BIOL 0510 Microbial Growth and Control

Prefix for sunlight (source of energy)

photo

Prefix for chemical (source of energy)

chemo

Prefix for inorganic (source of electrons)

litho

Prefix for organic (source of electrons)

organo

Prefix for CO2 (source of carbon)

autotroph

Prefix for organic (source of carbon)

heterotroph

Media

Nutrient source to support growth of bacteria

Media types

1) Macronutrients or micronutrients

2) Chemically defined media vs Complex

3) Agar (slant, liquid broth)

4) Selective or Differential

Chemically defined media

We know the exact molarity and type (ex. glucose salts agar)

Complex media

What we're using is nutricious but we don't know what it's made of (ex. beef broth)

Agar

Red seaweed that's a solidifying agent of broth

When should you use a slant (agar)?

-Takes less space + materials (1/3)

-Use if you don't need pure culture

Selective Media

selects for growth of some microorganism against others

Examples of Selective Media

EMB is selective for Gram-negative bacteria

In EMB (Eosin Methylene Blue) Agar, what inhibits the growth of Gram+ organisms?

Aniline dyes

Differential Media

Changes color/appearance of certain microbes

examples of differential media

EMB is differential for lactose fermentation

Is mannitol salt agar selective or differential?

both

Obligate Intracellular microbes

Require cell culture

Examples of obligate intracellular microbes

Chlamydiae (STDs), rickettsia (ticks)

Facultative intracellular Examples

Legionella (pneumonia) listeria (food borne illnesses) mycobacterium (TB)

facultative anaerobes

Bacteria that can adapt to either environment

Aerotolerant anaerobes

do not utilize oxygen but can survive and grow in its presence

Microaerophiles

They like a tiny bit of oxygen

Reducing media

Contain chemicals (thioglycolate or oxyrase) that combine O2

Heated to drive off O2

Anaerobic culture methods

1. reducing media

2. anaerobic jar

3. anaerobic chamber

Capnophiles

Microbes that require high CO2 conditions

Many body environments have lower oxygen and higher CO₂, which creates the ideal conditions for capnophilic bacteria to grow.

How to study capnophiles?

CO2 packet

Candle jar

Examples of capnophiles

Haemophilus influenza

Neisseria gonorrhoeae

Streptococcus pneumoniae

Binary Fission

A form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size

What ring forms at the middle of a cell and becomes smaller as the cell pinches into two (binary fission)?

FtsZ ring

What is an inhibitor of FtsZ?

Doxorubicin

Simple budding examples

Pirellula, Blastobacter

Budding from hyphae examples

Hyphomicrobium, Rhodomicrobium, Pedomicrobium

Cell division of stalked organism Example

Caulobacter

Types of unequal products of cell division

simple budding, budding from hyphae, cell division of stalked organism

Generation time

time that it takes one cell to divide into 2---dependent on bacteria and environment

Generation time of E.coli

20 min

Generation time of mycobacterium tuberculosis

20 hours

Phases of growth

lag phase, log phase, stationary phase, death phase

Lag phase

intense activity preparing for population growth, but no increase in population---FLAT

Log phase

The period of exponential growth of bacterial population.

Stationary phase

# of bacteria dying and doubling is equal

Death phase

population is decreasing at a logarithmic rate

continuous culture

A culture system in which new medium is continuously added to replace old medium.

Use if we want to continuously grow (log phase)

Batch culture

a liquid medium within a closed system

Ways to determine bacterial number

1) plate counts following dilutions (25-250: pour plate and spread plate)

2) Counting Bacteria by Membrane Filtration

3) Direct Microscopic Count

4) Turbidity

Pour plate method (plate counts)

1) Inoculate empty plate

2) Add melted nutrient agar

3) Swirl to mix

4) Colonies grow on and in solidified medium

The spread plate method (plate counts)

1) Inoculate plate containing solid medium

2) Spread inoculum over surface evnly

3) Colonies grow only on surface of medium

Plate count formula

(bacterial colonies counted x dilution factor)/volume plated

CFU

colony forming units

hemocytometer

Instrument used in counting blood cells--GRID

Turbidity can:

1). compare relative growth

2) be used to extrapolate bacterial number if a standard curve is made comparing the absorbance values vs the bacterial number is established

List of Microbial Control

1) Physical methods

2) Chemical methods

3) biological methods

4) mechanical removal methods

Sterile

absence of microbes, cells, acellular entities, and spores

Sepsis

refers to microbial contamination--life threatening disease where bacteria are released into the bloodstream

60% of death (last straw)

Asepsis/aseptic

absence of contamination

Antiseptic

antimicrobials applied to living tissue---germicide, bacteriostatic

Disinfectant

antimicrobials applied to objects (non-living)

The effectiveness of a treatment depends on...

- Number of microbes

- Environment (organic

matter, temperature, pH)

- Time of exposure

- Concentration

- Microbial characteristics

(endospores,

glycocalyx/capsule,

biofilm)

Types of heat sterilization

autoclave, dry heat, pasteurization, freezing

Psychrophile and an example

really cold extremophile

ex. polaromonas vacuolata

Desiccation

loss of water = microbes can't grow (dehydration blocks metabolism)

400 nm

Bacteria are more sensitive here---they see it as UV while it does nothing to us...maybe could be put into hospitals?

Microwaves

water molecule vibrates at such high rate that they puncture cells

What is sonication?

use of high-intensity sound waves (ultrasound) to disrupt or break microbial cells.

How do high wave amplitudes in sonic waves affect microbes?

Acoustic streaming

cavitation (bubble implosions due to microjets that rupture microbial cell walls)---

MICROBIAL INACTIVATION

How do low wave amplitudes in sonic waves affect microbes?

ONLY acoustic streaming

Microbial growth

How can sonic waves be beneficial?

Novel treatment of some cancers

Homogenizer

pump milk thru high pressure to pasteurize

High pressure _____ bacteria

kills

How to test if a substance is an effective disinfection?

Use-dilution test (rings placed in bacterial culture)

Disc diffusion test (papers and zone of inhibition--sensitive. No growth = not sensitive)

List of oxidizing agents

halogens, chlorine, iodine, bromine, and chlorine

dioxide

Oxidizing agents

High-level disinfectants and antiseptics.

Peroxides, ozone, and peracetic acid kill microbes by releasing reactive oxygen that chemically damages the enzymes the microbes need to live

Halogens

disinfectants and antiseptics used to kill microbes.

Iodine and chlorine

How does iodine kill microbes?

iodinates (modifies) proteins, disrupting protein synthesis and cell membranes.

What is the active antimicrobial compound in bleach?

Hypochlorous acid (HOCl)

Alcohols--what do they do and what are some examples?

Denature proteins, dissolves lipids

Ethanol, isopropanol

Heliobacter pylori

bacteria that causes most ulcers

What enzyme does Helicobacter pylori produce to survive in the stomach?

Urease

How does H. pylori survive stomach acid?

Urease produces ammonia (NH₃) which neutralizes stomach acid, raising the local pH.

What does a positive urease test look like? Negative?

Pink and yellow respectively

In osmosis, water moves from ______ to ______ solute concentration.

From low solute concentration → high solute concentration.

What happens to cells in an isotonic solution?

No net movement of water.Cell stays normal.

What happens in a hypertonic solution?

Water moves out of the cell → cell shrinks. This is called plasmolysis.

Most end up like this---death of cell

What happens in a hypotonic solution?

Water moves into the cell → cell swells.Cell wall prevents bursting.

Why can bacteria survive hypotonic environments?

Their cell wall prevents lysis (bursting).

Bdellovibrio

Predatory bacteria that attack other bacteria like E.coli, salmonella, shigella (food borne illnesses)

Trichoderma

predator of soil fungi

Qualities of Phage therapy

Highly specific

Self limiting

HEPA (filtration)

removes

microbes >0.3 µm

Membrane filtration (Filtration)

removes microbes

>0.22 µm