Question

a giant microbe discovered in a mangrove swamp, the bacterium thiomargarita magnifica grows up to 2 cm long and has its genome encased in a membrane. say you are examining a cell of t. magnifica under the microscope. which of the characteristics below would support the classification of this organism as a bacterium rather than a eukaryotic cell?

• the presence of plasmids
• the presence of a circular chromosome
• the presence of a peptidoglycan cell wall, plasmids, and a circular chromosome
• the presence of a peptidoglycan cell wall

Explanation:

To determine which characteristic supports classifying \( T. magnifica \) as a bacterium (prokaryote) rather than a eukaryote:

• Plasmids: Some eukaryotes (e.g., yeast) can have plasmids, so this alone is not unique to bacteria.
• Circular chromosome: Some eukaryotic organelles (e.g., mitochondria) have circular DNA, so this alone is not definitive.
• Peptidoglycan cell wall: Bacteria have peptidoglycan cell walls, while eukaryotes (plants/fungi have different cell wall components, animals have none). However, combining peptidoglycan, plasmids, and circular chromosome (all prokaryotic traits) is more conclusive.
• The option with peptidoglycan, plasmids, and circular chromosome includes all key prokaryotic features, distinguishing it from eukaryotes.

Answer:

the presence of a peptidoglycan cell wall, plasmids, and a circular chromosome