Introduction to Bacteria Flashcards
Describe the structure and function of the surface of a bacterial cell.
The cytoplasmic membrane is very thin, elastic and semi-permeable.
Outside the membrane and closely covering it is the cell wall - which is rigid and gives the cell its strength and shape, however it is permeable.
(in gram negative bacteria, there is an outer membrane - outer than the cell wall)
Describe the chromosome of a bacterial cell.
The chromosome of a bacterial is a singular, circular plasmid.
Describe the fimbriae of bacterial cells.
They are also important in helping bacterial cells adhere to surfaces.
Describe the flagella of bacterial cells.
Long thin filament that gives the cell motility.
A - Has only one
B - Come from one point
C - Come from both sides
D - All over
Describe the surface of a gram negative bacterial cell.
Has a cytoplasmic membrane containing the contents of the bacterial cell. There is a thinner layer of peptidoglycan than in gram positive. There is also a second membrane (LPS - lipopolysaccharide outer membrane).
Describe the structure and function of the cell wall.
The cell wall is made of peptidoglycan. It is thick and strong, maintaining the shape of the bacterial cell.
If the wall is ruptured or weakened, osmosis means the cell will swell and burst.
+ plays an important role in cell division.
Describe peptidoglycan.
Peptidoglycan is:
N-acetylglucosamine acid and N-acetylmuramic acid molecules linked alternatively in a chain, with short peptides forming cross-links.
Describe the structure and function of LPS outer membrane.
Only present in Gram negative bacteria.
Protects peptidoglycan from bile salts (in the gut), also from lysosomes.
Blocks antibiotics.
Lipid A (within LPS) forms endotoxin which, when released into the blood stream (when multiplying or when lysed) may give rise to endotoxic shock - fever and low blood pressure.
Describe the structure and function of bacteriophages.
These are “bacteria-eaters”.
They are composed of a nucleic acid molecule surrounded by a protein structure.
It attaches itself to a susceptible bacteria and infects it.
Following infection, the bacteriophage hijacks the bacterium’s cellular machinery.
Preventing it from producing bacterial components - forcing cell to produce viral components.
Bacteriophages (lots of them) then burst out of the cell (lysis).
Describe the structure and function of ribosomes in bacterial cells.
Consist of RNA and associated proteins.
Function is to synthesis proteins.
Bacterial ribosomes are divided into 2 subunits (50s and 30s)
Describe spores released from bacterial cells.
Spores are a defence mechanism of bacterial cells, they have thick walls and can sustain very high temperatures, humidity and other environmental conditions.
Describe how bacteria replicate and create genetic variation
Bacteria replicate by binary fission - identical progeny.
Genetic variation by by spontaneous mutation and transfer of DNA.
Describe briefly the detection of bacteria.
Individual bacteria-
Only seen with microscope
Stain used (gram or fluorescent drugs)
Colonies of individual bacteria-
Cultured on solid medium agar.
Colonies can be seen with the naked eye.
Describe briefly the classification of bacteria.
Phenotypically (relating to observable physical properties) or genotypically (relating to DNA)
List some examples of phenotypes of bacteria.
Gram stain
Growth requirements (e.g. aerobic, anaerobic, microaerophilic).
Serologic
Mass spectrometry (protein profiling).
