Beginning part of the bacterial growth curve

The time that is needed to kick start division

May or may not be in the curve

When binary fission begins

Bacteria grows exponentially

When the culture runs into problems

Lack of nutrients, build up of waste, less O₂ (respiratory)

For every time a cell divides another cell dies

Survival mode

More cells dying than dividing

Culture population goes down

However it is over a long period of time (months)

Based on binary fission

On a per hour basis

Only based on when the bacteria are in the exponential phase

Generation Time?

A way that you can look at the "per hour" growth constant

A "generation per hour"

Produced based on their primary metabolism

Produced during the exponential phase

(Ethanol, Carbon Dioxide, Lactic Acid)

Produced during stationary phase

Convert primary metabolism to secondary metabolism

Endospore, Antibiotics

Bacteria produce toxins to kill off others and we steal it for antibiotics if it isn't toxic to us 

During death phase there are many different communities of bacteria. When one bacteria lyse or die, another community uses the nutrients from lysis. Why the death phase is longer and they are called "persister" cells.

Sort of like bacteria canabolism

In a flask, growth stops when...

Waste builds up

Nutrients run out

 Cells become too crowded to get oxygen

Growth factor is determined by the bacteria (how well they harvest nutrients)

It is in a chemostat

Nutrients continually added at slow rates

Trickle out waste w/valve (along with some culture)

Bacteria perpetually in exponential phase

Growth rate determined by nutrient resupply rate (the researcher)

A device that researchers use to grown a continuous culture

They are able to add nutrients at a controlled rate and get rid of excess waste as needed so bacteria are always in the exponential phase.

Where you count each individual cell

Counts living and dead cells

Allows counts of all cells within a grid square of known size.

It has fixed volume in place of where you put the culture so you should be able to get a count of the number of bacteria per mL

Doesn't work for motile bacteria because they swim away

When you use a vacuum and electrical current to count the number of cells in a culture.

When the cell gets sucked into a hole, current flow stops so you can count how many there are based on how many times the current flow stops.

Cannot differentiate between living and dead cells

A method to count the number of bacteria in a diluted solution by pouring in the bacteria first, then pouring in the agar into the petri disk

Bacteria grow in 3D

Used for large volumes of liquid

Pour liquid through the membrane filter and collect the bacteria in the filter

You can then count the number of bacteria on the filter paper left over

A statistical method based on the +/- growth in large number of tubes at 3 different dilutions

Based on the statistics performed in the past you can then use the "most probable number" as a way to count the bacteria

 Not a reliable method of counting

more cells = more light scattered = higher OD

barely any scatter ~10⁷ cells/mL

Need to correlate OD with cell number for a give species

You can determine if bacteria are present and how many there are based on how much acid they produce

The acid from fermentation you can measure with a pH electrode

So if it produces a current it can tell you how many bacteria there are

Upside down tube to collect gas at the top

Shows you gas that is being produced by bacteria due to fermentation

The amount of gas produced is proportional to the number of bacteria

An enzyme that reacts with ATP

It glows if ATP present

This test of putting luciferase in a test tube just tells you if bacteria are present or not