A 22-year-old man presents with a painless 1-cm ulcer on the shaft of his penis. Inguinal lymphadenopathy is present. The patient admits trading drugs for sex and has several sexual partners. An RPR test result is positive, and syphilis is suspected; however, a Gram stain of a swab specimen from the ulcer shows no bacteria. Treponema pallidum, the causative agent of syphilis, cannot be visualized by light microscopy because
(B) It cannot be stained by ordinary stains.
(C) It has a diameter of less than 0.2 μm.
(D) The wavelength of white light is too long.
(E) Rapid movement of the organism prevents visualization.
Chloramphenicol, an antibiotic that inhibits bacterial protein synthesis, will also affect which of the following eukaryotic organelles?
(D) Endoplasmic reticulum
Which of the following structures is not part of the bacterial cell envelope?
A group of teenagers became ill with nausea, vomiting, severe abdominal cramps, and diarrhea after eating undercooked hamburgers from a local restaurant. Two of the teenagers were hospitalized with hemolytic-uremic syndrome. Escherichia coli O157:H7 was isolated from the patient’s stools as well as from uncooked hamburgers. The H7 refers to which bacterial structure?
Which of the following components is present in gram-negative bacteria but not in gram-positive bacteria?
Group A streptococci are the most common bacterial cause of pharyngitis in school-age children 5–15 years of age. The most important cell component involved in adherence of this bacteria to fibronectin, which covers the epithelial surface of the nasopharynx is
In the fall of 2001, a series of letters containing spores of Bacillus anthracis were mailed to members of the media and to U.S. Senate offices. The result was 22 cases of anthrax, with five deaths. The heat resistance of bacterial spores, such as those of Bacillus anthracis, is partly attributable to their dehydrated state and partly to the presence of large amounts of
(D) Sulfhydryl-containing proteins
Which of the following terms does NOT describe the bacterial chromosome?
Lysozyme cleaves the β1→4 linkage between
(A) d-Alanine and the pentaglycine bridge
(B) N-Acetylmuramic acid and d-alanine
(D) N-Acetylmuramic acid and N-acetylglucosamine
(E) d-Alanine and d-alanine
Mycoplasma species lack which of the following components?