In Episode 1 Obi-Wan Kenobi says that:
You and the Naboo form a symbiotic circle, what happens to one of you will affect the other, you must understand this...
Being that a 'symbiosis' means:
the living together of two dissimilar organisms, as in mutualism, commensalism, amensalism, or parasitism.
It’s worth noting that the language used in the novelizations can be a little different:
“You and the Naboo are connected,” Obi-Wan insisted, his youthful face intent, not ready to concede the matter. “What happens to one will affect the other. You must understand this.”
This suggests that the notion of “symbiosis” is not meant to be take strictly literally, but in a more metaphorical sense.
Indeed, it seems that Obi-Wan’s main point is that the Naboo are all that stand between the droid army and the Gungans:
“After that army takes control of the Naboo, they will come here and take control of you,” Obi-Wan said quietly.
That said, it is possible that Obi-Wan is referring to something more concrete, such as trade between the Naboo and the Gungans, as mentioned here (though that information may now be non-canon). As far as canon information, on the one hand the leader of the Gungans himself has communicated rather infrequently with the Naboo:
Boss Nass chuckled. “No, me think not. Me talk mebbe one, two times wit Naboo in whole life, and no talk ever wit maccaneks. Maccaneks no come here! Dey not even know Gungans exist!”
On the other hand, as a relatively non-industrial society, it seems likely that the Gungans must trade for a lot of the technology they use.
Still, Gungans are described as having "developed" advanced tech, and so may be more industrial (if less conventionally so), than one might assume, and thus less dependent on trade with the Naboo.
While most spacefarers would dismiss Gungans as primitives, they have developed an advanced, albeit unique, technology. They grow the basic structures of buildings, vehicles and technology and adorn them with artistic flourishes and organic lines. This gives Gungan technology a very fluid, non-rectilinear look.
It is also possible that they buy their bubble generators and so forth more directly from offworlders, rather than trading with the Naboo.
Still, if there is trade between the Naboo and the Gungans (presumably by people less isolated than Boss Nass), this could be another justification for Obi-Wan’s assertion of symbiosis.
