Final answer:
Translation initiation in bacteria involves the formation of an initiation complex consisting of the small ribosomal subunit, mRNA, initiation factors, and initiator tRNA. The complex is completed when the large ribosomal subunit binds, and translation occurs immediately after or sometimes simultaneously with transcription.
Step-by-step explanation:
Initiation of Translation in Bacteria
Translation initiation in bacteria involves the assembly of various components to form the initiation complex. The small ribosomal subunit attaches to the mRNA template along with three initiation factors (IF-1, IF-2, and IF-3) and an initiator tRNA carrying N-formyl-methionine (fMet-tRNAMet). This special tRNA recognizes the start codon AUG on the mRNA. In E. coli, the ribosome is assisted in finding the start codon by a sequence called the Shine-Dalgarno sequence which is located upstream of the start codon and pairs with the rRNA within the small ribosomal subunit.
After the initiator tRNA has base paired with the start codon AUG, the large ribosomal subunit binds to this complex, completing the formation of a functional ribosome ready for translation elongation. This process is energetically driven by guanosine triphosphate (GTP). During this phase, a polypeptide chain is synthesized as tRNA molecules continuously bring in amino acids that match the codons on the mRNA being translated.
Translation occurs after transcription in bacteria and can sometimes be simultaneous due to the lack of a nuclear envelope, allowing ribosomes to begin translating an mRNA while it is still being transcribed. This close proximity of transcription and translation is a unique feature of prokaryotic cells.