Chapter 4 Flashcards
Two types of asexual reproduction in microbes
Binary fission and budding
Microbial growth
How often they reproduce. Not an increase in size of the individual cell
During binary fission
The bacteria cell doubled in size. Replicated chromosome. Two chromosomes attached to separate sites on the plasma membrane. Cell wall forms between the chromosomes and separates the cells producing two daughter cells.
Binary fission
Primitive form of cell division that does not use a spindle fiber apparatus. A spindle fiber apparatus made of protein filaments that move chromosomes during cell division. Bacteria do not have the structures.
Budding
A few bacteria and some eukaryotes (including yeast) may also replicate by budding. The cell forms a bubble-like growth that enlarges and separates from the parent cell
Phases of growth
Microbial lab culture typically passes through four distinct sequential phases of growth: lag phase, exponential phase, stationary phase, and death phase
Lag phase
Preparing to grow; gearing up for cell division. There’ll be no perceivable change in the number of bacteria lot of chemical reactions are taking place so when the light “turns green” they can reproduce as quickly as possible.
Exponential phase
Cell numbers increase exponentially. The phase is limited and will last 4 to 10 hours. This phase quickly uses up most of the nutrients found in the medium. Cells in this phase are very virulent, easily cause infection or disease but the cells are most susceptible to antibiotics
Stationary phase
Number of cells don't increase, but changes within cells occur. The cells become smaller and begin producing structures that help them become more resistant and are able to survive. Structures formed: Glycocalyx Endo spores Cytoplasmic inclusions
Antibiotics in the stationary phase
Antibiotics is this phase are not very effective. You must clean, drain, cut the abscess or growth away this will take the nutrients and bacteria away and fresh nutrients come in causing the leftover bacteria to be very vulnerable, more bacteria will come in and will also bring in antibiotics
Termination phase
Cells begin to die out. Death occurs exponentially, but at a low rate. Death occurs because cells have depleted intracellular ATP reserves.
What is generation time?
Length of time it takes one cell to divide into two cells. Varies between bacteria.
Why can microbes exist in many environments?
Because they are small, easily dispersed, need only small quantities of nutrients, Are diverse in their nutritional requirements.
Temperature
Bacteria can usually grow over a range of temperatures. Minimum temperature, maximum temperature, and optimum temperature
Minimum temperature
Is the lowest temperature that will permit growth and metabolism but usually at a very slow pace. Very cold temperatures do not usually denature proteins or destroy microorganisms.
Maximum temperature
Maximum temperature that permits growth and metabolism but again usually at very slow rates. Going above maximum temperatures enzymes will become denatured and metabolism will stop which destroys the cell
Optimum temperature
Typically cover the small range in which organisms metabolic processes and growth are the fastest.
Psychrophiles (cold living)
Will grow from -5°C to 20°C. they are responsible for spoiling of refrigerated and even some frozen food
Mesophiles (middle-loving)
Will grow from 20°C to 50°C. Common to be found in humans because our temperature is around 37°C
Thermophiles (heat loving)
Will grow in temperatures above 50°C to 80°C. Found in natural Hot Springs, volcanic vents etc
Hyperthermophiles
Will grow in temperatures above 80°C. Found in compost heaps and in boiling hot springs
Why does a pH of a fluid matter for any living organism?
Because enzymes work best at certain pHs
