Question

Which of the following organisms most closely resemble a bacterium?
A. Yeast
B. Virus
C. Amoeba
D. Anabaena

Answer 1

A bacterium is a type of microscopic living organism that is single-celled. This microorganism can present in large numbers in almost every environmental condition of earth. They are present in deep-sea vents as well as deep below earth’s surface, and are also present in the digestive tracts of humans.

Complete answer:
Bacteria are a type of microscopic biological cell. Bacteria is a unicellular microorganism which has no membrane-bound nucleus and other definite internal structures. The bacterial cell is approx. one-tenth of the size of eukaryotic cells. Bacteria can be either spherical or rod-shaped. Curved or coiled-shaped bacteria are also found. Bacterial cells are enclosed by a cell membrane, which is primarily composed of phospholipids.
Yeast is a species of single-celled fungi. This eukaryotic organism belongs to the phylum of Ascomycota and only a few belong to Basidiomycota. They can be spherical or egg-shaped or filamentous. Yeasts reproduce asexually by budding. Yeasts are present in soils and on plant surfaces. Yeasts have great economic importance which is commonly used in the production of bread, beer, and wine. Some yeasts act as dangerous pathogens of humans and other animals.
The virus is an infectious agent of small size and simple composition that can reproduce only in host cells of animals, plants, or bacteria. They do not belong to plants, animals, or even prokaryotic bacteria. Viruses are generally not considered as an organism. Viruses contain nucleic acid which is either DNA or RNA and protein.
Amoeba is a single-celled organism that can change its shape. They are generally found in water bodies such as ponds, lakes, and slow-moving rivers. These unicellular organisms can also enter and breed inside the human body which results in serious various illnesses.
Anabaena is a genus of cyanobacteria found as phytoplankton. They have the ability of nitrogen-fixing and they form symbiotic relationships with certain plants. They have a close biochemical and structural resemblance to bacteria.

Therefore, the correct option is option D.

Note: Bacteria are microscopic organisms present on the earth. These microorganisms are unicellular and prokaryotic in nature as it does not have any membrane-bounded nucleus. Blue-green algae is an example of Anabaena which belongs to the genus of cyanobacteria. They have a close resemblance to the structure of bacteria.