Structure Of Bacteria And Fungi Flashcards
Importance of Bacterial Structure and Morphology
Useful in laboratory for Identification:
Shape
Staining
Presence of special structures. eg. Spores
Presence of unique chemicals. eg. Antigens
Prokaryote vs Eukaryote
Different types of bacterial morphology (referring to their shape)
*Coccus (round shaped)
*Rod/Bacillus
Vibrio (curved rods)
Spirillum (spiral shape)
Spirochete (tightly spiralled)
Branching filaments (branched)
List structures of prototype bacterial cell (diagram on anki) not all have this structure)
Plasmid
Ribosomes
Fimbriae/Pilus— allow bacteria to attach to tissue
Inclusion bodies
Cytoplasm— contain inclusion bodies (food storage)
Cytoplasmic membrane
Cell wall
Capsule— antiphagocytic, present on pathogen that cause blood stream infections
Nucleotide— chromosome genetic material
Flagellum— allow movement in viscus surfaces
Bacterial Nucleoid (chromosome)
-what is it
-condensed?
-histones present or not?
-microscopic appearance
-single closed circle of DNA- 1000um in length
-highly condensed
-not enclosed by membrane
-not complexed with histones but associated with histone-like proteins
-microscopically appears as amorphous mass roughly at centre of cell
Ribosomes
-composed of what
-site of what
-sensitive to what
-proteins and rRNA
-site of translation (protein synthesis)
-sensitive to antibiotics
Peptidoglycan
-what is it
-what does it do
-polymer of what
-held together by ________ chain
-Cell structure/cytoskeleton of bacteria
-provides strength & rigidity to cell
-protects cell from variations in external osmolarity
-Polymer of NAG-NAM-tetrapeptide.
-Cross-linked via peptide chain.
What are the unique amino acids of peptidoglycan?
D-alanine, D-glutamate, diaminopimelic acid (DAP)
What happens if peptidoglycan or Lipid A (LPS) gets into blood stream?
Causes shock
What does penicillin do and how does it work?
Destroys cell wall aka peptidoglycan of some bacteria
Works by inactivating an enzyme necessary for cross linking bacterial cell walls which causes bacteria to lyse
Enzyme which penicillin inactivates allowing destruction of bacteria
Transpeptidase
Bacteria grouped into 4 main characteristics
- Shape
- Atmospheric requirements for respiration
- Presence of spores
- Gram stain
Gram stain type depends on…
Cell wall structure
Amount of peptidoglycan
Presence of teichoic acids
2 types of gram stain bacteria
Gram positive and gram negative
Process of gram staining bacteria
Dry and heat fix cells
Stain with crystal violet (stains purple colour)
Stain with iodine
Decolourise with acetone (at this point gram negative should lose its colour)
Counterstain with dilute carbol fuchsin (gram negative stains red)
— after this bacteria should be either red or purple
Which colours do gram positive and gram negative stain?
Positive: Purple
Negative: Red
Examples of gram positive bacteria
Staphylococci, Streptococci, Corynebacteria, Bacillus, Clostridia, Listeria, Nocardia, Trueperella
Examples of gram negative bacteria
Pasteurella, Mannheimia Salmonella, Escherichia, Campylobacter, Yersinia, Pseudomonas
What does gram positive cell wall consist of?
(from out to inner)
-lots of peptidoglycan
-Periplasmic space
-plasma membrane
No outer membrane
What does gram negative cell wall consist of?
(From outer to inner)
-outer membrane
-periplasmic space
-thinner peptidoglycan wall
-periplasmic space
-plasma membrane
What is the gram negative outer membrane made up of?
3 main constituents:
-Lipid A
- Core polysaccharide’s
-O. Antigen/ O side chain
—all make up the lipopolysaccharides (LPS)
What do outer membrane proteins of gram negative bacteria allow?
Allow essential nutrients access through outer membrane
Name the proteins found in outer membrane of gram negative and what do they transport and what do they form
Porins; transport nutrients & form non-specific pores
Specific receptors; transport
-iron complexed side phones
-sugars e.g maltose
-vitamins e.g B12
Expression of porins is affected by what?
Surrounding environment e.g if in soil (little nutrients) porins might not be produced at all
Describe O side chain of LPS
-length
-function
-properties
-Long in enteric bacteria e.g salmonella (LPS)
-short in respiratory pathogens e.g Haemophilus (lipooligosaccharide; LOS)
-acts as barrier to toxic hydrophobic compounds, shields from bacteriophages, bacteriocins and antibodies
-very immunogenic, highly variable
Diagram of LPS
On ankicards!
Flagellum
-function
-made of what
-bound via motor unit, energy provided by:
-bacterial motility
-globular protein flagellin
-ion gradient across membrane converted into rotary movement
Do bacteria have to be motile cause disease?
Not all, some do
4 types of arrangement of flagella
-Monotrichous: A single flagellum at one end
-Ampitrichous: one or more flagella at each end
-Lophotrichous: two or more flagella at one or both ends
-Peritrichous: flagella surrounding all round the cell
Fimbriae/Pili
-present where
-what are they
-function, what do they do
-composed of…
-expression affected by what
-Present on gram negative bacteria
-Long, thin finger-like structures
-Allow bacteria to adhere to cells, some are very specific
-bind carbohydrate residues: lectins
-composed of protein subunits called pilin
-expression affected by environment;not expressed at low temp
What are lectins
Sugars that recognise receptors on surface of epithelial cells
Endospores
-produced by what
-formed when…
-form where
-describe their function
-germinate to ______________ once conditions become more favourable
-properties
-Produced by gram positive bacteria (Bacillus sp and
Clostridium sp)
-formed when conditions are unfavourable for survival of bacteria
-form inside bacterial cell and contain their genetic DNA so when released when bacteria lyses, can spread their genetic material allowing survival of bacteria
-germinate to vegetative cells actively growing cell). once conditions become more favourable
-resistant to heat, desiccation, extremes of pH
-have low water content & large amounts of calcium dipicolinate
-difficult to kill
Endospores diagram
On ankicards!
Exceptions to gram positive and gram negative bacteria
-Acid fast bacteria —>
Mycobacteria (cause tuberculosis)
Actinomycetes, Nocardia, Streptomyces
Acid fast bacteria properties
-gram positive-like but can’t be stained with gram stain- resists staining)
-tough, waxy cell wall
Mycobacteria
Type of acid fast bacteria
Cause tuberculosis
Contain mycolic acid & wax D
Extremely slow growth rate
Very acid fast
Actinomyces, Nocardia, Streptomyces
Type of acid fast bacterias
Filamentous,branching bacteria
Less acid fast than mycobacteria
Mycoplasmas
-what are they
-properties
-cause what
-resistant to what
A type of Mollicute
Smallest free living organisms
Lack cell wall, no peptidoglycan, pleomorphic shape
Contain cholesterol in cell membrane
Small genome
Unusual genetic code
Cause infection of mucosal surfaces
Resistant to penicillin as lack peptidoglycan
Chlamydia
Small gram negative bacteria
Cell wall lacks peptidoglycan, contain LPS
2 forms of life cycle inside cell:
—Elementary body: Small, dense, resistant, infectious
—Reticulate body: Larger replicating form
Fungi- properties
-components of carbohydrate
-Aerobic, eukaryotic cells with characteristic organelles
-Uni/multi cellular organisms
-Defined nuclei
-No chloroplasts (not plants!)
-Thick cell wall, mostly carbohydrate:
—Chitin, mannans and glucans most common components
—ergosterol in plasma membrane
3 types of fungi
-Yeast
-filamentous fungi
-dimorphic fungi
Yeasts
-Multi/unicellular?
-how do they grow
-w hat happens if daughter cells dont bud off?
-Unicellular fungi
-grow by division:
—budding
—binary fission
-sometimes daughter cells dont bud off; result is a pseudohyphae
Filamentous fungi (moulds)
-multi/uni cellular?
-made of what
-grow at what tip?
-2 types of hyphae
-multicellular
-made of hyphae; long thin filaments like branches
-hyphae branch and cross link
-growth occurs at hyphal tip
-hyphae may be divided by cross walls (septa) into unicellular units or non septate hyphae
Sept contain pore, all cytoplasms connected
Dimorphic fungi
-mixture of multi/uni cellular
-fungi able to switch between growth as mycelium and a yeast; depends on environmental conditions-temp
-2 forms; pathogenic and saprophytic
Yeast form of dimorphic fungi is pathogenic or saprophytic?
Pathogenic
3 types of fungal spores (vegetative spores) and examples
-Arthrospores, eg, Dermatophyte fungi -Chlamydospores, eg, Candida albicans
-Blastospores, eg, Candida albicans
