EK Microbiology COPY Flashcards
“cocci”
circular bacteria, sphere
ex. streptococcus refers to round like shape to it!
“bacilli”
rod shaped bacteria
ex. e.coli famous rod shape but exception not with last name bacilli, but does have this apperance thats an important exception* very often tested
** think bascillus in Harry Potter, killed with a rod through the head- so rod shaped bacteria**
spirilli
spiral shaped bacteria. tells us spiral like spagetti, squiggle line.
ex. Syphilis an std has this cork screw shape, uses cork screw shape to its advantage once it happens to pass by if there is some nic in the skin, will take that cork screw and screw into tissue make that infection. Imagine in mind says has to be doing that, three different shapes expected to know
flagella
“______” trichous, this ending refers to fact bacteria does have a flagella! a couple of different ways to describe flagella, so if you were to see monotrichous means only has one flagella
can be: monotrichous, amphi trichous, peritrichous
mono- means one flagella
amphi- arrangement of flagella either end of bacteria
peri - many many flagella all over the place, all over bacteria
prokaryotic cells
Unicellular
Lack a nucleus & membrane bound organelles
Two classes of prokaryotes: archaea and eubacteria
archaea
Ancient prokaryotes, distinct from bacteria
Some biochemical mechanisms are eukaryotic-like (transcription, translation)
Some but not all live in extreme environments
Thermophiles – grow and thrive in very hot environments (e.g., boiling ocean vent)
Halophiles – can grow in saturated salt
Methanogens – generate methane during their growth
Less is known than about eubacteria
eubacteria (bacteria)
DNA is double stranded circular chromosome
Transcription and translation occur in the cytoplasm
Peptidoglycan cell wall: sugar and peptide polymer
Ribosomes similar to eukaryotic ribosomes but smaller
One or more plasmids – circular DNA molecules, often confer antibiotic resistance
Roughly 1/10 size of eukaryotic cells; 10× bigger than virus
Observable with light microscope
Targets of antibiotics are ribosome and cell wall synthesis
Basal unit connected to hook, hook connects basal unit to filament, reverse spin of filament to go counterclock wise in opposite direction*
two diff arrangements for cell wall and membrane gram positive or gram negative
bacterial shapes
Bacteria can be classified by shape, gram-staining, and metabolism
Shapes are rod (bacillus), sphere (coccus), or helical (spirilla, spirochete)
gram staining
Gram stain is retained by peptidoglycan wall
Gram positive bacteria are stained purple
Gram positive bacteria: thick peptidoglycan wall
Gram negative bacteria: very thin peptidoglycan wall, outer membrane
Gram positive bacteria are vulnerable to antibiotics that target cell wall synthesis
gram negative bacteria
Very thin peptidoglycan wall, outer membrane
LIGHT PINK COLOR b/c cell wall a lot thinner, because a lot thinner cannot retain as much as hte stain as gram positive would be able to so its lighter in color as a result
Gram positive bacteria are vulnerable to antibiotics that target cell wall synthesis
cell wall is btw two membranes outer membrane and inner membrane, so one thing that happens with gram negative bacterium tend to be more antibiotic resistant*** a lot harder for antibiotic to make it through two membranes we have shown here* so if you are readin a passage tells you particular pateint has bacteria infection given antibiotics not working what is the reason for this?….. describe scenario with gram negative or gram positive situation, it will be gram negative that most likely causes that particular infection because tends to be more antibitoic resistant*-
to remember=think did the antbotics works “NEGATIVE” so gram negative thin wall pink
space in btw membranes calld periplasmic space contains enzymes that say an antibiotic happens to get in well those enzymes happen to break down that antiobitc so no effect on particular bacteria- so a couple raesons why can fight off antibiotics!
gram positive
Gram positive bacteria are stained dark purple
Gram positive bacteria: thick peptidoglycan wall
Thick cell wall keeps dye stuck in cell, within cell wall molecule peptidoglycan is found in cell wall to rpovide it with strength and stability
Cell wall surrpounds cell membrane, helps prevent cell from taking on too much water and what lysozyme will punch holes into to make sure can’t regulate osmosis take on too much water and break open
aerobes and anaerobes
Aerobic growth uses oxygen for metabolism
Anaerobic growth occurs in the absence of oxygen
Obligate aerobe (bacteria) requires oxygen and cellular respiration for growth, use it and survive bound to lifestyle of living with oxygen, if oxygen not there will die off
Obligate anaerobe utilizes anaerobic fermentation, does not grow in oxygen; in this case they prefer to live with oxygen absent and can only live with oxygen absent, if oxygen is prsent they will die off! ex bacteria in gut mainly obligate anaerobe, they are living in lumen where food passing through** not physically living in cells that make up lining so yes oxygen in cells supply with oxygen they need but in lumen by time food gets down to gut that is why they are obligate anerobes****
Facultative anaerobe can grow in aerobic or anaerobic conditions; in case oxygen is there can actually use it!!! and still survive! so use it and still survive, but prefer to ferment adn survive without oxygen! much rather be fermenting “think faculty make it work”
tolerant anaerobe- oxygen doesnt kill them but not using it; so doesn’t use it doesnt kill them
heterotrophs and autotrophs
Heterotroph – consumes organic matter for food
Most bacteria are heterotrophs
Autotroph – synthesizes its own food from inorganic substances (e.g., CO2, H2S, NH3)
Photosynthetic autotrophs use light to generate energy
Chemosynthetic autotrophs use chemical nutrients for energy
Some bacteria are photosynthetic autotrophs (e.g., cyanobacteria)
symbiosis and parasitism
Symbiotic relationship: bacteria (symbiont) lives together with host
Three types of symbiotic relationships
- Mutualism: both organisms benefit (e.g., bacteria in our gut synthesize vitamins B, K)
- Parasitism: one organism benefits at the other’s expense (e.g., tuberculosis)
- Commensalism: benefits bacterium, neutral for host
Opportunistic infections: normally harmless bacteria cause disease in certain situations
• Example: intestine penetrated, mutualistic bacteria enter and infect abdominal cavity
bacterial toxins
Exotoxins – secreted proteins can cause pathology in absence of bacteria
Endotoxins – toxins that are integral part of bacterial membrane
*some bacteria cause symptoms because they secrete proteins becuase they are toxic, they are secreted by bacteria and then cause all kinds of symptoms like coughin in the host*
other bacteria that have endotoxins meaning proteins that cause symptoms are actually part of the bacterial membrane, not released from host, certainly aggregavate host part of host cell; if bacteria causing symptoms becuase of endotoxin attached to bacteria, if kill bacteria symptoms end, if having bacteria releasing some exotoxin you cna kill the bacteria and the person will still be very sick for a while*** ex of that is whooping cough, bacteria causes whoopign cough releases toxin that causes ppl to cough for months and months can get rid of bacteria completley done and person will still have horribel cough for months becuase of exotoxin, thsi is why if traeated with antibitoics immediately before they even have symptosm then antibitoics will ehlp, but realisatically until ppl do not cough heavily because they do not know they are infected- why this vaccine is so so improtant***
bacteria reproduction
Bacteria reproduce asexually by binary fission, forms a colony; basically like mitosis
Can undergo fission each ~20 min under optimal conditions
Chromosome replicates, septum forms between cells
Growth kinetics have (1) lag phase, (2) exponential growth, (3) saturation, and (4) death
- Lag phase: bacteria acclimate to nutrients in surroundings, adapt gene expression
- Exponential phase: bacteria double robustly
- Saturation phase: growth subsides as bacteria compete for limiting nutrients
- Death phase: bacteria die from lack of nutrients and accumulated toxic waste products, waste products start killing cells*
ALL ASEXUAL could be sponatenous mutaiton but no genetic change built in! in contrast with the processes with dna transfer and sexual reproduction: 3 processes that alter dna of bacterial cells: transformaton, transduction and confirmation
bacteria genetic diversity
Bacteria can mutate spontaneously
Rapid growth affords significant genetic diversity
Can incorporate DNA by recombination (see below)
bacteria can exchange DNA by 3 mechanisms:
Bacteria can exchange DNA by three mechanisms:
Transformation: uptake of DNA from external environment
Transduction: phage transfers bacterial genes from one cell to another
Conjugation: transfer of DNA via mating
- transformation
Transformation: uptake of DNA from external environment
In nature, DNA released from lysed bacterial cells or elsewhere can be taken up
In the laboratory, can force bacteria to take up plasmids
- transduction
Transduction: phage transfers bacterial genes from one cell to another
Bacterial DNA can be incorporated during imprecise prophage excision (specialized)
Bacterial DNA can be mistakenly encapsulated by phage (generalized)
- conjugation
how bacteria does want to gain any genetic variability!!!
Conjugation: transfer of DNA via mating
Conjugation is sexual reproduction
Requires a conjugative plasmid that carries a gene producing a pillus
F and R plasmids: F = Fertility, R = Resistance
F+ bacteria (male) mates with F– bacteria (female)
F+ makes pillus and transfers plasmid DNA to recipient
Integration of F plasmid to chromosome allows transfer of chromosomal genes
F plasmid integrant = Hfr strain (High frequency recombination)
R plasmids can spread antibiotic resistance
one where there is a bridge! where dna gets passed over the bridge from one cell to another*
the plasmid has the genes required to build the mating bridg,e but there can also be other genes on F plasmid, most common example is gene for antiobitoic resistance, so if ever get question or passage abotu soemone who is becomign resistant to a certain antibtoic answer will be= conjugation, main mechnaism for antiobiotic resistance spreading in patients**
endospores
When growth conditions are unfavorable, bacteria can form an endospore
Endospore forms within bacterium and is released by breakdown of the cell wall
Endospore is tough and can survive adverse conditions (e.g., poor nutrients, heat, UV)
Dormant endospore can persist for long periods of time
Endospore will germinate when conditions for growth are good
Examples of bacteria that form endospores: anthrax, tetanus
bacterial flagellar movement
Bacteria often use a flagellum for movement
Flagellum has three components: filament, hook, basal body
Filament is hollow tube made up of flagellin protein subunits
Hook is a curved structure that connects the filament to the basal body
Basal body is composed of rings that anchor the flagellum to the cell wall and membrane
Basal body contains a motor protein that is driven by protons
Chemotaxis = movement of cell toward or away from a chemical cue (like food or toxin)
general characteristics of fungi
Fungi are eukaryotes VERY VERY DIVERSE
Share properties of complex eukaryotes (organelles, introns, linear chromosomes)
Cell wall made of chitin (nitrogen-containing sugar)
Most fungi are multicellular (e.g., molds and mushrooms)
Some fungi are unicellular (i.e., yeast)
Fungi are heterotrophs: require carbon energy from outside sources
Fungi are typically saprophytes: consume dead organic material, so they have asked before fungi are X….. they are saprophytes becuase they consume dead organic material
Most are aerobic, some are facultative anerobes (e.g., yeast)
Can form filamentous stalks called hyphae
Mycelium is a bunch of hyphae
Fungi can be helpful (antibiotics, alcohol) or pathogenic (athlete’s foot)
very varied category- can reproduce asexually or sexually
fungi life cycle
Fungi have two life forms: haploid and diploid
Typically grow as haploids
Haploid = 1 copy of each chromosome (1n)
Haploid fungi reproduce asexually by budding or binary fission
Budding is the formation of a smaller daughter cell from a mother cell
In adverse conditions, fungi undergo sexual reproduction and become diploids
During sexual reproduction, two haploid cells fuse to form a diploid
Diploid = 2 copies of each chromosome (2n)
Diploid cells undergo meiosis and yield 4 haploid spores
Spores can survive adverse conditions before germination
viruses
Viruses are acellular
Need host cells for reproduction = are obligate intracellular parasites: means they can only reproduce inside of a host* can’t complete their life cycle* in a nutrient broth vs why bacteria*
NOT TECHNICALLY ALIVE, but everything else is alive*
Smaller than bacteria (need an electron microscope to visualize virus)
Can pass through filters that catch bacteria, because so tiny
Contains DNA or RNA, not both
DNA or RNA can be single-stranded or double-stranded- very diverse, usually DNA or RNA surrounded by protein coat claled a capsid* the protein coat around the virus
Capsid is the external protein coat
Some viruses also have an outer membrane envelope
Envelope is derived from host cell membrane and contains viral proteins
Single virus particle is called a virion
viral vs bacterial distinctions
Bacteria can grow in purified nutrient broth, virus cannot
Virus requires host cells to infect and propagate itself
Bacteria is susceptible to antibiotics (ribosomes, cell wall)
Virus not affected by antibiotics (no ribosomes, no cell wall)
Virus can pass through filters that trap bacteria (virus is smaller)
bacterial viruses
BACTERIOPHAGES
Bacteriophages (phages) are viruses that infect bacteria
Capsid coat has a head and tail
Head contains nucleic acid
Tail attaches to bacterium and injects nucleic acid
After injection of DNA, capsid remains outside of cell
If protein is labeled with radioactive sulfur and DNA is labeled with radioactive phosphorus, the signal for phosphorus will end up inside the bacterial cell and the signal for sulfur will remain outside (Hershey-Chase experiment).
After entering bacterium, 2 alternative pathways for growth: lytic and lysogenic
lytic growth
In lytic growth, phage enters cells and replicates
Uses host machinery to synthesize viral components
Viral components self-assemble and form mature virions
Lytic enzymes cause bacterium to burst, releasing phages
Burst can release hundreds or thousands of phages
Phages that only reproduce via lytic growth are called virulent
Punches a hole (plaque) on a bacterial lawn
lysogenic growth
In lysogenic growth, phage DNA integrates in bacterial chromosome
Integrated phage DNA is called prophage
Prophage replicates along with host chromosome
In adverse conditions (poor nutrients, stress) prophage will enter lytic cycle
Occasionally, prophage will spontaneously enter lytic cycle
Phages that reproduce by lysogenic cycles are called temperate
receptors + virus entry
Coat proteins of the virus determine which cells can be infected
Coat proteins bind to a cell surface receptor to enable viral entry
Tissue- and species-specificity of infection depends on host receptor expression
Can use different receptors in different tissues
viral life cycle
Virus binds and gains entry to cell via a receptor
Some viruses bind to receptor and fuse with membrane directly
Some viruses bind to receptor, are endocytosed → into endosome
Then must escape endosome
Within cell, capsid opens and releases nucleic acid and proteins
Nucleic acid enters nucleus and is replicated
Viral mRNAs are synthesized
Viral proteins are produced on host ribosomes
Virus assembles and is released from cell by lysis or budding
Virus infection may inhibit host DNA, RNA, protein synthesis and damage the cell
retroviruses
Retrovirus is class of RNA virus (e.g., HIV)
Contains an RNA to DNA polymerase = reverse transcriptase
RNA is reverse-transcribed to ssDNA and then dsDNA
DNA is stably integrated to host chromosome
Integrase is enzyme for integration
Virus can remain dormant for a long time
Ability to integrate into DNA makes retroviruses possible route for gene therapy
REMEMBER WE DO NOT HAVE REVERSE TRANSCRIPTASE, HIV so hip brings its own
anti-HIV and antiviral drugs
Virus growth not affected by antibiotics
Anti-viral drugs target certain steps of life cycle
Some antiviral drugs often block nucleic acid synthesis (e.g., AZT for HIV)
Other antiviral drugs affect viral entry or assembly