Which bacterial arrangement is characterized by irregular clusters?

The arrangement characterized by irregular clusters is indeed staphylococci. This term refers to a specific formation of cocci (spherical bacteria) that grow in clusters resembling grape-like bunches. The irregular clustering occurs as the bacterial cells divide in multiple planes without separating completely, leading to groups of cells that appear haphazardly arranged when viewed under a microscope.

In contrast, streptococci form chains of cocci due to dividing in a single plane, while sarcinae form cubical packets because they divide in two planes at right angles to each other and remain attached. Diplococci, on the other hand, typically are seen in pairs because they divide in one plane and remain connected only at one point. Therefore, staphylococci stand out for their unique cluster formation, making them easily recognizable in microbiological studies.