microbiology lecture test
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What is generation time? "doubling time" and give 2 examples:
-the time required for a cell to divide (most about 1-3 hours)
- *E. COLI : 20 min
- *Mycobacterium Tuberculosis : 24 hrs
Bacteria reproduce through what?
Binary fission (asexually)
Bacterial growth is?
Increase in the # of cells
MacConkeys agar is selective for what? and differential for what?
- -selective for gram (-) bacteria
- -differentiates non lactose fermenters
One example of a selective and differential media is Mannitol Salt Agar. Explain how this works.
- -Used to identify Staphylococcus Aureus
- -Contains high salt concentration:7.5% so it inhibits most bacteria (One that can ferment is Staphylococcus Auerus
- -Contains mannitol=sugar (turns to acid)
- -Contains PH indicator= turns yellow when acid
MRSA stands for what?
Methicillin Resistant Staphylococcus Aureus
Another example of selective and differential media is MacConkey's Agar. Explain this.
- -Used to identify salmonella
- -Contains bile salts and crystal violet (inhibit gram (+) bacteria
- -Lactose=sugar (acid)
- -PH Indicator= (acid:red-if ferments lactose)(Basic:Clear)
- *Many gram (-) enterie non-pathogenic bacteria can ferment lactose, Salmonella cannot.
In Mannitol Salt Agar it is selective for what and differentiates what?
- -Selective for Staphylococcus
- -Differentiates-what type of staphylococcus(aureus)
Name the 3 types of classifications of Streptococcus when on blood agar plate?
- 1)Alpha Hemolytic Streptococcus-secrets hemolysin that cause the incomplete lysis of RBC's (yellow-greenish zone)
- 2)Beta Hemolytic Streptococcus-"bad ones"-secretes hemolysin that cause the complete lysis of RBC's (clear zone)(most human infections caused by this)
- 3)gamma hemolytic streptococcus-secretes no hemolysins (no zones)
What are hemolysins?
enzymes that attack RBC's
What is differential media? give an example:
differentiates between different organisms growing on the same plate.
- ex. Blood agar plates (bright red)
- (TSA with 5% sheep blood)
- (is used to differentiate types of streptococci)
Dyes inhibit what? and select for what?
- -inhibits the growth of gram(+) bacteria
- -selects for gram (-) bacteria
Most GI tract infections are caused by what type of bacteria?
gram (-) bacteria
Give 2 examples of selective media:
- -Brilliant Green Agar
- -EMB=Eosin Methlyne Blue (Red dye)
- *E.Coli gives off bright green sheen when on EMB
What does selective media do?
inhibits the growth of some bacteria while selecting for the growth of others
Name 5 pathogens that are microaerophilic and what they cause:
- 1)Neisseria Gonnorrhoeae-Gonnorrhea
- 2)Campylobacter Jejuni- Gastroenteritis
- 3)Borrelia Burgdoferi- Lyme Disease
- 4)Helicobacter pylori- Stomach ulcer
- 5)Haemophilus influenzae- pneumonia and meningitis (Blood loving)
What can you use for microaerophilic bacteria?
- 1)Candle jar-consumes O2 and gives off CO2
- 2)CO2 generating packet-break class gives off CO2 and consumes O2
What are the microaeophilic levels of O2 and CO2?
The anaerobic indicator strip can be what two types?
Methlyene Blue = O2=blue and no O2= clear
resazurin = O2=pink and no O2=clear
What is the normal atmosphere level of O2 and CO2?
You can determine the O2 requirement classification by the location on what 2 processes?
Agar stabs and agar shakes
Anaerobic bacteria are put in a gas pak system: inside are pallidium crystals, and H+ and CO2 generating envelope. What are the importance of these?
- -Pallidium crystals-make system work causing 2H+ to combine with O2 to make water(get rid of all free O2)
- -H+ and CO2 generating envelope releases H+ and CO2
Anaerobic bacteria has resazurin in it which is what?
an anaerobic indicator
Anaerobic bacteria contains a reducing media called? explain why it works:
Fluid thioglycollate broth- works because Sodium thioglycollate which binds to and removes free O2
What are the 2 special culture techniques used in O2 requirements?
- 1)Anaerobic Bacteria (no O2)
- 2)Microaeophilic bacteria (grow best under refuced O2 levels and increased CO2 levels)
Name 2 culture medias and define them:
- 1)Chemically defined:exact chemical composition is known. Used to grow fastidious organisms.
- 2)Complex media: exact chemical composition is not known. Most bacteria and fungi are grown with this.
Microbial growth refers to:
# of cells, not the size of the cells
define tonicity and name the 3 types:
- *Strength of solution
- 1)Isotonic-same dissolved concentrate inside and outside cell-most bacteria cells like to be this.
- 2)Hypertonic-greater concentration outside than inside cell
- 3)Hypotonic-Lower concentration outside cell than inside cell
Microbes obtain almost all their nutrients in solution from?
surrounding water. (osmotic pressure)
diffusion of water through semipermeable membrane from higher to lower concentration of water
very few bacteria can grow at below what PH? give example
- PH of 4.0
- -many foods, such as sauerkraut, pickles and cheese are preserved from spoilage by acids produced during fermentation
- ex=Helicobacter pylori=stomach ulcer:grow there because it secretes Urease which takes Urea and water and converts it into pneumonia ("base" that neutralizes stomach acid) and CO2
most bacteria grow between the PH of?
Name the 3 types of temperatures and the ranges
- 1)Pyschrophile-range OC-20C
- 2)Mesophile-range 20C-40C*most common and contains 2 types:normal microbial flora and human pathogens
- 3)Thermophile-range 40C-100C
Name the 3 physical requirements for growth
- 3)Osmotic pressure
What are the 2 requirements for growth?
O2 is lethal to some organisms, all organisms produce superoxide(O2-) define what it does: and give another example of an enzyme anaerobic bacteria are missing:
molecule of O2 that steals electrons from other molecules; therefore, are toxic to cells. They must be neutralized.
O2 is lethal to anaerobes because they lack what 2 things?
- -superoxide dismutase (SOD)
Give example equation for catalase:
- 2H2O2---->2H20 + 02
- (hydrogen peroxide)
Give chemical equation for superoxide dismutase:
- 02 + 02 + 2H- ----> H202 + 02
- *Hydrogen peroxide-also toxic to cells and must be neutralized
bacteria can be classified based on their oxygen requirements: name them (4)
- 1)aerobe-need 02 bc it is final electron acceptor
- 2)anaerobe-something other than 02 is final electron acceptor
- 3)facultative-grow with or without 02
- 4)microaerophilic-loves small amounts of 02 and grows in refuced concentrations of 02
give the macro and micro elements
C HOPKINS CaFe Mg NaCl
Look at notecards for tonicity review!!!
If E. Coli is unchecked for about 24 hours how many cells has it grew?
72 generations = 1x10 to 21 power
Name 6 limiting factors in the environment:
- -lack of food, water, or nutrients
- -accumulation of metabolic wastes
- -lack of 02(02 requirements)
- -changes in PH
Name the 4 phases of growth:
- 1)Lag Phase
- 2)Log Phase
- 3)Stationary Phase
- 4)Death Phase
- *Cells that survive death phase go to lag phase and starts over*
Review picture of phases of growth!!!
Describe Lag Phase:
- -bacteria are first introduced into an environment or media, and check out surroundings.
- -cells are very active metabolically
- -# of cells changes very little (1 hr to several days (even weeks) depending on conditions)
Describe Log Phase:
- -rapid cell growth (exponential growth)
- -population doubles every generation
- -microbes are sensitive to adverse conditions:antibiotics and anti-microbial agents
- ***Generation time happens here***
name this phase: death rate of reproduction, cells begin to encounter environmental stress and endospores would form here.
Name this phase:death rate is greater than rate of reproduction due to limiting factors in the environment. Population is reduced to a tiny fraction or population dies out completely.
A turbid culture contains how many cells?
10 million bacterial cell per ml
Enumeration of bacteria can be figured out by doing what?
Study paper on serial dilution!!!!
Name five causes in humans vs. microbes:
Ring around the rosie is a nursery rhyme from what epidemic?
Bubonic Plague or the Black Death
describe what happened during the bubonic plague:
- *epidemic swept thru Europe in the middle ages (13th and 14th centuries)
- *40 million people were killed (about 1/3 of the population of the continent)
- *Etiological Agent= Yersinia pestis (gram (-) rod)
What are 2 vectors for Yersinia pestis?
flea and rat
Explain the process of infection from Bubonic plague:
- 1)flea bite with yersinia pestis
- 2)Bacteria enters the bloodstream (bacteremia)
- 3)Bacteria localize in lymph nodes especially axillary and groin areas.
- 4)hemorrhaging occurs in lymph nodes resulting in "black and blue" swellings or buboe
- 5)if untreated about 50% mortality rate
- 6)if spread to lungs 99% mortality rate
when the bubonic plague infection spreads to lungs it is called?
"wouldn't touch from a 10 ft pole" came from what?
people took a long pole to scrape the dead people out of barrell so they wouldn't touch and get sick
in the last 100 years or so the battle between humans and microbes, humans are winning. why?
we are increasing our knowledge of how to CONTROL MICROBIAL GROWTH
Most of history, who was winning humans or microbes?
Name 2 methods to control microbial growth:
what microbe or disease is no longer in human population? and who are the only places that have it:
small pox= variola virus-eradicated in 1977(somalia africa)
- -CDC:center of disease control in Carolina
- -Institute of virology USSR
- -WHO: world health organization
- *wondering what to do with smallpox virus. some want to destory some want to research
destroying all forms of life
destroying normal pathogen or unwanted organisms
antimicrobial agent used on inaminate objects
anti microbial agent used on living tissues
inhibits bacterial growth
name 7 factors that effect antimicrobial activity:
- 3)concentration of antimicrobial agent
- 4)type of microbe (sensitivity of microbe)
- 5)activity of microbe
- 6)presence of organic matter
- 7)degree of contamination
- **work better against gram (+) bacteria
Name 3 targets of antimicrobial agents:
- 1)cell membrane
- 2)enzymes and proteins (cell wall)
- 3)DNA and RNA
1 physical method of microbial control is heat. how does this work?
by denaturing enzymes and proteins
define thermal death point:
lowest temperature at which all microorganisms in a liquid culture are killed in 10 mins
the minimum length of time in which all microorganisms in a liquid culture are killed at a given temperature is what?
thermal death time
*Food industries are more concerned about this** because if temp is too high it can discolor bacteria and damage product. but at a certain length and temperature the product isn't damaged.
give 2 types of moist heat:
boiling water and an autoclave
boiling water kills vegitative bacterial cells, fungi, and many viruses, but isnt effective against what?
- endospores and some viruses
- *some spores can survive boiling water for up to 20 hours. ex. Hepatitis A survives 30 mins.
this uses steam under pressure
what is the universal time and temp for moist heat sterilization?
- 121C for 15 minutes
- **NO known disease/organism can survive this
what is believed to be the most resistant bacteria?
spores of Bacillus Stearothermophilus
If your wondering if your autoclave is working right you can do what?
- a kilit ampule
- *put in spores of bacillus stearothermophilus
- *fermentable sugar-common end product acid or gas
- *PH indicator-basic = purple and acidic=yellow
for a kilit ampule you put it in what?
special incubator at 55C
what are 3 ways to use dry heat?
- 1)direct flaming
- 3)hot air sterlization
inoculationg loop and needle is 100% effective when you get it to a red glow. what is this called?
the disposable wastes (paper cups, bags, dressings, etc) are burned to ashes. (100%effective) what is this called?
hot air sterilization is done how and used for wat?
- put in oven at 170C for 2 hours.
- -used on substances that would be damaged with moist heat; gauzes, dressings, and powders.
this removes microorganisms from solutions that might be damaged by heat
filtration is used for what?
- -culture media
filtration wont remove viruses because?
they are smaller, but still sterile because viruses are not considered alive.
this consists of gamma rays and xrays, because it pentrates most substances. It is used on substances that could be damaged by heat:plastic petri dishes, plastic syringes, catheters, surgical gloves. what is this?
This uses UV light which does not penetrate plastic, glass, or proteinaceous matter very well. it cannot be used for sterilization but can be used to reduce microbial populations(hospital rooms, nurseries, operating rooms) this is called?
non-ionizing radiation kills using mutations called what that causes bump in DNA?
this is a disinfection-not a sterilization:
back in the day milk creamer shops used pasteurization to kill bacteria by 63C for 30 minutes. Now what do we do?
72C for 15 seconds. This is called HTST (high temp short time)
pasteurization kills what specific type of pathogen?
pathogens that survive the high temp short time is called what?
name 4 methods used to control microbial growth:
- 1)heat (most heat:boiling water/autoclave & dry heat:direct flaming/incineration/hot air sterilzation)
- 3)radiation (ionizing radiation/non-ionizing radiation)
what are the structures and functions of genectic material?
- DNA (deoxyribonucleic acid)
- RNA (ribonucleic acid)
- nucleotides (phosphate group/pentose sugar/nutrogenous base
What are the complementary base pairings?
Look at picture for DNA strands!!!!!!
DNA replication occurs where?
at the replication fork (5' to 3')
DNA strand is unzipped due to what ?
the leading strand (5' to 3') contains what?
the lagging strand (5' to 3') contains what?
- RNA polymerase (RNA primer)
- DNA polymerase (extends primer and digests RNA)
- DNA ligase
This needs double strands:
Look at picture for DNA and RNA replication!!!
REMEMBER: 5 to 3 thats the way we need to be!!
bidirectional replication consists of what two things?
- -origin of replication
- -termination site
- **two replication forks going in different directions all the way around to termination site
this has continuous replication
the leading strand
this has discontinous replication:
the lagging strand
Dogma referres to what?
one strand of DNA is used as a template to form a complimentary strand of mRNA
it is translated into a protein
give equation for protein synthesis:
how life works and protein synthesis equation DNA--->mRNA-->protein ... is referred to as what?
Central Dogma of Molecular Genetics
in mRNA the m stands for?
- -single stranded
- -5 carbon sugar ribose
- - complimentary pairings of A-U and G-C (Uracil replaces Thymine)
- -double stranded
- -5 carbon sugar deoxyribose
- -complimentary pairings of A-T and G-C
this begins here, where DNA is unzipped by DNA helicase. RNA polymerase attaches here, and ends with termination site. It always occurs 5' to 3'. What is this?
name the 3 types of RNA:
- 1)mRNA:contains the codons-3 base sequence on mRNA that is complimentary to the DNA triplet code
- 2)rRNA: ribosomes (70S)
- 3)tRNA: transfer amino acids to ribosomes for protein synthesis-3 base sequence on tRNA that is complimentary to the codon (anticodon)
the triplet code is on what?
anticodons are on what?
codons code for a specific what?
how many amino acids are there?
how many possible combinations are there for 3 base code and 4 bases.
- **amino acids are coded for by more than one codon**
genetic code is considered what two things?
- -Degenerative (conserved)-helps to prevent lethal mutations
- -Universal-supports theory of evolution-come from same ancestor)
61 code for amino acids are called?
3 codons that do not code for amino acids are called what?
- non sense codons or stop codons
- **translation ends here**
what is a special codon and why is it special?
AUG-because it is the start code **translation always starts here**
translation has 3 steps:
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