Spheroid shaped bacteria that appear in chains under a microscope are known as what?

The correct choice refers to streptococci, which are spherical-shaped bacteria that form in chains. This characteristic formation occurs due to the way these bacteria divide. Instead of separating completely after cell division, they remain attached, leading to a chain-like arrangement.

In contrast, staphylococci, another type of spherical bacteria, group together in clusters resembling bunches of grapes, due to their division in multiple planes. Bacilli are rod-shaped bacteria and do not fit the description as they do not have a spherical form. Vibrio are comma-shaped bacteria and, again, do not align with the characteristics of being spheroid or forming chains. Understanding these distinctions helps clarify why streptococci are identified by their specific formation and shape under microscopic observation.