Tooth 3.6 has a disto-occlusal amalgam restoration with a gingival overhang. There is radiographic evidence of bone loss and deep probing depths with bleeding upon probing. Which of the following types of microorganisms are most likely associated with the subgingival environment in this site?

Gram-negative and anaerobic.

Gram-negative and aerobic.

Gram-positive and anaerobic.

Gram-positive and aerobic.