Microbiology Flashcards
Microorganisms
organisms that are too small to be
seen with the unaided eye
Major groups of microbes
- Bacteria
- Fungi
- Parasites
- Microalgea
- Viruses
Size comparison of microoganisms
Molds > Protozoa > Yeasts > Bacteria > Viruses > Prions
Microoganism cellular
- Bacteria is monocellular
- molds are pluicellular
Acellular
- Without a cellular
structure - Virus and prions
3 domains
- Bacteria
- Archaea
- Eukarya
Bacteria
- E-coli
- Prokaryotes mostly unicellular
Fungi
- Eukaryotes
- Yeasts
- Moulds
Saccaromyces
Parasites
- Eukaryote
- Protozoa - Unicellular
- Helminths - multicellular
- Paramecium
Microalgae
Mostly eukaryotic
* Both unicellular and
pluricellular
Microorganisms as non-cellular entities
- Microorganisms include nonliving agents
- Not made up of cells
Virus
- Acellular small infectious particles consists of a nucleic acid
- coat enclosed in lipid
- don’t divide
- invade the cell and replicate
Prions
Simpler infectious particles made up only protiens no genetic material protien that changes chape
Microbes
- Organic waste
- Produce food
- Drugs synthesis
- Digestion and molecule generation
- Oxygen generation
- Nitrogen fixation
Normal microbiota
- Constant contact with body in mucus membrane
- Prevent growth of pathogens
- produce growth factors
- boost immune system
Bacteria shape
- Round (coccus)
- Rod (Bacillius)
- Curve rod (Vibrio)
Arranged as pairs
- Diplobacilli
- 2 joined together
Bionomial nomenclature
- both italic
- genus capitslise
- genus can be abbreviated
Structure of bacteria and archea
- Without nucleus
- Without membrane bound organelle
- Simple organisation
Struture
Plasma membrane
- Fluid mosaic model
- 2 layer of amphiphatic phospholipid layers
- Lack sterols with sterol like molecules (hopanoids)
Function
Plasma membrane
- Selective permiable membrane controls movement
- Infolding mesosmes site of DNA replication and cellular respiration
Function
Plasma membrane
- Selective permiable membrane controls movement
- Infolding mesosmes site of DNA replication and cellular respiration
Cell wall funtion
- Maintains bacterial cell integrity and shape
- Prevent cell from bursting water flows in by osmosis
- Contribute to pathogenicity
what does antibiotics target Bacteria
- Few bacteria have cell walls target many antibiotics
Peptioglycan
component for bacteria cell wall
- Ridgid multi-layer
- Each cahin has repeat identical disaccaride
- N- aceytlglucosamine and acetylmuramic acid
- tetrapeptide chain of 4/5 amino acids
- Chains are linked by peptide cross bridges
Peptidoglycan formation
- Subunit of NAG and NAM repetition by tetra peptide
- 2 diffrent chains are joined together use bridge of D-alanine
Penicillin
β-lactam antibiotics
- Inhibit the peptidoglycan synthesis of the bacterial cell wall
- Interfering with the formation of peptide bridges
between peptidoglycan chains
Gram +ve
- thick structure (several layers) of
peptidoglycan, separated from the plasma
membrane by a thin periplasmic space - contains teichoic acids, made up of an
alcohol and a phosphate group
Pupose of gram +ve
- Bind to and regulate movement of cations into cell
- Regulate cell growth and prevent cell lysis
- Linked also to the cell membrane
Gram -ve
- Thin fewer layers and are more susceptible to mechanical breakage
Funtion of gram -ve
- Thin peptidoglycan layer
- periplasmic space, containing degradative
enzymes and lipoproteins - Outer membrane (the most external)
Outer membrane in gram bacteria
- Phospholipid bilayer
- Lipopolysaccharides acts as antigen and endotoxin
- porins - membrane pores that allow passage of molecule
- Lipoprotien
Funtion of outer membrane
- Evade phagocytosis and immune system
- Permeability barrier to antibiotics
(penicillin), digestive enzymes, etc
Main difference
Gram-positive
- Thick peptidoglycan
- Teichoic acids
Gram-staining
- Distinguished groups of bacteria according to cell wall structure
- Staining - better visual observation to highlight differences
Gram positive
Fixation - white
Primary staining - crystal violet turn blue
Mordant application iodine treatment turns violet
decolourisation - keeps it looking violet
counterstaining with safarnin keeps violet
Gram negative
Fixation - white in colour
Primary violet staining
Mordant iodine treatment turns violet
decolourisation - keeps violet
Counterstaining counter stain with safrafnin - turns pink
Positive
Gram staining
- Cells are stained blue due to the crystal
violet-iodine complex - Alcohol dehydrates peptidoglycan (thick layer)
forming crystals inside and the dye is retained
Negative gram staining
- Cells stain pink as the counterstain
- Alcohol dissolves outer membrane and leaves holes in peptidoglycan
- crystal violet-iodine complex washes out; cells are colorless
- Safranin (pink) added to stain cells
Components external to cell wall
network of polysaccharides, lying outside the cell wall
- Has capsule thick and well organised
- Slime layer thin and unorganised
Components external to cell wall in bacteria
- Confer pathogenicity (only capsule)
- Prevent phagocytosis by host phagocytes
- Avoid desiccation by preventing water loss
- Aid in attachment to solid surfaces
Cytoplasm
- Location of most biochemical activities
Nucleoid
Central region containing circular DNA
Plasmids
- Small, nonessential, circular DNA that repliate independantly
Ribosomes
- Bacterial ribosomes are termed 70S ribosomes (50S + 30S), which
- Distinguish them from the 80S of eukaryotic cells. Selective antibiotic target
Inclusion bodies
- granules as reserve deposits of nutrients in the form of high
- molecular weight polymers. E.g. glycogen, polymeric phosphates
Flagella
- Hairlike filamentous appendages external to the cell
- Propel bacteria (process requiring ATP) toward or
away from stimuli, detected by chemoreceptors - May also be a sensory organelle
Structure
Flagella
- Filament: outermost region
- Hook: attaches to the filament
- Basal body: consists of rod and
pairs of rings; anchors flagellum to
the cell wall and membrane
Fimbriae
- Thin hairlike appendages that allow for attachment
- Some types are involved in a twitching motility
Sex pilli
- Hair-like tubular structure
- Conjugation pili involved in DNA transfer from
one cell to another
