Lecture 2 - Bacteriology Flashcards
What types of doman bacteria are there?
Autotrophs - Photosynthetic bacteria (can produce energy from light + CO2), Chemosynthetic bacteria (can produce energy from inorganic chemicals such as hydrogen sulfide, methane, etc
Heterotrophs - 4 common groups (gram+ cocci and bacilli, gram - cocci and bacilli)
3 less common (spirochaetes, rickettsia, mycoplasma
how can you describe bacteria?
morphology
size - of individual cell
arrangement
if gram stain available, include if gram pos or neg
Describe the cocci morphology
spheres, always give diameter
Describe bacilli morphology
rods, can be filamentous (long and thin; almost string-like)
describe coccobacilli morphology
short, plump rods; almost ovals in appearance
Describe vibrios morphology
comma shapped, curved rod, singular
describe spirilla morphology
rigid helix, flagella for motility, singular, less commonly found in short chaings
Describe spirochetes morphology
corkscrew (telephone cord), move using flagella to wind by or spring-type creeping, singular
What is pleiomorphism
Having more than one shape or form, refers to variability in shape
How do you describe size in bacteria?
always measure individual cells in microns
most bacteria are 0.5-3 microns in width
Rods - give diameter
Cocci - give WxL of individual cell
Filamentous, spirilla, spirochetes - give length while curved/folded
slight pleomorphism - describe most commonly represented size
How large is 1 micron?
1 mm = 1000 micron
Describe each arrangement of cocci and what their names are/what they look like
Coccus – singular
Diplococci – pairs
Streptococci – chains
Staphylococci – grape-like
clusters
Tetrads – 4 cocci in a square
Sarcinae – 8 cocci in cube13
Describe each arrangement of bacilli and what their names are/what they look like
Bacillus – singular
Diplobacilli – pairs
Streptobacilli – chains; 3 or
more arranged end-on-end
Palisades – picket-fence;
arranged side-by-side; least
common
What is a bacteria colony?
a discrete mound of bateria cells visible to the naked eye
all cells in mound derived from a single bacteria cell
can exist in vitro or in vivo
What is an in vitro bacteria colony
diff bacteria produce colonies with distinct shapes and colors when grown in vitro under specific growth conditions
What is a colony forming unit?
A SINGLE colony is created frm a SINGLE bacterium that replicates many times until there are enough cells to see with the naked eye
A CFU refers to the single bacterium that started the colony because all cells within the colony are identical
Describe the cytoplasmic membrane of a bacteria
aka cell membrane, plasma membrane
phospholipid bilayer
contains diff types of proteins, carbs, cholesterol,
surrounds contents of EVERY living cell
thin, flexible, selectively permeable
What are the different types of proteins a cytoplasmic membrane can have? (6)
Channels + transporters
signal receptors
metabolic proteins
attachment proteins
Surface antigens
What are channels and transporter proteins in regards to the cytoplasmic membrane?
Move substances ( nutrients, toxins, waste) in/out of cells
Some antibiotics are designed to only target bact cells using these transporters to move into cell
What are signal receptors proteins in regards to the cytoplasmic membrane?
proteins that bind to “signals” from outside enviro
tell bact to: start/stop replicating, move from harm, prod enzymes to metab nutes, prod enzyme req to inactive specific antibiotics
What are metab proteins in regard to the cytoplasmic membrane?
bact have no mitochondria
energy prod machinery loc along folds/invagination in cytoplasmic membrane (mesosomes)
What are attach proteins in regard to the cytoplasmic membrane?
bact use these proteins to attach to specific cells in host animal
certain bact only attach to certain cells
essential for infection
What are surface antigens proteins in regard to the cytoplasmic membrane?
any protein or portion of a protein on the surface of a bact cell that can be recognized by the animals immune system
antigens = molecular ID tags found on all cells
diff bact have hiff surface antigens (used as methods of ID diff strains of same species)
What are the fuctions of the cytoplasmic membrane
encloses the cytoplasm
barrier prot
regulates movement of molecules in/out of cell
inter. w/ enviro via signal receptors
site for energy prod
attachment - part of infect process
What is cytoplasm?
Fluid or gel that fills the cel
60-70% water
cytoskeleton - molecular scaffold
metabolically active - biochem reactions
What are ribosomes?
complex structures consisting of protein and ribosoma RNA
sit of protein synthesis where the RNA is read and used to assemble proteins in translation
What is chromosomal DNA
A single strand of DNA contains all essential genes
fewer genes than in eukaryotic cells
Strand of DNA organized by DNA binding proteins and super coiled into tight bundle
bundled chromosomal DNA loc in the nucleoid
immune system can recog bact DNA
What are plasmids?
“extra”, sm, circular pieces of DNA containing 1 or 2 genes
NOT part of chromosomal DNA
loc outside of nucleoid
Genes on plasmid not essential to life, but beneficial to survival by evolutionary advantage
-proteins that provide antibiotic resist (ex beta-lactamase enzyme)
-genes for specific toxins or attachment proteins
genes that enable the bact to prod capsules
can have none, one or more than one diff plasmid
How do plasmids replicate?
replicate independently of the chromosomal dna
once a bact aquires a plasmid, it will duplicate itself inside the cell until there are 100s-100000s of copies per cell
very resist to degration - may remain stable in the enviro after bact cell has died
What are the three ways plasmids are transferred btw cells?
during replication
transformation
bacterial conjugation
Describe plasmids replicating through replication
any time the bact cell divides, plasmids also duplicate and an equal # of plasmids are transferred to the daughter cell
Describe plasmids being transferred through transformation
Process where the cell membrane opens up and allows the bact cell to take up a plasmid from the enviro
describe plasmids being transferrred thru bacterial conjugation
process where there is direct contact btw 2 bact cells thru creation of a temp cytoplasmic membrane bridge to allow plasmid transfer
What are the external structures of bact?
cell wall, periplasmic space, flagella, fimbriae and pilli, capsules, slime layers
Describe the cell wall
All bact (except mycoplasma) have a cell wall
rigid -surrounds cytoplasmic memb
categories - Gram +/-, acid fast
necessary for survival
What is the func of the cell wall in bact?
maintain bact shape
protect cell from lysis due to osmotic pressure
helps protect from toxi materials (inc. antibiotics, sm molecules (<2nm) can diffuse btw peptidoglycan chains; lg molecules excluded)
helps w/ attachment
prevents phagocytosis by WBC in immune system
How can you break down the bact cell wall?
lysozymes - enzyme found in tears/saliva
beta-lactams - class of antibiotics (inc penicillins + cephalosporins) prevents proper synthesis of the cell wal
What are the two components of the bact cell wall?
Peptidoglycan layer
peptide cross-links
What is gram staining? What use does it server?
A method of staining bact
separates most bact genera into 2 groups based on diff in cell walls structure
whether bact are gram +/- is important for certain growth req, pathology + tx during infection
Gram pos cell wall
thicc - 40-90% of total cell mass
20-80 layers of peptidoglycan, layers joined by peptide cross-links
enzyme called transpeptidase is req to make the cross links
Teichoic acid
may have additional teichoic acids on surface of cell wall that help bact to attach to other bact and/or animal cells
What is teichoic acid?
long molecules that help embed the cell wall to the cytoplasmic membrane
What is the relationship between gram + cell wall and beta-lactam antibiotics
gram + bact are suspectible to the beta-lactam class of antibiotics
beta-lact antibiot binds to and block funct of the transpeptidase enzyme to prevent formation of peptide cross links btw peptidoglycan strands
w/o cross-links, cell wall cannot withstand osmotic pressure and cell lyses
Describe the gram - cell wall
Thin, roughly 10% of total cell mas
multiple layers
peptidoglycan layer - closest to the cytoplasmic membrane (1-2 layers)
outermembrane - complex, composed of 2 layers. 1 - inner layer is single sheet of phospholipids. 2 - outer layer is single sheet of lipopolysaccharide (LPS)
periplasmic space - space bwn the cytoplasmic plasma membrane and outer membrane
What is LPS?
Lipopolysaccharide
molecule that makes up the outmost layer of gram - cell walls, outer membrane layer
important to bact for establish infection: important to host while fighting off an infection
3 parts - O antigen, core polysacc, lipid a (endotoxin)
What is the O antigen of LPS?
repeats of polysacc units
“smooth” bact with long O chains
“rough” bact with very short or lacking O chains
hydrophilic
certain species or strains are distinguished by the specific sugar molecule in their O chain
What are O antigen’s of LPS important for? How can they help the cel:
Imp for back to estab infection
WBC are unable to grab smooth bac; WBC can easily phagocytose rough cells
o-anti take part in attach to epithel cells
some bact can alter sugars to make up o-anti, variation over time allows bact to evade the immune system
immune system uses o antigen when trying to fight off infection
sometimes, immune system can recog sugars in chain and target these cells for destruction
presence of o chain will trigger non=specific inflam
what is the lipid a portion of LPS?
endotoxin
“tail” made up of lipid chains
same in all gram neg bact
hydrophobic
fuct to hold the lps molecule in place
normally hidden from enviro- if gram neg bact dies, sm amount is released into enviro
one of the strongest activators of inflam
What is endotoxic shock?
Condition in body where overwhelming inflam causes vasodilation- drops BP -systemic shock
caused by sudden release of lg amounts of lipid a during gram ned infect
lipid a enters circulation and turns on systemic inflam
can be fatal if not treated immediately
What are some bacteria that do not gram stain?
acid-fast bacteria + mycoplasma
They do not have the cell wall structures like gram +/-
What is acid-fast bact?
cell wall structure is vry sim to gram + but contain lg numbers of mycolic acid (waxy molecules) in the cell wall. ex mycobacterium
