Microbiology Revision

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  • Created by: ImFord
  • Created on: 04-04-23 11:10
What is LUCA?
Last Universal Common Ancestor
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What is the Submarine Mound hypothesis?
The flow of substances through ocean crust in hot hydrothermal water created mineral pores, which grew more complex and dispersed after forming bilayers
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What is the Clay Hypothesis?
A fatty acid soup was formed, creating micelles and vesicles. Aqueous HCN formed after energy from a meteorite and UV light created a nucleotide precursor. A single-strand nucleic acid was formed, leading to vesicles, ribozymes and then, eventually LUCA.
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What is endosymbiosis?
When a cell is taken up by another and they live and function
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What is used to measure molecular phylogeny in microorganisms?
16S + 18S rRNA
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What is Multilocus Sequence Typing?
Several house-keeping genes are studied to examine phylogenetic relationships
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What are the three methods of bacterial classification?
Phylogenetic, Phenotypic and Genotypic
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What is the standard reference used for bacterial taxonomy?
Bergey's Manual of Systematic Bacteriology (1923)
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What defines the prokaryotic species?
Share same "core house-keeping" genes
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How can strains differ?
Biochemistry, morphology and antigens
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Who first described microorganisms and when?
Robert Hooke (1665)
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Who first observed bacteria with a single-lens microscope?
Antony van Leeuwenhoek (1676)
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What is spontaneous generation?
Microorganisms arise spontaneously from non-living matter
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What were Pasteur's experiments?
Using a swan-neck flask, Pasteur found that contamination only occurred upon environmental exposure, suggesting life doesn't emerge spontaneously.
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What are culture-based techniques?
Using a medium to grow and study microorganisms
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Why is metagenomics useful?
The whole community can be used and identified
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Is this structure Gram-positive or Gram-negative: cytoplasmic membrane and thick cell wall?
Positive
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Is this structure Gram-positive or Gram-negative: cell membrane, thin cell wall and outer membrane
Negative
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Is this structure Gram-positive or Gram-negative: pili?
Negative
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Both Gram-positive and Gram-negative bacteria have repeating NAM and NAG lattices connected with glycosidic bonds but what's the difference between them?
Gram-positive have interbridge links to reinforce strength whereas Gram-negative have direct NAM-NAM links.
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Which substances produce antitoxins or immunogens (if its Gram-positive) in each type?
Lipoteichoic acid and teichoic acid (Positive) and lipopolysaccharide (Negative)
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What is the correct order for Gram staining?
Crystal violet, iodine, alcohol wash, safranin
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Why are Gram-positive bacteria purple and why are Gram-negative bacteria pink?
The iodine is a mordant and reinforces the bonds between the purple crystal violet dye and the peptidoglycan bonds in Gram-positive cell walls, which has a much higher quantity.
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What is the glycocalyx?
An extracellular polymeric substance responsible for virulence and biofilm
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What are inclusions?
Storage for excess nutrients or energy within cytoplasmic structures
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What are the three components of a flagellum?
Filament (extension and spin), hook (attach) and basal body (motor)
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What are fimbriae used for?
Attachment for biofilm formation
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What are pili used for?
Motility and DNA transfer (F+ to F-)
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Describe the bacterial flora on the skin
Approximately 180+ types of bacteria and several fungi, including Propionibacterium acnes (acne)
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Which bacteria is present in the oral cavity?
Fuscobacterium spp. (dental plaque)
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Which bacteria are particularly prevalent in the GI tract (causing disease)?
Helicobacter, Clostridium and Escherichia
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What are pathogens within the respiratory tract?
S. aureus and S.pneumoniae
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Which is the correct order for binary fission?
Origin of replication, oriC protein binds, cell elongation, chromosome replication, cell division
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What are the four phases of bacterial growth?
Lag, log, stationary and death
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What is the equation for generation time?
Number of cells = initial cells x 2^(number of generations)
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What does MPN and CFU mean? (Measuring microbial growth)
Most probable number and colony-forming units
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In order of lowest to highest, rank these bacteria based on the temperature of their conditions.
Psychrophile, mesophile, thermophile, hyperthermophile
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What is a cell wall adaptation for bacteria at LOW temperatures
Unsaturated fatty acids and short chains
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What are halophiles?
Optimum growth is at a salt concentration higher than 0.4M
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What are the two phases of glycolysis?
Energy investment and energy payoff
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What occurs in each stage of glycolysis?
Glucose is phosphorylated in the investment phase by using 2 ATP and oxidised (becoming pyruvate) in the payoff phase. 4 ATP and 2NADH are produced in the payoff phase.
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What occurs in the Krebs cycle (or the Citric Acid Cycle)?
Pyruvate reacts with coenzyme A to form Acetyl coenzyme A and then it reacts with carbon dioxide and NADH to produce carbon dioxide, NADH, FADH2 and GTP.
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What are the two types of fermentation?
Lactic acid (Streptococcus) and Alcohol (yeast)
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What does bacteria use in anoxygenic photosynthesis instead of water?
12 H2S and produces 12S
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What's the difference between cyclic and non-cyclic phosphorylation?
Two separate photosystems are used in non-cyclic whereas the electrons are recycled when the need for ATP exceeds the need for NADPH in cyclic.
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What are the three stages of the Calvin Cycle?
Fixation (RuBP+CO2->PGA), Reduction (3-PGA->G3P) and Regeneration (G3P+6ATP->RuBP)
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What are the four stages of the Nitrogen Cycle IN ORDER?
Ammonification, nitrification, denitrification and nitrogen fixation
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What are the two kinds of oxidation in nitrification?
COMAMMOX and ANAMMOX
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What are methanotrophs?
Aerobes that use methane monooxygenase to utilise methane as a carbon and energy source.
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What is the main difference between methanotrophs and methylotrophs and methanogens?
Methylotrophs use simple methyl compounds as well as methane and methanogens have carbon dioxide as their terminal acceptor.
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What are the two pathways for methanotrophs and who takes them?
Serine (alphaproteobacteria) and Ribulose (gammaproteobacteria)
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What is syntrophy?
Two organisms cooperate as they cannot complete a process alone
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Which direction does DNA replication go?
5'-3' (continuous) and 3'-5' (lagging)
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What are the three stages of RNA synthesis?
Initiation, elongation and termination
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What is an operon?
A unit of linked genes which regulates other genes in protein synthesis
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What's the difference between constitutive and regulatory genes?
Constitutive are constantly on whereas regulatory are on occasionally
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What must bind to the catabolic activator protein (CAP) on the lac operon to initiate transcription?
cAMP
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When is transcription induced in the lac operon?
When lactose is present and glucose is depleted
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What is attenuation?
Mechanisms that control both transcription and translation
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What is a riboswitch?
A naturally-occurring noncoding segment of RNA that mRNA can regulate directly for a conformational change
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What is the difference between vertical and horizontal gene transfer?
Vertical is parent to daughter whereas horizontal can be to any bacterial cell
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Which cycle incorporates the viral genome into the host DNA?
Lysogenic
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What is virulence defined by?
Virulence factors, including invasiveness, toxicity and tissue damage
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What is the difference between permissive and susceptible viruses?
Permissive completes the entire life cycle whereas susceptible doesn't
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How can you quantify bacteriophage activity?
Plaque assays (Pfu)
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What are prions responsible for?
Transmissible Spongiform Encephalopathies (TSEs) like Kuru kuru
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Which viral entry pathway is described incorrectly?
Endocytosis - absorbing other cells to spread disease
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What is a distinguishing trait of Neisseria gonorrhoea
"2 kidney" shape of the bacterial cells
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What is Neisserira gonorrhoea
Gram-negative and obligatory aerobe
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What's the difference between poisoning and infection?
Poisoning is where you ingest a preformed microbial toxin whereas infection is where food is contaminated with bacteria.
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Which bacterium has which toxin?
Clostridium perfringens: cytolytic toxin and Clostridium botulinum: AB toxin
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Why is the Shiga toxin in E.coli dangerous?
It produces a verotoxin, which can cause bloody diarrhoea and kidney failure
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What is an Hfr cell?
A bacterium with a conjugative (F) plasmid integrated
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What is NOT a feature of transposons?
Have no gene for transposase
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What's the difference between conservative and replicative transposon mechanisms?
Replicative produces a new copy whereas conservative does not
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What other vectors are available (excluding cloning vectors)
Shuttle and expression vectors
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What is environmental gene mining?
Isolating potentially interesting genes from the environment without culturing
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What is synthetic biology?
Genetic engineering to create novel biological systems
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Which definition is correct?
Both
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How do you make a polyvalent vaccine?
Combining a recombinant vaccine and a carrier virus
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What is the most diverse proteobacteria?
Gamma
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What metabolism do alphaproteobacteria use?
Intracellular oligotrophs
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How are firmicutes, tenericutes and actinobacteria classified?
G + C ratios
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What do archaeal cells have instead of a peptidoglycan cell wall?
S-layer protein
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What produces asexual spores (conidia) in multicellular fungi?
Hyphae
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What is the chitin cell wall made up of?
NAG Polymer
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What are the types of reproduction fungi are capable of and what are their functions?
Both
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What are the different classifications of fungi?
Ascomycete, basidiomycete, chytridiomycete, glomeromycete, zygomycete
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What is the order of phylogeny for fungi based on 18S rRNA screening?
C, Z, G, A, B
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Most protists are unicellular, but which is an exception?
Plant-like algae (ie kelp/brown algae)
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Protists can be capable of movement: what do they use to move?
Both
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What are the two distinct cytoplasm layers that give protists their unique shapes?
Ectoplasm (outer) and endoplasm (pellicle)
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Schizogony is an important component of asexual reproduction of protists. What is schizogony?
The cell nucleus rapidly divides to form a schizont, dividing more to form smaller merozoites.
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What is biochemical oxygen demand (BOD)?
Dissolved oxygen required by microbes to oxidise all inorganic and organic matter in 5 days at 20°C.
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How is anaerobic wastewater filtered?
Complex organic matter is hydrolysed, then fermented to break down the monomers. Acetogenesis occurs and then methanogenesis produces methane, carbon dioxide and water.
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ANNAMOX is anaerobic ammonium oxidation and can be conducted by chemolithoautotrophic bacteria for direct nitrogen removal. What does it produce and what bacteria does this?
N2 and Planctomycetes
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To create biofilm, what are the steps IN ORDER?
Reversible adhesion (planktonic bacteria), irreversible adhesion (EPS secretion), colonisation, active dispersal
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What is quorum sensing?
Communication via release/detection of diffusible chemical signals that regulate gene expression
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What is the difference between endo- and ectomycorrhizae?
Endo- consists of deeply-embedded fungus within cells, compromising root tissue. Ecto- are fungal cells forming an extensive sheath on the outside of a root.
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Polycyclic aromatic hydrocarbons (PAHs) increase in what as solubility decreases?
Sorption
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Increase in rings equals...
Increased toxicity
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What are the two stages of clean-up?
Confinement via booms/dams and removal with skimmers, sorbents and chemical dispersants
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