Bacterial cells lack a nucleus and most of the internal membrane-bound compartments eukaryotic cells rely on, their DNA floats free in the cytoplasm rather than being enclosed inside a separate nuclear membrane. That structural simplicity is part of why bacteria can grow and divide so remarkably fast, some species can double their entire population roughly every twenty minutes under ideal conditions, a pace no eukaryotic cell, with its far more elaborate internal machinery to duplicate first, comes anywhere close to matching.
A bacterial cell's simpler structure is genuinely, not just superficially, different from a eukaryotic one
Bacterial, or prokaryotic, cells have no nucleus, no membrane-bound organelles of the kind eukaryotic cells rely on, and typically a single circular chromosome rather than multiple linear ones. That's a genuinely different structural plan, not simply a smaller or less developed version of a eukaryotic cell, and bacteria also have a cell wall built from peptidoglycan, a molecule genuinely different in composition from the cellulose-based walls plant cells build.
That structural simplicity is part of what makes such fast division possible
Bacteria reproduce through binary fission, one cell simply dividing into two genetically identical daughter cells, and under ideal nutrient and temperature conditions, a bacterial population's growth follows a distinct curve, an initial lag phase, then a rapid exponential phase where the population genuinely can double roughly every twenty minutes for some fast-growing species, before nutrient depletion and waste accumulation force the population into a stationary phase and eventually decline. That extremely fast division rate reflects both the cell's mechanical simplicity, less internal machinery to duplicate before each division, and typically a smaller genome that takes less time to replicate and segregate than a eukaryotic cell's.
What we're still unsure about
That bacterial cells are structurally simpler than eukaryotic cells, and that this simplicity contributes to remarkably fast division rates, is well established, uncontroversial microbiology. What's genuinely a live, actively mapped research question is that this same fast generation time is exactly what lets bacterial populations evolve antibiotic resistance so quickly, and exactly how large a role horizontal gene transfer between different bacterial species and strains plays in actually spreading specific resistance genes, compared with resistance arising independently through mutation separately in each lineage, is still being actively worked out by microbiologists tracking how particular resistance genes have actually spread.
This sits inside Bacterial Cell Structure & Growth, one of seven topics in Microbiology, one of six domains in Biology, one of seventeen subjects the app can quiz you on.