Transcription and translation can occur simultaneously in bacteria because bacterial mRNA does not require processing before translation.

Here's why:

* No nucleus: Bacteria lack a nucleus, meaning their DNA is not separated from the ribosomes where protein synthesis occurs. This allows for direct access to the mRNA transcript.

* No introns: Bacterial genes don't contain introns (non-coding regions). In eukaryotic cells, introns are spliced out of the mRNA transcript before translation. This processing step doesn't exist in bacteria.

* Coupled processes: As the mRNA is being transcribed, ribosomes can attach to the 5' end and start translating the message. This "coupled" process ensures efficient protein synthesis.

In contrast, eukaryotic cells have a nuclear envelope that separates transcription and translation, requiring additional processing steps for mRNA before it can be translated.