Microbiology test 2 - Dr. Collins

Macronutrients

C, O, H, N, S, P (found in organic molecules such as proteins, lipids, carbs, and nucleic acids)

K, Ca, Mg, and Fe (cations and serve in variety of roles inc. enzymes, biosynthesis)

Required in relatively large amounts

Micronutrients

Mn, Zn, Co, Mo, Ni, Cu

Required in trace amounts

Often supplied in water or in media components

Serve as enzymes and cofactors

What is the backbone of all organic components present in a cell?

Carbon

Where are hydrogen and oxygen found? (besides water, u stoopid)

They are in organic molecules

What role do electrons play?

They help w/ energy production and reduction of CO2 to form organic molecules

What are the requirements for carbon, hydrogen, and oxygen?

Often satisfied together (carbon source often provides H, O, and electrons)

Heterotrophs

Use organic molecules as carbon sources which often also serve as energy source

Can use a variety of carbon sources

Autotrophs

Use carbon dioxide as their sole or principal carbon source

Must obtain energy from other sources

Growth factors

Organic compounds

Essential cell components that the cell can NOT synthesize

Must be supplied by environment if cell is to survive and reproduce

Classes of growth factors

Amino acids (protein synthesis)

Pruines and pyrimidines (nucleic acid synthesis)

Vitamins (are enzyme cofactors)

Heme

Microbial production of growth factors

microorganisms can synthesize a bunch, on a large scale industrial production (specifically vitamins and stuff)

What are some media components?

Peptones (protein hydrolysates prepared by partial digestion of various protein sources)

Extracts (aqueous extracts, usually of beef or yeast)

Agar (sulfated polysaccharide used to solidify liquid media; most microorganisms cant degrade it)

Selective media

Favor the growth of some microorganisms and inhibit growth of others (see: MacConkey agar - selects for gram negative bacteria)

Differential media

Distinguish between different groups of microorganisms based on their biological characteristics (ex. blood agar - hemolytic v non hemolytic bacteria)

Reproductive strategies for microorganisms

Reproductive strats of eukaryotic microbes = asexual and sexual, haploid or diploid

Bacteria and archea = haploid only, asexual [binary fission, budding, filamentous]. All must replicate and segregate to the genome prior to division

Binary Fission

Bacterial cell cycle

It’s a sequence of events from formation of new cell through the next cell division (most bacteria divide by binary fission)

What are the two pathways that function during bacterial cell cycle?

DNA replication and partition

Cytokinesis

What’s the shape of most bacterial chromosomes?

Circular

Whats the chromosome “terminus”?

The site at which replication is terminated, it’s located opposite of the origin

What’s the chromosome “single origin of replication”?

Site at which replication begins

What’s the chromosome “replisome”?

Group of proteins needed for DNA synthesis

Cellular growth

Increase in cellular constituents that may result in:

-Increase in cell NUMBER

-increase in cell SIZE

Bacterial growth

Population growth (NOT growth of indvidual cells)

What is the growth curve?

Observed when microorganisms are cultivated in batch culture

Usually plotted as logarithm of cell number v time

What are the 4 distinct phases of a growth curve?

Lag, exponential, stationary, senescence (death)

What does a growth curve look like?

Lag phase of growth

Cell synthesizing new components (to replenish spent materials or to adapt to new medium)

Varies in length (can even be absent)

Exponential phase (or log phase) of growth

Rate of growth and division is constant and maximal (balanced growth, cellular constituents manufactured at constant rates relative to eachother)

Population is most uniform in terms of chemical and physical properties during this time

Whats unbalanced growth?

When the rates of synthesis of cell components vary relative to eachother

Can occur when there’s a change in nutrient levels or environmental conditions

Stationary phase in cell growth

Active cells stop reproducing or reproductive rate is balanced by death rate so total number of viable cells remains constant

What are possible reasons for stationary phase?

Nutrient limitation

Limited oxygen availability

Toxic waste accumulation

Critical population density reached

Senescence (death) phase

Two alternative hypotheses

-Cells are Viable But Not Culturable (VBNC) [cells alive, but dormant, capable of new growth when conditions are right]

-Programmed cell death [fraction of the population genetically programmed to die]

What happens if there’s a prolonged decline in cell growth?

Bacterial population continually adapts

Process marked by successive waves of genetically distinct variants

Natural selection occurs

What is generation (doubling) time?

How long it takes for a population to double in size

Varies on the specific microorganism

Can be anywhere from 10 mins to several days

Extremophiles

Organisms that grow under harsh conditions that would kill most other organisms

Hypotonic solution

Lower osmotic concentration (lots of h2o, not a lot of solutes)

-Water enters the cell

-Cell walls may burst

Hypertonic solution

Higher osmotic concentration (not a lot of h2o, high solutes tho)

-Water leaves the cell

-Membrane shrinks from the cell wall (plasmolysis)

Halophiles

grow best at solutions with >.2M NaCl

Extreme Halophiles

Grow best at NaCl concentrations of >2M

Cell wall, proteins, and plasma membrane NEED high salt to maintain stability and activity

pH

Measure of the relative acidity of a solution

-log (H+ concentration)

Acidophiles

Growth optimum between pH 0 and pH 5.5

Neutrophiles

Growth optimal between pH 5.5 and pH 7

Alkalophiles

Growth optimum between pH 8.5 and 11.5

What pH do most microbes have?

They maintain an internal pH close to neutrality

What’s the cell’s acidic tolerance response?

Pump protons out of the cell

Some synthesize acid and head shock proteins that protect proteins

How do most microorganisms change the pH of their habitat?

They pump out acidic or basic waste products

Can microbes regulate their own temp?

No, they cannot regulate it

Do enzymes have an optimal temp at which they function best?

Yes, they do have an optimal temp

Psychrophiles

0°C-20°C

Psychrotrophs

0°C-35°C

Mesophiles

20°C-45°C

Thermophiles

55°C - 85°C

Hyperthermophiles

85°C-113°C

Aerobe

Grows in the presence of atmospheric oxygen (20% O2)

Obligate aerobe

Requires O2

Anaerobe

Grows in the absence of O2

Obligate anaerobe

killed in the presence of O2

Microaerophiles

Requires 2-10% O2

Facultative anaerobes

Don’t NEED O2, but grow best w/ it

Aerotolerant anaerobes

Grow with or without O2

What’s the basis for different oxygen sensitivities?

Oxygen easily reduced to toxic reactive oxygen species (ROS)

-Superoxide ratical (O2-)

-Hydrogen peroxide (H2O2)

-Hydroxyl radical (HO)

Aerobes produce protective enzymes

-Superoxide Dismutase (SOD)

-catalase

-peroxidase

All strict anaerobic microorganisms lack or have very low quantities of

Suerpoxide dismutase (SOD)

Catalase

These microbes cannot tolerate O2, and must be grown without O2

Barotolerant

Adversely affected by increased pressure, but not as severely as nontolerant oraganisms

Barophilic (peizophilic) organisms

Require or grow more rapidly in the presence of increased pressure

Change membrane fatty acids to adapt to high pressures

Microbial environments are

complex, constantly changing, often contain low nutrient concentrations and may expose a microorganism to overlapping gradients of nutrients and environmental factors

How do most microbes grow best?

Attached to surfaces (sessile) as opposed to free floating (planktonic)

How do microorganims in a biofilm communicate with eachother?

They send “words” (quorum) to eachother via ____

What’s a mature biofilm?

A complex, dynamic community of microorganisms

What’s heterogeneity?

Differences in metabolic activity and locations of microbes

How do biofilms form?

Microbes reversibly attach to conditioned surface and release polysaccharides, proteins, and DNA to form the extracellular polymeric substance (EPS)

Additional polymers are produced as microbes reproduce and biofilm matures

What does the EPS protect the microbes from?

It protects them from harmful agents like UV light, antibiotics, and antimicrobials

Can biofilms form on medical devices? if so, is it bad?

Yes they can, yes its very bad when its on an implant or something

Cell to cell communication w/ gram positive cells

Produce small proteins that increase in concentration as microbes replicate and convert a microbe to a competent state

DNA uptake occurs, bacteriocins are released

Ex. S. Pneumoniae

Cell to cell communication w/ gram negative cells

AHL is an autoinducer molecule produced by many gram negative organisms

It diffuses across the plasma membrane, and once inside the cell it induces expression of target genes that regulate a variety of functions

Vibrio Cholerae

Gram negative

curved-rod shape

1 or more flagella

quorum-sensing

Growth conditions for vibrio cholerae

Facultative anaerobe (Don’t NEED O2, but grow best w/ it)

Marine and estuarine environments

Intestinal contents of plankton of fresh, brackish, and salt water

How is cholera transmitted?

From person to person

Ingestion of contaminated food or water (bathing, playing, and related activities in water contaminated by sewage)

How much bacteria of vibrio cholrae will cause cholera in a healthy person?

10^6 bacteria

What people are more susceptible to getting cholera?

People with type O blood

People with type A are more susceptible than type B, but less than O

People w/ a weakened immune system

People w/ decreased gastric ability

the malnourished

What blood type is the least susceptible to Cholera?

type AB

Where do vibrio cholerae multiply?

In the mucosal surface of the small intestine, where they produce a toxin “choleragen”

What does the toxin “choleragen”, produced by vibrio cholerae, do?

Releases fluids and electrolytes into the intestinal lumen

In several hours to 3 days, explosive, watery diarrhea with vomiting and abdominal pain

How is cholera diagnosed?

Stool and swab samples in acute stage of the disease

Direct microscopy unreliable

How is cholera treated?

Water and electrolyte replacement (oral rehydration effective and safe, intravenous rehydration in severe cases)

Antibiotic therapy

How is cholera prevented?

Sanitation practices (advance water treatment and sanitation systems)

Vaccine (used outside US, short lived in efficacy, and not recommended by the CDC)

What are the two parts of cell metabolism?

Catabolism and anabolism

Catabolic pathways…

…break down macromolecules into simple component parts, releasing energy in the process

Anabolic pathways…

…build up macromolecules by combining simpler molecules, using energy in the process

Catabolistic reactions are also called

Fueling or energy-conserving reactions

What do catabolistic reactions offer?

Provide ready source or reducing power (electrons)

Generate precursors for biosynthesis

What do anabolic reactions offer?

The synthesis of complex organic molecules from simpler ones

Require energy from fueling reactions (catabolic reactions)

What are the 3 types of work in a microbial cell?

Chemical work

Transport work

Mechanical work

What is chemical work in a microbial cell?

Synthesis of complex molecules

What is transport work in a microbial cell?

Take up of nutrients, elimination of wastes, and maintenance of ion balances

What is mechanical work in a microbial cell?

Cell motility (movement) and movement of structures within cells

How do microorganisms get nitrogen from environment?

They can decompose protein material

Some bacteria use NH4+ or NO3– to get N from organic material

A few bacteria use N2 in nitrogen fixation

Exergonic Reaction

Reaction happens spontaneously

If A+B ⇌ C+D, then

Keq = [C][D] / [A][B] > 1.0

Endogonic Reaction

Reaction does not happen spontaneously

If A+B ⇌ C+D, then

Keq = [C][D] / [A][B] < 1.0

What, out of glycolysis, the krebs cycle, or the ETC, makes the most ATP?

The ETC makes the most ATP, and specifically oxidative phosphorylation