identifying bacteria
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what are cocci bacteria
• round / spherical • Appear in groups / chains • Common in skin and respiratory infections
what are bacilli bacteria
• rod shaped • Straight / slightly curved • Found in soil, gut, and infection sites
what are Spirilla bacteria
• spiral or corkscrew shaped • May have flagella • Less common but include some waterborne and zoonotic pathogens
what is Colony morphology
how bacteria look when they grow on an agar plate, the visible characteristics help identify the type of bacteria without using a microscope, each species tends to produce colonies with distinct appearances
what are the key features to observe when identifying bacteria
• size • shape • colour • texture • elevation
what colours may bacteria be
white, yellow, cream, red or green, some bacteria produce colourful pigments
what does it tell us if bacteria have grown on an agar plate
they are able to survive the selective agents in the media.
what does it tell us if bacteria have not grown on an agar plate
bacteria may be inhibited by the selective substances.
what does it tell us if bacteria have produced a certain colour on an agar plate
what metabolic activity such as fermentation is taking place
why might agar sometimes change colour around certain colonies
chemical reactions such as change in ph level
what do clear zones indicate on blood agar
beta hemolysis complete destruction of red blood cells.
what do greenish zones indicate on blood agar
alpha hemolysis indicate partial breakdown.
what do no changes indicate on blood agar
gamma hemolysis no hemolysis.
what does it mean if macconkey agar has pink colonies
there are lactose fermenters
what does it mean if macconkey agar has colourless colonies
non-fermenters
what does it mean if Mannitol Salt Agar has a yellow zone
there are mannitol fermenters
what does it mean if Mannitol Salt Agar has No colour change
non-fermenters