biology of bact Flashcards
Domain bacteria
gram negative, gram positive, mycoplasma
what are serovars
distinct antigenic properties
Genetic basis of classification
1) nucleotide base composition- similar%GC composition means related
2) DNA hybridization-determine the extent of formation of molecular hybrids from two DNA strands of different origin
3) ribosomal RNA hybridization/sequencing-useful in comparing distantly related organisms
4) base sequence comparison- sets of selected genes or whole genomes of related bacteria
what is the best target for antibiotics
surface components such as 70S ribosomes because they are unique to the bacteria
What is the structure of bacterial capsule and slime
- -amorphous, polymeric, often gelatinous material lying outside the cell wall
- -most are polysaccharides some polypeptides
- ***are visualized by negative staining (india ink)
- ***confer K antigen used for diagnosis
what is the function of the capsule and slime of bacteria
**retard phagocytosis
**confer adherence
***cover surface antigens
capsule is not essential structure can be removed and still survive
structure of gram positive bacteria cell wall
- **thick peptidoglycan (stains purple)
- **teichoic acid
- **acid-fast organisms contain mycolic acid derivatives
Mycolic acid
wax like and extremely hydrophobic
must be heated before dying to melt waxy layer
carbol-fuchsin stain
structure of gram negative bacteria cell wall
- **thin peptidoglycan
* **outer membrane contains LPS and porins which are channels through which molecules <600-700Da can go through
function of bacterial cell walls
- **determine their resistance in the enviroment (especially acid-fast bacteria)–confer shape, counteract osmotic pressure, provide physical barrier
- **sites of many antibiotic action–antibiotic sensitivity
- **immune and vaccine target
Peptidoglycans (murein)
composed of N-acetylglucosamine and N-acetylmurmic acid and peptides consisting of 4 or 5 amino acids
unique structure of bacteria=site of action for number of antibiotics (least toxic)
ex. penicillin breaks down peptide bonds
lipopolysaccharide (LPS)
unique to gram negative bacteria
- **serologic specificity of the O-antigens of gram-negative bacteria reside in O-specific chain
- **lipid moiety of LPS is called lipid A and is the toxic component (endotoxin)
periplasm structure
space between the PM and outer membrane
contains various hydrolytic enzymes and binding proteins
***absent in gram positive bacteria–secrete enzymes analogous to those of gram neg, into the medium
periplasm function
aid in transport of various compounds into and out of the bacterial cytoplasm and to soak up sugars and amino acids from medium
cytoplasmic membrane function
phospholipid bilayer
no sterol (except for mycoplasma spp., ehrlichia and anaplasma spp.)
higher protein content than eukaryotic cells
transporters and signal sensors
mesosomes(infoldings of membrane) have DNA attatment site for replication
Function of cytoplasmic membrane
Impervious need active transport
electron transport chain for ATP synthesis
synthetic and catabolic enzymes
DNA replication
Flagella structure
Composed of mostly protein monomer called flagellin
consists of 3 parts: filament, hook, and basal body
monotrichous (one polar flagella), lophotrichous (tuft of several polar flagella),amphitrichous (flagella at both poles), or peritrichous
***Axial filament
axial filament of flagella
filament located in the periplasmic space between the inner and outer membrane (spirochetes)
Functions of flagella
***confer rapid motility and H antigen
Common pili (fimbriae) structure and function
made of pilin mostly on gram negative bacteria (exception=corynebacterium renale) peritrichous distribution FUNCTION **adherence antigenic
Sex pili structure and function
made of protein only a few per cell FUNCTION genetic transfer (conjugation) antigenic
cytoplasm structure and function
70S ribosomes, nucleoid(one circular chromosome plus plasmids), storage granules
FUNCTION
**70S ribosome target of various antibiotics
site of transcription, translation, and DNA replication
nucleotide structure and function
plasmids,chromosome(s)
FUNCTION
encode genes essential for bacteria, and genes for virulence factors, antibiotic resistance and toxins
Bacteria spores
highly resistant thick walled structures
endospore (bacillus an dclostridium spp.)
**Spore coat–hydrophobic keratin like protein
**spore cortex–poorly polymerized peptidoglycan synthesized in the space between 2 layers of PM
high Ca content
SASPs-acid soluble spore protein bind DNA and protect it from reacting with molecules such as oxygen radicals
FUNCTION=survival one cell produces one spore and antigen different from mother cell
Exospore
nocardia and dermatophilus spp.
chain of spores:conidia produced at the end of chains of bacteria (hypha)
