bacterial morphology and growth Flashcards
pleomorphic
no defined shape
most common bacterial shapes
- coccus
- bacillus
a cell that divides in one plane gives rise to short or long chains described as?
- diplo-:pair
- strepto-:chain
staphylo-:
grapelike cluster
- cell divided in two or more planes
sarcina
- packet of 8 cells
- cell divided in two or more planes
most bacterial cell membranes do not contain what compound?
sterols
a bacterial cell wall is found in what relation to cell membrane?
outside of cell membrane
virtually all bacterial cell walls contain what structure?
Peptidoglycan
what is Peptidoglycan
- repeating disaccharides (NAG and NAM) cross-linked by tetrapeptides
in Peptidoglycan, tetrapeptide linkage is between what
NAMs
function of Peptidoglycan
important for bacterial cell support
organisms can kill bacterial cells by interfering with the synthesis/structure of peptidoglycan. Name two ways
- secretion of various antimicrobial compounds
- secretion of lysozyme
cell wall inhibitors only affect cells in what stage?
cells that are actively growing, as these cells are synthesizing peptidoglycan
effect of lysozyme of peptidoglycan
degrades the glycan backbone of peptidoglycan
- lysozyme is found in tears, saliva, and mucus
gram negative bacteria have what peptidoglycan layer
a thin peptidoglycan layer
gram positive bacteria have what peptidoglycan layer
thick peptidoglycan layer
describe the staining technique to differentiate between gram positive and gram negative bacteria
- stain with primary stain: crystal violet
- bacteria will stain purple
- stain with counterstain: safranin
- gram negative bacteria will turn red
- gram positive bacteria will remain purple
what group of bacteria can not be classified with gram staining
- acid fast bacteria
- cell wall contains peptidoglycan
- unique cell wall structure
- do not stain using gram stains
what are the three main types of cell walls found in bacteria?
- gram negative
- gram positive
- acid-fast
gram negative cell wall contain 1-2 layers of peptidoglycan plus the following structures?
- outer membrane
- periplasmic space
outer membrane is bi-layer. Inner layer is identical to cell membrane, outer later of the outer membrane is composed primarily of what?
lipopolysaccharide (LPS)
lipopolysaccharide (LPS) contains what three parts?
- O antigen
- core polysaccharide
- Lipid A
function of O antigen part of lipopolysaccharide (LPS) in gram negative bacteria
- outer portion of LPS
- serves as attachment site
- highly variable and immunogenic: used to identify bacterial stains
function of core polysaccharide part of lipopolysaccharide (LPS) in gram negative bacteria
- connects lipid A to O antigen
function of Lipid A part of lipopolysaccharide (LPS) in gram negative bacteria
- has toxin activity
which structure of LPS is responsible for bacterial sepsis?
Lipid A
function of porins in gram negative cells
- trimeric outer membrane protein channel
- non-specific channels allowing water and small molecules across the outer membrane
what is the most abundant protein of gram negative cells? Function?
lipoprotein
- stabilizes the outer membrane and anchors the outer membrane to the peptidoglycan layer
location of periplasmic space in gram negative cell walls
- between outer membrane and cell membrane
- houses thin peptidoglycan layer
