Final answer:
The average size of a Lactobacillus bacterial cell is a few micrometers (µm) in length. Bacteria such as Bacillus cereus are approximately 4 µm long and would appear significantly enlarged when viewed under a high power microscope.
Step-by-step explanation:
Lactobacillus, a type of bacteria cell, is on average a few micrometers (µm) in length. Typically, bacteria cells like lactobacillus are about 1 µm, depending on the species and environmental conditions; however, they can range from 0.5 to 10 µm. These cells belong to a broader category of rod-shaped bacteria called bacilli. When observed under a microscope at high power, a cell like Bacillus cereus, which is approximately 4 µm long, would appear significantly enlarged.
To provide some perspective, most bacterial cells are around 1 µm, and it would take about 10 of these tiny cells to fit within a cubic micron. Looking at a microscopic field, depending on the density and arrangement of the cells, one might see a varying number of rod-like bacteria. The Lactobacillales order, which includes lactobacillus, houses both bacilli and cocci shaped bacteria.