introduction to microbiology Flashcards
The study of very tiny organisms
microbiology
the study of microorganisms that is capable of infecting and causing diseases for human
medical microbiology
what are the characteristics of bacteria
-Unicellular
-primitive nucleus
no nuclear membrane
the genome of bacteria is
Single circular double stranded DNA
can harbour plasmids
Define plasmids
small circular DNA
where does the bacteria mostly develop
in liquid or solid media
when does the bacteria can be seen
when the colony is formed
organisms adapt to new environment
grow in size
making metabolic enzymes
Lag phase
what are the typical growth curve in favourable conditions
1-lag
2- log
3-stationary
4-decline
in what phase does the antibiotics work
log
the rabid growth happen in…
log
nutrients begin to deplete in what phase ?
stationary
the toxic products accumulates
in what phase
in stationary
the number of dead cells = living cells
stationary
cells stop dividing
stationary
what happen during decline phase
number of living cells less than the dead cells
what is the optimal ph for bacteria to grow
7
the natural range of ph oc bacteria to live is ?
from .5 to 10.5
the bacteria that live in extreme ph is?
acidophils and alkalophils
the optimal temperature for bacteria is
37 c
the important medically species live in temperature
from 25 to 40
bacteria needs to live in most temperatures
is
water
the effect of o2 in obligate Aerobe
utilized for aerobic respiration
In aerobic environment the obligate Aerobe
grow
the effect of o2 in obligate Anaerobe
Toxic
facultative Anaerobe/Aerobe
not required for growth but utilized when present
the effect of o2 in microaerophile
required at low level below 0.2
the effect of o2 in aerotolerant Anaerobe
not required and not utilized no benefit
function of cytoplasmic membrane are:
Selective permeability.
Active transport of nutrients.
Secretion & excretion of toxins
Site of respiration.
Cell wall synthesis.
Role in DNA replication.
bacterial cell wall functions:
1- Rigid structure that maintains the shape of bacteria.
2- Osmotically insensitive; it protects the cytoplasmic
membrane from bursting in hypotonic solutions.
3- Participate in cell division.
4- The cell wall composition plays role in
determining the cell’s reaction to gram stain.
gram positive cell wall contain
peptidoglycan (thick)
Teichoic acid
what is responsible for cell wall rigidity
peptidoglycan
peptidoglycan contain :
Sugar derivatives
– N-acetyl muramic acid
– N-acetyl glucosamine
*
Amino acids
– D and L alanine; glutamic acid
– AND EITHER Lysine or diaminopimelic acid (DAP)
layers of gram negative cell wall
-cytoplasmic membrane.
-periplasmic space : (lying between cytoplasmic membrane and outer layer)
-outer membrane (OM) layer composed of lipopolysaccharide.
periplasmic space contents:
contain a gel like substance composed of proteins and enzymes including the thin peptidoglycan.)
composed of lipopolysaccharide
(LPS) called endotoxin with special channels consisting of protein
molecules called porins.
outer membrane OM
are species of bacteria which are naturally
devoid of cell wall. They are the only bacterial species
deficient in cell wall.
mycoplasm
mycoplasm shape
pleomorphic
mare not destroyed by penicillin which acts on the bacterial cell
wall, and can not be stained with gram stain.
mycoplasm
what ore other techniques that used to differniate bacteria
Acid-fast staining
* Waxy cells do not readily Gram stain
* Mycobacteria and Ziehl Neelsen stain
. Structural stains
* Spores
* Flagella
* Capsules
endospores function :
Resistance to
– Heat, radiation, chemicals
* Environmental dispersal
how can endospores visuilased
Malachite green as primary stain
and safranin as counterstain.
organs of motility in all motile bacteria.
flagella
flagella function:
They move the bacteria towards nutrients and other attractants.
where does the flagella attached
basal body in cytoplasmic membrane
how is movement of bacteria mediated ?
random untill the cell reaches the chemical or physical agents
examples of bacteria movement :
Chemotaxis – response to chemicals
Phototaxis – response to light
Aerotaxis – response to oxygen
Osmotaxis – response to ionic strength
Hydrotaxis – response to water
where is the attatchement of pilli
extend outwards from the cell surface.
where the pilli usually found
gram negative
the flagella composed of
subunits of a protein, pilin.
