Question

Delia, a five-year-old, woke up one morning complaining that she had a sore throat, headache, and stomachache. Her tonsils appeared swollen, and a tonsular exudate, appearing as a cream-colored pus, was evident upon examining the child’s oropharynx. Her mother also took Delia’s temperature and noted the girl was running a low-grade fever. Suspecting strep throat (streptococcal pharyngitis), her mother made an appointment with the pediatrician.

The doctor first performed a rapid strep test, which works by detecting certain cell surface proteins on group A streptococci (GAS). This test is inexpensive and can detect GAS in a matter of minutes. However, rapid strep tests that come back negative are not especially reliable; about five out of every 100 patients with streptococcal pharyngitis will have a negative rapid strep test result. Therefore, despite Delia’s rapid strep test being negative, the doctor went ahead and ordered a bacterial culture. This was a wise decision, since Delia had signs and symptoms that pointed to a case of streptococcal pharyngitis caused by the Gram-positive, nonmotile, encapsulated prokaryote Streptococcus pyogenes.

When cultures to detect S. pyogenes are performed, the patient’s sample (in this case a swab of the throat) is streaked out onto a specialized nutrient-rich agar called blood agar. Actively growing S. pyogenes can break down red blood cells (a process called beta hemolysis) and therefore is readily detectable on blood agar plates because a clear zone develops around its colonies. Based on the microbiology data that came back, Delia was treated for streptococcal pharyngitis. After 48 hours on an antibiotic, Delia felt much better and returned to school.

QUESTION: Would S. pyogenes be classified in the domain Archaea? Explain why or why not.

Answer 1

Answer:

Based on the given information:

Streptococcus pyogene is a Gram-positive, nonmotile, spherical, encapsulated prokaryotic microorganism (Domain: bacteria)

Domain Archaea consists of single-celled prokaryotic organisms that are different from bacteria and eukaryotes based on their characteristic features. Some of the aspects that distinguishes Archaea from bacteria are:

• Composition of membrane lipids
• Absence of peptidoglycan and presence of proteins in Archaea cell wall
• Methionine as a initiator amino acid in translation process in Archaea
• Association of histones with DNA
• Archaea don't respond to antibiotics such as Streptomycin and Chloramphenicol
• Presence of several types of RNA polymerases

The characteristic features of S. pyogenes are similar to bacteria: such as susceptibility to β lactam antibiotics including penicillin, cell wall structure etc .Therefore, S. pyogenes will be classified in the domain Bacteria.