Unit test 2

chapter 9,11,12

biofilm

In nature most microorganisms exist in communities attached to surfaces known as biofilms.

BINARY FISSION

Prokaryotes undergo asexual reproduction. This results in genetically identical daughter cells (unless a mutation occurs).

BACTERIAL GROWTH

The parental cell divides and gives rise to two daughter cells. Each of the daughter cells, in turn, divides, giving a total of four cells in the second generation and eight cells in the third generation. Each division doubles the number of cells.

DOUBLING TIME

The generation (doubling) time is the amount of time for the population to double in number. The equivalent of one round of division for every cell.

Doubling Factors

1. The type of species; different metabolic capabilities
2. The environmental conditions; the same type of organism in optimal vs suboptimal conditions will not reproduce at the same rate

Formal for generation time

Nn = N02^n

Nn is the number of cells at any generation n
N0 is the initial number of cells,
n is the number of generations.

BACTERIAL PHASES OF GROWTH

Log phase, stationary phase, Death or decline phase, Lag phase

Log phase

exponential increase in number of living bacterial cell; this is where we could be calculating our double time (party is popping there is plenty of water, food and o2)

Stationary Phase

Plateau in number of living bacterial cells: rate of cell division and death roughly equal (end of party vibes are there but can of off)

Death or decline Phase

Exponential decrease in number of living bacterial cells; no food and water (party is over)

Lag Phase

No increase in number of living bacterial cells

QUANTIFICATION METHODS

A number of methods may be used either by Direct counting of cells or colonies or Indirect calculations based on evidence of bacterial growth

Direct counting

Sitting down in front of a microscope and literally counting cells or counting colonies

Indirect

Do math and then can guess how many bacteria are in the Sample.

A PETROFF-HAUSSER CHAMBER

is gonna be a special slide that is going to have little grid in it; put the live sample in and going to count how many Organisms are in a square.

Quantitive Plate Count

a way for us to directly count how many

bacteria cure in a sample; we perform a serial delusion → Plate cur dilations on a TSA Look for Plates that have 20 to 200 Colonies, we count them (do math to figure now many organisms are in our sample

QUANTITATIVE PLATE COUNT TECHNIQUES

Instead of us directly Counting we are going to be counting Colony forming units

- one cell give rise to one Colony. (assuming)

-want to decrease the number of bacteria, a controlled amount every time

What is something we keep the same when doing quantitative plate count

Serial dilution happens before we do either of these methods (stay the same)

The pour plate method

empty petridish→

melted agar and sample →

Swirl → count

30-300 (counting range)

The spread plate method

TSA → Sample+

Plate

hockeystick→

set → done.

Counting range 20-200

MOST PROBABLE NUMBER

Doing this for samples that you know are numbers low bacterial numbers like (drinking water, Fresh water, food samples)

• Multiple tube MPN test

• Count positive tubes

Step for most probable numbers

• tubes have sort of lactose broth in them

• gonna have 15 tubes first five

Put lo ml next-five tube or 1000ml → Next five

100 wL Put in incubater for 24 hours looking for lactose fermentation (color change) originally yellow turn red

INDIRECT METHODS (turbidity)

-Turbidity the cloudiness that you see when ever you growing organisms in broth

- Indirect measuring absorber do it and figure out how many cells are there.

- Another way would be a centrifuge take my sample

→ Spin it down → it going to be an pellet

→ take the weight of that pellet & calculate how many organisms are in that sample(Calculating cell density)

Used to measure indirect

spectrophotometer is commonly used to measure the turbidity

• measuring how many light gets t the sensor

• cloudy whole bunch of bacteria blacking the light ; no bacteria light pass

Quorum sensing

how organisms within a biofilm Communicate

Auto inducers

How they communicate though releasing chemicals

gram positive organisms- Qs

Communicating with Short Peptide

gram negative organisms

Communicating via acetylated homoserine lactane

QUOR SENSING Purpose

Purpose of Communicating

• Food

• water

• attacking them

- endospore producers within that biofilm auto inducers will tell them to make endospore

BIOFILMS

made through bacteria living together through extra cellular matrix

- if the majority or organism are like hey we don’t got no food they are going to agree to move

-Depending on which one wins determines what happens

• majority win

• how many auto inducers are present wins

BIOFILMS AND HEALTH RISK

• 80% of human bacterial infections are caused by bacterial biofilms

hard to get rid of because of Quorum Sensing and auto inducers warn the other organism beneath them

• Plaque is on your teeth (biofilm)
  develop on implants

hyperthermophiles

extremely hot condition like volcanoes

psychrophiles

Colder temperatures

• decomposers

• Listeria monocytagenies

• anything that can live a refrigerator the temperature

• things that live in Soil

• Cold-loving organisms with optimal growth temperatures between 0°C and 15°C. They cannot survive at human body temperature.

Psychrotrophs

Prefer cooler temperatures (15°C to 30°C) but can grow at refrigeration temperatures (0°C to 7°C). While a few can cause food spoilage or foodborne illness (e.g., Listeria monocytogenes), they are not the general category for human pathogens.

simple term for doubling time

doubling time is the amount of time usually in minutes it takes for and bacteria population to double

Things that are going to be impact and doubling time

Environmental conditions and the metabolic capabilities of that organism; In perfect conditions meaning that we have everything right like temperature, ph , and carbon source

Obligate Aerobes

Obligate it is obligated to be in the presence of O2 to grow

Facultative Anaerobes

Tight band on top; growth is best where most oxygen is present but occurs throughout tube ( they don’t need it )

Obligate Anaerobes

Growth occurs only where there is no oxygen

Aerotolerant Anaerobes

No tight band on top, equal growth distribution through the whole tube (meaning it tolerates the presence of O2)

-ase

Enzyme

-Ose

sugar

Growing Anaerobes (no O2)

Brewer Jar- grows anaerobic organisms grow them in

Acidophiles

like low PH; range 1-5 Optimal is 3.5

Neutrophile

likes Neutral PH 5.5-8.5 Optimal 7

alkaliphile

like alkaline conditions basic 8-14; Optimal 9.5