Core RNA polymerase consists of five of the six subunits of RNA polymerase. This is the form that adds nucleotides to synthesize the RNA transcript.  
The holo form of RNA polymerase consists of all six subunits with the sixth being the sigma subunit. This allows for specificity of RNA polymerase to interact with different promoters of genes. The holo form is present during initiation, but elongation begins when the sigma subunit dissociates from RNA polymerase.

Core vs. Holo RNA Polymerase in Prokaryotes

RNA polymerase adds nucleotides to synthesize RNA transcripts in transcription. It does not require the RNA primer for initiation of transcription like DNA polymerase. 
RNA Polymerase interacts with the -35 and -10 sequence relative to the start of DNA transcription (+1) to begin initiating transcription. 

University of Wisconsin - Madison

Initiation of bacterial transcription involves the interaction of the transcription machinery proteins to begin transcription. This occurs at the promoter sequence which is recognized by RNA Polymerase. RNA Polymerase which requires the sigma subunit to bind to the promoter.

Initiation of Transcription in Prokaryotes

To dissociate the core RNA polymerase enzyme from the DNA template and release the RNA, transcription is terminated from termination signals in the DNA. RNA polymerase stalls and then releases from the DNA template and frees the RNA transcript.

Termination of Transcription in Prokaryotes

Elongation occurs when the sigma subunit of RNA polymerase dissociates from RNA polymerase. This activates the polymerization activity of the core enzyme RNA polymerase to synthesize RNA. 

Elongation of Transcription in Prokaryotes

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Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

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