Cells in the Hospital Lab

From Sore Throat to Slide

Kwame Mensah woke up with a sore throat and a fever, so his mother took him to the doctor. The doctor looked into his throat and saw red, swollen tissue, but nothing that looked like germs. She explained that a sore throat is often caused by a virus but is sometimes caused by bacteria, and a lab test would help show which. She gently rubbed a sterile swab on the back of his throat and sent it to the hospital lab.

In the lab, a technician named Mr. Harlan spread the swab across a dish of nutrient gel and kept it warm overnight. By the next morning, small white dots called colonies had appeared, and they kept getting larger during the day. Under the microscope, each colony was made of huge numbers of tiny round bacteria. Each bacterium took in nutrients from the gel and split into two.

Kwame asked to see more, so Mr. Harlan showed him four other slides. Cells from the inside of Kwame's cheek, scraped gently with a clean swab and stained blue, were flat with a dark nucleus and a thin outer membrane. A drop of blood showed many round red blood cells with no nucleus and a few larger white blood cells, each with a dark nucleus. Baker's yeast grown in sugar water showed oval cells, and some had small buds growing on their sides. A dried drop of the salt water used to rinse slides showed only clear, sharp-edged crystals. Mr. Harlan added that the human eye can see objects down to about 100 µm (0.1 mm) wide without a microscope.