mr11787/6M

Catalase reaction:

(2)H2O2 >> (2)H2O + O2: 2 hydrogen peroxide molecules converted to 2 water molecules and 1 oxygen

Chemically defined media

(Culture Media): Exact chemical composition is known

Chemical requirements /growth

1.Carbon, nitrogen, sulfur, and phosphorous 2.Trace elements 3. Organic growth factor 4.Oxygen

Physical requirements/growth

1.Temperature 2.pH 3.Osmotic pressure

• Carbon• Oxygen• Phosphorus (DNA, RNA, ATP)• Nitrogen (amino acids, proteins, nucleotides)• Hydrogen• Sulfur (amino acids, thiamine, biotin)

6 fundamental elements for life:chemical requirements

death phase

number of living cells declines

thioglycolate

combines with dissolved O2 to deplete O2 in medium....so bact doesn't grow. (reducing media)

Reducing media

(Culture Media): Contain chemicals that deplete oxygen in the medium; thioglycolate: combines with dissolved O2 to deplete O2 in medium; oxyrase: bacterial respiratory enzyme that combines O2 with H+to remove O2 by forming H2O

Complex media

(Culture Media): Extracts and digests of yeasts, meat, or plants, which composition varies slightly from batch to batch

Differential Media

(Culture Media): Make easy to distinguish colonies of different microbes, such as Staphylococcus and Streptococcus; Examples: EMB, MSA, and Blood agar

Selective Media

(Culture Media): Suppress unwanted microbes and encourage desired microbes; Dyes or salts inhibit bacterial growth. Examples: EMB and Mannitol Salt agar

Superoxide radical

(Why can oxygen be toxic?) O2 + e(-) >> O2(-) ox. plus neg. electrosn are converted to neg. oxygen

Hydrogen peroxide

(Why can oxygen be toxic?) O2(-) + e(-) + 2 H(+) >> H2O2 neg. oxy. plus neg. electron plus 2 posit. hydrogen molecules converted to hydrogen peroxide

Superoxide dismutase (SOD):

(microbe detoxify toxic oxygen species?) Removes superoxide radicals. • Reaction: (2)O2[-] + 2H[+] >> H2O2 + O2 : 2 neg. oxy + 2 pos. hydrogen molecules converted to hydrogen peroxide & oxy.

microareophile

2-10% oxygen; enzyme content (+SOD; +/-catalase>low levels)

Trace elements

Inorganic elements required in small amounts (copper, zinc, molybdenum, etc.)

colony-forming unit (CFU)

A colony is often called a

Bacteria have an acidic tolerance response (Salmonella and E. coli):

ATPase pumps protons out of the cell• acid shock and heat shock proteins are synthesized

Facultative Anaerobes

Both aerobic and anaerobic growth: greater growth in presence of oxygen. - Growth is best where most oxygen is present, but occurs throughout tube. - Presence of enzymes catalase and SOD allows toxic forms of oxygen to be neutralized; can use oxygen.(Escherichia coli)

a pure culture

contains only one species or strain

Agar

Complex polysaccharide extracted from marine red algae; Used as solidifying agent for culture media in Petri plates, slants, and deeps; Generally not metabolized by microbes; Liquefies at 100°C; Solidifies at ~40°C

complex media

Extracts and digests of yeasts, meat, or plants, which composition varies slightly from batch to batch ( selective media)

Peroxidase reaction:

H2O2 + (2)H[+] >> (2)H2O: hydrogen peroxide plus two pos. hydrogen molecules converted to 2 water molecules

plasmolysis

Hypertonic environments or an increase in salt or sugar cause

bacteria

Most ? grow between pH 6.5 and 7.5

Autotrophs

Nutritional Classification: use inorganic compounds as carbon source (need to be reduced)• examples: carbon dioxide (CO2)

• Heterotrophs

Nutritional Classification: use organic compounds as carbon source (already reduced)• examples: protein, carbohydrates, lipids

Microaerophiles

Only aerobic growth; oxygen required in low concentration. - Growth occurs only where a low concentration of oxygen has diffused into medium. - Produce lethal amounts of toxic forms of oxygen if exposed to normal atmospheric oxygen. (Borrelia burgdorferi) 2-10% O2

Obligate Aerobes

Only aerobic growth; oxygen required. - Growth occurs only where high concentrations of oxygen have diffused into the medium. - Presence of enzymes catalase and superoxide dismutase (SOD) allows toxic forms of oxygen to be neutralized; can use oxygen. (Mycobacterium tuberculosis)

Aerotolerant Anaerobes

Only anaerobic growth; but continues in presence of oxygen. - Growth occurs evenly; oxygen has no effect. - Presence of one enzyme, SOD, allows harmful forms of oxygen to be partially neutralized; tolerates oxygen. (Lactobacillus acidophilus)

Obligate Anaerobes

Only anaerobic growth; ceases in presence of oxygen. - Growth occurs only where there is no oxygen. - Lacks enzymes to neutralize harmful forms of oxygen; cannot tolerate oxygen. (Clostridium botulinum)

Catalase and Peroxidase:

Removes hydrogen peroxide

(halophilic)

Some bacteria ? can live in high concentration of salt

Carbon

Structural organic molecules, energy source

streak plate method

The ? is used to isolate pure cultures

superoxide radicals and hydrogen peroxide.

Why can oxygen be toxic? In the cell, during aerobic respiration, oxygen may be readily reduced by electrons, thus forming toxic (and extremely reactive) products:

Trace elements

Usually as enzyme cofactors 1.Copper (Superoxide dismutase) 2.Zinc (Alcohol Dehydrogenase) 3.Molybdenum (Nitrogenase)

Beta:

bacteria able to lyse red blood cells completely (S. pyogens)

Alpha

bacteria that are able to oxidize hemoglobin in green methemoglobin (S. pneumoniae)

Gamma:

bacteria that do not possess any hemolysin

oxyrase

bacterial respiratory enzyme that combines O2 with H+ to remove O2 by forming H2O

Optimum growth temperature

enzymatic reactions occurring at maximal possible rate

superoxide dismutase

enzyme that catalyzes the conversion of superoxide into hydrogen peroxide and oxygen; "oxygen free radicals are normally removed in our bodies by the ? enzymes"

catalase

enzyme that catalyzes the reduction of hydrogen peroxide.

log phase

exponential growth phase; rapid growth; shortest generation time possible

lag phase

following transfer to new media; adjustment period; very slow growth

Hyperthermophiles

grow at 55-113C (even 140C!)• found in geothermal areas of seafloor

Molds and yeasts

grow between pH 4 and 6

strict anaerobe

hates oxygen; enzyme content (-SOD; -catalase)

aerotolerant anaerobe

ignores oxygen; enzyme content (+SOD; -catalase)

a colony

is a population of cells arising from a single cell or spore or from a group of attached cells

Minimum growth temperature

membrane gelling; transport processes so slow that growth cannot occur

obligate aerobe

needs oxygen; enzyme content (+SOD; +catalase)

stationary phase

nutrients are limited; cell growth slows down; # of living cells= # of dying cells

generation/doubling time

population will double in number during a specific length of time

facultative anaerobe

prefers oxygen; enzyme content (+SOD; +catalase)

Maximum growth temperature

protein denaturation; collapse of the cytoplasmic membrane; thermal lysis

Extreme thermophiles

require high concentration of salt• high intracellular [K]+ or [Na]+ exchange proteins

Extreme or obligate halophiles

require high osmotic pressure (bacteria of the Red Sea)

Facultative halophiles (halotolerant)

tolerate high osmotic pressure

Psychrophiles

• Cold-loving• grow at 0-20C (optimal temperature: 15C or less)• found in Arctic and Antarctic habitats • cell membrane is rich of unsaturated fatty acids

Psychrotrophs

• Facultative psychrophiles• Tolerate cold temperatures• grow at 0-35C • major cause of food spoilage

Mesophiles

• grow at 15-45C • all human pathogens fall within this category

Thermophiles

• grow at 45-85C • Mostly bacteria and archaea, few protists and fungi• found in hot springs, compost piles

Thermophiles and Hyperthermophiles

• have heat-stable enzymes that function well at high temperature• proteins have highly organized hydrophobic interiors, hydrogen and non covalent bonds• high amount of proline and chaperone proteins• membrane are highly saturated, more branched, high molecular weight proteins• Archaea have membrane lipids with ether linkages