Flashcards
General Microbiology - Module 2 FLASH CARDS
Cards in this deck (28)
- 1What are the main shapes of prokaryotic cells?Cocci, rods, bacillus, spirals, filaments (single cells joined together).
- 2Why do small cells have an advantage in some environments?Higher surface area: volume ratio, therefore more efficient access to nutrients/substrates
particularly in low nutrient environments - 3What is the main function of a cytoplasmic membrane?- separation of cell constituents from environment
- selectively permeable: controlling substances coming into and out of the cell). - 4How do bacterial and archaeal cytoplasmic membranes differ?- ester (bacterial) vs ether (archaea) linked lipids
- archaea often have mono-lipids rather than a bilayer
- unique lipids (hydrocarbons – isoprenoids)
- branched lipid structure in archaea - 5. What is likely to happen to a freshwater bacterium put into a high salt environment?Water flows out of the cell by osmosis and would undergo plasmolysis (shrink).
- 6How does diffusion differ to active transport?Requires energy and moves the substance against a concentration gradient
- 7What is the importance of the outer membrane of Gram negative bacteria?The lipopolysaccharide contains O antigens (protection against host defences), core
polysaccharide (negative charge – important in attachment), lipid A (exotoxin). The outer
membrane confers virulence to Gram negative bacteria. - 8Where is the periplasmic space of Gram negative bacteria?- periplasm = substance that occupies periplasmic space
- usually the gap between cytoplasmic (plasma) membrane and outer membrane in gramnegative bacteria. Sometimes also describes the gap between cytoplasmic membrane and
cell wall in gram-positive bacteria - 9What is the main difference between gram positive and gram negative cell walls?Main difference is the amount of peptidoglycan and the outer membrane of the Gram
negative wall - 10Penicillin is used to treat bacterial infections, especially those from gram positive bacteria. Why is penicillin non-toxic to us?It stops production of peptidoglycan by preventing cross-linking of sheets. Therefore it is not
toxic to humans because we do not have peptidoglycan in our cells. - 11Why are gram positive bacteria generally more sensitive to penicillin?Gram positive cell envelopes are made up of mainly peptidoglycan so they are more
sensitive than Gram negative walls. The outer membrane of the gram negative wall also
provides extra protection and slows diffusion of penicilli - 12When treated with lysozyme in isotonic solutions, gram positive bacteria form protoplasts and gram negative bacteria form spheroplasts. Why? What is the difference?Lysozyme completely breaks down cell wall in gram positives to form protoplasts (no wall
just membrane). The outer membrane of gram negative limits movement of lysozyme in,
therefore wall often is only partially broken down to form spheroplasts - 13How do bacterial and archaeal cell walls differ?- More variation in Archaea than Bacteria, which just have peptidoglycan
- Most common cell walls in Archaea are protein/glycoprotein (S-layer) outside membrane or
pseudomurein (similar to peptidoglycan) with N-acetyltalosaminouronic acid (NAT) and Nacetylglucosamine (NAG), and peptides
- Others can have polysaccharides - 14What is the role and structure of flagella in bacteria?External appendages for movement
- 15Name some other types of structures for movement in prokaryotes?- Axial filaments
- Gas vacuoles
- Magnetosomes - 16How could you show that a bacterium produced endospores?- Test for heat resistance, e.g. survival at 90-100°C
- Stain with malachite green (endospore stain procedure) - 17Why are bacterial spores important?- Provide resistance and survival in adverse conditions for bacteria that produce them.
- Important in the food industry particularly heat treated foods e.g. canning, pasteurisation,
can cause spoilage and food poisoning e.g. B.cereus, C.botulinum
- Spores are also important in wound infections, e.g. C. tetani (tetanus), C. perfringens (gas
gangrene)
- Some strains have been used in bioterrorist activity, e.g. B.anthracis ( - 18. Name some other survival structures of prokaryotes.- Cysts
- Inclusion bodies & storage granules e.g. polyphosphate, sulfur, polyhydroxybutyrate - 19. Why is glycocalyx of importance in the infectious process of pathogenic microbes?- Various external viscous polymer material (polysaccharides or glycoproteins) that
surrounds the bacterial cell wall/outer membrane, collectively called glycocalyx (usually
a capsule or slime layer)
- Allows adherence to surfaces and tissues
- Difficult to remove and treat e.g. more resistant to antibiotics, immune system - 20What is the role of an inclusion body in a bacterial cell?Usually used for storing nutrient and/or energy sources
- 21What are silent mutations and why do they occur?A mutation that occurs with a change in the DNA base sequence but there is no change in
the protein encoded by that gene. Commonly occur when one nucleotide is substituted for
another in the DNA. - 22What is a frameshift mutation?A mutation caused by the addition or deletion of one or more bases in the DNA
- 23Explain the process of DNA transformation.The process in which genes are transferred from one bacterium to another as DNA
fragments in solution. Competent cells have DNA binding proteins to transport DNA strand
into cell and then integrated into recipient chromosome - 24What two key findings came out of Frederick Griffith’s classic experiment?- First demonstration of transformation
- Showed the importance of capsules of the infection process by preventing phagocytosis of
Streptococcus pneumoniae cells - 25Distinguish between generalised and specialised transduction.- Transduction is DNA transfer from donor cell to recipient cell via bacteriophages
- Generalised: random fragments of the chromosome are packaged into phage particles and
transferred
- Specialised: specific regions of the chromosome adjacent to a prophage are transferred
following induction of a lysogenic infection by temperate virus - 26What is the Ames test?A test for carcinogenicity of chemical compounds. Measures reversion of histidine
auxotrophs of Salmonella in response to the exposure to a mutagen/carcinogen. - 27What is the difference between conjugation by F+ and Hfr donor cells?Conjugation is the transfer of DNA by direct contact. F+ donors have F plasmid (F factor)
separate to chromosome and just transfer the plasmid. Hfr donors have F plasmid
integrated into the chromosome and transfer only part of the plasmid and part of the
chromosome to recipient. - 28The CRISPR system is said to protect genome integrity in prokaryotic cells by acting as a type of "immune system." Explain how the CRISPR system works.The CRISPR system is based on a region of the genome that contains DNA sequences
from previously encountered foreign DNA separated by short palindromic repeats. The
CRISPR region is translated into a long RNA molecule and then cleaved at each repeat to
create short RNA molecules (crRNAs) that are complementary to foreign nucleic acids. If the
crRNA binds to a piece of nucleic acid, associated proteins called Cas proteins will destroy
the foreign nucleic acid and prevent it from recombining with the genome or replicating
Information
- Description
- Flashcards on General Microbiology - Module 2 FLASH CARDS, created by Dean Nguyen on 23/03/2020.
- Created by
- Dean Nguyen
- Views
- 0
- Rating