microbio Flashcards
major groups of life (3) inc. eg’s
- eukaryotes (protozoa/fungi)
- prokaryotes (bacteria)
- non-living (viruses)
components of cell structure (4)
- plasma membrane
- cell wall
- ribosomes
- capsule/flagellar/pili
is the cell wall gram +ve or -ve
can be both (LPS= component of gram -ve outer membrane)
importance of cell wall
target of penicillin
what is the gram -ve outer membrane layer composed of
lipopolysaccharide (LPS)
are fimbriae gram -ve or +ve
gram -ve
role of fimbriae
adherence and sex
steps involved in prokaryotic protein synthesis (3)
- gene (DNA) -> mRNA (DNA dependent RNA polymerase) = transcription
- mRNA -> ribosome (tRNA)
- ribosome (tRNA) -> protein (translation)
importance of prokaryotic protein syntheses
target for antibiotics
where does prokaryotic protein synthesis take place
cytoplasmic membrane
what food source is required for prokaryotic growth (4)
- C source (organic e.g. proteins/sugars, and inorganic e.g. fix CO2)
- oxygen and hydrogen
- N source (amino acid ammonia)
- inorganic salts (P, S, K, Mg, Ca, Fe)
what is the most important requirement for prokaryotic growth
oxygen
prokaryotic growth requirements
- nutrition (food)
- environment (temp., hydrogen ion conc/pH, osmotic protection, oxygen)
bacteria involved in dental caries and classification (2)
- cocci (streptococci)
- bacilli (lactobacilli)
- > both facultative anaerobes
- > GRAM POSITIVE
bacteria involved in periodontal diseases and classification
- bacilli (GNABS)
- > anaerobic
- > GRAM NEGATIVE
tb
bacteria in lungs
DNA evidence techniques involved in molecular analysis of bacteria (2)
- 16s RNA
- metagenomics
classification/taxonomy of the animalia kingdom:
- kingdom
- phylum
- class
- order
- family
- genus
- species
- kingdom = animalia
- phylum = chordata
- class = mammalia
- order =primates
- family = hominoidea
- genus = homo
- species = sapiens
classification/taxonomy of the bacteria kingdom:
- kingdom
- phylum
- class
- order
- family
- genus
- species
- kingdom = bacteria
- phylum = firmicutes
- class = bacilli
- order = bacillales
- family = bacillaceae
- genus = bacillus
- species = subtilis
important ways of classifying bacteria (3)
- shape (coccus, bacillus, etc)
- cell wall (grams stain)
- metabolism (growth in oxygen- aerobic, anaerobic, facultative)
why is classifying bacteria and identifying the organism involved in infection so important
it is the first step in treatment
bacteria shapes (3)
- cocci (spheres)
- bacilli (rods)
- spiral shaped
eg. of rigid spiral bacterium
spirillum
eg. of flexible spiral bacterium
spirochaete
difference in gram -ve and gram +ve cell wall
gram -ve:
- > cytoplasmic membrane
- > peptidoglycan
- > outer membrane
- > lipopolysaccharide
gram +ve:
- > cytoplasmic membrane
- > peptidoglycan
- > teichoic acid
aerobic bacteria definition
grow in oxygen
obligate aerobe bacteria definition
require oxygen
obligate anaerobe bacteria definition
killed by oxygen
facultative anaerobic bacteria definition
tolerate oxygen
how do most bacteria divide during the bacterial cell cycle
binary fission (into 2 identical daughter cells)
bacterial chromosome of most prokaryotes
single circular chromosome
chromosome replication steps (3)
- initiation site = the origin oriC
- two replication forks proceed bidirectionally
- termination = in a 100Kb region opposite the origin
steps involved in prokaryotic cell cycle eg. escherichia/E. coli (2)
- C period (40 minutes) = period of initiation of chromosome replication to completion of replication
- D period (20 minutes) = division
what determines the rate of E.coli growth
no. of chromosome replication origin sites
division of 35 minute bacterial cell cycle (2)
- 15 minutes for replication/C period
- 20 minutes for D period
what regulates chromosome replication
availability of DnaA protein (DnaA-ATP binds to DnaA boxes within origin)
central event of bacterial cell division
assembly of FtsZ ring
what controls bacterial cell division
regulation of FtsZ
key proteins involved in bacterial cell division (2)
- FtsZ
- PBP3 (penicillin binding protein, encoded by ftsI)
role of penicillin binding protein
target of penicillin (cross links peptide side chains/transpeptidation)
summary of prokaryotic (bacterial) cell cycle (4)
- chromosome replication
- chromosome segregation
- elongation
- cell division
virus definition
obligate intracellular parasite
components of virus structure
- nucleic acid genome
- protein capsid, protecting/delivering genome
- sometimes a lipid envelope consisting of lipid bilayer and containing viral proteins
why are viruses unique
other organisms divide, viruses assemble from components
steps involved in virus replication cycle (5)
- attachment (attachment proteins on surface of virus particle bind to receptors on host cell surface)
- entry (via 2 mechanisms = direct fusion or endocytosis)
- gene expression (transcription of genome into virus mRNA, translation into virus proteins and modification into mature proteins) and genome replication once inside host cell
- assembly of proteins and genomes into virus particles
- release from host cell (via cell lysis for non enveloped viruses, and via budding for enveloped viruses)
what is a bacteriophage and what is lysogeny
- a virus which parasitizes a bacterium by infecting it and reproducing inside it
- > an obligate intracellular parasite/virus that multiplies inside bacteria
- > lysogeny is a way of a virus entering its host cell, incorporating its DNA into its host chromosome, so that it replicates, then synthesising viral proteins in order for cell lysis and large numbers of viruses to be released
how do viruses enter the host (4)
- resp tract by inhalation/touch
- GI tract by ingestion/inhalation
- urogenitary tract by sexual transmission
- blood via blood products, needles, mother-child spread, insect bites