Which bacterial genus is commonly associated with colonies that display a lobate margin when grown on solid media?

• A. Serratia
• B. Escherichia
• C. Streptomyces
• D. Bacillus

Answer: (C)

Verified step by step guidance

1. Understand the terminology: A 'lobate margin' refers to the edge of a bacterial colony that appears irregular and lobed, rather than smooth or entire. This characteristic can help in identifying bacterial genera based on colony morphology.
2. Recall common colony morphologies for the given genera: Serratia often produces smooth, red-pigmented colonies; Escherichia typically forms smooth, round colonies; Bacillus colonies can be irregular but are often rhizoid or filamentous; Streptomyces colonies are known for their complex, filamentous growth and lobate margins.
3. Focus on the genus Streptomyces, which is a filamentous actinomycete. Its colonies grow with branching filaments that create a lobate or irregular margin on solid media, distinguishing it from the other genera listed.
4. Use the colony margin characteristic as a key identification feature: since lobate margins are typical of Streptomyces, this genus is commonly associated with such colony morphology on solid media.
5. Conclude that among the options, Streptomyces is the genus most commonly linked to colonies with lobate margins, based on its unique filamentous growth pattern.