Which of the following is a characteristic of Gram-negative bacteria?

Question

BlackTom AI · Accepted Answer

To approach this question, let's evaluate what characterizes Gram-negative bacteria and contrast it with Gram-positive features.
Option 1: 'Thick peptidoglycan layer' — This is a hallmark of Gram-positive bacteria, not Gram-negative. Gram-negatives have a comparatively thin peptidoglycan layer sandwiched between an inner cytoplasmic membrane and an outer membrane, so this statement is incorrect for Gram-negative cells.
Option 2: 'Presence of an outer membrane containing lipopolysaccharides (LPS)' — This is a defining feature of Gram-negative bacteria. The outer membrane with LPS acts as a barrier to certain antibiotics and contributes to the endotoxin activity of LPS when released; its presence is a key distinguishing trait from Gram-positive bacteria. This option correctly identifies a Gram-negative characteristic.
Option 3: 'Teichoic acids in the cell wall' — Teichoic acids are typically found in the cell wall of Gram-positive bacteria and contribute to the negative charge and rigidity of their thick peptidoglycan layer. Their absence is typical of Gram-negative bacteria, so this statement is inaccurate for Gram-negatives.
Option 4: 'No periplasmic space' — Actually, Gram-negative bacteria possess a defined periplasmic space between the inner and outer membranes that contains enzymes and transport proteins. Saying there is no periplasmic space contradicts the known architecture of Gram-negatives, so this option is false.
In summary, the only statement that aligns with Gram-negative cell envelope structure is the presence of an outer membrane containing lipopolysaccharides (LPS). The other options describe features characteristic of Gram-positive bacteria or misstate the cellular architecture of Gram-negative organisms.

Which of the following is a characteristic of Gram-negative bacteria?单项选择题

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