An Introduction to Bacteria Flashcards
What does the structure of bacteria contain?
Capsule
Cell wall
Cytoplasmic/inner/plasma membrane
Cytoplasm
Ribosomes
Single chromosome, no nucleus
Flagellum
Finbriae
What does the cytoplasm do?
Contains nutrients taken up from the environment
What do ribosomes do?
Site of protein synthesis
What does the cytoplasmic membrane do?
Diffusion of ions and nutrients
What does the cell wall do?
Combats osmotic stresses
What does the capsule do?
Helps the bacteria to survive in humans, for example escaping macrophages
What do flagellum do?
Allows the bacteria to move
What does fimbriae do?
Important for attachment
What do chromosomes do?
Contains DNA
What does the plasmid do?
DNA outside of the chromosome
What kind of bacteria has an additional membrane?
Gram negative bacteria
What kind of bacteria has a thicker layer of peptidoglycan?
Gram positive bacteria
What are the layers (going inwards to outwards) in gram positive bacteria?
Plasma membrane
Periplasmic space
Peptidoglycan
What are the layers (going inwards to outwards) in the plasma membrane of gram negative bacteria?
Plasma membrane
Periplasmic space
Peptidoglycan
Periplasmic space
Outer membrane (lipopolysaccharide and protein)
What does the outer membrane of gram negative bacteria contain?
Lipopolyassacharide and proteins
What colour does gram positive bacteria appear in gram staining?
Purple
What colour does gram negative bacteria appear in gram staining?
Red
What are two classes of bacteria after aerobic/anaerobic?
Cocci or bacilli
What do cocci bacteria look like?
Spherical shaped
What do bacilli bacteria look like?
Rod shaped
What proteins are present on the cell surface of bacteria that creates cross links?
Penicillin binding proteins (PBP)
What are examples of penicillin binding proteins?
Transpeptidases
Carboxypeptidases
Endopeptidases
What are lipopolysaccharides?
They are present only on gram negative bacteria and elicit a strong immune response in animals and humans
What does the capsule provide bacteria with?
Water to survive in many environments
What are the different kinds of flagellum?
A-monotrichous vibrio cholera (one)
B-lophotrichious spirillum spp (one point)
C-amphitchous rhondospirillum rabrum (both sides)
D-peritichous (all over)
What do some bacteria release?
Spores which help it to obtain nutrients
When does spore formation occur?
When there is not enough nutrients for fission or environmental factors do not allow it
What does spore formation allow?
The bacteria to survive in tough environments
What is the process of spore formation?
1) DNA condenses and lines itself in the centre of the cell
2) DNA divides into two copies
3) Mother cell invaginates to form developing forespore
4) Moth cell engulfs developing spore which is surrounded by two membranes
5) Mother cell DNA is degraded
6) Peptiglycan laid down to form cortex
7) Ca2+ enters and water is removed from the spore
8) Protein coat forms exterior to cortex
9) Some spores form exosporium
10) Enzymes destroy mother cell and mature spore is released
What are exoporium?
Outer surface layer of mature spores
What provides a mechanism for antibiotic resistance?
The plasmid
What kinds of bacteria prefer what during mating?
Gram negative prefers gram negative
Gram positive prefers gram positive
What is conjugation?
Process by which bacterium transfers genetic material to another through direct contact
What are other names for gram positive and gram negative bacteria?
F+ are gram positive
F- are gram negative
What do gram positive bacteria contain in terms of mating?
F plasmid which allows them to form F pills
What eventually happens when gram positive and gram negative bacteria are mixed together?
They all become gram positive
What is the process of conjugation?
1) F pills of donor cell (gram positive) recognises and binds to proteins on gram negative cell wall
2) Plasmid becomes mobilised for transfer
3) Single strand of plasmid enters the recipient cell
4) Inside recipient cell a complimentary strand is synthesised
What is binary fussion?
The process by which bacteria replicates
What may genetic variation occur due to?
Spontaneous mutations
Transfer of DNA
What are spontaneous mutations?
Mutations that occur randomly with no influence from the environment
What does transfer of DNA occur by?
Conjugation
Transformation
Transduction
What is transformation?
Genetic alteration due to uptake of extracellular DNA that is advantageous
What is transduction?
Foreign DNA is introduced into a cell by a virus
What is transduction caused by?
Bacteriophages
What are bacteriophages?
Viruses that infect bacteria
What do bacteriophages contain?
Head
Collar
Tail
End plate
Tail fibre
What does the end plate and the tail on a bacteriophage do?
Helps it to attach to bacteria cells
What are the two cycles that bacteriophages enter their DNA into bacteria through?
Lytic
Lysogenic
What is the lytic cycle?
Where the phage overtakes the machinery in the bacteria and starts replicating to form more phages, bacteria cell then bursts and releases them
What is the lysogenic cycle?
DNA from the phage integrates with the hosts chromosome, it can remain dormant or replicate
What can individual bacteria be seen by?
Microscope at 1000x with an oil immersion lens
Staining (such as gram or flourescent)
What can the naked eye see?
Colonies of bacteria
What is culturing used for?
To identify exactly what species of bacteria is present
What do selective mediums allow?
Certains species to grow
What is bacteria naming based on?
The genus and the species
For example for Staphylococcus aureus Staphylococcus is the genus and aureus is the species
What properties do strains of bacteria within the same species have?
Similar characteristics
What can be used to identify strains?
DNA typing
