Lecture 1 (17)-classification and ID Flashcards
how are bacteria classified
via nutrition, looks, surface molecules, end pdt
Lipoarabinomannan
related to LPS that activate the immune system and are on acid fast bacteria
arabinogalactans
polysaccardides in acid fast bacteria that allow mycolic acid to bind LPS
mycolic acid
in acid fast bacteria, fatty acid that causes a waxy film over the LPS and makes it difficult to kill bacteria but also makes the bacteria slow-growing
how does LPS cause inflammation
binds CD14/TLR4 on phagocytes/antigen presenting cells and causes immune response that can lead to septic shock
components of LPS
Lipid A- virulent portion of the bacteria
core polysaccharide- maintains structure of bacteria
antigen O- variable polysaccharide that causes us to classify bacteria
gram neg vs gram pos
neg- has outer membrane, thinner envelope due to less peptidoglycan, outer membrane with LPS and porins
pos- teichoic acid, thick peptidoglycan envelope with lots of crosslinkers, no outer membrane (thus NO LPS)
features of outer membrane
porins- allow passage of only small molec
maintains structure
contains and tx secretory proteins
asymmetric phospholipid bilayer caused by LPS
teichoic acid
only in gram pos bacteria
promote attachment of other bacteria and host cells
virulent factor
what is peptidoglycan made up of
NAM and NAG plus peptide crosslinker
layers of a gram neg bacteria
outer membrane with LPS, peptidoglycan, periplasmic space, plasma membrane
what does peptidoglycan do?
its the internal capsule that provides structure to bacteria, protection, it’s what stains pos or neg, uniquely on bacteria
pili/fimbrae
- have pilin that are small protein subunits that form hollow tubes
- allow for attachment to endothelial cells and used by both gram neg and gram pos bacteria
- 2 types- common or somatic
- involved in gene tx via plasmid thru the hollow tube to other bacteria
Flagella
allow for locomotion of bacteria
on plasma membrane
have H antigen
important virulence factor-if remove flagella, hard for bacteria to cause disease
capsule
- loose polysac/protein layer surrounding some gram pos or neg bacteria- called slime layer is nonuniform or loosely adherent
- aids in protection from immune system and is ANTIPHAGOCYTIC
- major virulent factor
- bacteria can grow without them but cant survive in the post without them
- serve as antigen for vaccines
biofilm
a community of microbial cells that has a capsule over everything
Quellung reaction
capsule visibly swells when anticapsular antibody used- therefore detects capsulated bacteria
how are capsulated bacteria cleared by the immune system
via the spleen therefore people with splenectomies have probs
endospores
what type of bacteria
what does it do?
what’s it like?
- occurs with some gram pos bacteria
- bacteria converted to a dormant state when conditions rough
- when conditions better, give rise to ONE bacteria- location in cell is a give-away for identification of bacteria
- dehydrated
- little amt of proteins/ribosomes, hi Ca2+ bound to dipocolinic acid
- super resilient-hi temp, pH, radiation, enzyme attack and chemical
- prob-bioterrorism
- lasts centuries
- can exist on medical equipment-autoclave at 120C and hi pressure >20min
in terms of nuclei, how are bacteria and fungi different?
- bacteria are prokaryotes so do not have nuclei
- fungi are eukaryotes so they do have nuclei
acid fast bacteria have peptidoglycan?
yes
what type of bacteria has endotoxin?
endotoxin is LPS so only gram negative bacteria have it
what virulence factor prevents phagocytosis?
capsule
