Bacteria - General info Flashcards
classification and structure
What kingdom do bacteria belong to?
Monera
Describe a prokaryote.
a single celled organism without a nucleus, endoplasmic reticulum, and mitochondria
Describe a eukaryote.
a multicellular organism with a nucleus with membrane, an endoplasmic reticulum, and mitochondria
What types of ribosomes do prokaryotes have?
30S +50S = 70S
What types of ribosomes do eukaryotes have?
40S + 60S = 80S
What are serotypes or serovars differentiated on?
the bases of their antigens
What are biotypes and biovars differentiated on?
the basis of some type of biological difference
What is is the criteria for classification of bacteria?
morphology, staining, cell arrangement, capsules, physiologic or biochemical properties, antigenic composition, and DNA homology
What is DNA homology used for?
it is used to determine the relationships between relatively closely related organisms
What percentage of same homology makes species the same?
70%
What is 16S rRNA homology used for?
it is used to determine relationshps between very diverse groups of organisms
What is MALDI-TOF-MS?
Matrix Assisted Laser Desorption Ionization Time-Of-Flight Mass Spectrometry
What does MALDI-TOF-MS measure?
it measures highly abundant, relatively small proteins in microorganisms
How is nuclear material kept in bacteria?
since there is no nuclear membrane, DNA may be attached to the cell membrane
What are plasmids important for?
the transfer of antimicrobial resistance, virulence factors, and may encode for important bacterial antigens
What are bacteriophages?
viruses that attack bacteria
How do bacteriophages work?
they insert their DNA into the bacterial DNA for purposes of replication and may lyse or may just replicate along with it
What do ribosomes in bacteria serve as?
they are attack sites for several antibodies such as tetracycline and gentamicin
What is the structure of the bacterial cell membrane?
typical lipid bilayer
What are the components of the cell wall in a gram positive organism?
capsule, a thick peptidoglycan layer, periplasmic space and the cell membrane
What are the components of the cell wall in a gram negative organism?
capsule, outer cell membrane, thin peptidoglycan layer, periplasmic space, and inner cell membrane
Draw the basic peptidoglycan structure of a gram positive bacteria.
it should look like this
Draw the basic peptidoglycan structure of a gram negative bacteria.
it should look like this.
What is cross-bridging of the peptidoglycan layer catalyzed by in gram positive organisms?
transpeptidase
What do antimicrobials attack in regards to the peptidoglycan layer?
transpeptidase to prevent cross-bridging from occuring
What does lysozyme do to peptidoglycan ?
it breaks the Beta-1, 4 linkage and lyses the peptidoglycan; this occurs in gram positive bacteria but not gram negative bacteria
What is the penultimate residue in S. aureus?
L-lysine
What is the penultimate residue in E. coli and other gram negatives?
diaminopimelic acid (DAP)
How does cross linking differ between the peptidoglycan layer in gram positives vs. gram negatives?
only 30-70% of the NAM is cross-linked making it weaker
What is the purpose of the peptidoglycan layer?
it is antigenic, protects the cell from the environment, increases the resistance of the host to infectious agents, and activates B-cells and stimulates macrophages to produce IL1, toxic effects, and adjuvant effects (MDP)
What is the role of MDP?
it causes an increase in body temp and has somnogenic effects
What are teichoic acids and what is their role?
polyribitol and polyglycerol phosphates, attach to NAM, is important in phage attachment and regulation of cell growth, and provide rigidity to the cell wall
Which bacteria are techoic acids found in?
gram positives only
What are lipoteichoic acids attached to and what is their purpose?
they are attached to the glycolipid in the cell membrane and may serve as an anchor for the peptidoglycan
What is the structure of lipoteichoic acids and how are they excreted?
they are amphiphiles (have both hydrophilic and hydrophobic regions) and are excreted as vesicles
Draw the structure of lipoteichoic acid.
it should look like this
What is lipoteichoic acid similar in shape to?
LPS
What does lipoteichoic acid do?
it induces IL6 and IL10 production in monocytes and stimulates nitric oxide release from macrophages
Where is the lipoprotein located on gram negative bacteria and what is its role?
it extends into the outer membrane and serves to anchor the outer membrane on the cell
What is different about the structure of the outer membrane in enteric gram negative bacteria from other gram negative bacteria?
the phospholipid is confined to the inner leaflet of the outer membrane in enteric gram-negative bacteria
What is needed to transport larger molecules through the outer membrane of gram negative bacteria and why?
the outer membrane functions as a coarse molecular sieve so specific transport proteins are needed to transport molecules >800 MW
What do porin proteins do?
form pores or diffusion channels for small hydrophilic molecules
What is the structure of porins?
it is made up of three proteins which in turn are composed of 19 transmembrane beta sheet peptides that form a large channel in each of the porin trimers
What does the outer membrane contain membranes for?
bacteriophages
What is the role of the outer membrane?
it releases vesicular blebs of LPS and protein that may have a secretory function and shields from lysozyme
What does the outer membrane of gram negative bacteria contain?
surface antigens, proteases, other enzymes, and virulence factors/toxins
What is the outer membrane of gram negative bacteria less permeable to?
hydrophobic and amphipathic molecules except for detergents, enzymes, chemicals, and macromolecules
What is the integrity of the outer membrane of gram negative bacteria disrupted by?
exposure to EDTA which removes divalent metal ions, LPS, and protein
What is LPS?
an endotoxin
What is the toxic portion of LPS?
Lipid A
When are lipooligosaccharides formed?
when the O-Ag portion is not produced in LPS
What do bacteria that have a complete O-Ag polysaccharide look like on an agar plate?
they look visually smooth
What do bacteria that lack a an O-Ag portion look like on an agar plate?
they look rough in appearance
What does the inner core of LPS contain?
2-keto-3-deoxy-octulosonic acid (KDO) that is unique to gram negatives and plant cell walls
What does KDO do?
it binds to lipid A and helps stabilize OM
What is the structure of flagella?
thin, several times the length of the cell composed of flagellin (protein) filaments
How do flagella move?
motion by rotation
Define peritrichous.
having flagella all over its surface
Define polar flagellation,
one or more flagella rising from either of the poles of the cell
What are periplasmic flagella?
flagella that are within a sheath in the periplasmic space
What antigen is associated with flagella?
H antigen
What is flagella’s role in virulence?
chemotaxis
What is the structure of fili or fimbriae?
they are shorter and thinner than flagella and composed of pilin and fimbrin
What antigen is associated with fili or fimbriae?
F antigen
What is the role of fili or fimbriae?
they serve roles as receptors and adherence to other cell tupes
What are almost all capsules composed of?
exopolysaccharides
Are most bacteria capsules hard or slimy?
slimy
In the bacillus species, what are capsules?
polypeptides
In Klibsiella and Rhodococcus species what is the structure of capsules?
thick
In regards to being antigenic, are capsules highly or poorly antigenic?
they can be highly antigenic but are most often poorly antigenic
What are some functions of the capsule?
antiphagocytic and masks other cell organisms
How does the capsule aid in survival in regards to phacocytosis?
some use the capsule to form microcolonies - phagocytic cells cannot ingest and kill a whole colony
What are spores resistant to?
drying, heat, disinfectants, and antibiotics
What enhances the germination of spores?
aging, heat, damage to the coat, and the presence of adequate moisture
