WEEK 1 - characteristics used in classification Flashcards
characteristics used in classification
differential media
sugar fermentation
gelatin liquefaction
characteristics used in classification
- differential media
incorporate tests for enzymes (catabolic)
indirectly related to genes
characteristics used in classification
- sugar fermentation
acid (pH indicator) and gas (Durham tube) produced during fermentation of sugars
differentiates enteric bacteria
characteristics used in classification
- gelatin liquefaction
some bacteria produce proteases which will hydrolyse gelatin
clinical diagnostics: the API strip
cupules contain dried reagents
inoculated with bacterial suspension
incubated at 37 degrees C
colour changes indicate metabolic properties
profile can be used to give identification
characteristics used in classification
morphological
- macroscopic (colony morphology)
- microscopic (size, shape, gram stain, motility, ultrastructure, endospore)
classification
gram stain
crystal violet
- purple
iodine
ethanol
counter stain
- pink
gram positive organisms retain the purple gram stain
gram negative organisms are counterstained pink
molecular approaches to classification
bacteria are all related by descent
sequence of the genome is a “record” of the bacterium’s ancestry
entire genome sequences are now avaliable
- not practical for taxonomy
uses sequences for specific genes/proteins
prokaryotic ribosomes
70S ribosome
–> 50S subunit –> 23S RNA, 5S RNA, 31 proteins
–> 30S subunit –> 16S RNA, 21 proteins
why is 16S rRNA useful in taxonomy
present in all the organisms to be compared
- all living things have ribosomes
has the same function
- the function of 16S rRNA is essential
conserved
- has stable regions
- has variable regions
- If sequence changed likely to be lethal
long
- ~1500 nucleotides
