Bacteria Key Facts Flashcards
(63 cards)
What size are bacteria typically ? There are bigger ones
0.2-5 µm
What are some of the functions of the bacterial cell membrane ?
Barrier function - separation of cell from its environment
Selectively permeable barrier
Site of respiration and photosynthesis
Energy conservation ( proton motive force )
What are the types of bacterial cell clusters ?
Diplococci
Streptococci
Clump of cocci
How does the gram - cell wall differ to the gram + cell wall ?
- = thin peptidoglycan
+ = thick peptidoglycan
-Lipopolysaccharide (LPS)
+ Lipoteichoic acid
How is a gram stain done ?
Stain with crystal violet
Add iodine ( forms a complex with crystal violet )
Wash with ethanol
Counterstain with safranin
What does lysozyme do to the peptidoglycan wall of bacteria /
Breaks G-M bonds
What is the function of fimbriae ?
Short, thin, hair-like, proteinaceous appendages (up to 1,000/cell)
Recognition and attachment
How do pili differ to fimbriae ?
Longer , thicker , less numerous
1-10 per cell, they are required for mating
What are the different types of flagella arrangement ?
Polar - at end
Monotrichous - one flagellum
Amphitrichous - one at each end
Lophotrichous - cluster at one or both ends
Peritrichous - spread over entire surface of cell
What are cellular inclusions ?
Granules of organic or inorganic material
that are reserved for future use
What are some examples of cellular inclusions in bacteria ?
Glycogen - polymer of glucose units
PHB - poly-b-hydroxybutyrate
Polyphosphate granules
Sulphur granules
Iron in form of magnetite
Gas vesicles
What is the difference between chemically defined media and complex media ?
Chemically defined : Exact composition is known
Complex media, exact chemical composition is not known, it is made of digests of complex material such as milk protein, beef, soybeans , yeast etc
What are the different phases of a typical growth curve for a bacterial population ?
Lag phase - cells are adjusting to new environment
Log phase - bacteria grow exponentially
Stationary phase - bacteria can no longer reproduce but are still alive , no nutrients left or growth inhibited by bacterial products
Death phase - bacteria die
What does viable but non-culturable bacteria refer to ?
Bacteria that are in a state of low metabolic activity, they do not divide but are alive and have the ability to become culturable once resuscitated
How can we distinguish between all bacteria, viable count, culture able count ?
Total count - non-specific dyes that stains all bacteria
Viable count - uses fluorescent activity dyes
Culturable count - can form colonies on solid media or increase turbidity in liquid media
What is a disadvantage of a direct microscopic count for measuring bacterial growth ?
It does not differentiate between live and dead bacteria
What is the assumption when using agar plates for measuring bacterial growth ?
Each culturable cell will grow and divide to yield one colony
Why does a negative test for cholera by culture not mean the water is definitely safe to drink ?
It could be present, it could be viable but not culturable, it is still pathogenic
What is an indirect method of bacterial growth ?
A cell suspension looks cloudy (turbid) : cells scatter light passing through the suspension
How does a bacteriostatic , bacteriocidal and bacteriolytic anti-microbial agent differ ?
Bacteriostatic - no change to total cell count or viable cell count
Bacteriocidal - decrease in viable cells but total stays the same
Bacteriolytic - total and viable cells count decreases
How does a heterotroph and autotroph differ ?
Heterotrophs : requires organic molecules made by other organisms
Autotrophs : CO2 is the principal carbon source
What is the difference between a phototroph and a chemotroph ?
Phototroph - uses light as an energy source (to produce ATP)
Chemotrophs - oxidise organic or inorganic compounds
What is an obligate aerobe ?
Needs O2 for growth
What is an obligate anaerobe ?
It cannot grow in presence of O2
