Figure 3.

Some known elements of the Crassvirales life cycle. Adsorption and infection of Bacteroides cells by crAss-like phages are regulated by the expression of alternating phase-variable capsular polysaccharide (CPS) types. Expression of non-permissive CPS prevents phage infection (a). while switching to permissive CPS allows phage attachment, hydrolysis of CPS by tail-associated depolymerase enzymes, and ejection of phage contents (b). Phage DNA is co-injected with cargo proteins, among which are virion RNA polymerase (vRNAP) subunits responsible for transcription of early (regulatory) and middle (DNA replication) genes (d). Formation of DNA polymerase (DNAP) as well as other enzymes, allows for DNA replication through an unknown mechanism, followed by expression of the late genes (large terminase, structural proteins, virion cargo proteins), carried out by the cellular bacterial RNA polymerase complex (cRNAP), (e). This results in the formation of new virions and the packaging of phage DNA (f).