Microbial Structure & Function Flashcards
What Greek words is the word prokaryotic derived from and their meaning
'Pro' = before 'Karyon' = the nucleus
Can eukaryotes be single celled?
Yes e.g. Some yeasts and protists
What are the 4 classes of protist?
- Sporozoa
- flagellate
- ciliate
- amoebae
Is pneumocystis jiroveci a protest or fungi ?
Fungi
*originally thought to be a protist
Why are fungi considered as their own kingdom rather than as plants ?
- unique cell envelope (chitin, glucans and mannans)
- mode of reproduction = budding or fission
- absence of chlorophyll
Define chemoheterotroph
Gains energy from redox reactions of organic compounds
Hetero= cannot make their own food, obtain nutrients via absorption Chemo = require organic chemicals
Where is chitin found ?
- fungal cell wall
- exoskeleton if Arthropods
What is budding in yeasts ?
One or more daughter cells grow as buds until they separate form the mother cell (asexual reproduction)
- most yeasts
Budding is one type of asexual reproduction in fungi, what is the other?
Binary fission - cell grows to a critics, size then splits in two
- some yeasts
Under what conditions would a fungi reproduce by binary fission?
Adverse conditions e.g, scarce nutrients
Define saprotroph
Obtain nutrients from dead or decaying matter
What is the mycelium
Network of hyphae in moulds
- form the vegetative body of moulds
Which plant pathogen produces ergotamine as a secondary metabolite?
Claviceps purpurea
- ergot fungus growing on the ears of rye and cereal plants
- ergotamine narrows blood vessels, so can be used or post partum bleeding and is hallucinogenic
Which fungus produces a carcinogenic secondary metabolite ?
Aspergillus flavus - aflatoxin
Which plant pathogen is used to produce quorn?
Fusarium graminearum
- found in cereal grains e,g, wheat and barley - causes ear rot in corn
The causative organisms of potato blight and the Irish potato famine ?
Phytophthora infestans
Botrytis cinerea causes which diseases ?
- noble rot of grapes on vine -> distinctive high quality wine
- grey rot
Define biotroph
Organism which feeds on the living tissue of its host
*they depend on the continued functioning if it’s host therefore don’t tend to kill it
What is the term for an organism which aggressively kills its hosts cells and then feeds on the dead and decaying tissue ?
Necrotroph
Define commensalism
Members of different species living together in close association without much noticeable influence to one another
Define symbiosis
The association of dissimilar organisms, usually to their mutual benefit
What are mycorrhizas ?
Fungi living in association with the roots of a plant in a symbiotic relationship
*the fungus assists in absorption of water and minerals and protects it from other fungi and nematodes, the fungi receives carbohydrates from the plant
Which gram negative bacillus caused the plague?
Yersinia pestis
- infected fleas which lived in the backs of black rats
- rat = vector
Examples of small bacteria:
- Bordetella pertussis (0.2x1 micron)
- Treponema pallidum (0.13x13)
- Mycoplasma spp. (0.1x0.25) SMALLEST KNOWN ORGANISM THAT CAN GROW OUTSIDE HOST CELLS
Examples of medium bacteria
- bacillus subtilis (0.7x3)
- E. coli (0.4x3)
- S. aureus (0.4x0.5)
Examples of large bacteria
- beggiatoa gigantea (5x13)
- Cyanobacteria (4-5 microns)
- thiomargarita namibiensis (diameter 750) *LARGEST PROKARYOTE
What are lysogens?
Bacteria which have been stably infected with bacteriophage - carrying the virus as a prophage
* bacteriophage DNA integrated into the chromosome of the bacterium
Bacteria which retain a crystal violet-iodine complex when treated with acetone or alcohol are said to be what?
Gram positive (purple)
Name the only biopolymer which contains D-amino acids
Peptidoglycan - in bacterial cell walls
What is the bacterial plasma membrane made of?
Conventional phospholipid bilayer, embedded with proteins
What does the outer leaflet of the gram negative of the gram negative outer membrane comprise of?
LPS with outer membrane proteins embedded
What is lipid A?
Endotoxic responsible for gram negative shock
- it is the lipid moiety of LPS
What is the appearance of colonies of bacteria which are encapsulated ?
Smooth colonies
Outline the main virulence factors of bacteria (6)
- encapsulated - resist intracellular killing
- slime - adherence
- flagella - motility
- fimbriae - adherence (gram neg)
- endospores
- sex pilus
Name the 2 main bacterial genus which produce endospores
- bacillus - aerobic, facultative anaerobes
- clostridium - obligate anaerobes
Which lacks a membrane bound nucleus, bacteria or fungi?
Bacteria, therefore they are simpler than fungi
Which Gran classification retain the crystal violet complex on treatment with acetone/alcohol? What colour are they seen as?
Gram positive - purple
Which bacteria need counter staining with red dye to be visualised easily ?
Gram negative bacteria - appear pink/red
Only biopolymer to contain D amino acids ?
Peptidoglycan
Describe the structure of peptidoglycan including:
- backbone
- cross linking
- amino acids
- Backbone of Alternating units of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
- NAM units cross linked with oligopeptides
- contains both D and L amino acids
- oligopeptides vary between species but all have terminal D-alanine residue
Additional polymers in Gram positive envelope as opposed to the Gram negative envelope ?
Teichoic and teichuronic acids
What does the bacterial cell envelope include ?
Inner cell membrane and cell wall
How many layers of peptidoglycan do Gram positive and Gram negative have in their cell envelopes?
- positive = 40
- negative = one or two
Role of bacterial capsule
Protection from phagocytosis
For which important disease causing bacteria are capsules a major virulence factor for ?
E. coli and S. pneumoniae
What year and by who was the gram stain developed ?
Christian Gram 1884
3 principle layers of gram negative cell envelope ?
- outer membrane
- peptidoglycan layer
- cytoplasmic or inner membrane
Which molecule is responsible for endotoxic shock caused by septicaemia as a result of gram negative bacterial infection ?
LPS
Function of the periplasm ?
Compartmentalisation allows gram negative bacteria to sequester potentially harmful degradative enzymes e.g. Alkaline phosphates
*thought to be evolutionary precursor of eukaryotic lysosomes
Where does the periplasm lie ?
Between inner and outer membrane in gram negative bacteria
- therefore includes the peptidoglycan layers
Which stain should be used for mycobacteria and why ?
Acid fast stain
- have waxy cell walls
Which genus of bacteria are aerobic or facultative anaerobes and produce spores?
Genus Bacillus
Which genus of bacteria are obligate anaerobes and produce spores?
Genus clostridium
Family of E. coli ?
Enterobacteriaceae
What Kingdom is E. coli in ?
Eubacteria
When and who by was E. coli discovered ?
1885
- Theodor Escherich
- German bacteriologist
What are the 4 classes of macromolecules within bacterial cell ?
- carbohydrates
- lipids
- proteins
- nucleic acid
Define chemoautotroph
Obtaining nutrition from redox reactions of inorganic compounds
Example of alkalinophile
Vibrio cholerae
Example of acidophile?
Lactic acid bacteria
Temp range and example of psychrophile ?
- 20 to +10
- pseudomonas antarticus
Temp range and example of mesophile ?
+20 a +40
- E. coli
Temp range and example of thermophile ?
+41 to +122
- geobacillus stearothermophilus
What factors does H influenzae require for growth on media ?
Factors X (haem) and V (NAD, cofactor, can get from lyses RBCs)
Describe satellitism between S. auerus and H. influenzae
H. influenzae grow bigger near colonies of S. aureus on blood agar as S. aureus provides NAD
How can H. influenza and H. parainfluenzae be distinguished in culture ?
Influenzae requires X and V, para only requires V
- culture on nutrient agar and add soaked discs, one with X and V, on with only
- influenzae will only grow near the one with X and V
