The ghost ants main form of interacting with other organisms comes from predator/prey relationships. T. melanocephalum has been recorded as preying on "diamondback moth larvae in India," "destroying eggs and larvae of houseflies in Puerto Rico," "two-spotted spider mites and aphids in glasshouses in Florida," "flea eggs and larvae," "the vector of Chagas' disease in coastal Venezuela," and many other small insects (Harris, 2005).

Another way ghost ants prey on other organisms but do not necessarily eat them is when they tend to sap producing plants. The ghost ant will consume honeydew excreted by insects such as mealy bugs of sugarcane, scale insects, and aphids that extract the sugar-rich fluid from plants (Wetterer, 2009; Harris, 2005). In areas where both organisms are prevalent, the ghost ant also tends to the fruit scales on the banana plant and a myrmecophilous butterfly of the genus Zizeeria (belongs to the same family as the Papilio glaucus butterfly) (Harris, 2005). 
In some instances Tapinoma melanocephalum aids in pollination as well, which can be observed with Jatropha curcas specifically (Luo et al, 2012).

For the reverse relationship of ghost ants being prey, "[N]o information was found on predators, parasites or parasitoids that attack T. melanocephalum." but with the increasing distribution this should soon be an aspect of interest (Harris, 2005).

When it comes to interacting with other ants that are present in the same habitat as T. melanocephalum, the ghost ants are usually out competed. This is because ghost ants can easily accommodate various food sources and habitats so they can easily move to different habitats and it is not a huge disturbance.  The ghost ants are also usually out numbered because they have smaller nests which causes foragers to have a hard time acquiring food. The end result is that the ghost ants leave the habitat almost immediately and there is no major interaction with the other species (Espadaler et al, 2002; Harris,2005).
Although, it has been documented that in Costa Rica a "slaticid spider (Continusa sp.) that resembles the ant builds silken retreats at the periphery of nests, seems to emigrate with the host, and is probably a symbiont (Shepard & Gibson 1972). The spiders provide the ants with protection from predators and parasites, while the ant nest is used as a foundation for web construction." (Harris, 2005).

To find out more interesting aspects of this organism, check out the facts page.