Variations in the Shape of Cocci

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Variations in the Shape of Cocci

Cocci are true spheres. However, some cocci will appear slightly oval in shape, while others may be lancet-shaped as shown in the illustrations below. As previously discussed, the colony morphology demonstrated from colonies growing on an agar surface can be less characteristic than direct smears or those grown in broth. On direct smears, Streptococcus pneumoniae typically demonstrates lancet-shaped cocci as shown in the top image on the right. The lower image on the right is a Gram stain of S. pneumoniae recovered from a blood agar plate (BAP).
Slightly oval-shaped cocci
Lancet-shaped cocci

S. pneumoniae on direct Gram stain
S. pneumoniae recovered from media