Bacterial Cell Flashcards
Bacteria with no cell wall
- Mycoplasma
- Ureaplasma
- Spiroplasma
- Anaeroplasma
2 alternating dissacharides in peptidoglycan/murein layer
- N-acetyl-D-glucosamine
2. N- acetyl-D-muramic acid
small circular molecule of DNA containing accessory information
Plasmids
most commonly found in gram negative bacteria, each carries genes for its own replication. It can confer resistance to antibiotices
Plasmids
What is the chromosomal DNA of prokaryotes?
Circular, complexed with RNA
Typical size of bacteria
- 4 - 2 micrometer in diameter
0. 5 - 5 micrometer in length
Site of energy production in prokaryotes
Cytoplasmic membrane
Present in most prokaryotes as an organized capsule or unorganized slime layer
Glycocalyx
gives the bacterial cell shape and strength to withstand changes in environmental osmotic pressures
Cell wall
Protects against mechanical disruption of the cell
cell wall
Offers some barrier to the passage of larger substances
cell wall
Characteristics of Gram positive cell wall
- Thich cell wall
2. Presence of techoic and lipotechoic acid
provides rigidity to cell wall by attracting cations such as magnesium and calcium
Teichoic acid
Characteristics of Gram negative cell wall
- Thin peptidoglycan later
- Periplasmic space
- outer membrane
Componentes of the outer membrane
- proteins
- phospholipids
- lipopolysaccahride
It acts as a barrier to hydrophobic compounds and harmful substances
Outer membrane
It acts as a sieve, allowing water-soluble molecules to enter through protein-lined channels called porins
Outer membrane
It provides attachment sites that enhance attachment to host cells
outer membrane
How long are the cells saturated/flooded with primary stain in gram staining?
60 seconds or 1 minute
How long will the mordant stay before rinsing off in gram staining?
60 seconds or 1 minute
How long is the slide rinsed with alcohol in gram staining?
20 seconds or until there is no run off of color
Color of gram positive bacteria
mid - dark purple
Color of gram negative bacteria
pink - red
what decolorizer is used in gram staining?
acetone alcohol
Reagents of gram staining
V (crystal Violet)
I (Iodine)
A (Alcohol)
S (Safranin red)
Characteristic exhibited by gram positive bacteria
Gram variability
Bacteria with natural gram variability
- Mobiluncus spp.
2. Gardnerella vaginalis
Contributing factors of gram variability
- Use of old culture
- pH of staining reagents
- Bacterial autolysis
- Staining reaction time
very difficult to stain using gram staining
Spirals
Result of gram staining in spirals
gram negative
contain a waxy layer of glycolipids and fatty acids (mycolic acid)
Acid fast organisms such as mycobacterium spp. and nocardia spp.
specifically designed for a subset of bacteria whose cell walls contain long-chain fatty (mycolic) acids.
acid fast staining
render the cells resistant to decolorization, even with acid alcohol decolorizers
Mycolic acid
most commonly encountered acid-fast bacteria
Mycobacterium
What specimen is used for Mycobacterium tuberculosis?
sputum or phlegm specimen
Partially acid-fast organisms
- Nocardia
- Rhodococcus
- Legionella micdadei
Distinctly acid-fast organisms
- Cryptosporidium
2. Isospora (Cystoisospora belli/Isospora belli)
Mordant used in Ziehl-Nee Isen method
Heat
Reagents used in Ziehl-Nee Isen method
- Carbol Fuschin
- Acid Alcohol
- Methylene Blue
Reagents used in Kinyoun method
- Carbol Fuschin
- Tergitol
- Acid alcohol
- Methylene blue
Acid alcohol in Ziehl-Nee Isen method
3% HCl in 95% Ethanol
Acid alcohol in Kinyoun method
3% H2S04 in 95% Ethanol
Color of acid fast organism
Red
Color of non acid fast organism
Blue
Fluorochrome stain used in Acid fast staining
Auramine-Rhodamine
Color of acid fast bacteria using fluorochrome stain
Yellow or orange
Stain used for observation of metachromatic granules
Methylene Blue / LAMB