Microbiology - Exam 2

Sepsis

Indicates bacterial contamination

Asepsis

Indicates absence of significant contamination

Antimicrobial agents that end in -cidal

Kills microorganisms

Antimicrobial agents that end in -static

Inhibit microbial growth

Sterilize

Destroying all microbes even endospores but not infectious prions (autoclave)

Disinfectant

Kills microbes but not endospores, at least not all (bleach)

Sanitize

Reduce microbial numbers, usually food/drink utensils, but not sterilize (industrialized dish washers)

Antiseptic

Kills/inhibits microbial growth but it’s nontoxic enough to be applied to living tissues (hydrogen peroxide/hand sanitizer - inhibits more than kills)

Degermation

The physical removal of microbes by primarily mechanical means (injection sites)

Heat steriization

Most common technique to control microbial growth

Moist heat works better than dry heat (humidity tends to help penetrate cells)

Thermal death time (TDH)

A test used for heat sterilization to measure the amount of time it takes to kill all cells at a given temperature

Determined by decimal reduction time = the amount time it takes to kill 90% of microbe population

(Exponent + 1) x DRT = TDT

Autoclave

A sealed device that used steam under pressure

The pressure prevents liquids/water from evaporating, enabling it to reach temperatures above 100°C and their boiling point to kill endospores/thermophiles

The temperature is what’s actually killing the microbes, not the pressure

Pasteurization

A process that uses precisely controlled heat to reduce (not kill) microbial growth/load in a sensitive liquid

Radiation

Used for sterilization

High energy light targets specific spots

Damages DNA

UV

A form of radiation that decontaminates surfaces, but it needs direct contact (ex-can’t go through glass)

Works by causing formation of thymine dimers, bonds in between thymine nucleotides that stop DNA/RNA polymerase = no translation/transcription

Darker skin tones have more pigment that gives them protection

Filters

HEPA filters

Membrane filters

Collect microbes that are larger than the pore size of the filter

HEPA = filter microbes >300nm (for viruses, not as effective)

Membrane filters = filters liquids

Minimum inhibitory concentration (MIC)

The smallest amount of agent/antibody needed to inhibit growth of microbe

Bigger zone = more susceptible bacteria = generally lower MIC = less antibiotic needed to inhibit growth

Culture medias

Nutrient solutions for laboratory growth (typically sterilized in autoclave)

Chemical constituents in culture medias

Defined media: exact chemical composition known

Complex: digests of microbial, animal, or plant products (yeast/meat extracts), where the exact amount of individual components are unknown (there’s a large excess of multiple components)

Physical nature of culture medias

Solid agar: provides a large surface area for growth

Semi-solid agar: has less agar and is useful for identifying motility

Liquid medium: no agar that supports suspended growth

Types of functions for culture medias

Enriched medias: complex mediums plus highly nutritious material = everything grows

Selective medias: inhibit some microbes while allowing others to grow

Differential medias: contain a dye that changes color with a particular metabolic reaction

Fastidious

Bacteria that need a lot of nutrients to grow

Mannitol salt agar

Shows selective (via salt) and differential effects (via color)

How do bacteria reproduce?

Binary fission

Generation/doubling time is the time for cell replication

Bacterial growth curve

LAG = getting used to/adapting to environment

LOG = rapidly growing in a short amount of time; ↑nutrients to support replication (replicating faster than dying)

Stationary = ↑wastes, ↓nutrients; endospores can form in this phase (dying and replicating at same rate)

Death = ↑wastes, no nutrients; endospores can form in this phase (dying faster than replicating)

Psychro

Cold

Meso

Intermediate

Thermo

Heat/hot

Hyper

High/excess

Hypo

Low/under

Halo

Salt

Phile

Loving

Osmo

Push

Xero

Dry

Macro

Large

Micro

Small

Obligate

Must

Faculative

Optional

Aero

Air

A/an

Not

How does temperature affect microbes/enzymes?

Lower temperatures slow transport and enzymes (typical range = <40°C)

Psychrophiles

Low, found in cold environments (<15°C)

What are some cold adaptations?

Enzymes that work optimally at lower temperatures

Mesophiles

Midrange, most likely to grown on humans (20-45°C)

Thermophiles

High, found in hot environments (45-80°C)

What are some heat adaptations?

Cytoplasmic/cellular membrane modifications for heat stability

Hyperthermophiles

Found in extremely hot environments like hot springs or deep see hydrothermal vents (>80°C)

How does pH affect microbes/enzymes?

pH changes can disrupt membranes and alter transport protiens/enzymes

Neutrophile

Neutral environments

ph = 7

Acidophile

Acidic environment

pH = ↓7

Alkaliphile

Basic environments

pH = ↑7

How does osmolarity affect microbes/enzymes?

Solute concentration (salt/sugar) in water

High solute concentrations inhibit microbial growth (explains salt as preservative)

Non-halophiles

Hate salt

Halotolerant

Tolerate added solutes but usually grow best without it (skin)

Halophiles

Love salt (sea-water)

Extreme halophiles

Love extremely salty environments

Osmophiles

Loves sugar

Xerophiles

Hate water

Love dry environments

Catalyse

An enzyme that breaks down toxins released by O2

What type is this bacterias O2 preference?

Microaerophile (ocean)

Catalyse

What type is this bacterias O2 preference?

Obligate anaerobe (gut)

Respiration: anaerobic

ECT: Fe/etc.

No catalyse because no O2

What type is this bacterias O2 preference?

Aerotolerant (strep)

Fermentation

Catalyse

What type is this bacterias O2 preference?

Obligate aerobe (skin)

Respiration: aerobic

ECT: O2

Catalyse

What type is this bacterias O2 preference?

Facultative anaerobe (gut)

Respiration: anaerobic or aerobic

More energy/ATP = more O2

Catalyse

Biofilms

Collections of microorganisms that attach to inert/living surfaces

Surround by a sugar glycocalyx

Planktonic growth

Suspended in liquid (swimming/moving around)

Sessile growth

Attached to a solid surface (stuck)

How do biofilms form?

Planktonic cells move towards surfaces via flagella and attach via fimbriae to produce a glycocalyx

More baceria join using pili to move onto the surface

Cells can detach into liquid and start a new biofilm

What are some advantages of biofilms?

Their sugary glycocalyx provides protection

Resists phagocytosis

Collects nutrients

Resists penetration of toxic molecules (antibiotics)

What are the steps in microbial evolution?

1. Mutation (rapid)

2. Transformation (environmental DNA)

3. Transduction (virus carries DNA)

4. Conjugation (direct contact0

Mutation

During replication, DNA polymerase makes mistakes while copying parental DNA

Transformation

Microbes take DNA from the environment/free floating DNA from dead bacteria and makes it a part of its own chromosome

Transduction (lysogenic cycle)

A virus takes specific bacterial DNA near where it was attached and carries it to another bacterium

Transduction (lytic cycle)

A virus accidentally picks up random bacterial DNA and carries it to another bacterium

Essentially, a virus packages a dead bacteria’s DNA instead of viral DNA

Conjugation

Transfer of DNA from one bacterium to another requiring cell-to-cell contact (via pili) and F-factor

F-

No F-factor

F+

F-factor located in a plasmid

HFR

F-factor located in the actual chromosome

What happens when F+ —→ F-

Pili grab, fuse, replicate, and split

Plasmid with F-factor is copied by DNA polymerase and can go infect another F- cell

START: F+/F-

END: F+/F+

What happens when HFR ——> F-

Pili grab, fuse, replicate, and split

START: HFR/F-

END: HFR, F- with ½ of F-Factor

Builds a level of resistance/overall beneficial function

Trp

Required for living

Builds tryptophan

Lac

Not required for living
Breaks down lactose

Where does RNA polymerase bind?

Promoter

Where does a repressor bind?

Operator to inhibit transcription

Inducible operon

Metabolite binds to repressor to keep it from binding to the operator

—LAC—

When Lac levels are high, Lac binds to repressor so transcription/translation can occur to break down lactose

Repressible operon

Metabolite binds to the repressor so it binds to the operator

—-TRP—

When Trp levels are high, Trp binds to the repressor so transcription/translation are STOPPED = lowering Trp levels

↑Trp

Trp bound to repressor = repressor on operator = blocked transcription/translation

↓Trp

No Trp to bind to repressor = repressor doesn’t bind to operator = transcription/translation occur

↑Lac

Lac bound to repressor = repressor isn’t bound to operator = transcription/translation occur

↓Lac

No Lac to bind to repressor = repressor binds to operator = blocked transcription/translation

Describe what happens with ↓Lac ↓Glucose

cAMP binds to the cap site on a Lac operon and increases RNA polymerase binding causing low levels of transcription/translation

What’s involved in DNA replication?

1. Helicase: unzips DNA

2. Topoisomerase: binds at region ahead of helicase to prevent supercoiling

3. DNA polymerase: adds complementary nucleotides

4. DNA ligase: seals any gaps between DNA fragments

What’s transcription and what’s involved?

Transcription: creates a single stranded mRNA copy of DNA for protein production

RNA polymerase: used to make RNA out of DNA

What’s the difference between DNA polymerase and RNA polymerase

DNA polymerase uses DNA to make DNA

RNA polymerase uses DNA to make RNA

How does RNA polymerase work?

Binds to the promotor and opens up the double stranded DNA

Makes complementary RNA copy of one DNA strand (nucleotides)

Stops at the terminator which then releases the mRNA

What’s translation and what’s involved?

Translation: uses mRNA to make protein at a ribosome

1. Ribosomes: site of protein synthesis

2. mRNA: carries instructions out of nucleus into ribosomes

3. tRNA: has anticodons with amino acids attached

4. rRNA: provides structural and catalytic components

What’s the sequence of translation?

1. Initiation: ribosomes scans mRNA dor AUG start sequence

2. Elongation: ribosomes read codons the tRNAs attached to amino acids bind forming a chain of amino acids

3. Termination: stop codon is reached and the protein is released

Semiconservative replication

One original DNA strand from the parent and one that was newly generated

Polyribosomes

Multiple ribosomes attached to one mRNA

Can transcription and translation occur at the same time in bacteria?

Yes, it allows for rapid protein production