Ex. 9 - Bacterial Endospores
_____ are very resistant to environmental stresses that kill bacterial cells, resistant to extreme desiccation, high temperature, ionizing radiation, and penetration by chemicals
endospores
The absence of _____ does not necessarily mean that the unknown bacterium is not one of the endospore forming genera
endospores - can mean it is too young or there is not the correct nutrition for endospore formation
The great resistance of the mature prokaryotic endospore to the penetration of chemicals is a property that can be used ______
for detecting them
The mature endospore has a _____ than the surrounding sporangium or vegetative cells. This property makes the endospores look very ____
greater density (mass per unit vol.); bright (refractile)
The most significant endospore characteristic is its resistance to ______; this is believed to be related to the dry, crystalline-like state of the mature endospore
high temperatures
The vegetative cells of Bacillus and Clostridium are only moderately resistant to ____, but the spores are extremely resistant
ionizing radiation
Endospores and free spores sizes are ____ enough to be seen with _____ microscope
large; a light microscope
You can quick freeze an endospore preparation by immersing a glass vial containing spore suspension in _______
liquid nitrogen and then freeze-dry (lyphophilize) the frozen block
You can force a dye to penetrate into a spore by raising the dye temperature to 100 deg C, like a dye called _____. However, the dye easily penetrates bacterial cells
malachite green
Mature endospores that are in a dry, crystalline state totally lack _____ so they resist drying by the environment
metabolic activity
To overcome problem of difficulty seeing endospore sporangium is by using a _____ microscope, which accentuates the differences in density between sporangium and ______, increasing the contrast between them
phase-contrast; suspending fluid
Most genera of bacteria that form endospores are _____ and _____
rod-shaped and gram-positive
It is difficult to see the surrounding sporangium of the endospore with a brightfield microscope because the sporangium density is ____ to that of suspending fluid
similar
After you perform a gram stain, cells with endospores appear similar to those that have been stained with ____
simple basic dyes - because all dyes used for gram stain are basic dyes
The phase-contrast microscope is helpful because _____ isnt necessary. You only need to prepare a wet mount to observe the cells in their growth medium. This avoids _____
staining; shrinking and distorting the cells during staining
Bacteria produce spores only at the ____ of exponential or rapid growth and also need _____
the end; need the correct nutrients
The only advantage of a Gram stain vs simple stain is you can check for two things at once:
the presence of endospores and the gram characteristics of the sporangium/vegetative cell
Once a mature endospore is formed, the rest of the cell surrounding it is called
the sporangium
Some spore-forming bacteria produce _____ that are poisonous to humans. Other spore-forming bacteria infect wounds and cause diseases such as _____ and _____
toxins; tetanus and gangrene
A cell that lacks an endospore
vegetative cell
Mature endospores contain much less _____ than vegetative cells
water
Malachite green is a ______ dye with a _____ positive charge that will not bind strongly to the surface or interior of the cell.
weak basic; weak
Dyes used for simple stains do not penetrate __(1)__. After you perform a simple stain, the __(2)__ is colored and the __(1)__ appears because of the absence of dye
(1) endospore, (2) sporangium
The most commonly encountered endospore forming bacteria by a beginning microbiology student are _____
Bacillus and Clostridium
The 5 common endospore-forming bacteria
Bacillus, Sporolactobacillus, Clostridium, Desulfotomaculum (all rod-shaped), and Sporosarcina (sphere-shaped)
If only a brightfield microscope is available, most rely on _____ or _____ stain to help detect endospores
Gram stain or simple stain
______ staining procedure is rarely used. Procedures for observing spores that are less time-consuming and less messy are the use of _________ to detect endospores and free spores
Malachite green; a wet mount and phase-contrast microscope
Endospore-forming bacteria are common contaminants on _____ because spores survive most natural stresses and commonly found on airborne dust particles
Petri dishes
If the resulting spore retains no visible evidence of the sporangium, it is called
a free spore
Various types of endospore-forming bacteria, usually rod-shaped, form endospores ______
at particular locations in the rod - central and terminal
After forcibly dying the bacterial endospore and the bacterial cell, it is difficult to remove the dye from ____ but easily washed away with water in _____
bacterial endospores; bacterial cells
_____ endospores from these bacteria are mass produced and produce toxins that kill insects, harmless to humans
bioinsecticides - the spore germinates inside the insect and the resulting vegetative cell produces a toxin that kills the insect
To be able to see a stained endospore inside a sporangium with a brightfield, the sporangium must be ____ with safranin or basic fuchsin
counterstained
As an endospore matures inside the sporangium, it becomes ____ and dries out
desiccated (loses water)
After forming an endospore, the sporangium may ______ and eventually _____
die ; disintegrate (cell lysis)
Neither the simple stain or Gram stain are a _____ spore stain because neither stains the endospore
differential
No dye will penetrate a bacterial ______ under normal environmental temperatures
endospore
_____ is a structure that is formed inside certain types of bacteria
endospore (endo - inside)
Microbiologists refer to all spores formed inside bacteria as _____ regardless of whether they are observed as free spores or surrounded by a sporangium
endospores