What type of bacteria are the first forming elements of plaque?

The formation of dental plaque begins with specific types of bacteria that first colonize the tooth surface. Aerobic gram positive bacteria, which are the correct response, play a crucial role in this initial stage of plaque formation.

These bacteria are typically the first to adhere to the pellicle formed on the tooth surface, as the pellicle provides binding sites for these microorganisms. The most common genera of aerobic gram positive bacteria involved in this process include Streptococcus and Actinomyces, which are well-adapted to the aerobic environment found in the oral cavity.

As the plaque matures, it becomes a diverse ecosystem incorporating different microorganisms, but the initial colonizers are predominantly this type of bacteria. They are essential for scaling up the biofilm and providing a foundation for the subsequent colonization by other bacteria, including anaerobic organisms that thrive in the further stages of plaque development.

The other types of bacteria listed, such as anaerobic gram negative and spirochetes, typically appear later in the plaque formation process, as they require different environmental conditions to thrive. Hence, the early stages of plaque formation are distinctly characterized by the presence of aerobic gram positive bacteria, making this the correct answer.