Exam 4 Flashcards
Two types of growth in prokaryotes
Intercalary and Polar
Most common form of intercalary growth
binary fission
4 types of polar growth
- Simple Budding
- Budding by hyphae
- Cell Division in Stalked Bacteria
- Polar growth without differentiation of cell size
The growth of most microbes occurs by the process of
binary fission
What are the progeny like after the cell goes through binary fission?
The two progeny are exactly the same as the original cell
Steps in Binary Fission
- Cell Elongation
- Septum Formation (pinch b/w cells)
- Completion of Septum
- Formation of Walls
- Cell Separation
What happens to the DNA during binary fission
The DNA is copied (1 origin of replication to 2). The origins more to opposite sides of the cell and pull it apart.
Enzyme that moves the origins of replication to the opposite sides during binary fission
translocase
Steps in cell division
- DNA replication
- Formation of Divisome
- Cell elongation
proteins that ensure divisive forms at cell center
Min
proteins form ring where cell begins division
FtsZ
proteins that help hold FtsZ ring to cytoplasmic membrane
FtsA
in all 3 domains, this relaxes supercoils ahead of the replication fork
type II topoisomerase (DNA Gyrase)
in all 3 domains, this unwinds double helix at the replication form
DNA helicase
in all 3 domains, this adds RNA primer
primase
in all 3 domains, this adds deoxyribonucleotides in a 5’ to 3’ direction, complementary to the 3’ to 5’ strand
DNA polymerase (mainly DNA polymerase III)
What is the direction of synthesis in DNA replication
5’ to 3’
How is replication terminated in circular chromosomes?
Tus proteins recognize Ter sites and block the progress of the replication fork
How is replication terminated in eukaryotic chromosomes?
eukaryotes have telomerase to complete the ends of linear chromosomes to form the telomeres at each end
what happens to telomeres as you age
Telomeres get shorter as you age, but the only thing you lose is repeats
proteins that ensure divisome forms at cell center
Min
protein that forms ring were cell begins division
FtsZ
protein that helps hold ftsZ ring to cytoplasmic membrane
FtsA
proteins that form filamentous spiraled bands around inside of cell under the cytoplasmic membrane to direct new cell wall to be made at certain locations
MreB
penicillin binding proteins that are transpeptidases that insert new peptidoglycan into expanding cell wall
FtsI
proteins that are DNA translocates that move DNA during cell division
FtsK
Direction of synthesis in the replication bubble
5’ to 3’
How do bacteria and archaea terminate replication?
Circular chromosomes have Ter sites across from the origin of replication are recognized by Tus proteins that block the progress of the replication fork
sequences in the DNA where the Tus proteins bind
Ter sites
How do eukaryotes terminate replication?
Eukaryotes have telomerase to complete the ends of linear chromosomes to form the telomeres at each end
How does the MinE protein change as it moves through the cell
MinE proteins increase in concentration as it goes to the center of the cell
where does cell division take place
where the MinE protein concentration is at it’s highest
where does the FtsZ ring form
at high concentration of MinE protein
create small openings in existing cell wall
Autolysins
When may autolysis (spontaneous cell lysis) occur
if there is an error in inserting new cell wall material
steps of cell wall synthesis
- Formation of peptidoglycan precursors
- Transport of Pep. Precursors to expanding cell wall
- Insertion of peptidoglycan precursors into existing cell wall
hydrophobic lipid alcohol that binds the peptidoglycan precursor and facilitates transport through the cytoplasmic membrane
Bactoprenol
peptide bonds formation between pentapeptide of peptidoglycan precursor and tetra peptide of an existing peptidoglycan unit
Transpeptidation
what is growth?
increase in the number of cells
An example of an organism that grows through simple budding
sacharomyces
an example of a microbe that grows by budding from hyphae
hyphomicrobium
the end of the cell that begins to elongate in budding by hyphae
hypha
What are the steps in budding by hyphae?
- End of cell begins to elongate and hypha lengthens DNA replication.
- Copy of chromosomes enters bud.
- Formation of cross-septum
- Progeny that gets release has flagella
What happens when the progeny produced in budding by hyphae are ready to divide?
They will drop their flagella and follow the steps for budding by hyphae
example of a microbe that divides using the steps for cell division in stalked bacteria
caulobacter
Steps of cell division in stalked bacteria
- Loss of flagellum
- Initiation of DNA synthesis and stalk begins to grow
- Elongated stalked cell (synthesis of flagellum) and stalk attaches to a surface
- Previsional cell - cross band formation
How do eukaryotes grow?
Sexual and/or asexual reproduction
2 parents (meiosis from haploid cells (egg & sperm); fusion of haploid cells yields diploid zygote)
sexual reproduction
1 parents (mitosis keeps policy the same, so haploid yields haploid and diploid yields diploid)
asexual reproduction
What is the life cycle of Saccharomyces cerevisiae
- Budding - replication of genome
- Haploid (1n) form
- Diploid (2n) form
haploid form of saccaromyces that are germinated
ascospores
How do alpha and A strains (mating types) affect the haploid form of saccharomyces
A gives rise to more A cells
alpha gives rise to more alpha
via mitosis
When can cells of opposite mating types fuse?
Only under stress-like conditions
What is the life cycle of Chlamydomonas?
During sexual reproduction (stressful state), + and - type fuse at their flagella. Once they fully fuse together, they form a crusty outer layer (zygote, protects meiosis happening).
Why does meiosis occur in Chlamydomonas?
It occurs so that when conditions are favorable, the zygote breaks open to release the mature haploid cells
transition period to allow synthesis of enzymes for biosynthesis
lag phase
period of regularly dividing cells, the culture is becoming more turbid
exponential phase
period where the essential nutrients have been depleted, toxic products build up, and growth stops while cells wait for the environment to be conducive for growth
stationary phase
What happens if conditions never look good in stationary phase?
Endospore forming microbes begin to form endospores
period where cells die and viable count can be taken
death phase
time required for one cell to form two cells
generation (doubling) time
growth pattern where number of cells doubles over a regular time interval
exponential growth
N=number of cells=
No2^n
Generation time=G=
t/n
counts the total number of cells by direct microscopic count (hemocytometer)
total cell count
How does a hemocytometer work?
Has grid to count cells. In five of the 25 squares, you count n cells in each. The grid of 25 squares has 0.1 microliters.
How do you count viable cells?
plate or colony count
continuous culture devices that maintain cell populations in exponential growth for long periods
chemostats
What must be controlled in a chemostat to keep the culture alive, and how is it controlled?
Dilution rate & concentration of limiting nutrients.
OverFlow (containing microbial cells) & Flow-Rate Regulator (introduces fresh medium)
What do the colors indicate in viability staining?
Green = Living Red = Dead
What does FISH stand for
fluorescent in situ hybridization
How is fluorescence microscopy used to distinguish between organisms? What does it distinguish between?
Fluorescing ogligonucéeotides complementary in base sequence to sequences in rRNA. It can distinguish between prokaryotes and eukaryotes. It can go further to distinguish between bacteria and archaea. It can go even further to distinguish certain groups in bacteria or archaea
What does FISH-MAR stand for?
FISH-microautoradiography
How can FISH-Mar determine an organism’s ability to use CO2?
Feed radioactive substance (CO2) and the ones that can metabolize it become radioactive and fluoresce
What property of a culture is being measured by turbidity measurements?
It measures how many cells are present, but not necessarily living cells
What measurement is used for a turbidity measurement?
spectrophotometer
What units is turbidity measured in?
optical density (OD)
What is the spectrophotometer measuring?
absorbency: an increase in cell numbers decreases the unscattered light measured and increases the OD
What does a standard curve represent?
Correlated turbidity measurements with actual cell number or mass to estimate cell number of future cultures
What is the difference between pasteurization and sterilization?
Pasteurization - reduces microbial load by killing most pathogens and inhibiting the growth of spoilage microbes
Sterilization - killing of all organisms
What is flash pasteurization?
Heat above which most microbes can survive for a brief period of time. 71 degrees celsius for 15 seconds
Four methods of physical sterilization
Heat (most common), Radiation, Filtration, and Cold/Gas
decimal reduction time
time it takes to kill 90% of the population. achieved better at higher temperatures
The temperature needed for heat sterilization depends on the ___ temp of growth for an organism
maximum
What equipment is used to heat sterilize?
Autoclave at 121 degrees celsius, using steam heat under pressure
What factors determine the amount of autoclave time needed for sterilization?
number, size, density
List 4 factors that increase heat resistance
high pH, high solute concentration, thermophiles, endospores (low water content)
What are the different types of radiation used for sterilization?
UV and Ionizing Radiation (more lethal)
What does UV Radiation do?
Sterilizes surfaces because it cannot penetrate solids. Causes thymine dimers in DNA.
What does Ionizing radiation (x rays, electrons, and gamma rays) do?
Causes breaks in the DNA strands. Breads hydrogen bonds and disulfide bridges in proteins. Can penetrate solids.
a device that has pores too small for microbes to git through but large enough for the liquid or gas to pass
filter
How do depth filters work?
Fibrous sheets or mats that trap filter particles from liquids and the air
What is commonly sterilized by depth filters?
liquids and gases
How do membrane filters work?
Thin sheets with 0.2 micrometer pores needed to filter our major pathogens. Act like sieves
What is commonly sterilized by membrane filters
antibiotics & other pharmaceuticals
freeze drying
lyophilization
chemicals that kill organisms
cidal agents
chemicals that inhibit (limit) the growth of microbes
static agents
antimicrobial growth agents that bind tightly to their cellular targets, lysis does not occur
Ex: triclosan blocks fatty acid synthesis in may bacteria
bactericidal agents
antimicrobial growth agents that kill cells by lysis
Ex: penicillin inhibits cell wall synthesis
bacteriolytic agents
antibiotic inhibitors of protein synthesis by binding to ribosomes
bacteriostatic agents
azoles prevent formation of normal fungal cell membrane
fungistatic agents
digests paper
cytophaga
Antimicrobial chemicals used in the petroleum industry
mercurics, phenols, cationic detergents, methylisothiazolinone prevent growth
antimicrobial chemicals used in the air conditioning industry
chlorine, phenols, methylisothiazolione to prevent growth of bacteria in cooling towers
British surgeon found that survival rate of surgical patients increased if he sterilized instruments and used disinfectants during surgery
Lister
4 Categories of chemical antimicrobial agents used to control microbes considered to be harmful to humans
- Sterilants
- Disinfectants
- Sanitizers
- Antiseptics and Germicides
destroy all forms of life (ex. ethylene oxide gas, formaldehyde 3% or 37%, glutaraldehyde 2%, hydrogen peroxide, and peroxyacetic acid)
sterilant
kill microbes, but endospores are typically resistant (ex. ethylene oxide gas, formaldehyde 3%, glutaraldehyde, hydrogen peroxide, and peroxyacetic acid)
disinfectant
reduce the microbial load but may not eliminate all microbes
sanitizers
kill or inhibit growth of microbes on living tissue (Ex. triclosan)
antiseptics & germicides
Who was the first to coin the term chemotherapy
Ehrlich
the ability to kill or inhibit a pathogen without harming the host
selective toxicity
The first chemotherapeutic antimicrobial drug (created by Ehrlich and used to cure syphilis)
Salvarsan - it did not meet the criteria of selective toxicity
How do synthetic agents differ from antibiotics?
Synthetic agents are manmade and antibiotics are organic
highest concentration the drugs that will eliminate microbe
toxic dose
lowest concentration of the drug that will eliminate microbe
therapeutic dose
How does the sulfa drug, sulfanilamide, disrupt folic acid synthesis in bacteria?
Folic acid comes from p-Aminobenzoic acid. The bacteria will try to use sulfanilamide to make folic acid but it won’t work. It confuses the cell.
How does ionizing disrupt mycelia acid synthesis in Mycobacterium?
inhibits mycelia acid synthesis and helps treat TB by making mycobacterial cells to look like any other gram positive cell
compounds that interact with bacterial DNA gyrate preventing the gyrase from supercoiling DNA
quinolones
What is the origin of all antibiotics?
Bacteria and Fungi
What term is used to describe the range of effectiveness for an antibiotic?
Antimicrobial Spectrum of Activity
effective against a wide variety of bacteria
broad spectrum antibiotics
effective on a subject of bacteria
narrow spectrum antibiotics
discovered by Alexander fleming because it was formed on Staphylococcus by chance
Penicillin made by Penicillium
What class of antimicrobial is penicillin?
Beta Lactan
bacteriolytic antimicrobial chemicals that are the most important and have low host toxicity
Beta Lactan
mode of action of beta lactan antibiotics
inhibit cell wall synthesis in bacteria by binding to transpeptidases
Made by fungus Cephalosporium. Same mode of action as penicillin but broader spectrum of activity and highly resistant to beta lactamases
cephalosporins
What do Carbapenems and Monobactams have in common?
They are derived from fungi
Derived from from Streptomycin cattle. Resistant to beta lactamase but degraded by kidneys. Must be given with a drug to prevent degradation. Broad spectrum
Carbapenems
Produced by Chromobacter violaceum. Beta-lactamase resistant. Helpful against Pseudomonas infections in CF patients.
Monobactams
Mutation rate of E. coli
1/100k - 1/1 billion progeny
genome replication and cell division that produces 2 identical cells
vertical gene transfer
steps of transformation
binding DNA from donor cell
update of ssDNA
Rica mediated homologous recombination
previously susceptible cell is now resistant to antibiotics
transfer of any gene from one bacterium to another via a virus
generalized transduction
transfer of a specific region of bacterial chromosome to another bacterium via a virus; requires a lysogen to be removed incorrectly, a rare event
specialized transduction
Describe how resistance plasmids can make a bacterium resistant to an antibiotic.
The contain genes encoding enzymes that actively pump antibiotic out of cell and inactivate antibiotic. Plasmid and chromosomes can be transferred by conjugation
