Microbiology Flashcards
what is the definition of taxonomy?
define systems by shared characteristic
what is the definition of classification?
arrange organisms into groups
what is nomenclature?
assigning names
what are the 3 cellular biological entities?
eukarya, archaea, bacteria
what are the 4 acellular biological entities?
viruses, viroids, virusoids, prions
what is the order of taxonomic ranks?
domain phylum class order family subfamily genus species
what is a the definition of species?
a group of living organisms capable of interbreeding even if geographically isolated
what is the definition of a species in microbiology?
collection of strains that share stable properties but differ significantly from other groups of strains
what is the definition of a strain?
a genetic variant or subtype of a bacterial species that varies slightly from other members of the same species
what is the definition of phenotype?
an organisms observable characteristics or traits
what is the definition of serotype
distinct variations in cell surface antigens within a species
what is the definition of genotype?
the part of the genetic makeup of a cell, which determines one of its characteristics
in terms of nucleic acid sequencing, why are 16s rRNA used?
- used in phylogenetics due to slow rate of evolution
- can also be used in diagnosis
what is vertical gene transmission?
passage of genetic information from parent to offspring
what is horizontal gene transmission?
the acquisition of genetic information by transfer from an organism that is not its parent
what is whole genome sequencing?
determines the complete DNA sequence of an organism at a single time
how can you characterise using the whole genome sequence? (4)
- presence/absence of genes
- gene mutations
- gene insertions/deletions
- phylogenetics
what is the definition of phylogenetics?
the study of evolutionary relationships among biological entities (within species)
what is the function of phylogenetic trees?
visualise evolutionary relationships between organisms
why do bacterial cells adapt more readily to environmental changes than eukaryotic cells?
they have the ability to metabolise wider range of substrates
what is peptidoglycan? what is its function?
a polymer of sugar and amino acids that lets particles less than 2nm through in both gram positive and gram negative membranes
what is the plasma membrane in a bacterial cell made up of? (3)
lipid bilayer, proteins, lipopolysaccharide (gram neg)
is there sterols in the lipid bilayer of a bacterial cell?
no
what are the two main types of proteins in the membrane of a bacterial cell?
integral and peripheral
what are some features of integral membrane proteins? (3)
- makes up 75% of the membrane proteins
- tightly attached or stretched across the lipid bilayer
- ion transport
what are some features of peripheral membrane proteins?
- makes up 25% of the membrane proteins
- aqueous solubility
- cholesterol oxidases
what are lipopolysaccharides?
they contribute to the structural integrity of bacterial cells
what are the 3 domains in a lipopolysaccharide?
- O antigen
- core antigen
- lipid A
what is the function of the flagella?
motility
different positioning terms of flagella: (4)
monotrichous- 1 on 1 end
lophtrichous- a few on one end
amphitrichous- one on each end
peritrichous- lots coming out all over cell
what are the flagella powered by?
H+ flow
on what type of bacteria are pilli found?
gram negative
what are the two types of pilli on bacteria and what are their functions?
- conjugative pilli: allow transfer of DNA between two bacteria
- type IV pilli: can generate twitching motility
what is the capsule and slime layer usually comprised of?
polysaccharides
if organised and permanent (bacterial cell components)
capsule
if loosely formed (bacterial cell components)
slime layer
what is the nucleoid?
the main component of bacterial genetic material
what are some features of the nucleoid? (3)
- not membrane bound
- single chromosome of double stranded DNA
- DNA highly coiled
what is a plasmid?
extrachromosomal pieces of DNA in bacterial cells
what are some features of plasmids? (2)
- can be transferred between cells
- often only contain non-essential genes e.g. antibiotic resistance
what is the function of a ribosome in bacterial cells?
they are a target for antibiotics
what does a rooted phylogenetic tree show?
each node is based upon inferred most recent ancestor
what does an unrooted phylogenetic tree show?
only how each leaf relates to others (no inference on ancestry)
what are the features of a category 1 organism? what can you do to prevent harm? (e.g E. coli)
- pose minimal levels of threat
- generally non-pathogenic
- wash hands and sterilise all equipment before and after use
what are the features of a category 2 organism? what can you do to prevent harm? (e.g staphylococcus aureus)
- can cause human disease and may be hazardous to environment
- unlikely to spread through the local population
- only handled by trained professionals
- perform in biosafety cabinets
what are the features of a category 3 organism? what can you do to prevent harm? (rabies virus)
- can cause severe human disease and may be severity hazardous to environment
- can travel through local population
- highly regulated
- trained and vaccinated professionals
- under negative air pressure
what are the features of a category 4 organism? what can be done to prevent harm? (e.g Ebola virus)
- causes severe human disease and usually death
- high risk of spread through local population
- no effective vaccination available
- highly trained personnel
what are the two ways to culture microorganisms?
- liquid media (broth)
- solid media (agar plates)
how do microorganisms grow in liquid media?
they grow as individual cells until available nutrients are exhausted, producing a suspension of cells
how do microorganisms grow on solid media?
bacteria and fungi form colonies with distinctive appearances, each colony deriving from a single cell
what is an undefined media?
it contains chemically undefined yeast/vegetable/meat extracts and digested proteins. it varies from batch to batch
what is a defined media?
all components are chemically defined and highly reproducible
name 3 methods that can be used for anaerobic cultures
- anaerobic cabinet
- GasPak sachets
- Candle extinction
give some features of an anaerobic cabinet (3)
- big insulator cabinet
- 95% N2 5% H2 with a palladium catalyst
- can be under positive pressure
how do GasPak sachets work?
produces CO2 and H2 from breakdown of citric acid, cobalt chloride and sodium borohydride
how does candle extinction work?
uses up oxygen by burning a candle in a jar
how do bacterial cells reproduce?
binary fission
what are some features off primary metabolism? (4)
- includes major metallic pathways
- energy production and release
- cell component synthesis
- enzyme production
what are some features of secondary metabolism? (3)
- non-essential metabolic pathways
- includes production of natural products e.g antibiotics
- production of secondary metabolites in disease states which can increase pathogenicity e.g pyocyanin
name 6 important criteria required when bulk culturing microorganisms
- maintain adequate mixing
- maintain high oxygen levels (aerobic)
- control pH
- control temp
- control foam
- initial starting concentration
what is evolution?
changes in population overtime
give two reasons why evolution might occur
- acquisition of new genes
- mutation of existing genes
what is the definition of a mutation?
a permanent change in a single cell, does not necessarily cause any noticeable change or get passed on.
why may a mutation not get passed on? (3)
- UV irradiation
- chemical exposure
- poor genome copy
name the three main mechanisms by which bacteria can evolve
- transformation
- transduction
- conjugation
what is transformation? (bacterial evolution)
direct uptake of DNA through cell membrane
what is transduction? (bacterial evolution)
introduction of genetic material via a viral vector
what is conjugation? (bacterial evolution)
the transfer of genetic material between two directly connected bacteria
