What term describes bacteria that form irregular grape-like clusters?

The term that describes bacteria which form irregular grape-like clusters is "staphylococci." This classification arises from the way these bacteria replicate and group together. Staphylococci are a genus of spherical bacteria that tend to cluster in groups resembling a bunch of grapes due to their division in multiple planes. This arrangement is a key characteristic that distinguishes them from other forms of cocci.

In contrast, streptococci consist of cocci that form chains or pairs, demonstrating a different pattern of cellular division. Bacilli refer to rod-shaped bacteria, which is a distinct morphology from the spherical shape of cocci. Diplococci are specifically defined as cocci that appear in pairs, another form that does not match the irregular clustering seen in staphylococci. Thus, the characteristic grouping of staphylococci is pivotal in identifying and categorizing these bacteria in microbiological contexts.