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 lasted 291 million years from the start of the Cambrian Period 542 million years ago until the end of the Permian Period 251 million years ago. Life of every â¦ kind went through great changes. The first evidence for plants predate the Paleozoic Era.