Applied Microbiology Lecture Notes - Flashcards

Why are some bacteria better adapted than others to survive at higher temperatures?
Certain bacteria, known as extremophiles, have evolved unique proteins and enzymes that maintain functionality at high temperatures. These adaptations include thermally stable enzymes, modified cell membranes with saturated fatty acids to maintain stability, and the ability to repair heat-induced damage.

How do bacteria respond to changes in pH?
Bacteria respond to changes in pH by employing proton pumps to regulate their internal pH, ensuring that metabolic processes can continue. Depending on their type, they may thrive in acidic (acidophiles), neutral (neutrophiles), or alkaline (alkaliphiles) environments, adjusting their metabolic pathways and enzymes accordingly to cope with the external pH changes.

What happens when a bacterium is put into hypotonic solution?
When a bacterium is placed in a hypotonic solution, water enters the cell due to osmotic pressure. If excessive, this can lead to cell lysis, as the internal pressure increases and the cell membrane may burst due to the influx of water.

What happens when a bacterium is put into hypertonic solution?
In a hypertonic solution, water moves out of the bacterium, causing it to shrink and potentially undergo plasmolysis. This dehydration inhibits cellular function and growth, as essential metabolic processes are disrupted due to the reduced internal volume.

What is a halophile?
Halophiles are a specific group of bacteria that thrive in high salt concentrations. They have adapted mechanisms to manage osmotic pressure and maintain cellular integrity, often utilizing specialized proteins and metabolic pathways tailored to saline environments.

Label the following containers:
Each container should be labeled according to the type of solution and bacterial growth conditions being tested, such as "Hypotonic Solution - Water + Bacteria," "Isotonic Solution - Equal Concentration + Bacteria," and "Hypertonic Solution - Saltwater + Bacteria."

Why does UV kill bacteria?
Ultraviolet (UV) light kills bacteria by damaging their DNA. It induces the formation of thymine dimers, which can lead to mutations that interfere with replication and transcription, ultimately resulting in cellular death if the damage is irreparable.

What is the typical growth curve for bacteria?
The typical growth curve for bacteria consists of four phases:

1. Lag Phase: where bacteria acclimatize to their environment;

2. Log Phase: characterized by rapid cell division;

3. Stationary Phase: growth levels off as resources become limited;

4. Death Phase: where the number of dying cells exceeds those that are dividing due to lack of nutrients.

How can we measure bacterial growth?
Bacterial growth can be measured through various methods including direct counting using counting chambers, serial dilutions followed by colony-forming units (CFU) calculations, and turbidity measurements using optical density assessments.

What is a biofilm and how is it formed?
A biofilm is a complex community of microorganisms attached to a surface, embedded in a self-produced extracellular polymeric substance (EPS). It forms through a series of steps: initial attachment, maturation into a three-dimensional structure, and eventual detachment of cells to colonize new areas. Biofilms exhibit heterogeneity, where different species may reside and interact, impacting their overall functionality.