The following following show expected expected colony appearances appearances and morphologies (shapes) of Escherichia coli and coli and Staphylococcus Staphylococcus aureus. aureus. Note characteristics characteristics such as edges, color, and whether the colonies are rough or smooth in texture. For colony appearances of E. coli and S. aureus, aureus, scientists often describe what they look like on agar. This is not the microscopic view (for example, as with a slide) but a “naked eye !iew of how the bacterial colonies look while growing on a medium. (This is one type of culture.) "f culture.) "f it is #ust plain nutrient agar (like below) $ and it depends on what kind of growth medium is used, the colors should be similar to the pictures below. ("n these examples, the time after plating is dierent for the two samples, so be aware that the colonies in these photos are dierent sies for a reason. ) %e will culture our bacteria for about &' days. haracteristics are most !isible if the bacteria are examined using a stereoscopic scope.
E. coli *hape (form)+ circular argin+ entire -le!ation+ raised *ie+ punctiform, small Textur Texture e (surface)+ smooth smooth /ppearance+ shiny 0igmentation+ 0igmentation+ nonpigmented (colorless) 1ptical property+ translucent
For all bacteria, they can be described on the basis of these traits (how the bacteria look) when grown on a medium, poured and allowed to harden in a petri dish. haracteristics of bacterial colonies become one of the type of signatures! keep in mind there are many ways that
S. aureus *hape (form)+ circular argin+ entire -le!ation+ con!ex *ie+ moderate, large Texture Texture (surface)+ (surface)+ rough rough /ppearance+ shiny 0igmentation+ 0igmentation+ tan, golden yellow 1ptical property+ opa2ue
bacteria can be identi3ed. This is #ust one of the ways that bacteria can be explored. 4ere are how these particular bacteria are classi3ed according to "ergy#s $anual of Systematic "acteriology. (5emember there are 6 7omains and 8 9ingdoms of :ife.) E. coli 7omain+ 0hylum+ lass+ 1rder+ Family+
;acteria 0roteobacteria
S. aureus 7omain+ 0hylum+ lass+ 1rder+ Family+
;acteria Firmicutes ;acilli ;acillales *taphylococcaceae Staphylococcus aureus
Taken from $icrobiology, %n &ntroduction , ==th edition (authors+ Tortora, Funke, and ase)+ Escherichi coli is one of the most common inhabitants of the human intestinal tract and is probably one of the most studied>familiar organisms in microbiology. "ts presence in water or food is an indication of fecal contamination. -. coli is not usually pathogenic. 4owe!er, it can be the cause of urinary tract infections, and certain strains produce endotoxins that cause tra!eler?s diarrhea and occasionally this type of bacteria can cause !ery serious foodborne disease.
Staphylococcus aureus is named for its yellow'pigmented colonies (aureus @ golden). embers of this species can li!e in the presence or absence of oxygen and they can adapt to either type of situation. They grow comparati!ely well under conditions of dilute salt concentrations and low moisture, which partially explains why they can grow and sur!i!e in nasal secretions and on the skin?s surface. The infection of surgical wounds by S. aureus is a common problem in hospitals. /nd its ability to de!elop resistance to such antibiotics as penicillin contributes to its danger to patients in hospital en!ironments.
