# Productive Phage Infection --- A **productive phage infection** is when a [[bacteriophage]] infects it's host cell (a bacteria) and immediately starts creating a while new bunch of viruses right away. Phages that can only do productive infections are called "lytic" viruses. ## Steps **Step 1 - Attachment:** The phage lands on the outside of the bacteria cell it wants to infect. **Step 2 - Penetration:** The phage injects its genetic information directly into the host cell. **Step 3 - Biosynthesis:** The phage get to work almost immediately creating new pieces. The first genes it expresses are called the "early viral genes", like *nuclease* for breaking up the host cells DNA. Once it's done that, the virus has free reign to use the bacteria's cellular machinery to make *its own* proteins. Another early viral gene that is expressed right away is*polymerase* that will get to work making 100s to 1000s of copies of the genetic code for the virus. Once these things. Once those early genes are expressed, the rest of the genes that make all the individual parts of the virus can be translated. **Step 4 - Assembly/Maturation:** The individual phage components are put together, including having the genetic material put into the head region. This is the stage that could mess up and put in some remaining host cell DNA that potentially results in [[horizontal gene transfer|transduction]]. **Step 5 - Release:** The phage produces *lysozyme* which breaks down the host cell's cell wall and the host of viruses can bust out and go on to continue the cycle anew. Some phages don't actually lyse the cell, instead they extrude out, leaving the host cell alive. ___