Gene expression refers to the processes of using the genetic code to make proteins.  This process occurs in two steps: transcription and translation. This occurs in all of the classifications of microbial genetics.
Gene expression is also described as the "Central Dogma of Molecular Biology" to describe the transfer of information of the genetic code in cells.

Gene Expression

DNA replication is the copying of the genome. It happens in prokaryotic, archaeal, eukaryotic and viral genomes. DNA replication is semiconservative. This describes how, during DNA replication, the DNA is separated and single strands serve as the template for the synthesized DNA. This was determined by Matthew Meselson and Franklin Stahl in 1958. 

DNA Replication

Horizontal gene transfer is the movement of genetic material between organisms other than by the vertical transmission of DNA from parent to offspring. In bacteria, this process is a primary driver for the rapid spread of genetic traits, including antibiotic resistance genes.

Horizontal Gene Transfer

The genetics of prokaryotic organisms. This is primarily focused on genes of the single, circular chromosome and extrachromosomal DNA found  in prokaryotes.

University of Wisconsin - Madison

Microbial genetics are classified in the three domains of life:
- Eukaryotic genetics
- Prokaryotic genetics
- Archaeal genetics 

Note:
Although they are not designated as living cells, viral genes also vary in their genetic material, genetic expression and replication compared to the three domains of life.

Classifications of Microbial Genetics

https://openstax.org/details/books/microbiology/

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.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

OpenStax Microbiology Textbook

Prokaryotic genetics

The genetics of eukaryotic organisms. This describes the genetic processes of eukaryotics that are distinct because their genetic material is contained in a nucleus. 

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