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1.19.1.11 - Introduction to Bacteria - Coggle Diagram
1.19.1.11 - Introduction to Bacteria
summary
Microbiology encompasses yeasts, protozoa (covered together with larger with parasites) bacteria, viruses and prion proteins
Key structures of bacteria include cell wall, cell membranes, DNA (chromosome & plasmids, capsule, flagella and pili. Some bacteria can form endospores
Bacterial morphology has limited diversity, generally bacteria are either rods/bacilli, cocci, vibrio/spirochetes or pleomorphic (if no cell wall).
Through stains (Gram stain and acid-fast Modified Ziehl-Neelsen stain) bacterial groups can be differentiated based their structures
Cell wall structures have implications for clinical choices, including antibiotics treatment, disinfection procedures and host response management
microbiology daily impact
prevention of infectious disease
treatment of ifectious disease
sterilatision of instruments
biosecurity
epidemiology & recognising emerging disease
antimicrobial resistance
understanding disease processes
empirical decision making
empirical: based on, or verifiable by “observation or experience” and “understanding
what is the site of infection?
suggest potential pathogens
what are the clinical signs?
suggests possible causes
is this expected or not?
what are sensible choices in treatment?
what do I need to confirm prior to treatment?
groups of microorganisms
eukaryotic
fungi
moulds
yeast
parasites
protozoa
prokaryotic
bacteria
gram negative
gram positive
acid fast
mycoplasmsa
non cellular
prions
single proteins
non cellular
viruses
understanding the size of things
clinically relevant
Understanding the comparative scale of the bacteria compared to eukaryotic microbes and host cells is important. As you will do this when looking at clinical smears
moulds and yeasts
light microscope
bacteria
light microscope
viruses
electron microscope
prions
molecule
key structure of a generalised bacteria
cell wall
cell membrane
single circular haploid chromosome
capsule
flagella
granules
ribosomes
pilus
mRNA
plasmids
chromosome
haploid
circular DNA
much longer than the typical prokaryote
must be compacted by supercoiling
DNA gyrase
unique to bacteria
DNA-protein complex called the nucleoid
like histones but not quite
carries essential core genes of the bacteria
carries other genes that define the properties of the bacteria
plasmid
not all bacteria have them
common
independent small DNA molcules
has partition genes
when bacteria divides they both get one
can transfer between related bacteria
can carry a range of properties
virulence
AMR genes
cell wall
structure and form
morphology
rod
coccus
spiral/vibrio
peptidoglycan chains
mycoplasmas dont have cell walls
tough and protects the bacterium from osmotic lysis
importance of lysozyme
cleaves the disaccharides
part of the non-specific host defence
bacterial membranes
passive transport
osmotic diffusion
simple diffusion
facilitatied diffusion
barrier
affected by osmotic effects
affected by diffusion
active trasnport
ATP
flagella
multi component protein tails
complex
motor
powered
different patterns
coordination and virulence
not all bacteria have them
essential virulence component
capsule
loosely associated to the surface
cannot take up dye
protection against desiccation (drying)
adherence
matrix for biofilms
interferes with phagocytosis
capsule polysaccharides
pili/fimbrae
strands of proteins attached to bacteria
made of pilin peptide subunits
adhesions - some are virulence factors
thin structures
some bind to sugars on host cells
plasmid transfer
conjugation
mobilisation of DNA between bacteria
stains
visualitation rwuires stains as they are trasnlucent
diagnostic purposes
counter stains contrast remaining parts
some capsules block stains
halo effect
call wall - structural differentiation
gram negative
added lipid bilayer limits access
lipidopolysaccharide molecule that is presented on the outside of the cell
immunogenic molecules
gram positive
acid fast
additional waxy layer
mycoplasmas
outer membrane of gram negative bacteria
polysaccharide
The outer membrane is a potential barrier to access the wall an inner membrane.
antibiotic choice
Porins allow diffusion through outer membrane They are literally a pore through the membrane. They are described as gated because they have charge and size limits.
Some porins are called outer membrane proteins (OMPs) but not all OMPs are porins
endotoxin
Lipid-A (Sometimes referred to as endotoxin as it can stimulate inflammation in the patient)
endospores
hard to penetrate by:
stains
disinfectants
chemical agents
resistant to higher temperatures
resistant to a lot of common agents that would kill vegetative cells
designed to survive hostile environments
can be free or within the mother cell
gram-positive only
one bacteria produces one endopsore
high levels of very acid soluble proteins
activation -> germination -> growth and shedding of remaining spore coat
mycobacteria
similar in structure to Gram positive bacetria and will stain Gram positive but they also have an acid-fast property for stains
waxy
impacts how stain was taken up and held
Acid Fast staining is used to identify acid-fast bacteria such as Mycobacteria but also stain a few other bacteria
lots of glycolipids - especially mycolic acid in their cell wall
mycoplasmas
have reduced genomes
lack a cell wall
no distict structural morphology
fragile
closely associated ot their host cells
rely on homeostatic mechanisms of the host to maintain their environment
pleomorphic - can change a lot