Chapter 6 Micro – Flashcards

time required for a population of microbial cells to double , during cell division each daughter cell receives a chromosome and sufficient

Ftsz

Zip A

ZipA: anchor that connects FtsZ ring to cytoplasmic membrane

helps connect FTSZ ring to membrane and also recruits other divisome proteins

related to actin most abundant protein in eukaryoyotes

MreB*** function

Major shape-determing factor in prokaryryotes

function of MREb

2 functions

   – Forms simple cytoskeleton in cells of bacter and archeae

Forms spiral shaped bonds around the inside of the cell underneath the CM

iN WHAT KIND OF bacteria can of MREb be found?

– Not found in COCCUS shaped bacteria only rod

–        Localized synthesis of new peptidoglycan and other cell walls compounds to specific location along the cylinder of rod-shaped cell during growth

coccus + peptido

Autolysins are a group of enzymes that exist in all bacteria containing peptidoglycan. these enzymes break down the peptidoglycan matrix in small sections so that growth and division of cells can occur. Autolysins do this by hydrolyzing the β-(1,4) bond between N-acetylmuramic acid and N-acetylglucosamine molecules.

Peptidoglyccan synthesis

requirements

 Preexisting peptidoglycan needs to be severed to allow newly synthesized peptidoglycan to form

autolysins

New cell wall material is added across the openings

Wall band: j

links in the peptidoglycan must be broken, new peptidoglycan monomers must be inserted, and the peptide cross links must be resealed.

1. autolysinsp-
2. Bactoprenol– l
   
3. Glycolases– e
4. Transpeptidation– 
   

autolysin

1. autolysinsp- break glycosidic bonds/ Break the peptide cross-bridges- FtsZ ring, small openings in the wall are created

wall band created- new and old peptidoglycan

step 3

1. Glycolases– enzymes interacting with bactoprenol- catalyze glycosidic bond formation to insert cell wall precursors into growing point of cell wall

1. Transpeptidation–  final step in synthesis- FORMS PEPTIDE CROSS LINKS B/W M residues adjacent glycan chain

PEPTIDE BONDS B/W G—M(peptidoglycin bond)

3. glycosidic bond b.w (M–M bond)

penicillin inhibits m–m bond causing inhibition  transpeptidase enzymes that catalyze this reaction. The activity of this enzyme is inhibited by penicillins

how does penicillin inhibit function of transpeptidation

mechanism and consequence

Bactoprenol is placed into MEMBRANE, autolysin begins GM interacts with peptidoglycan with assistance of glycolases enzyme, and autolysin assist in separating membrane

1. growth medium- the amount of resources needed to grow

2. incubation conditions- temp/ heat/ ph/ enviroment

2^n

too nice

Specific growth rate (k)

division (v)

k = log2/g =

v= 1/g

g= t/n

N= N. * 2^n

N= final cell number

N.- intital cell number

n- number of generations during period of expoenential growth

a closed system microbial culture of fixed volument

lag phase– time b/w culture is inoculated and when growth begins

expoential phase- phase are typically in healthiest state

stationary phase– growth rate of population is zero, someetimes some die while others are growing static

death phase

stationary phase how we come to crystic growth

rate of cell death is MUCH lower than the rate of expoential growth

this doesnt mean everything is dead

we can c ontrol the growth of CHEMOSTAT

stat- keep track of

what are the limitations of microscopic counts

1. live vs dead(w/o staining)
2. small cells difficult to see and can be overlooked
3. precision difficult to achieve
4. phase-contrast microscope required if stain is not used
5. cell suspension- low density hard to count
6. motile cells need to be immobilized
7. debris- mistaken for cells

we already know

spread plate method

pour- plate method

always dilute sample.

DILUTION

FIGURE 6.16**

Direct microscopic counts of natural samples typically reveal more organism then are recoverable on plates of any given culture medium.

why is it in great plate anomaly does Direct microscopic counts of natural samples typically reveal for more organism then are recoverable on plates of any given culture medium.

Microscopic methods count dead cells; whereas viable (plate counting) methods do not

Different organisms in even a very small sample may have vastly different requirements for resources and conditions in laboratory culture

indirect but:  very rapid and useful method of measuring microbial growth.

(Most often measured with a spectrophotometer and measurement referred to as optical density (O.D.)

To relate a direct cell count to a turbidity value what must be done** and why

A standard curve must first be established

Typically do not require destruction or significant disturbance of sample

Sometimes problematic

       Microbes that forms clumps or biofilm in liquid medium

min/ optimum/ and maximum temperatures at which an organism grows

prokaryotes can grow at higher temp then eukaryotes

archaea can live in hottest

1. more alpha helic- flexible
2. more polar less hydrophobic AA
3. fewer weak bonds
4. dec interaction b/w protein domains

ratio of vapor pressure of air in equilibrium with a substance or solution to the vapor pressure of pure water (nothing in water except H2O) no living org in i, water activity decreases with increases of solute such as Na

think osmosis

glycinbetainse

prolinse

sucrose

trehalose

very dry enviroments

–        High solute concentration outside= water moves out to prevent this

o   Pumping inorganic ions from environments into cells.

o   Synthesize and accumulation of organic solutes called compatible solutes( glycin betains, preline, sucrose, trehalose):compound used by cells to counteract low water activity in surrounding environments.

single oxygen

superoxide

h2o2

hydroxyl radical

catalase

enzyme that destryo toxic oxygen spcies