introduction to bacteria Flashcards
what are the estimated types of bacteria in the human body
500 - 1000
how can we describe bacteria
shape, size, colony shape size and colour, smell
what are the two categories of cell shape
cocci and bacilli
what shape are coccci
sphere
what shape of bacilli
rods
what are appendaged bacteria
group of bacteria that can change shape during their reproductive cycle
when was the first grown bacteria
1887
What is gram positive bacteria
thick peptidoglycan layer and no outer lipid layer
what is gram negative bacteria
thin peptidoglycan layer and have an outer lipid membrane.
what are phototrophs?
bacteria that can utilise light as an energy source
what are chemotrophs
can only gain energy from chemical compounds
what element do all bacteria require?
CO2
obligate anaerobes will not survive when exposed to
oxygen
what do extreme obligate anaerobes require
an abundance of o2
what do facultative anaerobes thrive on
oxygen
what is unique about aerotolerant anaerobes
they are indifferent in the presence of oxygen, they do not need oxygen to survive
what are the four components of the growth curve?
lag phase, log phase, stationary phase, death/decline phase
How do bacterial reproduce
binary fission
what happens during the lag phase
cells are not diving but the cells are growing in size and synthesising proteins
what happens during the log phase
bacterial cells are actively diving by binary fission and their numbers grow exponentially
what happens during the stationary phase
when growth rate decreases, waste products accumulate and nutrients are gradually used and O2 is depleted.
Cells dying and cells dividing is equal causes a plateau
what happens during the dead/decline phase
nutrients are exhausted and toxin waste accumulates. Bacterial cells die quicker than they divide
what is an indirect method to measure the growth curve
turbidity of the culture by using a spectrophotometer. light wavelength is shown onto the sample. measures the amount of light that passes through.
what is a direct method of measuring the growth curve
using CFU, the culture is diluted and small sample is poured onto a plate. We count the colonies
