantities in tap water

Growth factors

-things we need, but can’t make on our own

-vitamins, certain amino acids, purines, pyrimidines, cholesterol, NADH, and heme

Physical growth requirements

-temperature, pH, and water

Temperature effects

-effects on proteins (denatures if too hot)

-Effect on membranes and organelles

If temperature too low

membrane becomes ridged and fragile

if temperature too high

-membrane too fluid and cannot contain organelles

-denatures proteins

-vibrate really fast, phospholipids start opening up and things can get in

what are the 4 types of bacteria?

Psychrophiles, mesophiles, thermophiles, and hyperthermophiles

which bacteria thrive in the human body?

mesophiles

pH growth requirements

H+ & OH- can interfere with H bonding in proteins and nucleic acids

Neutrophiles

grow best in a narrow range around (6.5-7.5)

Acidophiles

grow best in acidic habitats pH 3 or less

alkalinophiles

up to pH 11.5

Water requirements

-dissolve enzymes and nutrients required in metabolism

-react 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 in environment for years

osmotic pressure

The pressure exerted on a semipermeable membrane by a solution containing solutes that cannot freely cross membrane

hypotonic

water moves in to cell. Cell may swell and burst in absence of cell walls

hypertonic

water moves out of cell. cell shrinks in absence of cell wall

obligate halophiles

grow in 30% salt, tolerates high concentration of salt on the outside

facultative halophiles

can tolerate high salt concentrations, prefers isotonic

Hydrostatic pressure

-deeper into water, pressure on body increases

-10m depth, water pressure increases 1 atm

Barophiles

organisms that live under extreme pressure

-their membranes and enzymes depend on this pressure to maintain their 3D functional shape

Biofilms

-develop an extracellular matrix that adheres cells to one another

-allows attachment to substrate

-sequesters nutrients

-may protect individuals within

Relationships within biofilms

antagonistic, synergistic, and symbiotic

Antagonistic relationship

one against the other

Synergistic

work together towards one common goal

symbiotic

both benefit from one another

quorum sensing

How bacteria communicate with each other in biofilms

Inoculum

-transfer from one spot to another

-introduced into medium (solid or broth)

culture

refers to act of cultivating microorganisms or the microorganisms that are cultivated

aseptic technique

to prevent contamination of sterile substances or objects

What are the two most common isolation techniques?

pour plates and streak plates

Defined media (know this)

exact

complex media (know this)

partial digests; don’t know full concentration of everything

Selective media (know this)

inhibitory; inhibits growth of other things

differential media (know this)

tests; color change to define difference from bacteria with the use of acidity

Anaerobic media (know this)

reducing; reduces amount of oxygen available to allow anaerobic bacteria

Transport media

to transport, keep organism alive, but not for growing

Special culture techniques

-animal and cell culture

-low-oxygen culture

-enrichment culture

-chemostats

Preserving cultures

refrigeration, deep-freezing, and lyophilization

Refrigeration

stores for shot periods of time; reactions slow down

Deep-freezing

stores for years; liquid nitrogen or ice; cells really slow down

Lyophilization

stores for decades; sucks out all H2O, so all reactions stop

Chemostat

huge containers to keep bacteria growing by feeding them culture media and using what they produce

Generation Time

time required for a bacterial cell to grow and divide

Microbial growth chart

-lag phase: susing out situation to see if its fit for survival

-log phase: exponential growth

-stationary phase: plateau due to limiting resources, born=death

-death phase: completely out of essential resources to survive

CFU

colonies X dilution factor

Viable plate count (know this)

serial dilution in broth, spread 0.1ml of each broth to plates, plates with about 30 colonies needed for statistical significance

Most probable number (know this)

-for faster results

-undiluted, 1:10, 1:100

-1.0ml into 5 tubes of phenol red at each dilution

-results give most probable number of bacteria per 100ml

Indirect methods of measuring microbial populations

spectrometer: more absorbance means more colonies