Microbiology 1 Flashcards
what is bacteria
bacteria is a type of prokaryotic cell in which the dna is not contained within a nucleus and doesn’t contain organelles.
Outline the terminology used to describe the different shapes of bacteria you may encounter
Coccus - Sphere
Bacillus - Rod
Spirillum - Spiral
Less common
Vibrio - Curved rod
Coccobacillus - Short rod
Spirochete - long loose spiral
Define the terminology attributed to the arrangement of bacteria
Coccus is used for a single coccus bacteria
diplococcus is a pair
tetrad is four cocci in a square
streptococcus is a chain of cocci
staphylococcus is a cluster of cocci
bacillus is a single rod
streptobacillus is a chain of many rods
Describe what major anatomical features are contained within the cell envelope.
plasma membrane
cell wall
capsule
describe the structural makeup of the the cell capsule
the cell capsule is not present in every bacteria but when it is present it is comprised of polysaccharides and proteins
Describe the role of the cell capsule (3)
capsules protect the bacteria from drying
they also allow for the attachment of phages
and for the attachment to surfaces
describe the structural makeup of the cell wall in a bacteria
the major component of the cell wall is called peptidoglycan which resembes a mesh
each layer is comprised of chains of alternating molecules known as
N-acetylglucosamine (NAG)
N actylmuramic acid (NAM)
Describe the differences that could be observed in a gram +ve bacteria cell wall versus a gram negative bacteria cell wall
in gram -ve there is direct cros linkage between nam units
whereas in gram positive bacteria they are linked by cross bridges
Gram positive wall are simple and have a thick layer of peptidoglycan
Gram negative walls are structurally more complex containing three layers
- inner membrane
- thin peptidoglycan
- lipopolysacharide layer
describe how the genetic information is organized in a prokaryotic cell
DNA is found within a circular haploid and not bound by a membrane and can also be found in plasmids which are small and contained double stranded DNA
describe what an endospore is and their role
a structure generated by a bacteria that can protect the bacterial genome when it is dormant when the environment is unfavourable
to the bacteria
allowing them to survive long time without food or water.
describe the process of binary fission and why it is important
Binary fission is the way bacteria cells reproduce.
Firstly a genome attaches to the membrane and the chromosomes replicate
then the septum forms and the 2 daughter cell begin to form
they then split leading to two identical daughter cells
Describe the purpose of gram staining and the process
the purpose of gram staining is to identify whether a bacteria is gram +ve or gram -ve
firstly you stain with crystal violet
then an iodine wash
then alcohol, this will decolorize gram negative cells from the purple but keep gram +ve this color
then stain with safranin to turn the gram -ve red
what factors affect bacterial growth
Affected by the chemical and physical nature of the environment so different species have different needs
Think
Nutrients
Temperature
pH
Solute
Oxygen or absence of
define how the pH of an environment can affect different species of bacteria growth
if the surrounding is acidic only acidophiles will be able to tolerate it and grow here
whereas if the environment was more alkaline then alkalophile would only grow here
define the terms used to describe a bacteria’s relationship with oxygen
obligative aerobe - need oxygen
facultative anaerobe - best with oxygen but can without
aerotolerant anaerobe - doesnt matter
obligate anaerobe - cant grow with oxygen
microaerophile - requires low oxygen level
