intro to bacteria

do bacterial, (prokaryotic), cells have nuclear membranes?
no
do bacterial, (prokaryotic), cells have nuclear sterol in their cytoplasmic membranes?
no for except mycoplasma
how do bacterial, (prokaryotic), cells reproduce?
binary fission
what chromosome form do bacterial, (prokaryotic), cells have?
circular, and it is haploid, (meaning any mutations are passed directly to daughter cells)
do bacterial, (prokaryotic), cells have membrane bound organelles?
no
other than humans, what other organisms have eukaryotic cells?
fungi, protozoa and helminthes
do most prokaryotic cells have peptidoglycan cell walls?
yes, except mycoplasma
where does respiration take place in prokaryotic cells?
on the cytoplasmic membrane
what are common distinctions for classifying bacteria?
macroscopic, microscopic, metabolic, antigenic, special, and genetic characteristics
what are examples of differences in bacterial colony morphology?
color, size, shape, elevation, smell and hemolysis
what are examples of differences in bacterial colony microscopic appearance?
size, shape/arrangement, ability to retain gram stain
what are the three primary bacterial shapes?
coccus, (spherical), bacilli, (rod-like), spirillium, (spirals)
what is the arrangement of streptococci?
in a single line, (2 planes of division)
what is the arrangement of staphylococci?
a triangle, (3 planes of division)
what is the arrangement of diplococci? what disease are they associated with?
pairs, gonorrhea
what arrangements are bacilli, (rod-shaped), found in?
alone, pairs, or in chains
what does gram staining determine? what bacteria cannot be classified by gram stain?
gram +/- relates to characteristic of cell wall. mycobacterium, (acid-fast bacteria -> thick waxy membrane), mycoplasma, (no cell wall), chlamydia, (intracellular bacteria), treponema, (very thin)
how does the gram staining technique work?
crystal violet is added, then gram’s iodine is added. at this point all bacteria will be purple. decolorizer is then added, and only gram positive bacteria will retain the dye. safranin red is then added to dye the gram negative bacteria red.
what is the acid fast staining technique used for? how is it done?
testing for mycobacteria, (TB). stain bacteria with carbol fusion, (red), then decolorize with acid alcohol. mycobaceria will be only ones that remain red, so “acid fast”. the remaining bacteria can be stained methylene blue.
how are mycoplasma tested for visually? treponema? chlamydia?
mycoplasma – culture and PCR, treponema – fluorescent stain, chlamydia – fluorescent stain
how are bacteria differentiated metabolically?
aerobic/anaerobic, a specific nutrient, specific metabolic products, or enzymes
what is a metabolic characteristic of salmonella? e. coli?
salmonella ferments glucose. e. coli ferments glucose, lactose, and sucrose
can bacteria be distinguished according to their antigenic features?
yes
what are some special features that can be used to differentiate bacteria?
spores, enzymes, antibiotic resistance
what is characteristic for clostridium tetani?
spores, appear as “drumsticks”
what
what is one way that bacteria can be distinguished genetically? what techniques are used to test this? what kind of situation would this form of testing be useful for?
guanine to cytosine ratio. DNA hybridization, PCR, plasmid analysis, ribotyping, chromosomal fragments, can all be used to classify subspecies. this kind of testing would be useful a faster diagnosis than waiting for a culture to grow.
what does the cell wall do? do all bacteria have one? what is a common diagnostic test for it’s characteristics?
the cell wall prevents the cytoplasmic membrane from osmotic lysis, and maintains the shape of the cell. the cell wall is the outermost component to all bacteria except for mycoplasma. the 2 basic cell wall types are determined through the gram stain test to either be gram -/+.
what kind of cell wall do mycobacteria have?
a waxy cell wall that does not gram stain, they are classified as acid-fast, b/c they resist de-colorization by acid alcohol
what does the cell wall of bacteria contain?
peptidoglycan, which is a polymer of sugars, (glycan), cross-linked by short chains of amino acids, (peptides), from the third amino acid in the upper peptide chain and the last AA of the peptide chain below it. this cross linking usually involved N-acetyl muramic amino acid. the peptides are usually diamino acids.
why is the biosynthesis of peptidoglycan a good target for antibiotics?
it is unique to bacteria
what does lysozyme, (found in human tears, serum, mucus), do to bacteria?
cleaves peptidoglycan between N-acetyl glucosamine and N-acetyl muramic acid
what does the cell membrane of gram + bacteria look like?
a very thick layer, (~20 layers), of peptidoglycan over the cytoplasmic membrane. it is thick, but has pores for things like glucose to get through. it has teichoic acid and lipoteichoic acid, (same, but binds to lipids), running throughout.
what does the cell membrane of gram – bacteria look like?
a periplasmic space between cytoplasmic membrane and a thin layer of peptidoglycan, covered by another outer membrane
how does the peptidoglycan layer affect gram + bacteria?
the thick layer protects from drying/dessication. they have higher levels of cross-linking than gram -. they are overall more sensitive to lysozyme and cell wall antibiotics than gram – bacteria
why might staph have more rigid cell walls? how does this affect its infectious ability?
they can have glyine bridges that extend cross-linking. this allows it to be passed from infected inanimate objects
what is teichoic acid? what does this determine? does it play a role in cell adherence?
polymers of glycerol or ribitol phosphate that are covalently linked to peptidoglycan. these sugars can be substitued with other AA, amino sugars to give different serotypes. these are major antigenic determinants and implicated in mediating adherence to cells.
what is lipoteichoic acid? does it determine antigenic properties?
lipoteichoic acid is a teichoic acid with a lipid moiety covalently linking it to the cytoplasmic membrane, (thought to help anchor peptidoglycan to cytoplamic membrane). lipoteichoic acid determines the majority of the cell’s antigenic properties.
what can lipoteichoic acid do in terms of the host’s immune system?
induce host response similar to endotoxin, (LPS), hypotension and shock
how many layers of peptidoglycan are found in the periplasmic space of gram – bacteria? what else might be found in the periplasmic space?
1-2. hydrolyzing enzymes might be found in the periplasmic space that eat incoming nutrients, nutrient-binding proteins that help transport, virulence factors, (antibiotic inactivating enzymes)
what is found in the outer membrane of gram – bacteria?
porin proteins, and on the outer leaflet, of the bi-layer, LPS, (lipidpolysaccaride), is found
what can LPS do?
stimulate the immune system to the point of morbidity/mortality
how are gram – bacteria different from gram +?
they have a thin layer in their periplasmic space, (not found in gram +), and less cross linking/rigidity. they are more protected from lysozyme and cell wall antibiotics due to outer membrane. they can also close porins as a defense sometimes.
what links the outer membrane of gram – bacteria to peptidoglycan?
lipoproteins
what are OMPs?
outer membrane proteins, help in protection
how do small molecules get into gram – bacteria?
through porins, (large and hydrophobic molecules are blocked)
how is the outer membrane of gram – bacteria considered asymmetric?
the inner leaflet has phospholipids, the outer leaflet has lipopolysaccharide, (LPS)
what is another word for LPS, (lipopolysaccaride)? what does it do?
endotoxin, it is a major mediator for fever and inflammation caused by gram – bacteria, (ok in local, but not in systemic infections). it also presents a permeability barrier to hydrophobic molecules such as antibiotics, (b/c the outer portion is hydrophilic).
what are the two components of LPS?
lipid A and core polysaccharide
what does the lipid A component of the LPS do? what is it composed of?
lipid A is responsible for endotoxin activity. it is a phosphorylated glucosamine disaccharide backbone with fatty acids that link it to the OM. it is the internal portion of LPS.
what is the core polysaccharide component of the LPS composed of?
the core polysaccharide links lipid A to the O antigen and contains the uncommon sugar KDO. this branched polysaccharide contains 9-12 sugars, and contains variable/invariable portions.
is lipid A/core polysaccharide portion of LPS similar among different gram – bacteria?
yes, for the most part
what is the outer portion of LPS called? what is it composed of? is it variable?
the O antigen is a linear polysaccharide of 50-100 repeating saccharide units. these units of 4-6 sugars are called O antigens or somatic antigens, it is highly variable and is the reason for different antigenic specificities among gram – bacteria. this is used to classify serotypes.
what makes the mycobacterial cell envelope thick and waxy?
an outer layer of complex long-chain hydrocarbons w/sugars
do gram – bacteria have teichoic or lipoteichoic acid in their walls?
no
how do gram +/- bacteria stain
gram +: purple
gram -: pink
where is the cytoplasmic membrane found? is it a bilayer? does it contain sterols/cholesterols?
just inside the peptidoglycan layer. it is a lipid bilayer, but does not usually contain sterols/cholesterols, (except mycoplasma).
where is the ETC found in bacteria?
in the cytoplasmic membrane, (bacteria lack mitochondria)
does ATP synthesis occur in the cytoplasmic membrane?
yes
where do DNA segregation and septum formation occur during bacterial division?
in the cytoplasmic membrane
where do synthesis of DNA and cell wall component formation occur in bacteria?
in the cytoplasmic membrane in a nucleoid
what is found in the cytoplasm of bacteria?
ribosomes, granules, nucleoid, and plasmids, (appears busy b/c of lack of compartmentalization)
why does the cytoplasm of bacteria appear granular?
it is packed with ribosomes
what is the nucleoid? is there a nuclear membrane?
area where DNA is located. the DNA is tightly packed and attached to the cytoplasmic membrane. there is no nuclear membrane.
what are plasmids?
extrachromosomal, double stranded circular DNA molecules that replicate independently of the chromosome.
are plasmids required for survival?
plasmids are not required for survival, but can provide a selective advantage
what is one of the most important virulence factors that can be expressed by a bacterium?
the capsule
what is the bacterial capsule composed of? what does it do?
it is a gelatinous and composed of a polysaccharide, (sometimes peptides). it can be used to establish serotypes by antigenic differences, (variations in bonds/sugars). it protects the cell from phagocytosis, (innate response), and promotes adherence to tissues, prostheses and catheters
what can some bacterial cells produce in addition to the capsule?
a biofilm/slime layer that is less discrete, it facilitates binding to host cells and surfaces, as well as provides protection from immune systems/antibiotics. it can cover many organisms, (think plaque on teeth)
what are flagella? what kinds of bacteria are they found on? are they antigenic? where are they located?
flagella are long helical protein filaments that propel bacteria toward nutrients. they are mostly found on rod shaped bacteria, and absent in cocci. they are antigenic, and can be used to ID species – they vary in number according to species and can be located at one or more end, or completely surround the bacteria
can flagella undergo antigenic and phase variation?
yes
what is antigenic and phase variation?
the bacteria changes its antigenic properties defensively
what are pili? what are they composed of? what kinds of bacteria are they found in? what do they do?
pili are hair-like structures composed of protein subunits called pilin and are found on mostly gram -, but some gram + bacteria. they have adhesin at the tip and mediate specific adherence to other bacteria/host cells, sometimes they are required for infection.
what are F-pili?
“sex pili” that are involved in genetic exchange between gram – bacteria, conjugation
what are endospores? what are some bacteria that use them?
metabolically inert structures formed by gram + bacteria in response to environmental stress such as nutrient depletion. they are resistant to heat, drying, and chemical agents for years and return to vegetative state when good conditions return. bacillus and clostridia both use endospores.
what is a common place endospores are found?
inside the mother cell
by what process do bacteria reproduce? what is the time required for doubling called?
bacterial cells reproduce via binary fission, an exponential process where the cells grow by increasing cellular constituents and dividing into 2 cells. the time required for doubling is called generation time.
what are the stages of bacterial growth called?
lag phase, log/exponential growth phase, stationary phase, and death/logarithmic decline phase
what is the lag phase of bacterial growth?
the cells are not dividing, but are very metabolically active. the bacteria are “feeling out” their environment as well as undergoing DNA and enzyme synthesis
what is the log/exponential growth phase of bacterial growth?
the period when bacteria actually start dividing, the quality of this growth can depend on the environment
what is the stationary phase of bacterial growth?
the period when the nutrients in the bacteria’s environment start to become depleted. the number of bacteria dying and being produced equals out, the nutrient begin to be exhausted and waste builds
what is the death or logarithmic decline phase of bacterial growth?
when the number of bacteria dying exceeds the number being produced in the media
what are some factors that affect bacterial growth?
the availability of major/minor essential elements such as carbon, (required by all organisms), nitrogen, (needed for protein synthesis), iron, (needed for ETCs of some organisms)
what pH do most bacteria grow best at?
7, though some like lactobacillus can grow at lower pH conditions
what temperature do most bacteria prefer?
around 37 degrees C, though it can range from 25-42 C. (enterococci – ~42 C, listeria – ~25 C)
what is the ideal salt concentration for bacteria?
osmotic conc. of around 8.5% is ideal, any higher, and water will start leaving the organism
how do bacteria protect themselves from oxygen? do bacteria need O2?
obligate aerobic bacteria need O2 and have superoxide dismutase to convert superoxide to hydrogen peroxide, and some have peroxidase or catalase to further break down hydrogen peroxide into water and O2. some bacteria need oxygen, however most pathogenic bacteria are facultative anaerobes, meaning they can grow with or without O2
what do facultative anaerobic bacteria do when there is no O2? when there is O2?
if no O2, facultative anaerobic bacteria can go through fermentation, if O2, aerobic respiration. some can even undergo anerobic respiration, using something other than N as a terminal electron acceptor
what are obligate anerobic bacteria? what happens if they are exposed to O2?
they cannot be in the presence of O2, and will die due to lack of superoxide dismutase, peroxidase, or catalase
what are aerotolerant anaerobes?
anaerobic bacteria that can tolerate O2, but won’t grow much in its presence. they do have superoxide dismutase
what are microaerophiles?
they can grow in the presence of O2, but only low levels
what are capnophilic bacteria?
bacteria that grow in a CO2 enhanced atmosphere
how does bacterial metabolism compare to mammalian? what are they geared toward? what about energy sources/nutritional requirements?
bacterial metabolism is geared toward higher growth, (10-100x faster), it is more versatile in terms of energy sources and can use other oxidants than oxygen in metabolism. they are also more diverse in terms of nutritional requirements
how do bacteria synthesize macromolecules as compared to mammalian cells? are there biosynthetic processes unique to bacteria?
bacteria’s simple structure makes it possible for them to synthesize macromolecules in more streamlined ways. production of murein, lipooligosaccharide, and teichoic acid are unique to bacteria
in increasing order of efficiency, how do bacteria produce energy?
fermentation, (2 ATPs), anaerobic respiration, aerobic respiration, (36 ATP)
why is the fermantation process of different bacteria significant?
many bacteria can be IDed according to their fermentative end products, some end products can be quite toxic
can aminoglycoside antibiotics be used on anerobic bacteria?
no, they only affect anerobic bacteria
what are some molecules anaerobic bacteria use as terminal electron acceptors?
NO—, SO4–, and CO2
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