Chapter 3 Flashcards
Identify the SEM and TEM
the TEM is a focused beam of electrons from an electron gun passes through a specially prepared, ultra thin section of the specimen.
Discussed in class list five shapes of morphology
Coccus, Bacillus, spirochete, spirillum, coco bacillus
Bacterial morphology
Bacillus, coccus, spirrillum or spirochete, cocobacillus.
Refraction is the bending of light
When light goes through different mediums the light can actually bend. It causes the light to bend into air. In order to not do that is to add oil. Oil has a similar density with glass, so no refraction of light occurs. This gives us better resolution. Oil immersion is to reduce or prevent refraction.
TEM and SEM
Magnifications above 50millionx
Look at internal structures, while SEM is looking at the surfaces, almost like a 3D effect.
The difference between the two is how we prepare them.
TEM - we embed the cells in a little cube of perafin which is a wax like substance. Then we come along with a microtome to make thin slices of the bacteria and put them on slides along with shooting electrons so that way we can see and record on the computer.
SEM- we spray the specimen with heavy metal like osmium or gold. This covers the bacteria and when shooting electrons at it … It shows the surface of the bacteria itself
Simple stain
Make a smear, let it air dry, and heat fix. Which allows you to do simple, gram, acid fast or endoscope stains. make a simple stain which could be crystal violet, safranin, or metheyne blue. Rinse it with DI water and dry it with bibulous paper.
You can see morphology with simple stain and bacterial arrangement.
Bacterial arrangement
Diplococci, streptococci (chain) staphylococci (grapes) tetradcocci (two by two)
Bacillus only has three
Streptococci, dibacillus, or bacillus itself
Gram staining
Differential stain, gram positive or gram negative bacteria
Gram positive and gram negative which has two plasma membranes? Which one is purple and which was is pink?
Gram positive is thin layer of membrane and gram negative has a very thick layer which has two cell membranes.
We wanna tell them apart so that way we can know how to treat them with antibiotics. For example penicillin can work really well with gram positive organisms. Penicillin doesn't really work with gram negative organisms. So have to find another antibiotic
Same advantages of simple staining but will tell you gram positive or gram negative.
Steps heat fixed emulsion, add crystal violet, add mordant so that way crystal violet will stay in the cell wall, next would put the alcohol to decolorizer will wash out the dye, and counter stain with safranin will tell the difference between gram positive (purple, thick peptidoglycan and thick cell wall) or gram negative (pink- thin peptidoglycan and thin cell wall)
Acid fast stain
Emulsion fixed step, this stain is for mycobacterium such as mycobacterium tuberculosis, acid fast positive is hot pink color
Endospore stain
Two genera can form spores is bacillus and clostridium, two pathogens that can form spores are bacillus anthracis, bacillus cereus. Clostridium pathogens are clostridium difficile, clostridium botulaitm, these are the species can form spores.
When do endospores occur?
Endospores occur when the environment becomes unsuitable for the cell to live in.The mother cell which is a bacillus senses that something in the environment that it’s not looking good for themselves in the future, such as pH or chemicals, the mother cell will develop into a spore. When conditions become favorable then it will turn into a new vegetative cell such as a bacillus. The cell is resistant to dying because of the keratin coating.
Process of Endospore
Starts off as a bacillus, as conditions gets bad it will double its chromosome that are identical. The cell membrane will enclose onto the second chromosome as well as the peptidoglycan cell wall covers around. Keratin then will start to form, when the condition reaches to an unfavorable point, then the cell will burst open. The Endospore is then released from the cell and is able to survive extreme heat, survive lack of water and survive against disinfectants. Last a hundred years and could even go back into bacillus form.
Ribosomes
Protein synthesis
Nucleoid
Location of bacterial chromosome
