lecture 32: bacteriophages

define bacteriophage

Bacterial viruses, diverse and found plentifully in the ocean, major impact on global energy/ nutrient cycles, coevolving w/ bacterial hosts

families of bacteriophages

Order Caudovirales, Families: Myoviridae, Siphoviridae, Podoviridae

how do phages alter bacterial communities

gene expression, cell physiology: virulence factors, facilitate the transfer of bacterial DNA: antibiotic resistance, give advantages for lysogenized cells

definition of host range

the breadth of hosts a phage can infect

describe the diversification of phage receptor binding proteins

aspect of bacteria-phage co-evolutions, mutations in bacterial surface receptors

What is CRISPR -cas

adaptive inherited immune system of bacteria, enabling them to generate and memorize resistance against foreign invading DNA

what keys steps are involved with CRISPR-Cas

adaptation, expression, and interference

explain adaptation for CRISPR-Cas

invading DNA is recognized by Cas proteins and incorporated into the spacer region of CRISPR

explain expression for CRISPR-Cas

Pre-crRNA is generated by transcription of the CRISPR region and is processed into smaller units of RNA, named crRNA

explain interference for CRISPR-Cas

By taking advantage of the homology of the spacer sequence present in crRNA, foreign DNA is captured, and a complex with Cas protein having nuclease activity cleaves DNA

how does anti-CRISPR mechanism work in phages

phages encode anti-CRISPR proteins, which inhibit CRISPR-Cas machinery