Exam 2 Flashcards
Chapter 6,7,9-10, 25-26 (143 cards)
1
Q
What is meant by microbial growth?
A
microbial growth is the increase in the number of cells, but not the size of the cells.
2
Q
What is a “colony”?
A
colony is an aggregation of cells that can be seen without a microscope that came from a single cell.
3
Q
What are the chemical growth requirements (nutrients) needed for bacterial growth?
A
bacteria need carbon, oxygen, nitrogen and hydrogen to grow.
4
Q
In terms of carbon sources, differentiate autotrophs and heterotrophs.
A
autotrophs use inorganic carbon to make organic compounds, while heterotrophs catabolize organic compounds, like glucose, that they get from other organisms.
5
Q
In terms of energy sources, differentiate chemotrophs from phototrophs.
A
chemotrophs gain energy from redox reactions—cellular respiration and fermentation, while photoautotrophs get energy from light source
6
Q
Describe the following 4 categories of organisms based on their carbon/energy sources, and give microbial examples of each.
A
a. Photoautotroph— light is source of energy, include algae
b. Chemoautotroph— gain energy from cellular respiration or fermentation, includes nitrifying bacteria and some archaea
c. Photoheterotroph— use light for energy and break down organic molecules, includes green non-sulfur bacteria
d. Chemoheterotroph— use organic molecules for energy and break down organic molecules as well, includes fungi, bacteria, protozoa
7
Q
What is the importance of electrons (or hydrogen atoms) for the growth of organisms? Distinguish organotrophs from lithotrophs.
A
Electrons/Hydrogen atoms are essential in redox reactions and allow H bonding and electron transfer. Organotrophs (heterotrophs) acquire electrons/H atoms from organic material, whereas Lithotrophs (autotroph) acquire electrons/ H atoms from inorganic molecules.
8
Q
What are: Obligate aerobes Obligate anaerobes Facultative anaerobes Microaerophiles Aerotolerant species
Which ones is O2 toxic to?
A
- Obligate aerobes— need O2 in order to gain energy
- Obligate anaerobes— not able to use O2 because it is toxic to them
- Facultative anaerobes—use O2 when available, otherwise survive without it
- Microaerophiles—require O2, can grow in low O2 concentrations
- Aerotolerant species—can tolerate O2, but don’t use it for their growth
obligate aerobes—oxygen NOT toxic, need it to survive
obligate anaerobes—oxygen TOXIC, unable to use
facultative anaerobes—oxygen NOT toxic, can use however if needed
microaerophiles—oxygen NOT toxic, but do not require a high concentration
aerotolerant species—oxygen NOT toxic, but do not use
9
Q
How can oxygen be toxic? Describe 4 types of toxic forms of oxygen.
A
Oxygen can be toxic because of it’s oxidizing power because it can steal electrons from other molecules, creating reactions. In this way it is highly reactive.
Toxic forms: Singlet—oxygen with electrons at a higher energy state during aerobic metabolism; Superoxide radicals—which are formed when oxygen is incompletely reduced during electron transport in aerobes; Peroxide anion—part of hydrogen peroxide; Hydroxyl radicals—from ionizing radiation from reduction of hydrogen peroxide when not fully complete
10
Q
Using the terms oxygen, superoxide, peroxide anions, superoxide dismutase, catalase, and peroxidase, discuss how some organisms are able to neutralize the toxic effects of oxygen radicals.
A
Some organisms, faculative anaerobes, obligate aerobes and aerotolerant bacteria have catalase and superoxide dismutatses so they can neutralize the toxicity of these toxic forms of oxygen.
11
Q
What do organisms use nitrogen for? What is the process of nitrogen fixation? What type of bacteria perform it?
A
Nitrogen is important in creating proteins, DNA and RNA. It is the growth limiting nutrient for organisms because it is not always available. Nitrogen is fixed by Rhizobia and cyanobacteria, which reduce nitrogen gas into ammonia during N fixation.
12
Q
What are trace elements? What are growth factors? Provide examples of each.
A
Trace elements are elements like Se and Zn that are only needed in small amounts. GF are organic chemicals needed for growth that cannot be created by an organism—such as vitamins or amino acids.
13
Q
What is minimum, maximum and optimum growth rate?
• What happens above above and below optimum growth temperature?
A
- Minimum growth temperature — lowest temp that an organism can maintain metabolism
- Optimum growth temperature— highest growth rate from metabolism
- Maximum growth temperature— highest temperature and growth as organisms metabolizesMetabolism function and growth rates change depending on the temperature at which the species will thrive. If a microbe that thrives in heat is in a cold environment, metabolism will slow and growth rate will decrease.
14
Q
What temps to Psychropiles, psychrotrophs, mesophiles, thermophiles, and hyperthermophiles like?
A
- Psychrophile— love below 15 C
- Psychrotroph (or pyschrotolerant…but I use the term psychrotroph)—same as above
- Mesophile— love moderate temp 20-40 C
- Thermophile— love heat above 45 C
- Hyperthermophiles— love heat above 80C
15
Q
To which group do most pathogens belong? Why? Why not other groups?
A
Mesophiles are human pathogens most of the time because they love moderate temps, which thrive in the environments provided by our body and our temperature.
16
Q
Why would psychotrophs cause food spoilage but not psychrophiles?
A
Psychrophiles do not cause food spoilage because they cannot grow at colder temperatures, which can cause food in the fridge to spoil. Psychotrophs can grow in colder temperatures.
17
Q
Explain the statement: Water may be present, but “osmotically unavailable”.
A
In a high solute concentration (hypertonic) water is removed from the cell, which makes it shrivel. Because of the concentration gradient, the water is not really available to the cell.
18
Q
What are:
Neturophiles
Acidophiles
Alkalinophiles
A
- Neturophiles— most bacteria and protozoa, grow in neutral pH
- Acidophiles (both obligate and acid-tolerant)— include bacteria, fungi, grow in acidic environment
- Alkalinophiles— live in alkaline soil and water, basic pH
19
Q
How is adding sugar or salt a food preservation method?
A
Salt or sugar can preserve food because it forces water out of the cell, so the cell cannot grow
20
Q
Distinguish obligate halophiles from facultative halophiles. Give examples of each.
A
Obligate halophiles need salty environments, whereas facultative halophiles can tolerate salt, but do not require it to survive. Staphylococcus aureus is a facultative halophile.
21
Q
Distinguish an antagonistic relationship from a synergistic relationship between microbes.
A
an antagonistic relationship means that one organism will harm the other in the relationship, whereas in a synergistic relationship, both parties receive benefits that exceed the results of living apart.
22
Q
What are biofilms? Discuss some of the traits they display as a result of their formation.
A
biofilms are synergistic communities of lots of microbes. They can cause dental plaque on teeth, on rocks in water, shower curtain film, catheters, mucus membranes of digestive tract. They can result in decay, disease.
23
Q
What is quorum sensing? What role does it play in biofilm formation.
A
Quorum sensing is a process in which bacteria will respond to the density of bacteria near them. This helps them grow and form their biofilm.
24
Q
What is: • Inoculum • Medium • Clinical specimen • Environmental specimena • Pure culture • CFU
A
- Inoculum— sample of bacteria
- Medium (media)— the nutrients that are made for growing the microbes
- Clinical specimen— any specimen from human, blood
- Environmental specimen— any specimen from environment, soil sample
- Culture— growing microbes in a media
- Pure culture— one strain of a microbe
- CFU— cells arising from one cell form this CF unit
25
Discuss (do not just list) 2 techniques used to obtain pure colonies.
Streaking plates is used to isolate pure colonies using an inoculation loop. Pour plates are made by separating colony forming units from one another using dilutions, which are poured into the petri dishes.
26
In order to culture a microbe, a media must have what characteristics?
Must contain right nutrients for specific microbe, contain water, proper pH for growth, meet oxygen needs, be initially sterile, and be incubated at correct temperature.
27
What is the difference between broth and agar?
| What is agar? What are some characteristics of agar that make it useful for use in microbiology?
broth contains beef extract, proteins and water, whereas agar is a polysaccharide derived from the cell wall of red algae.
Agar is a polysaccharide derived from the cell wall of red algae. It is useful because it resists bacterial degradation, survives high temps, stays solid at low temps to high temps, and is translucent to see colonies that grow.
28
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What are the types of media:
• Defined
• Complex
• Selective
• Differential
• Anaerobic (reducing)
• Transport media
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* Defined (or chemically defined)— used to grow fastidious microbes
* Complex— contains many GFs that can grow bacteria and fungi, ex: broth or agar
* Selective— favor growth of certain microbes/inhibition of others
* Differential—changes in medium by colonies helps distinguish microbes
* Anaerobic (or reducing)— provides conditions that are conducive to culturing anaerobes, contains compounds that combine free oxygen and remove it from the medium
* Transport media— used by health personnel to carry clinical specimens of bodily fluids to make sure that clinical specimens are not contaminated or spread to people.
29
Which are diff or selective?
Blood agar, EMB, mannitol salt
* Blood agar: differential media, ingredients in media are used in different ways by diff bacteria
* EMB: selects for gram neg bacteria by inhibiting growth of gram positive
* Mannitol salt: selects for bacteria that tolerate high concentrations of salt
30
Why might a bacteria need to be cultured in animal cells?
The bacteria may need an animal cell host in order to survive and replicate.
31
Describe 3 ways to preserve bacterial cultures.
can be preserved by refrigeration (short time), deep freezing (years) and lyophilization (store for decades)
32
Discuss the steps of binary fission.
1--cell first replicates its chromosome
2--then the cell elongates and the chromosomes are pushed apart
3--then the septum forms across the middle of the cell
4--then the daughter cells move apart
33
What is meant by exponential growth? What is meant by generation time? What is the average generation time of bacteria? What is the typical generation time of E. coli?
exponential growth is the logarithmic growth/doubling of population. generation time is the time needed for the cell to divide and for the population to double. Average generation time for bacteria is 1-3 hours (e-coli), but varies depending on chemical and physical factors.
34
What are some limitation on bacterial growth?
food, water, nutrients, space, waste accumulation, oxygen supply, pH changeds, temp, interactions with other microbes
35
Discuss the 4 phases of bacterial growth. Draw out a graph of bacterial growth and label the phases. Make sure you discuss the characteristics of each stage.
- -Lag phase—bacteria introduced to environment, metabolically active, not reproducing
- -Log phase—rapid growth/reproduction, reproductive rate is greater than death rate
- -Stationary phase— cells run into issues that inhibit growth, death rate is equal to repr rate
- -Death phase— death rate is greater than reproduction rate
36
What is chemostat? How are they useful?
chemostat is a divide that maintains microbial cultures in a certain phase of growth. They are used to look at microbial growth under certain conditions to maintain useful products.
37
Briefly discuss the following direct ways of estimating bacterial populations. Provide enough detail so that you can gain a basic understanding of how each method works:
- -Serial dilution
- -Membrane filtration
- -microscopic counts
- -electronic counters
• Serial dilution/viable plate counts:
Look at diluted samples that are plated on agar to estimate size of population from number of colonies formed
• Membrane filtration
sample is poured through filter to trap cells, transferred to medium and colonies are counted
• Microscopic counts
sample placed on cell counter (slide) and viewed through microscope. bacteria counted through grid.
• Electronic counters
device that counts cells as they interrupt electrical current flowing across tube held in front of detector.
38
List and briefly describe 4 methods of indirectly measuring bacterial populations:
- Measurements of metabolic activity—how the microbes are growing in media
- Measurement of turbidity of a broth— the more cloudy the medium, the denser the population
- Filter bacteria, dry and physically weigh them
- Rate at which a population uses nutrients is proportional to the size of population, indirectly measures cells number by measuring pH change, waste production etc.
39
Define genetics, gene and genome?
o Genetics—The study of genes, the information that they possess and how that information is translated into what we see and how genes are replicated
o Gene—segment of DNA that encodes a protein, codes for trait
o Genome—the summation of all the genetic information contained within a cell
40
Describe the structure of DNA. What is it made of? How are the 2 strands held together? What direction do the strands run?
DNA is made of nucleotides (phosphate and sugar) and is a double stranded helix. It is held together by hydrogen bonds. The strands run anti-parallel, 5’ ends with phosphate and 3’ ends with sugar (ribose).
41
What are the nitrogenous bases that make up DNA? What are the complementary base pair rules? What does this allow for?
Nitrogenous bases in DNA: Adenine (A), Guanine (G), Thymine (T), Cytosine (C). Rules: A binds with T, and C binds with G. This organization allows for DNA to code for tons of information and makes sure that no errors occur.
42
How is the length of DNA measured? How does the length of bacterial DNA compare to eukaryotic DNA?
Length of DNA is measured by it’s base pairs. The length of bacterial DNA is much shorter than that of eukaryotic DNA.
43
Describe some characteristics of Prokaryote DNA (including what ccDNA means).
Prokaryotic DNA is a single circular chromosome (ccDNA) and is haploid, meaning that there is no corresponding homologous chromosome that contains another copy of gene. The DNA is found in the nucleic area, not in a nucleus. Cells also contain plasmids, which carry genes that regulate functions that are not essential to life (extrachromosomal DNA molecules)
44
What are plasmids? Do all bacteria have them? What sort of genes can be found on plasmids?
Plasmids are encasements of extrachromosomal DNA molecules, which contains genes for functions that are not life-essential. For example: bacterial conjugation gene, pathogenicity genes, resistance genes
45
Describe several ways that a eukaryotic genome different than a prokaryotic genome?
The eukaryotic genome is diploid, with 2 sets of chromosomes, whereas prokaryotic genome is haploid, with one. Prokaryotic DNA can be found anywhere in the cell and is made up of coding DNA.
46
What is meant by the semi-conservative model of replication?
Every new DNA molecule has one new strand and one old (parental) strand.
47
What are the functions of the following enzymes during DNA replication:
o DNA helicase—unwinds and separates the parent DNA strands, forming replication fork.
o DNA polymerase—adds new nucleotides to the template in the 5’ to 3’ direction, fixing mistakes along the way
o DNA ligase—brings together the Okazaki fragments on the lagging strand
48
What is the difference between the lagging and leading strand? How does replication differ on these 2 strands (make sure you describe Okazaki fragments).
Lagging strand is a discontinuous synthesis of protein, whereas leading is continuous. In the leading strand, the 3’ end is towards the replication fork, and in lagging the 3’ end is away from the fork. In the lagging strand, segments of DNA are added one at a time at the replication fork, called Okazaki fragments (stitched together by DNA ligase).
49
What happens in DNA methylation? What is its function(s)?
Methylation of DNA occurs after replication, where a cell adds a methyl group to one or two bases in the sequence. Some genes are turned off. Methylation plays a role in initiating DNA replication, repairing DNA or defending against viral DNA.
50
What is the central dogma of molecular genetics?
In transcription, DNA is used to make mRNA, and in translation, mRNA is used to make protein
51
Describe the 3 main types of RNA involved in transcription/translation.
In transcription, RNA is synthesized from a DNA template. Messenger RNA carries the genetic code from DNA to the ribosome, Transfer RNA carries the amino acids to the ribosome during translation, and Ribosomal RNA act as primers for DNA replication, regulating gene expression.
52
Briefly describe the 3 steps of transcription (do not just list them!).
RNA polymerase first binds to the promoter, initiating the process by adding nucleotides and unwinding DNA. RNA polymerase then synthesizes RNA (elongation) during transcription 5’ to 3’ until it reaches the terminator sequence.
53
What is RNA polymerase? How is it different from DNA polymerase?
RNA polymerase aids in transcription. DNA polymerase and RNA polymerase add nucleotides. RNA polymerase adds RNA nucleotides, U replaces T, unwinds DNA without helicase, transcribes only one DNA strand, is slower and not as thorough of a proofreader.
54
How is transcription in eukaryotic cells different than transcription in prokaryotic cells?
Eukaryotic cells transcribe RNA within the nucleus, whereas prokaryotic transcription occurs in the cytosol. Eukaryotic cells also have 4 types of RNA polymerase, and process mRNA before translation through introns and exons.
55
What is RNA processing? What are introns? Exons? Does RNA processing occur in prokaryotes? Why or why not?
RNA processing is splicing of DNA. Introns are the parts of DNA that are non-coding and eons are the parts that code for protein.
56
Discuss the role of the following in translation: codons, tRNA, ribosomes
o Codons—code for certain amino acids (21 acids total)
o tRNA—delivers amino acids
o ribosomes—Site of protein synthesis
57
What is meant by the genetic code? What does the following mean: the genetic code is redundant (or degenerative) and universal.
Genetic code is the nucleotide triplets of DNA and RNA molecules that carry genetic information in cells.
58
Briefly describe (do not just list) the 3 steps of translation.
Translation is the process of protein synthesis form mRNA. In initiation, 2 ribosomal subunits join to form the initiation complex at the start codon. In elongation, tRNA delivers amino acids based on genetic message on mRNA. In termination, the stop codon is red, releasing amino acid sequence, mRNA, and the ribosome disassembles.
59
What are polyribosomes?
Polyribosomes are a group of ribosomes that reassembles the proteins in translation.
60
What is the purpose of gene regulation?
Gene regulation has the purpose of making sure that not all genes are expressed simultaneously, so only proteins that are needed at certain times are synthesized.
61
Describe the following: constitutive gene, operon, repressible operon, inducible operon
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o Constitutive gene—genes that are expressed 75% of the time
o Operon (what is it? What does it consist of?)—transcription-level regulation in prokaryotes involves operons, which are made of a promoter sequence, operator and genes that are repressed or induced by the operator.
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o Repressible operon—set of genes that are continuously transcribed until they are deactivated by the repressor
o Inducible operon—set of genes that are not transcribed and have to be activated by inducers
62
In detail, describe the components and the function of the lac operon. Draw a picture if it helps.
The lac operon is in charge of induction, needed for lactose metabolism. Usually turned off; includes 3 genes: lacY, lacZ and lacA which encode enzymes.
63
Describe the components and function of the Trp operon.
The Tryptophan operon is an amino acid operon that is a repressor, which represses the transcription of the required enzymes
64
Describe the following types of mutations:
| --point mutation, frameshift mutation, substitutions, insertions, deletions
o Point mutation—most common, only one base pair affected, includes insertions, deletions, substitutions
o Frameshift mutation—single nucleotide base pair switched out for another
o Substitutions—big insertions/deletions, includes inversions, duplications, transpositions
o Insertions—part added
o Deletions—part taken away
65
What is a silent mutation, missense and nonsense mutation?
o Silent mutation—results from a substitution without changing amino acid sequence in genetic code
o Missense mutation—different amino acids get coded for, most are deleterious, some beneficial
o Nonsense mutation—substitution changes amino acid into a stop codon, results in non-functional proteins
66
What are mutagens? Give an example of 2 mutagens and their effects.
mutagens are agents in the environment that cause mutation, speed up the mutation rate. Ex: chemical, like gases that created changes, or radiation like UV radiation that causes cellular changes. These changes prevent proper replication and transcription
67
Briefly discuss the 4 types of DNA repair.
| --Base-excision repair, light repair, dark repair, mis-match repair
- -Base-excision repair: enzyme system takes out the erroneous baser and DNA polymerase fills the gap
- -light repair: DNA photolase breaks bonds between dimers
- -dark repair: enzymes repair dimers by cutting damaged DNA from the molecule and create a gap to be repaired by DNA polymerase and DNA ligase
- -mis-match repair: enzymes scan unmethylated DNA for mismatched bases, remove and replace if error found
68
What is genetic recombination?
exchange of genes between 2 molecules of DNA, results in new genetic combos
69
Differentiate vertical gene transfer and horizontal gene transfer.
Vertical: genes passed from parent to offspring
Horizontal: genes transferred between organisms of sam generation (transformation, conjugation, transduction)
70
List the 3 types of horizontal gene transfer (later questions will ask you the details of each).
Transformation, conjugation, transduction
71
Describe transformation in bacteria. Describe the famous study that showed this occurred (and who performed the experiment).
Genes are transferred from a bacteria to another as donor cell lyses and releases chromosomes which are integrated into the other cell’s chromosome.
72
What is conjugation (do not just say bacterial sex!)?
Conjugation is the process of transferring genetic information from one bacteria to another via sex pili
73
Regarding conjugation, what is the F factor, F+, F- cell, Hfr cell?
What is the outcome of a conjugation event between an F+ cell and an F- cell? Why?
What is the outcome of a conjugation between an F+ cell and an Hfr cell. Why?
o F-factor—fertility factor
o F+ cell—donor, have sex pilus
o F- cell—recipient, lacks sex pilus
o Hfr cell—cell with F factor integrated into it
--When the F factor is transferred from the donor, F+, to a recipient, F-, the F- is then converted into and F cell because the whole plasmid is copied and transferred to the recipient cell.
--When the F-factor is integrated into the chromosome, the Hfr cell is created. During conjugation between an Hfr cell and F- cell, the Hfr cell replicates its chromosome and begins transferring it over to F- cell.
74
What is transduction?
DNA is transferred from one bacteria to another through a virus. The virus (bacteriophage) picks up the donor DNA
75
What are R plasmids? Where would you commonly see R plasmids?
R plasmids carry antibiotic resistance, and are found often in hospitals, where antimicrobials are available, in non-pathogens. They exist most where antimicrobial selection is high.
76
What are transposons? Who discovered them? Differentiate insertion sequences from complex tranposons.
Transposons are jumping genes/DNA segments that can move from one region of DNA to another, code for transposase enzyme. Discovered by Barbara McClintock, 1940s. Insertion sequences are the simplest form and carry only one gene for transposase.
77
Describe how complex transposons and R- plasmids play a role in spreading antibiotic resistance among bacteria. Be sure to explain the role of horizontal gene transfer (such as conjugation), vertical gene transfer, trasnsposons, and R-plasmids!!!
R plasmids carry resistance to antibiotics, so therefore the bacteria can survive and spread the resistance when they share DNA during conjugation. This can happen via horizontal gene transfer, genes being transferred from one organism to another of the same generation. Resistance plasmids can also be transferred via vertical gene transfer, where it is passed form parent to offspring. Transposons allow small segments of DNA, which could be for resistance, to transfer from one DNA region to another.
78
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Define:
sterilize
aseptic
disinfect
antiseptic
sanitization
degerming
pasteurization
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* Sterilize—to remove/destroy all microbes
* Aseptic—an environment that has been freed of pathogens
* Disinfect—using a disinfectant to inhibit or destroy pathogens
* Antisepsis (and antiseptic)—reduction in the number of microbes and viruses
* Sanitization—decrease the amount of bacteria to minimize disease transmission
* Degerming—removal of microbes from a surface by scrubbing
* Pasteurization—using heat to kill pathogens
79
What is the difference between the suffixes –cidal and –static?
-cidal means kill, -static means inhibit growth
80
What is meant by microbial death? At what rate do bacteria die?
bacteria die at a constant rate, 90% of population killed every min
81
What are the 2 main modes of actions of antimicrobial agents?
Agents alter walls or cytoplasmic membranes and damage proteins and nucleic acids.
82
What are some properties of a “perfect antimicrobial agent”?
inexpensive, fast acting, stable during storage, harmless to humans, effective against 2 types of microbes
83
Describe, in some detail, 5 factors that affect the efficacy (effectiveness) of antimicrobial methods.
fragile/sensitive surfaces like tissue can’t be treated with really harsh substances, susceptibility of microbe, number of microbes, environmental conditions, time of exposure needed.
84
Rank Gram (+) bacteria,, Mycobacteria, Enveloped viruses, Naked viruses, Endospores, prions, fungi in order from most resistant to least.
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MOST
endospores
prions
Gram (-) bacteria
Gram (+)
naked viruses
enveloped viruses
LEAST
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85
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Why are each of the following are generally resistant to antimicrobials?
• Gram negatives
• Mycobacterium
• Bacillus (and Clostridrium)
• Naked viruses
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* Gram negatives, such as Pseudomonas—External LPS layer contains selective porins that won’t let the antimicrobial penetrate
* Mycobacterium—waxy cell walls resist water-based chemicals
* Bacillus (and Clostridrium)—endospores survive extreme environments
* Naked viruses—more resistant than enveloped viruses
86
Describe the 3 levels of germicides, based on susceptibility.
High level—kill all pathogens
Intermediate level—kill fungal spores, protozoan cysts, viruses, pathogenic bacteria
Low level—kill vegetative bacteria, fungi, protozoa, some viruses
87
What are biosafety levels 1-4?
1--handling non pathogenic microbes, wash hands, disinfect surfaces (E.coli)
2--hazardous agents, have limited access to work areas, work under ventilated hoods (influenza)
3--True pathogens, work with HEPA cabinets to contain (anthrax)
4--most dangerous pathogens, security controlled buildings (ebola)
88
What is the effect of heat on microbes?
What is meant by Thermal Death Point (TDP) and Thermal Death time (TDT)? Decimal reduction time?
high heat denatures proteins which interferes with nucleic acid function and cytoplasmic membrane and cell wall
- -thermal death point—lowest temp that kills in broth in 10 min
- -thermal death time—time to sterilize volume of liquid at set temp
89
Why is steam more effective than dry heat? How effective is boiling pathogens in general?
water is a better conductor for heat than air is, so hot water kills pathogens easier.
90
What is the function of an autoclave? Why is it more successful than boiling water (steam) alone?
autoclave steams under pressure and gets hotter than boiling water in order to create pure sterility. The pressure is what allows it to be more effective.
91
What is pasteurization? What is its function?
What are the 3 types of pasteurization?
Pasteurization is the method of heating foods to kill pathogens and control the spoilage organisms.
Batch method, flash pasteurization, ultrahigh-temp pasteurization
92
What is UHT?
UHT—ultra-high temp sterilization is passing liquid through heated steam and cooling immediately after.
93
What are several methods of using dry heat?
used for materials that cant be sterilized with moist heat (powders, oils, dressings). Methods: direct flaming, incineration, hot air sterilization.
94
What type of effect (bacteriostatic or bacetiocidal) does refrigeration have on microbes?
prevents growth of most pathogens which are mesophiles, ice crystals form and puncture cell membranes
95
What group of microbes is refrigeration NOT effective against?
Psychrophilic microbes can multiply in refrigerated foods.
96
Why is slow freezing better than quick freezing?
Slow freezing allows ice crystals to form and puncture membranes
97
What is filtration?
| What is it used for?
--passage of liquid/gas through a filter with pores that are small enough to catch microbes
--used for sterilizing heat sensitive microbes
98
What is a HEPA filter?
High Efficiency Particulate Air filters
99
What is dessication? What is dessication primarily used for?What is lyophilization? What is it used for?
desiccation: drying out, inhibits microbial growth, used for preservation of foods
lyophilization: freeze drying, used for preserving microbes and cells for many years
100
What type of organisms are likely to survive changes in osmotic pressure?
viruses and endospores are usually resistant to osmotic pressure changes.
101
Contrast ionizing and non-ionizing radiation.
What are some uses of radiation?
- -ionizing: short wavelengths, electron beams, gamma rays, x ray, create ions that disrupt H bonding and ends up reacting with DNA
- -non-ionizing long wavelengths: UV radiation, damages DNA by causing thymine dimers
--used for UV lamps to sterilize hospital equipment, rooms, vaccines.
102
What are some disinfectants?
* Phenols and phenolics: disrupt plasma membrane, low/intermediate germicidal
* Alcohols: denatures proteins/enzymes, intermediate
* Halogens (what are the 4? Examples?): iodine, chlorine, bromine, fluorine—denatures proteins, intermediate level
* Surfactants: surface active chemicals, reduce water surface tension, low level
* Heavy metals: denature proteins, zinc, mercury, silver, copper, low level
* Aldehydes: denatures proteins/enzymes, inactivates nucleic acids, high level
* Oxidzing agents: denature
* Gases (ethylene oxide): denatures proteins, used to sterilize syringes etc.
103
What is an antimicrobial?
drugs that treat infections (antibiotics, semisynthetics, synthetics)
104
What is the technical definition of antibiotic? How is the term generally misused today? Contrast semisynthetic from synthetic from natural antibiotics.
Antibiotic: biologically produced, one product of an organism used to kill another.
105
What bacteria is the source of over 50% of antibiotics on the market?
streptomyces
106
What is meant by selective toxicity?
magic bullet, chemotherapy that targets pathogen by not host
107
Why are fungal, protozoan, and helminth infections harder to treat than bacterial infections? Why are viral infections harder to treat than bacterial?
fungus, protozoa and helminths are eukaryotes and so are humans. It is harder to target the pathogen without also targeting the host when they are more closely related. Viral infections are farther away form humans than humans and bacteria.
108
What is meant by a drug’s spectrum of activity?
Differentiate broad-spectrum and narrow-spectrum antimicrobial drugs. Give an example of each. Give an advantage and disadvantage of broadspectrum antimicrobials.
number of different pathogens that a drug fights
- -broad spectrum: antimicrobial agent generally effective against variety y of gram pos and neg bacteria
- -narrow spectrum: antimicrobial agent that generally works against just gram pos bacteria, gram neg, or only a few bacteria
109
what are the 6 targets of antimicrobial drugs?
1. inhibition of cell wall synthesis: prevents peptidoglycan formation, cell lyses (Beta-Lwctams, Penicillins)
2. inhibitors of protein synthesis: reacts with ribosomal subunits, inhibit translation, inhibit nucleic acids (ciprofloxacin, rifampin)
3. injury to plasma membrane: change permeability (antifungals, nystatin)
4. Inhibition of nucleic acids: interfere with DNA replication/RNA transcription (ciprofloxin, rifampin)
5. metabolite inhibitors: antimetabolic agents interfere with metabolic processes (sulfa drugs, protease inhibitors)
6. prevention of virus attachment: attachment to host cell blocked by peptide and sugar analogs (hepatitis and polio virus)
110
Briefly describe the structure of penicillin.
Describe how natural penicillin works. What type of microbe is it effective against? Describe some advantages and disadvantages of natural penicillin.
penicillin is composed of beta-lactam ring.
prevents peptidoglycan from cross-linking properly in the last stages of bacterial cell wall synthesis. This greatly weakens the cell wall and causes the bacterium to lyse, or burst open, because of osmotic pressure. Penicillin is bactericidal because it directly kills bacteria.
111
What is penicillinase?
an enzyme which can inactivate penicillin, produced by certain bacteria.
112
Describe some different groups of semisynthetic penicillins (how they work, examples).
produced by penicillium mold and synthetically. Advantages are that they are more stable in acidic environment, more readily absorbed, less susceptible to deactivation
113
What are several characteristics of the ideal antimicrobial agent?
ideal antimicrobial agent inhibits translation, injures plasma membrane, inhibits nucleic acids, inhibit metabolism.
114
How does a doctor decide which antimicrobial drug to prescribe?
Susceptibility tests (such as disk diffusion), Patient allergies (many allergic to penicillin), Target (what tissue or location does it need to go), Route of administration (topical, oral, or intravenous), Concentration (child vs. adult), Side effects, Cost, Insurance
115
Describe the Kirby-Bauer disk-diffusion method as it relates to antimicrobials. What is meant by a zone of inhibition?
In the disk-diffusion method, how would you interpret a large zone of inhibition? A small zone of inhibition
Does the disk-diffusion method indicate bacteriocidal or bacteriostatic activity?
tells us which antimicrobials are successful, the larger the ZOI, the more susceptible the given microbe is to the drug.
Large zone indicates that microbe is more susceptible to drug.
Does not indicate this. Does not show if drug slows or kills bacteria. Just shows how susceptible it is.
116
Describe how broth dilution tests can determine the MIC (explain what this is too!) and bacteriostatic/bacteriocidal activity (MBC).
Bacteria is grown in liquid media with diff concentrations of antibiotic. Determines MIC minimal inhibitory concentration, showing us whether an antibiotic kills or inhibits microbial growth.
117
In what 2 basic ways to bacteria acquire antibiotic resistance?
gain resistence through new mutations of chromosomal genes or by gaining R plasmids via transformation, transduction, or conjugation.
118
what are the 7 mechanisms of how microbes resist a drug
1. Produce enzymes that deactivate the drug
• For example, beta-lactamases
2. induce changes in the cell membrane that slow or prevent entry of the drug into the cell
• For example, change in porins of Gram negative LPS layer
3. alter the drugs target so it binds less effectively
4. alter the cells own metabolic pathways so drug no longer effective at inhibiting pathway
5. pump the drug out of the cell (efflux pumps) before it can act
6. Biofilms retard drug diffusion and alter metabolic rates in bacteria, reducing the effectiveness of antimicrobials
7. Protect the target of an antimicrobial drug to inhibit its binding
119
Resistance is the result of misuse and overuse. What are 4 ways that resistance can be prevented?
Misuse is when drugs are used over the counter, wrong dosages. Overuse is the use of antibiotics when not necessary.
Resistance is prevented by maintaining high concentrations of a drug for a sufficient length of time to kill sensitive cells and inhibit others. Another way is using antimicrobials in combination with drug. Another way is penicillin based antibiotics. Another way is limiting the prescribing of antibiotics except for necessary times.
120
What is a starter culture?
A collection of microorganisms meant to perform fermentation, for example, making yogurt.
121
What is fermentation
The partial breakdown of glucose by microbes that creates foods/drinks we enjoy. Also a way of preserving foods.
122
what is Spoilage?
Changes that occur to food with microbial growth that can lead to illnesses.
123
what is food microbiology and industrial microbiology?
a. Food microbiology
The utilization of microbes in order to produce food and prevent spoilage.
b. Industrial Microbiology
The application of microbes to an industrial setting to solve issues with the environment, health fields and agriculture.
124
What are some food products (name several) that come from lactic acid fermentation?
Yogurt, milk, sour cream, kimchi, soy sauce, chocolate and pickles all require lactic acid bacteria.
What is alcohol fermentation? What is a typical starter culture for alcohol fermentation? What are some products of alcohol fermentation?
Yogurt, milk, sour cream, kimchi, soy sauce, chocolate and pickles all require lactic acid bacteria.
Alcohol fermentation is when microorganisms convert sugars to alcohol and CO2. Yeast is used as a starter culture for alcohol fermentation, which can produce bread, wine, beer, vinegar.
125
What is the difference between extrinsic and intrinsic factors when it comes to food spoilage. Give examples of each.
Intrinsic factors include characteristics of the food, whereas extrinsic are how the food is processed and made. Intrinsic properties: nutrient and water content, pH, microbial competition—moist foods are more likely to spoil than dry. Extrinsic properties: degree of processing, amount of preservatives, storage temp, packaging—if not packaged correctly, microbes could contaminate and spoil the food.
126
What is perishable, semi, and nonperishable?
a. Perishable— foods like milk, meat—nutrient rich, moist and not protected by packaging
b. Semi-perishable—tomato sauce, can be stored for long duration of time as long as can is sealed
c. Nonperishable—canned or dried foods that can be stored forever, like pasta, dry rice, canned foods like beans
127
```
What are:
Industrial canning
Pasteurization
Dessication/Lyophilization
Gamma and UV radiation
Refrigeration
Use of preservatives
```
a. Industrial canning—canned foods are exposed to high heat to discourage the presence and survival of microbes that are unwanted
b. Pasteurization—Heating foods to a temperature that kills mesophilic bacteria, lowering the amount of pathogens, used to preserve flavor also (beer, wine, dairy)
c. Dessication/Lyophilization—Dessication is drying and lypophylization is freeze drying, removing moisture prevents spoiling
d. Gamma and UV radiation—Gamma is used on fruit, nuts and meat to kill microbes
e. Refrigeration—Cold temperatures decrease the microbes ability to grow, preventing spoilage
f. Use of preservatives—salt and sugar remove water from food, thus making it unavailable for the microbes to survive. Salt is used in bacons, jam and pickling. Some spices (cloves, cinnamon, oregano) create oils that are harsh on microbe membranes. Chemical preservatives are also prevent microbial growth.
128
What is meant by a foodborne illness? What is the difference between food infections and food intoxications? Give a few examples of foodborne illnesses.
Food borne illnesses occur when spoiled food is consumed containing harmful microbes. The two categories are food infections, which is consuming living microorganisms, and food intoxications, which is the consumption of the toxins of the microbes instead of the microbe itself. Examples would be consuming meat that sat out too long and grew harmful microbes that produce stomach cramps, vomiting, nausea, diarrhea, fever, and other food poisoning symptoms.
129
What is physical, chemical and biological water pollution?
a. Physical—When you can see the contamination, such as dirt, mud, debris. Main example is sediment.
b. Chemical—Inorganic chemicals like mercury, pesticides, fertilizer. Excess fertilizer can lead to eutrophication
c. Biological—When there are too many microbes present, or when they are non-native. Examples would be fecal contamination, viruses, bacteria, and protozoa parasites
130
What is meant by potable water? What is an indication of biological (fecal) contamination?
What is the accepted EPA level of coliform in water? How about for bottled water? Why is there a difference?
Potable water is safe drinking water. When water is contaminated with fecal matter, coliforms are present.
Accepted coliform level in water is 0 for every 100 mL of water. For bottled water, it is higher than that. It is higher because it is contained within a bottle.
131
What are the 4 steps of drinking water treatment?
- -Sedimentation—water pumped into holding tanks to settle particulate matter
- -Flocculation—water pumped into another tank, where alum is added and joins to particles
- -Filtration—Microbes reduced to 10% with sand filters, charcoal filters, membrane filters
- -DIsinfection—Ozone, UV light or chlorination are used to kill microbes before people are able to consume water
132
What is meant by wastewater? What is the ultimate goal of effective waste water treatment?
Wastewater is water that leaves a structure/place after being used that foes down sink, toilet etc. The goal of wastewater treatment is to remove contaminants and reduce the BOD (biochemical oxygen demand), which is the amount of O2 required by bacteria in order to metabolize all of the waste in the water.
133
What are the 4 steps of wastewater treatment?
- -Primary Treatment—Removal of sludge/solid material
- -Secondary Treatment—dissolved organic matter removed along with pathogens by using microbes to break down organic matter
- -Tertiary treatment—Chlorination disinfects water
- -Sludge treatment—anaerobic sludge digesters convert organic material to methane gas, and left over sludge is dried and used as fertilizer/landfill
134
What is nitrogen fixation? What role do bacteria play?
In nitrogen fixation, Nitrogen gas is converted into nitrate (ammonia) so that it can be used by plants to make genetic material and proteins. Nitrogen-fixing bacteria are able to do this (Azobacter, Cyanobacteria, Clostridium, Rhizobium)
135
Describe the relationship between Rhizobia and legumes?
Rhizobia infect the roots of legumes and form nodules on roots, creating a symbiotic relationship. The bacteria fix nitrogen, which the legume needs, and the plant makes anaerobic conditions for the bacteria.
136
What is nitirification? What role do bacteria play?
Nitrification is the process of nitrite/nitrate being produced from ammonium ions, performed by bacteria.
137
In anaerobic respiration, what is nitrate used for (by some bacteria)?
Nitrate is used as an electron acceptor in anaerobic respiration.
138
What is denitrification? What role do bacteria play?
What is denitrification? What role do bacteria play?
139
what is Eutrophication and hypoxia?
Eutriphication:When excess nutrients enter water bodies and cause an excess in nutrients in the water, leading to the overgrowth of certain microbes, like algal blooms. This can lead to hypoxia, which means little oxygen in the water.
140
What 2 nutrients cause eutrophication? Where do these nutrient come from?
Nitrogen and phosphorus in excess can cause eutrophication—these can come from runoff of fertilizer, sewage, feedlots, detergents.
141
Describe how eutrophication can lead to hypoxia? Make sure you discuss the role of microbes (both algae and bacteria) in the process.
When too much nitrogen and phosphorus are present in the water, the excess nutrient enrichment allows for algal blooms to flourish as they are decomposed by aerobic bacteria, which out-compete other microbes. The oxygen levels in the water drop and cannot support other life.
142
What are some solutions to eutrophication?
Solutions are to monitor fertilizer waste and limit it, sewage properly disposed of and reducing waste into water bodies, including reducing the pollution of phosphate soaps and detergents.
143
What is bioremediation? What are OEMs?
Bioremediation is the use of microbes to detoxify pollutants. OEMs are oil eating microbes that break down petroleum and degrade the oil.
