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.
The Paleozoic era represents the longest timespan from the list. It ran from 542 to 251 million years ago, a total time of 291 million years. It is also worth noting that an â¦ era always represents a longer timespan than a period and in fact an era will be composed of a number of periods.he Paleozoic era was from 540 million years ago to about 245 million years ago. After that came the Mesozoic era, and that lasted from the end of the Paleozoic to 65 million â¦ years ago, when the earth entered the Cenozoic era.