Infection of E. gingivalis is transmitted by None.

Explanation:
E. gingivalis, also known as Porphyromonas gingivalis, is a gram-negative anaerobic bacterium that is commonly associated with periodontal disease. It is primarily found in the oral cavity, particularly in the subgingival (below the gum) pockets.

The transmission of E. gingivalis does not occur through cysts. The bacterium is primarily transmitted through direct contact with infected oral fluids, such as saliva or blood. The transmission can occur through various routes, including:

1. Close contact: Direct contact with an infected individual's saliva, such as through kissing or sharing utensils, can lead to transmission.

2. Respiratory droplets: E. gingivalis can be present in respiratory droplets when an infected individual coughs or sneezes. Inhaling these droplets can lead to transmission.

3. Vertical transmission: Infected mothers can transmit E. gingivalis to their infants during childbirth or through breastfeeding.

It is important to note that E. gingivalis is not typically transmitted through cysts. The formation of cysts is not directly associated with the transmission of this bacterium.

Prevention of E. gingivalis transmission involves maintaining good oral hygiene practices, such as regular brushing and flossing, visiting the dentist regularly for check-ups and cleanings, and avoiding behaviors that increase the risk of transmission, such as sharing toothbrushes or engaging in high-risk sexual practices.

In conclusion, the correct answer to the question is option 'D' - None. E. gingivalis is primarily transmitted through direct contact with infected oral fluids, such as saliva or blood, and not through cysts.