Gene Bombs were created by Arcturus to destroy high value targets in Zelem's Nexus.
Arcturus made the Gene Bombs to destroy Zelem's Nexus, but he created more than were needed, in case of a failed mission. There were no failed missions and the remainder of the Gene Bombs were sent to Scaldron, and now wander the wastes, looking for new targets.
Gene Bombs are some the most dangerous Darkspore in the Game as they take exploding baddies to a whole new level. When they are first seen, Gene Bombs will attack in melee, dealing a decent amount of Physical damage. When they are down to about to about a third of their Health, the Bombs will go in to detonate mode chasing after the Heroes, and when they get near enough they will explode, dealing High Energy damage, enough to usualy take the Hero down to half of its Health.
The easiest way to defeat such Lieutenants is to keep them at range, using such attacks as the Arcane Variant ability Will-O-Whisp which will keep it at range (hopefuly) Dazzled. Another is any of Andromeda's Abilities. The explosion is about 20 meters in radius, so if you have to run, hope that you are fast.