Final answer:
Porphyromonas is a Gram-negative rod often found in the human oral cavity. Other examples like Pseudomonas aeruginosa and Escherichia coli are Gram-negative rods, but typically not found in the oral cavity. Streptococcus, Staphylococcus, and Lactobacillus are not Gram-negative rods.
Step-by-step explanation:
The question seeks to identify Gram-negative rods found in the oral cavity. Among the choices provided, Porphyromonas is a Gram-negative rod-shaped bacterium, often found in the oral cavity. However, it is worth mentioning that there are additional types of Gram-negative rods that can be found in the oral cavity or other areas of the body. For instance, Pseudomonas aeruginosa and Escherichia coli are other examples of Gram-negative rods, but they are typically not found in the oral cavity.
Streptococcus, Staphylococcus, and Lactobacillus are not considered Gram-negative rods. In fact, Streptococcus and Staphylococcus are Gram-positive cocci, while Lactobacillus is a Gram-positive rod.
Learn more about Gram-negative rods