Bacterial structure Flashcards
What are bacteria?
single-celled organisms, prokaryotic cells
How can bacteria exist?
as independent (free-living) or as parasites
Do prokaryotes have a nucleus?
no
Where is their genetic material stored?
in the nucleoid region in the cytoplasm; it’s protected and encased by the cell membrane
Are eukaryotic cells bigger than prokaryotic cells?
yes
Which has a cell wall?
prokaryotes
What is the size range for bacteria?
0.2 to 2 um in diameter and 2 to 8 um in length
What are the different shapes of bacteria?
spherical, rod shaped (bacillus), spiral
How do spherical bacteria reproduce?
they remain attached to one another
Define diplococci
cocci that remain in pairs after dividing
Define streptococci
cocci that remain attached in a chain
Define staphylococci
cocci that divide and form grapelike clusters
How do rods reproduce?
Most divide only across their short axis and appear as single rods
How do spiral bacteria reproduce (spirochetes)?
they have one or more twists and are NEVER straight.
What is the size difference btw the different shaped bacteria?
cocci < bacilli < spirochete
Name some structures external to the cell wall?
glycocalyx, flagella, fimbriae(pili)
Define Monotrichous, lipotrichous, amphitrichous and peritrichous
Mono - 1 flagellum
Lipo - many flagella on 1 side
Amphi - 1 flagellum on each side
Peri - many flagella on both sides
What do capsules look like under the microscope?
halos surrounding bacterium
What structure impacts staining?
peptidoglycan
What’s the difference btw the structure of gram + and gram - cell wall?
gram + has a thick layer of peptidoglycan and greatly cross-linked while gram - has a thin layer
How does that reflect in staining?
gram + appears purple and gram - appears pink
Do all bacteria have flagella?
no
what are flagella used for?
attached to cell wall and provide motility
What are characteristics of flagella?
composed of glycoproteins, highly immunogenic and are called H antigens
What are fimbriae (pili)?
smaller protein appendages used for motility
Are there more cilia or flagella?
cilia
what can cilia help with?
attachment to host cells
What are capsules?
outermost layer covering some bacteria, provide a “slime” covering; important virulence factors
Do gram stains show capsules?
no, typically need special stains
How do capsules help in pathogenesis?
1) disrupt phagocytosis
2) mediate attachment to host mucous layers
3) prevent dessication of the cell
4) resist lysis by complement
5) inhibit lysis within phagolysosomes
What can several bacteria form?
spores
What are spores?
resting stage that enables the organism to endure adverse conditions (for long period of time)
What happens with spores when conditions improve?
spores transform into active bacteia
Examples of spores that cause disease
anthrax, botulism and tetanus
do all bacteria form spores?
no
What is sterilization?
any process that effectively kills or eliminates transmissible agents from a surface, equipment, article of food or medication, or biological culture medium
what does sterilization NOT remove?
prions
How is sterilization achieved?
application of heat, chemicals, irradiation, high pressure or filtration
Name 2 types of sterilization
dry and moist heat
What does dry heat sterilization involve?
utilizes hot air; 320F for 2hrs or 340F for 1hr; destroys microorganisms by causing coagulation of proteins
What is dry heat sterilization used for?
metal, glass and other solid material; UNSUITABLE for rubber and plastics
What does moist heat sterilization involve?
utilizes hot air that is heavily laden with water vapor - moisture plays imp role; coagulates the proteins in organisms and aided by water vapor - high penetrating property –> death
What is moist heat sterilization used for?
culture media, laboratory items and surgical equipment
What is icineration used for?
destruction of infected carcasses; to kill spore-former bacteria, viruses
What is gamma irradiation?
electromagnetic radiation of high frequency (short wavelength)
What is gamma irradiation used for?
ionizing rays - sterilization of disposable plastic lab and surgical equipment; UNSUITABLE for glass and metal equipment
What is UV light?
electromagnetic radiation with a shorter wavelength than that of visible light; non-ionizing rays with poor penetration
What is UV light used for?
biosafety cabinets
What is membrane filtration used for?
filtering out bacteria from heat sensitive fluids -serum, tissue culture media
