Bacterial physiology Flashcards
How does bacterial growth occur?
- asexual replication
- occurs by binary fission
- single bacteria divide to produce two daughter cells
- bacteria population double in each replication round
One bacteria can generate many = source of infection - how fast can fast growth bacteria replicate?
- every 10-15 minutes
Describe the steps in binary fission?
- cell replicates its entire DNA - including plasmids
- the cytoplasmic membrane elongates separating DNA molecules
- DNA molecules separate into individual entities and move towards poles
- cross wall forms, membrane invaginates
5/ cross wall forms completely - daughter cells are formed
What does growth by binary fission mean for cell mass?
- means cell mass doubles each generation
What can bacterial growth time be measured in?
- generation time
- population doubling time
How quickly does E.coli double?
- every 20 minutes
How quickly does M.bovis double?
- every 20-24hrs
How often does M. leprae double?
- every 20 days!!
What affect does bacteria doubling time have?
- has an impact in treatment and culturing methods
What are the minimum nutritional requirements for bacteria?
- water
- carbon source to generate proteins and ATP
- nitrogen source
- inorganic salts
What can autotrophs do?
- synthesise own organic compounds
What can heterotrophs not do?
- cannot synthesise own organic compounds
Some heterotrophs are pathogenic - what are some examples?
- Pseudomonas spp.
- Klebsiella spp.
- Escherichia spp.
- Salmonella spp.
- Campylobacter spp.
What have heterotrophs evolved to do?
- host-pathogen co-evolution (reliance) = leads itself to infectious disease
What are autotrophs’ typically?
- non-pathogenic
- clostridium difficile
What can labs use to cultivate bacteria?
- liquid media and solid media (agar)
Not all bacteria will grow on the same media - what may we need to supplement them with?
- blood products
- salts to cultivate bacteria outside of host
What is the general temperature bacteria need to grow?
- 37 degrees
- species differences as they grow at body temp of host
What can we do to identify and determine antibiotic resistance profiles and what can this help with?
- isolation
- helps apply correct treatment
What bacteria require complex media?
- pathogenic and clinically relevant ones
How can you collect bacteria?
- swabs
- tissue samples
What is MIDGET?
- dye in media that gives off a signal as soon as bacteria begins to divide
- such as colour change
How can we measure antibiotic resistance?
- clinical isolates are screen against antibiotics
- bacteria spread in plate
- paper disks soaked in antibiotics laid on top
- bacteria allowed to grow
- measure zones of clearance
What does it mean if there are clearance zones with no bacterial growth?
- sensitive to antibiotics
What does it means if there is no clearance zone and bacterial growth?
- resistant to antibiotics
What’s the optimal growth temperature range for thermophiles?
- 50-80ºc
What’s the optimal growth temperature range for Mesophiles?
- 20-45ºC
What’s the optimal growth temperature range for Psychotrophs?
- 4-24⁰C
What’s the optimal growth temperature range for psychophiles?
- 0-15ºC
Some bacteria are capable of growth between wide ranges - name an example?
- Listeria monocytogenes – optimal growth range 30-37°C
- Capable of growth between 1-45°!!
Clinical isolates are typically cultured at what pH?
- neutral
How can you classify organisms by pH?
- Neutrophilic organisms
E.g., E. coli, S. aureus, Salmonella spp. - pathogenic ones - Acidophilic organisms
e.g., Lactobacillus spp. - Alkalophilic organisms
e.g., Vibrio spp.
How do microaerophile use O²?
- use O² but only at very low cons
How do obligate aerobes use O²?
- require O² and cant survive without it
How do obligate anaerobes use O²?
- unable to use O² and cant survive if its present
How do facultative aerobes use O²?
- use O² but can can survive without it
How do aerotolerant anaerobes use O²?
- don’t use O² but can grow in its presence
How do bacteria grow in liquid?
- in a defined manner
What does measurements over intervals create?
- growth curve
What are the 4 stages of bacterial growth?
- lag
- log
- stationary
- decline
What happens during the lag phase?
- bacteria increase in size
- small numbers of doubling
What is the logarithmic stage?
- bacteria start dividing or doubling
- exponential increase in bacterial numbers
What is the stationary phase?
- bacterial division ceases
- depletion of nutrients
- build up of toxic products
- can produce antimicrobial to control communities around them
- in solids some bacteria change colour due to stress
What is the decline phase?
- actively start lysin = dying
– no more nutrients and toxic build up products
– see clarification of culture
What is bacterial physiology important for?
- Important for identification of bacteria
-Understanding nutritional requirements - useful for pathological niche, environmental survival
- Control of clinically relevant bacteria
- Antibiotic resistance
- Reducing spread
