Physical Growth Factors

Temperature

An important physical factor in microbe growth as it affects protein structure and lipid fluidity, affects the 3D shape and functionality of proteins as well as the activity of enzymes. Lipid membranes are sensitive to this

Temperature Too Low

Cell membrane becomes too rigid or fragile and breaks

Metabolism slows down, growth slows down

Temperature Too High

Cell membrane melts and proteins unfold or lose their structure

Psychrophiles

Generally grow best below 15 degrees celsius and are found in cold water, ice and snowfield

These are unable to infect humans because they cannot thrive in our body temperature

Mesophiles

Generally grow best between 20-40 degrees celsius and are found in most environments

Bacteria that are pathogenic to humans fall into this category since our body temperature is 37 celsius and also within the mesophilic temperature range

Thermophiles/Hyperthermophiles

These bacteria can grow in extreme heat which includes the boiling waters of hot springs

Proteins avoid denaturing/damage as they often have extra hydrogen bonds and covalent bonds to maintain structure

Minimum Temperature

The lowest temperature the bacteria will grow at; growth is very slow at this temperature

Maximum Temperature

The highest temperature the bacteria will grow at; growth is very slow at this temperature

Optimum Temperature

The growth of the bacteria is the fastest at this temperature

H+ and OH- Ions

Changes in the concentration of these (pH) will interfere with hydrogen bonding that is responsible for protein folding

Neutrophiles

Microorganisms grow in a very narrow pH range that is close to neutral and are classified as this

Acidophiles

Thrive in environments with a pH less than 5

Alkalinophiles

Live in alkaline soils and water up to pH 11.5

Water

Requires this as a medium to dissolve nutrients and minerals, along with numerous metabolic reactions. Bacterial cell walls help retain this inside the cell

Osmosis

The movement of water across a semipermeable from high concentration to low concentration

Hypotonic Solution

Have a low solute concentration or high water concentration compared to the inside of the bacteria cell. Will fill up with water and burst

Cell wall helps cell from swelling

Hypertonic Solution

Has a high solute concentration or low water concentration compared to the inside of a bacteria cell. Will lose water and shrink

Biofilm

Slime like material in response to the presence of other microorganisms and factors in the environment. Allows the bacteria to adhere to the environment or bacteria, take in additional water and nutrients, and is a form of protection

This will make microorganisms more harmful or pathogenic, can have channels develop to transport water

Quorum Sensing Molecules

Secreted by bacteria and detects the presence of other individuals (population density). Will activate genes involved in the production of biofilms