Select the wrong statement.
A. Cyanobacteria lack flagellated cells.
B. Mycoplasma is a wall-less microorganism.
C. Bacterial cell wall is made up of peptidoglycan.
D. Pili and fimbriae are mainly involved in motility of bacteria cells.

Hint: Bacterial cells possess various appendages on their surface meant for various functions like movement, attachment. However, there exist some bacterial cells that either do not possess such structures or have very little wall material.

Complete answer:
Cyanobacteria are motile or non-motile non-flagellated, ubiquitous gram negative bacteria. Mycoplasmas are the smallest self-reproducing gram negative bacteria. They lack cell walls and thus placed in a separate class ‘Mollicutes’. Bacterial cells are bounded by complex chemicals. Their cell wall is composed of peptidoglycans also termed as murein. Peptidoglycans are unique to bacterial cells. Peptidoglycan is a polymer containing two sugar derivatives N-acetylglucosamine (NAG) and N-acetylmuramic (NAM) acid joined through β-(1,4)-glycosidic bonds.
Bacteria may or may not possess surface appendages. Three main types of appendages are recognized on certain bacterial cells. These include Flagella, Pili and Fimbriae. Flagella are long filamentous structures made of flagellin protein and are meant for locomotion. Whereas pili are thin hair-like appendages on the surface of bacterial cells meant for conjugation process, and also act as receptors for donor-specific phages. Pili has a more rigid structure as compared to that of flagella. However, fimbriae are filamentous structures that mediate cell attachment. Their number can vary from few to several hundred per cell.
Therefore, bacteria show motility due to the presence of pili and fimbriae.

The correct answer is option D, which states that pili and fimbriae are mainly involved in motility of bacteria cells.
 

Note:- Bacteria are microscopic relatively simple prokaryotic organisms. Prokaryotic cells are morphologically simpler than eukaryotic cells. Although most structures are similar to both cell types certain structures are exclusively found in prokaryotes.