MICR 221 Lecture Notes - Lecture 6: Peptidoglycan, Cell Membrane, Gram-Negative Bacteria
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1.This week, you will be conducting Gram stains of bacteria.Which of the following statements are true? (Mark all thatapply)
Gram-negative bacteria do not stain purple because they do nottake-up crystal violet or iodine | ||
The peptidoglycan in the walls of Gram-positive bacteria bindsto the crystal violet stain more easily than walls of Gram-negativebacteria do | ||
Gram-positive bacteria have cell walls with a thickerpeptidoglycan layer than walls of Gram-negative bacteria | ||
Gram-negative bacteria do not stain purple, because their cellwall structure allows purple-colored iodine-dye complexes to washout of the cells more easily than the cell wall structure ofGram-positive bacteria does | ||
Gram-negative bacteria have an outer membrane (outside thepeptidoglycan layer in their wall) that Gram-positive bacterialack |
2.
What evidence is used to inform our understanding ofrelationships among species? (mark all that apply)
Biochemical similarities between existing species | ||
Fossils | ||
Morphological similarities between existing species (presence ofhair, backbones, etc.) | ||
DNA sequences and molecular clocks |
3.
For each of the groups of organisms below, indicate whether theybelong in (A.) Archaea, (B.) Bacteria, or (C.) Eukarya
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4.
Select all true statements about the relative diversity ofdifferent groups of organisms from among the followingstatements:
There are more species of plants on Earth than species ofmolluscs | ||
There are more plant species on Earth than mammal species | ||
There are more species of plants on Earth than species offungi | ||
There are more species of fungi on Earth than mammal species | ||
There are more species of plants on Earth than species ofarthropods | ||
There are more flatworm species on Earth than mammal species |
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 childâs oropharynx. Her mother also took Deliaâs 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 Deliaâs rapid strep test being negative, the doctor went ahead and ordered a bacterial culture. This was a wise decision because 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 patientâs 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: Assuming that Delia is not allergic to penicillin-based drugs, would a penicillin-family drug (amoxicillin, for example) typically be effective against S. pyogenes?
| A. Penicillin-based drugs would effectively target the thick peptidoglycan layer within the pathogenâs cell wall. |
| B. Penicillin-based drugs would be ineffective since the cell wall of S. pyogenes does not contain peptidoglycan. |
| The porins within the pathogenâs outer membrane would exclude penicillin-based drugs, rendering these antimicrobials C. ineffective. |
| D. Penicillin-based drugs would effectively target the mycolic acids present in the pathogenâs cell wall. |