Which term best describes a colony with an irregular, non-round outline?

• A. Round Bacterial Colony
• B. Irregular Bacterial Colony
• C. Filamentous Bacterial Colony
• D. Rhizoid Bacterial Colony

Answer: (B)

Colony shape on an agar plate is a basic way to describe bacterial growth. When a colony grows with an uneven, non-circular edge, that shape is described as irregular. This term captures the lack of symmetry and jagged or lobed borders that set it apart from a smooth, round outline. The other descriptors point to specific shapes: a round colony has a smooth, circular outline; a filamentous colony shows thread-like extensions; a rhizoid colony spreads with root-like, branched projections. So describing the outline as irregular best fits a non-round, uneven edge.