Applied Microbiology Flashcards
What is the key enzyme in the production of ethanol during fermentation?
pyruvate decarboxylase (PDC)
converts pyruvate to acetaldehyde which is reduced to ethanol by NADH
What is saccharification?
the conversion of polymeric substrates into fermentable sugars
eg starch broken down by amylase and amyloglucosidase (glucoamylase)
cullose by endoglucansase, exoglucanase and beta-glucosidase
Define different antibiotics and other antimicrobials
antibiotic: an agent which kills microorganisms
disinfectant: a chemical which can be used for killing microorganisms on surfaces
antiseptic: a disinfectant that can be used on human flesh eg to clean wounds and prevent infection
antibiotic: a substance produced by a microorganism (or derived from such a substance) which inhibits or kills other microorganisms
bactericidal: killing bacteria
bacteriostatic:
How does penicillin work?
suicide inhibitor of transpeptidases (penicillin-binding proteins) of peptidoglycan synthesis
forms a covalent bond to the target which forces the cell to lyse due to a lack of growth
humans do not produce peptidoglycan so has no effect
effective of gram+ bacteria, but little effect on gram- (except gonorrhoea
In what phase of bacterial and fungal growth are antibiotics produced?
trophophase and idiophase
What is an example of a semisynthetic antibiotic?
penicillin G is converted to semisynthetic penicillins by removal of the side chain and replacement w new side chain
Why are gram- bacteria generally resistant to antibiotics?
they possess a hydrophilic outer membrane that prevents hydrophobic compounds (like most antibiotics) from entering the cell
What are the ESKAPE bacteria?
the most problematic hospital acquired antibiotic resistant infections
Enterococcus, Staphylococcus, Klebsiella, Acinetobacter, Pseudomonas, Enterobacter
What enzyme in bacteria degrades/alters antibiotics? Give an example.
beta-lactamases
eg clavulanic acid
What resistance mechanisms do bacteria have against antibiotics?
resistance genes often encoded on plasmid which allows easy transfer
degradation/alteration of antibiotic
altered target
efflux pump
modifications of cell wall
What are some alternatives to antibiotics?
- bacteriophage therapy
- quorum sensing inhibitors, prevents attack
- antimicrobial peptides from animals have wide spectrum (are expensive and unstable)
What are areas in a metabolic pathway that are aimed to be improved?
- titre - product concentration: downstream processing (purification) cost
- yield: efficiency of substrate conversion
- productivity: product produced per time per yield
- robustness: survival of harsh conditions in reactor eg toxic products
What are some methods for improving a strain?
mutagenesis: mutation inducing chemicals
screening: examine many strains for improved phenotype
selection: culture so that only strains w desired phenotype grow
How was penicillin initially improved?
rational selection: penicillin chelates heavy metals, so strains that produce more penicillin can survive in higher heavy metal concentrations
Give an example of a method used to make a bacterium produce more product?
mutants resistant to toxic anti-metabolites often have mutant forms of the feedback inhibition enzyme so lacks allosteric regulation
