Unit 1 Flashcards
What are the 4 types of bacterial cell organization?
- individual
- pairs = diplo
- chains = strepto
- three-dimensional clusters = staphylo
Why is it beneficial for bacterial cell organization to be disrupted and for cells to be broken apart?
It allows them to initiate new groupings
What are the 4 general shapes found among bacteria?
- round = coccus
- rod-shaped = bacillus
- slightly curved = vibrio
- spiral = spirillum
To which kingdom do all bacteria belong?
Kingdom Monera
What is quorum sensing?
The manner in which bacteria monitor their population. When the bacterial population goes up the concentration of signature molecules goes up and the bacteria respond by slowing down their metabolism.
What is the twofold purpose of quorum sensing?
- survival depending on nutrients
2. defense mechanism against antibiotics
What does antibiosis mean?
It means competition, that is where the word antibiotic comes from.
What is symbiosis?
It is when bacteria work together in a way that helps each other out
What percentage of bacteria has actually been studied (cultured and observed)?
1%
Generally, what size are eucaryotic cells?
10-20 micrometers
Generally, what size are procaryotic cells?
1-2 micrometers
What are the 4 primary
distinguishing characteristics between procaryotic and eucaryotic cells?
- size
- nucleus
- organelles
- cell wall
If procaryotic cells do not have a nucleus, what is the region where the DNA is located called?
It is called the nucleoid
Which type of cell does not have organelles?
procaryotic cells do not have membrane bound organelles
What is contained inside of the nucleoid?
a single (unpaired), single (just one), circular chromosome
What 3 things are contained in the cytoplasm of a procaryotic cell?
- plasmids
- enzymes
- cytoskeleton
What are plasmids?
smaller circles of DNA, they are polyploid with 10-20 genes
What types of things are enzymes used for?
metabolism, replication, transcription
What does the cytoskeleton provide to a cell?
It used for internal movements, for example it partitions the chromosome and plasmids during duplication
What is the shape of the cytoskeleton?
It is shaped like a figure 8 or like a two-headed arrow
What are exonucleases?
They are enzymes that cut the ends off of linear DNA
Why do procaryotic cells have exonucleases?
As protection against viruses
Why are ribosomes differences between eucaryotic and procaryotic cells so important?
Because they have the essential function of translating mRNA to proteins, the difference in structure allows for antibiotics to exploit ribosomes in procaryotic cells without causing any damage to the host
What is a plasma membrane made up of?
It is made up of a phospholipid bilayer
What are two are the primary differences between the plasma membrane of a eucaryotic and procaryotic cell?
- procaryotic do not have cholesterol in their membranes
2. the sodium channels are different
What are pili (fimbrae) made up of?
They are made up of chains of proteins
What 3 components make up a flagella?
basal body, hook, and filament
How does the molecular motor of a flagella work?
It is powered via a hydrogen ion electrochemical gradient.
What is a flagella made up of?
proteins
What is hypotonic lysis?
It is when water diffuses into a cell in order to equilize conc. and too much water entering leads to hydrostatic pressure pushing out on the plasma membrane and the bacteria exploding
What is the primary function of a cell wall?
It holds the PM in, preventing hypotonic (osmotic) lysis, but still allow nutrients to enter the cell. It can do this because it is both strong and porous.
What is a cell wall composed of?
peptidoglycan which is: glycan -> two alternating sugars linked by glycoslytransferase enzymes and peptido -> 4-5 amino acids covalently connecting the sugar chains, these are linked by transpeptidase enzymes.
What are teichoic acids?
Phosphate-glycerol polymers with amino acid or sugar side chains.
What type of bacteria have teichoic acid?
gram positive bacteria
What function do teichoic acids serve?
Because they are negatively charged, teichoic acids attract essential positively charged ions and the positive poles of water molecules
What is different about the walls of gram negative walls?
They only have a few PG layers and they do not have teichoic acid. They do however have an outer membrane
What is an outer membrane?
It is similar to a plasma membrane containing many channels, lipoproteins, and liposaccharides
What does the word ‘glycocalyx’ mean?
sugar coat
What is a glycocalyx?
It is a layer on the outside of a bacterial cell wall made up of usually polysaccharides
What is the function of a glycocalyx?
clumps of bacteria sharing glycocalyces make up a biofilm, it also allows for surface adhesion, h20 absorption and it shields against phagocytosis
What is a thin glycocalyx layer called?
a slime layer
What is a think glycocalyx layer called?
a capsule
What is the name of the smallest known bacteria?
Mycoplasma
What is significant about the structure of Mycoplasma?
They do not have a cell wall, but they do have lipoglycans in an outer membrane like plasma membrane. Since they do not have a cell wall they can only live in isotonic environments
How is the outer membrane attached to the peptidoglycan layer in a gram negative bacteria?
via lipoproteins
Most bacteria constantly progress through cycles of growth and division and most are eventually killed by?
drying out (desiccation)
What does it mean to say that a bacteria is able to become dormant?
That it is able to slow down its growth rate all the way to zero when conditions are unfavorable and are capable of staying alive that way for indefinite periods of time
What does it mean to say that dormant forms of bacteria are resistant?
That they are not susceptible to harsh environmental conditions, they can even resist desiccation
What is the dormant pattern of the bacterial genus Chlamydia?
It does not have peptidoglycan and it is capable of condensing into a dormant, resistant form called an elementary body
What is the dormant pattern of the bacterial genus’ Bacillus and Clostridium (both gram +)?
They form endospores which are resistant to UV light, desiccation, heat, and chemicals. They are capable of surviving centuries in this form. When conditions improve they germinate into vegitative cells.
How are endospores formed? What are endospores made up of?
When the environmental conditions become unfavorable the parent cell creates a copy of the chromosome that is even more condensed and it is placed inside of a PM that is surrounded by PG and also surrounded by a protein spore coat. When the parent cell dies, the resistant endospore is released into the environment.
What are 5 endospore producing bacteria that commonly cause human diseases?
- Clostridium tetani
- Clostridium botulinum
- Clostridium perfringens
- Clostridium difficile
- Bacillus anthracis
Where are Clostridium tetani endospores commonly found? What effect do they have?
In dry soil (dust), causes rigid paralysis = tetanus
Where are Clostridium botulinum endospores commonly found? What effect do they have?
In fruit or vegetable canning. Produce an extremely potent toxin which causes flaccid paralysis
Where are Clostridium perfringens endospores commonly found? What effect do they have?
In dry soil, are capable of causing gangrene
Where are Clostridium difficile endospores commonly found? What effect do they have?
They can be found in the GI tract of humans and they produce a potent diarrhea-producing toxin when body defenses are weakened
What are the effects of Bacillus anthracis endospores?
They cause anthrax
Why is bacterial metabolism medically important?
Because knowing about it allows us to exploit the enzymes and this can control bacterial growth (and bacterial growth is what causes infections so….)
Do bacteria have mitochondria?
No, they do not. But they essentially act like a mitochondria all on their own and they are capable of performing glycolysis and the electron transport system
What is the endosymbiant hypothesis?
That a long time ago, bacteria were endocytosed into eucaryotic cells and became mitochondria
Why are some bacteria able to survive without oxygen?
Because they are able to oxidize both organic and inorganic molecules. They are able to use other atoms as a final electron acceptor in the final electron transport system
What are two ways in which glucose can be broken down in pyruvic acid?
- glycolysis
2. Entner-Doudoroff pathway (unique to certain bacteria; Pseudomonas)
Give three examples of final electron acceptors that are not oxygen?
- N2
- S04 -2
- CO3 -2
If they don’t get their energy from glucose -> pyruvic acid -> final electron acceptors; How else can bacteria get energy?
Fermentation
Fermentation
Uses the products of glycolysis (pyruvic acid and NADH2) and yields ATP as well as lactic acid and 2NAD+
Generally what is the effect of an increase in temperature on enzymatic activity?
Heat generally increases enzymatic activity because it increases the rate of diffusion of enzymes and their substrates
However, if heat increases beyond a certain maximum what is the effect on enzymatic activity?
It decreases dramatically because the enzymes become denatured and bonds are not able to be formed with substrates
What are the effects of slightly higher or lower pH values than optimum on enzymes?
It causes them to lose their affinity for their substrates, so the rate of reaction is reduced. Because OH- and H+ ions bind to the enzyme
What are the effects of much higher or lower pHs than is optimum on enzymes?
The enzymes become denatured
How does substrate/nutrient concentration affect metabolism?
If there is little to react with, ATP production will be slowed
What are the two types of enzyme inhibitors?
- competitive
2. non-competitive
What is a competitive inhibitor?
It is a molecule which competes with the normal substrate by binding to the active site on the enzyme. This results in no products or reactions
What is a non-competitive inhibitor?
It is a molecule which inhibits an enzyme’s activity by binding to an allosteric site, this causes a conformational change to the active site, preventing the substrate from binding
What effect does the release of haptoglobin from the liver have on an infection?
Haptoglobin binds to Fe, which is an essential molecule for bacteria, bacterial growth is slowed as a result.
Why do bacteria require an acceptable temperature range in order to grow?
Because of the effects of temp on enzymatic activity
What is an acceptable temperature range for a mesophile?
25-40 degrees C
What is an acceptable temperature range for a psycrophile?
-5-20 degrees C
What is an acceptable temperature range for a thermophile?
40-70 degrees C
What is an acceptable temperature range for an extreme thermophile?
70-105 degrees C
What is the effect of refrigeration on mesophiles?
It limits their growth
What is the effect of freezing a mesophile?
It stops their growth, and if the ice crystals puncture their cell walls than it kills the mesophiles
What is the acceptable pH range for most bacteria?
6.5 - 7.5
Why is an acceptable pH so important for bacterial growth?
Because it alters enzymatic activity otherwise
Why can bacteria tolerate hypotonic environments?
Because they have their cell walls to protect them from osmotic lysis
Why can most bacteria not tolerate hypertonic (more than .9% ) environments?
Because all of the water inside of the cell would diffuse out of the cell causing the cell to die
What are halophiles?
Bacteria that are able to survive in hypertonic environments (literally means “salt-lovers”)
What salt conc. are facultative halophiles able to tolerate?
up to 10 %
What salt conc. do extremem halophiles require?
approximately 30 %
What are the 3 major physica/environmental requirements for bacterial growth?
- acceptable temperature range
- acceptable pH
- tolerable osmotic pressure
What are the 5 major chemical requirements for bacterial growth?
- source of energy
- source of carbon
- source of mineral nutrients
- source of vitamins
- source of oxygen
What 2 things can bacteria use as a source of energy?
They can use either organic or inorganic molecules when oxidizing
What are the 2 main sources of carbon for bacteria?
- other organic molecules - recycling
2. photogenic bacteria use CO2 and the energy from the sun
What mineral nutrients does bacteria need for growth?
N, S, P
Where do bacteria get their mineral nutrients?
They get N from things like N2, NO3- and NH4+ and they get S and P from recycling host cell molecules
Where do bacteria get vitamins?
Most bacteria synthesize their own, those that can’t get them from their environment
For what two purposes might a bacteria need oxygen?
- organic synthesis
2. as a final e- acceptor in cellular respiration
What are obligate anaerobes?
They are bacteria which require oxygen in order to produce ATP. They are able to deal with the byproducts of this : superoxide dismutase and hydrogen peroxide because they have these two enzymes : 1. superoxide 2. catalase ( or peroxidase)
What are facultative anaerobes?
They are bacteria that can use oxygen because they can express the necessary enzymes, but they are also able to do fermentation instead.
What are obligate anaerobes?
They are bacteria that lack superoxide dismutase, catalse, and peroxidase, and are therefor unable to use oxygen as a final e- acceptor becuse the by-products would be too toxic
What is the mechanism of bacterial growth by binary fission?
- cell elongates as cytoplasmic components are duplicated
- chromosome is replicated and copies move to opposite ends of the cell
- wall forms between the now two cells which may or may not spontaneously break apart
What the 4 main characteristics regarding
bacterial growth?
- growth is exponential as a power of 2
- generation time varies
- exponential growth cannot be maintained
- bacteria must adjust to a new environment before exponential growth can occur
Why is bacterial growth exponential?
Because of binary fission. After each division the number of cells doubles
What is generation time?
The amount of time it takes for a bacterial population to double
What 2 factors cause a generation time to vary?
- the species of bacteria
2. how well it’s growth requirements are being met (temperature, pH, O2 supply etc.)
Why can exponential growth not be maintained? (5 reasons)
- acidic waste products accumulate
- nutrient supplies diminish
- quorum sensing
- host cell’s defenses counter-attack in an infection
- host may take antibiotics
What is the name of the time during which bacteria adjust to their environment before growing at exponential rates?
Lag phase
Why does a lag phase occur in bacterial growth?
Because many times in a new environment the different nutrients that are present require different enzymes to be broken down than are currently being expressed.
What are the 4 stages on a bacterial growth curve?
- lag phase
- log phase
- stationary phase
- decline phase
What is occurring during the log phase?
Cells are dividing exponentially
What is occurring during the stationary phase?
The number of cells being produced is equal to the number of cells dying
What is occurring during the decline phase?
The number of cells dying is greater than the number of cells being produced.
What are 5 important things to take into consideration when observing the growth of a bacterial colony?
- daughter cells will be able to divide more times than parent cells and will last loner
- bacteria in the colony are being exposed to different environments depending on their location
- differences in populations can occur due to mutations
- recycling of nutrients (cannibalism) can occur in a bacterial population
- endospores will allow a bacterial colony to survive longer
How is the low dose risk of something determined?
By testing fewer animals at much higher doses and than extrapolating to low doses
What is hormesis?
exposure to extremely low doses of toxic substances induces the up-regulation of body defense mechanisms, yielding less disease than no exposure at all
What is homeopathy?
the claim that diseases can be treated or prevented by exposure to extremely low doses of toxins that cause similar symptoms (law of similars)
What is the law of infintesimals?
That less is better, more dilute is better
What are 4 reasons why homeopathy might work?
- natural course of disease
- placebo effect
- drugs relieve anxiety
- some pseudoscience drugs release endorphin’s
What are three categories of treatment for bacterial growth control?
- pharmaceuticals - FDA approved
- dietary supplements - not FDA approved but must have disclaimers
- homeophathic - not FDA approved & no disclaimers
