Microbiological Concepts (W2) Flashcards
what are the 4 characteristics of the cell wall in bacteria
- rigidity and strength
- protection
- permeability
- determines whether the cell is gram neg or gram pos
what determines whether a bacteria is gram pos or gram neg
gram pos: thick layer of peptidoglycan + has teichoic acid and lipoteichoic acid in this layer
gram neg: thin layer of peptidoglycan + has an outer-membrane over the top (with lipids and proteins)
what chemicals are used in what order in a gram stain
- Crystal Violet
- iodine
- Alcohol
- Carbol Fuchsin
what are the 4 principle shapes of bacteria
- bacillus
- coccus
- spirals
- vibrio (comma shaped )
what are the main arrangement
- single (random)
- cluster
- chains
- pairs
what is a glycocalyx and what are the 2 main types
the glycocalyx is the material around the cell wall (in some organisms)
1. capsule
2. slime
what are the characteristics of the capsule glycocalyx (4)
- highly organised
- firmly attached
- protects against phagocytosis
- some bacteria are typed (distinguished) by capsule composition
what are the characteristics (5) of the slime glycocalyx
- not highly organised
- not firmly attached
- helps to slide on surfaces
- protects the bacterium from drying
- it is easily washed off
what do bacteria with a glycocalyx have a higher virulence (more pathogenic)
the glycocalyx permits;
- Adherence
– Protection from phagocytosis
– and potentially some protection from antibiotics
what does a capsule glycocalyx look like on a gram stain
- it does not absorb stains but it is permeable so the colour will still stain the cell wall but there will be a colourless area outside the cell
what are the 3 outer structures (projections) on some bacteria and what are their roles
- Flagella - motility
- Fimbriae - adherence
- Pili - adherence and conjugation
what structure in bacteria is bristle like, present in multiple numbers, and adheres to host tissues.
Fimbriae
what structure in bacteria is bristle like, present in pair or singularly, long projections, and adheres to other bacteria during dna transfer
Pili
what is the name of the polar distribution
with one flagella from one end
monotrichous
what is the name of the polar distribution
with multiple flagella from one end
lophotrichous
what is the name of the polar distribution
with multiple flagella from both ends
amphitrichous
what is the name of the polar distribution
with multiple flagella around the whole cell
peritrichous
What are bacterial endospores and what are they for
They are a copy of the bacteria’s dna made from its cytoplasm, that is enclosed in a thick protein layer, for survival.
why are bacterial spores harder to kill
they are resistant to heat and disinfectants and they can survive years in soil and dust
how do bacteria reproduce, and give details on the process
- they reproduce asexually, by binary fission
this is where one single cell splits into 2 identical daughter cells
what is generation time and what factors affect it (for bacteria)
generation time is the time it takes for the number of bacterial cells to double.
it is affected by environmental conditions and location
eg - it is faster in vitro (lab) and slower in vivo (humans)
what are the 4 stages of the bacterial growth curve in broth solution
- Lag phase
- Exponential phase
- Stationary phase
- Death/decline phase
what are the 5 atmospheric preferences that bacteria have and what do they each mean
- Obligate aerobe - must have O2 (grow in air)
- microaerophiles - must have low O2 (6-16%)
- Obligate anaerobes - must have no oxygen
- facultative anaerobes - can grow with or without O2
- Carboxyphiles - grows best in increased O2
what are the 3 temperature preferences that bacteria have and what do they each mean
Psychrophiles - prefer cold (0-20)
Mesophiles - prefer medium (10-45)
Thermophiles - prefer hot (45-85)
what is the optimum temperature for a psychrophile
15
what is the optimum temperature for a mesophile
37
what is the optimum temperature for a thermophile
50-55
what are the 3 ph preferences that bacteria have and what do they each mean
Acidophile - prefers ph below 5.5
neutrophiles - prefer ph between 7.2 to 7.6
Alkalophiles - prefer ph between 8.5 to 11.5
Catabolism is…
larger molecules into smaller molecules
anabolism is…
smaller molecules into larger molecules
what type of reactions mediate energy storage
redox reactions
what are the products of respiration and fermentation
respiration:
- lots of atp
- H2O and CO2
fermentation:
- low atp
organic waste (eg alcohols and acids)
what are the 3 types of Host-Microbe relationships
mutualism - both benefit
commensalism - symbiotic (one benefits without harming the other
parasitism - one benefits while other is harmed
what are 4 beneficial roles of Normal flora
- compete with foreign microbes for colonisation site
- normal flora in large intestine produces vitamin B and K
- secrete chemicals that antagonise foreign microbes
- stimulate developing immune system in children
what are the 5 stages of infectious disease
- incubation period
- prodromal phase
- invasive phase
- decline phase
- convalescence
what happens during the incubation period of infectious disease
colonisation of microbe (overcoming host immune system)
host has no symptoms
what happens during the prodromal phase of infectious disease
increase in numbers of microbe
host has mild symptoms
what happens during the invasive phase of infectious disease
it becomes an identifiable disease
there is a dramatic increase in microbes
- this stage will continue to death if no intervention
what happens during the Decline phase and convalescence of infectious disease
Decline phase- reduction of microbes and decline in symptoms
Convalescence- recovery
what are endotoxins and exotoxins and what do they contribute to
they are toxins produced during an infection, they contribute to the virulence of a microbe as toxins can kill host cells
what 4 things can a cell produce that will increase its virulence
- toxins
- enzymes
- adherence factors
- haemolysins
what is the difference between endotoxins and exotoxins
Exotoxins are secreted by living bacterial cells
( Primarily gram pos bacteria)
Endotoxins are released when the organism dies and the cell wall breaks down (primarily in gram neg organisms with lipopolysaccharides)
what are haemolysins, what are the 3 types, and how are they identified
they are lipids or proteins that cause lysis of red blood cells
the 3 types are
- Alpha (green/grey zone) - Partial lysis
- Beta (clear zone) - complete lysis
- Gamma - no lysis
where are microbial biofilms found and give some examples
- wet surfaces
- eg. teeth, dental implants, contact lenses, water supplies
what makes up microbial biofilms
- microbes
- cell debris
- extracellular
how does plaque lead to tooth decay
increase in plaque = increase in bacterial numbers = increase in acid production = increased demineralisation
how does oral bacteria produce acid
by fermenting carbohydrates
what are the 3 types of microscopes (and subtypes for 2 of them)
- Compound light microscope
- Dark ground
- Bright field
- Phase contrast - Fluorescent microscope
- Electron microscope
- transmission
- Scanning
what controls light in a Compound light microscope
- Condenser
- Diaphragm (iris)
How would you increase contrast when looking at an unstained preparation with bright field illumination?
closing the condenser diaphragm
what is the difference between selective and differential media
selective - only allows certain bacteria to grow + inhibits others
differential - allow bacteria to be distinguished from each other
