Microbiology Flashcards
Example of eukaryotic microbe?
Fungi, protists
Why are there so many microorganisms?
Rapid growth in environment, many chances of speciated through random mutations (ability to adapt), lateral gene transfer, very long evolutionary history (3.8b years)
When did bacteria / archaea first originate?
Around 3.8b years ago
How was the history of the earth driven by microbial processes?
Earth slowly became oxygenated - origin of oxygenic photosynthesis by cyanobacteria. oxygen accumulates in atmosphere allowing for origin of eukaryotes
What are nutritional categories based on?
Sources of energy, electron donors and cell carbon
Organotroph?
utilises organic compounds as electron donors. (already fixed carbon sources) e.g. glucose, methanol
Lithotroph?
Utilises inorganic compounds as electron donors, eg. reduced compounds, NH3, CO, H
Autotroph?
CO2 as carbon source, fix carbon dioxide (photosynthesis)
Heterotroph?
organic carbon as carbon source (glucose) e.g. humans
Prototrophs?
Synthesise all their own cellular components (all amino acids, nucleotides) -can turn one carbon source into anything
Fastidious bacteria?
Need organic compounds (diet), vitamins, to grow in a media
How does bacteria grow and multiply?
Using binary fission, cells double in size and split into 2, EXPONENTIAL GROWTH
Why is exponential growth of bacteria good?
an efficient way of growth when plenty of nutrients are available
How is bacterial growth limited?
all environments are limited - space and nutrients, max. carrying capacity
What is the lag phase on bacterial growth curve?
no growth first - bacteria need time to adapt to new media / conditions to grow in (switch on genes)
What is the log phase on bacterial growth curve?
growing as fast as they can - exponential growth, abundance of nutrients and space
What is the stationary phase on bacterial growth curve?
growth stopped: media has become too crowded / too many waste products / running out of nutrients
What is the death phase on bacterial growth curve?
bacterial cells die, but remaining living cells can use energy released from dying cells
How can we measure bacterial growth?
Haemocytometry - microscope + grid to estimate number of cells, Turbidmetry - bacteria scatter light shone through beaker - optical density used to see how cloudy solution is
Dilution plating - create dilutions and measure how many cells are in beginning and end of exp. phase
Problems with identifying microorganisms?
limited morphological diversity - microbes look similar down a microscope
What is differential media?
contains compounds which allow groups of microorganisms to be visually distinguished - certain compound produced by bacteria interacts with compound in media e.g. colour change of media
What is selective media?
selects for certain characteristic of bacteria = if certain bacteria only grows in one sugar
Methods of identifying microorganisms?
Microscope and staining, growth on sel / diff media, testing substrate spectrum supporting growth, testing of enzyme activities (e.g. antibiotic resistance enzyme), cell chemical constituents
MODERN: sequencing of specific genes - but have to compare to something we already know
Why is selective media used in clinical diagnostics?
only a few organisms are associated with certain symptoms, so easy to grow and identify + find treatment
