Unit 2 Lecture 6

Environmental factors significantly influence the survival and growth of microorganisms.
Key factors include temperature, atmosphere (specifically oxygen levels), pH, and osmotic pressure (related to water availability and salinity).

Each organism has a minimum temperature (the lowest temperature it can live at), a maximum temperature (the highest temperature it can live at), and an optimal temperature (where it grows best).
Psychrophiles are microorganisms that prefer cold environments.
- Their minimum temperature can be as low as -5^
  \circ C (below freezing).
- Their maximum temperature is around 20^
  \circ C.
- Their optimal growth temperature is typically between 10^
  \circ C and 15^
  \circ C.
Mesophiles grow best at moderate temperatures, such as the normal body temperature of humans. These are important to monitor as many can be pathogenic. They can be beneficial, harmful, or neutral.

Metabolic processes involving oxygen can produce toxic byproducts within cells.
Catalase is an enzyme that detoxifies these metabolic oxygen byproducts by breaking them down, often forming water, which is not damaging.
- 2H2O2 \xrightarrow{Catalase} 2H2O + O2 (Though the chemical equation wasn't explicitly stated, the function of breaking down metabolic oxygen into water was described).
The ability to process toxic oxygen byproducts varies among microorganisms; some possess enzymes like catalase, while others do not.
Obligate aerobes are microorganisms that absolutely require oxygen for their growth and survival.

Acidophiles are organisms that thrive in extremely acidic environments.
- An example given is organisms that exist at a pH less than 1. These highly acidic conditions are often the only environments in which they can survive.

Osmosis is the process where water moves into or out of a cell across a semipermeable membrane (like the cell membrane) to achieve balance.
- Aquaporins are protein channels that facilitate the rapid movement of water across cell membranes.
Isotonic Environment: If the water concentration outside the cell is equal to that inside, water moves back and forth in equilibrium, and the cell maintains its normal shape and function.
Hypotonic Environment: If there is more water outside the cell than inside, water will flood into the single-celled organism, causing it to swell and potentially burst (lyse), destroying the cell.
Hypertonic Environment: If there is more water inside the cell than in its environment, water will leave the cell, causing it to shrink (crenate or undergo plasmolysis) and lose its ability to function.
Halophiles are organisms that live in environments with high salt content.
- Examples include microorganisms in the Dead Sea, the Great Salt Lake, or the Gulf, which differ from those found in freshwater lakes or rivers due to the significant difference in salinity.

Microorganisms are constantly competing for resources (e.g., nutrients, space) in their environments.
They have evolved various mechanisms to outcompete other species. When one organism successfully outcompetes another, the less competitive organism may die out.
Symbiotic relationships are interrelationships between living organisms that are beneficial to them but are not strictly required for their survival.
Biofilms are communities where microorganisms work together and share resources. In a biofilm, organisms cooperatively distribute tasks (e.g., "you take care of this, I'll take care of this") to collectively benefit the entire group, even though they live together as individuals.