colony
a visible population of micro organisms arising form a single cell or colony-forming unit living in one place, grows in size as the number of cells increases. most microbes live as biofilms, that is in association with one another on the surface
chemical nutrients
including carbon, hydrogen, oxygen, nitrogen, are required to grow microbes
photoautotrophs
use carbon dioxide as a carbon source and light energy to make their own food
chemoautotrophs
use carbon dioxide as a carbon source but catabolize organic molecules for energy
photoheterotrophs
photosynthetic organisms that acquire energy from light and acquire nutrients via catabolism of organic compounds
chemoheterotrophs
use organic compounds for energy and carbon
organotrophs
acquire electrons for redox reactions from organic sources whereas, lithotrophs acquire electrons from inorganic sources
obligate aerobes
require oxygen as the final electron acceptor of the electron transport chain
obligate anaerobes
can't tolerate oxygen and must use an electron acceptor other than oxygen
4 toxic forms of oxygen
1. singlet oxygen
2. peroxide anion
3. hydroxyl radicals
4. superoxide radicals
singlet oxygen
neutralized by pigments called carotenoids
superoxide radicals
are detoxified by superoxide dismutase
peroxide anion
detoxified by catalase or peroxidase
hydroxyl radicals
most reactive of the toxic forms of oxygen
microbes are described regarding their oxygen requirements and limitations
some categories are aerobes, aerotoelrant anaerobes, ect
strict aerobes
require oxygen
strict anaerobes
can't tolerate oxygen
facultative anaerobes
can live with or without oxygen
aerotolerant anaerobes
prefer anaerobic conditions but can tolerate exposure to low levels of oxygen
microaerophiles
require low levels of oxygen
nitrogen
acquired from organic or inorganic sources, an essential element for micro organisms
some bacteria can reduce nitrogen gas into a more usable form via
nitrogen fixation
along with the main elements found in microbes there are also small amounts of trace elements required
vitamins are among the growth factors that are organic chemicals required in small amounts for metabolism to occur
what is minimum and maximum growth temperature
a temperature range where microbes can survive
microbes are often defined by their temperature requirements some common names are
psychrophiles, mesophiles, thermophiles or hyperthermophiles
optimum growth temperature
the temperature where an organism's metabolite activities produce the highest growth rate
osmotic pressure can cause cells to
die from swelling/bursting or die from shriveling
crenation is a synonym for
cell shriveling due to water output
the cell walls of some micro organisms protect them from
osmotic shock
obligate halophiles
require high osmotic pressure whereas, facultative halophiles don't require but can tolerate such high osmotic pressure conditions
neutrophils
grow best at a neutral pH
acidophiles
grow best at an acidic pH
alkalinophiles
live in alkaline habitats
barophiles
organisms that normally live under the extreme hydrostatic pressure at great depth below the surface of a body of water, often can't live at the pressure near the surface
quorum sensing
process where bacteria respond to changes in microbial density by utilizing signal and receptor molecules
biofilms
communities of cells attached to surfaces used quorum sensing
microbiologists culture micro organisms by
transferring an inoculum from a clinical or environmental specimen into a medium like broth or solid media.
the micro organisms grow in a culture
on solid surfaces cultures can be seen as colonies
clinical specimen
sample of human material. standard precautions are guild lines to protect health care professionals from infection
pure cultures aka axenic cultures
contain cells of only one species and are derived from a colony forming unit consisting of one cell or one type of cell
CFU
a colony-forming unit
how do you obtain pure cultures
use sterile equipment and use of aseptic techniques are critical
streak-plate method
allows Colony forming unit's to be isolated by streaking
pour-plate method
isolates CFUs by a series of dilutions
petri dishes that are filled with solid media are called
petri plates
slants aka slant tubes
are test tubes containing agar media that solidified while the tubes were resting at an angle
defined medium aka synthetic medium
provides exact known amounts of nutrients for growth of a particular microbe
complex media
contains a variety of growth factors
selective media
either inhibit the growth of unwanted micro organisms or favor the growth of particular micro organisms
why do micro biologists use differential media
to distinguish among groups of bacteria
reducing media
provide conditions conducive to culturing anaerobes
transport media
designed to move specimen safely from 1 location to another while maintaining the relative abundance of organisms, preventing contamination of the specimen or environment
some special culture techniques include the
use of animal and cell cultures, low oxygen cultures, enrichment cultures, and cold enrichment cultures.
capnophile
grows best with high carbon dioxide levels in addition to low oxygen levels
cultures can be preserved for short periods by
refrigerating and long term by deep-freezing and lyophilization
generation time
the time where a population of micro organisms doubles - this time also required for a single cell to grow and divide
a graph plots the number of organisms growing in a population over time shows the
growth curve
when organisms are grown in a broth and the growth curve is plotted on a semi-logarithmic scale the populations growth has four phases
1. lag phase
2. log phase
3. stationary phase
4. death phase
lag phase
organisms adjust to environment
log phase
population is most actively growing
stationary phase
new organisms are being produced at the same rate they are dying
death phase
organisms are dying more than new organisms are being produced
direct methods for estimating population size include methods requiring incubation
viable plate counts, membrane filtration and the most probable number MPN method
direct methods that don't require incubation are microscopic counts and electronic counters including flow cytometry
indirect methods include
measures of metabolic activity, dry weight, and turbidity and analysis of numbers and kinds of unique genetic sequences
what is turbidity
the level of cloudiness