RNase E is a widely-conserved bacterial endoribonuclease with diverse roles in cellular RNA metabolism, and is also the central component of the bacterial RNA degradosome. Essential for viability in many species, RNase E is involved in processing of housekeeping RNAs and in general RNA turnover, and impacts many aspects of general physiology, environmental adaptation, and regulation of virulence. In particular, the crucial role of RNase E in post-transcriptional regulation via biogenesis of small regulatory RNAs and regulated decay of coding transcripts has emerged. Beyond its widespread importance to bacteria, RNase E has also been a model for understanding how RNA metabolism is organized across kingdoms of life. Here, we review the molecular details of RNase E and its protein partners as revealed from studies in Gram-negative models such as E. coli and Salmonella, and contrast them with themes uncovered in other species. We also discuss shared aspects of the RNase E degradosome with other RNA decay complexes that appear to have evolved convergently, such as those based on RNase Y/J and the eukaryotic exosome. Finally, we present emerging themes in RNase E, such as its role in phase separation and RNA networks, and propose that application of global deep sequencing approaches (TIER-seq, CLASH/RIL-seq, and Grad-seq) to additional species will provide a broader understanding of its structure and function.