Enterobacter is a genus of common Gram-negative, facultatively anaerobic, rod-shaped, non-spore-forming bacteria of the family Enterobacteriaceae.nterobacter is a genus of common Gram-negative, facultatively anaerobic, rod-shaped, non-spore-forming bacteria of the family Enterobacteriaceae.
Trilobite fossil from the Cambrian Period. Photo Credit: Archbob. The first period in the Paleozoic Era is known as the Cambrian Period. Many of the ancestors of the species that have evolved into what we know today first came into existence during the Cambrian Explosion in the early Cambrian Period.
Most creepily, this era is sometimes referred to as the Age of the Cockroaches, because roaches' ancient ancestor (Archimylacris eggintoni) was found all across the globe during the Carboniferous. The last period of the Paleozoic was the Permian Period, which began 299 million years ago and wrapped up 251 million years ago.