biology of bact

Question 1

Domain bacteria

Answer 1

gram negative, gram positive, mycoplasma

Question 2

what are serovars

Answer 2

distinct antigenic properties

Question 3

Genetic basis of classification

Answer 3

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

Question 4

what is the best target for antibiotics

Answer 4

surface components such as 70S ribosomes because they are unique to the bacteria

Question 5

What is the structure of bacterial capsule and slime

Answer 5

• -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

Question 6

what is the function of the capsule and slime of bacteria

Answer 6

**retard phagocytosis
**confer adherence
***cover surface antigens
capsule is not essential structure can be removed and still survive

Question 7

structure of gram positive bacteria cell wall

Answer 7

• **thick peptidoglycan (stains purple)
• **teichoic acid
• **acid-fast organisms contain mycolic acid derivatives

Question 8

Mycolic acid

Answer 8

wax like and extremely hydrophobic
must be heated before dying to melt waxy layer
carbol-fuchsin stain

Question 9

structure of gram negative bacteria cell wall

Answer 9

• **thin peptidoglycan

* **outer membrane contains LPS and porins which are channels through which molecules <600-700Da can go through

Question 10

function of bacterial cell walls

Answer 10

• **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

Question 11

Peptidoglycans (murein)

Answer 11

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

Question 12

lipopolysaccharide (LPS)

Answer 12

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)

Question 13

periplasm structure

Answer 13

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

Question 14

periplasm function

Answer 14

aid in transport of various compounds into and out of the bacterial cytoplasm and to soak up sugars and amino acids from medium

Question 15

cytoplasmic membrane function

Answer 15

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

Question 16

Function of cytoplasmic membrane

Answer 16

Impervious need active transport
electron transport chain for ATP synthesis
synthetic and catabolic enzymes
DNA replication

Question 17

Flagella structure

Answer 17

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

Question 18

axial filament of flagella

Answer 18

filament located in the periplasmic space between the inner and outer membrane (spirochetes)

Question 19

Functions of flagella

Answer 19

***confer rapid motility and H antigen

Question 20

Common pili (fimbriae) structure and function

Answer 20

made of pilin 
mostly on gram negative bacteria (exception=corynebacterium renale)
peritrichous distribution
FUNCTION
**adherence
antigenic

Question 21

Sex pili structure and function

Answer 21

made of protein 
only a few per cell
FUNCTION
genetic transfer (conjugation)
antigenic

Question 22

cytoplasm structure and function

Answer 22

70S ribosomes, nucleoid(one circular chromosome plus plasmids), storage granules
FUNCTION
**70S ribosome target of various antibiotics
site of transcription, translation, and DNA replication

Question 23

nucleotide structure and function

Answer 23

plasmids,chromosome(s)
FUNCTION
encode genes essential for bacteria, and genes for virulence factors, antibiotic resistance and toxins

Question 24

Bacteria spores

Answer 24

highly resistant thick walled structures

Question 25

endospore (bacillus an dclostridium spp.)

Answer 25

**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

Question 26

Exospore

Answer 26

nocardia and dermatophilus spp.

chain of spores:conidia produced at the end of chains of bacteria (hypha)