Bacteriophages, Viruses of Archaea, and DNA Animal Viruses PDF

Bacteriophages Infect a wide variety of organisms, mostly prokaryotes Single-stranded DNA genomes of the plus configuration infect plants, animals, and bacteria and share molecular similarities contains a circular single-stranded DNA genome inside an icosahedral virion ve...

Bacteriophages Infect a wide variety of organisms, mostly prokaryotes Single-stranded DNA genomes of the plus configuration infect plants, animals, and bacteria and share molecular similarities contains a circular single-stranded DNA genome inside an icosahedral virion very small genome with overlapping _ genes (parts of genome read in different reading frames; Figure 10.6a) frame sthifting - Replication occurs via rolling circle replication (like phage lambda; Figure 10.7). Lysis occurs through inhibition of peptidoglycan synthesis phage kill hostcells. to releaerealiatecd gene encodes (4) means it protein aot, so transctiye ( t) pRNkfirnt CG ) - does.  Bacteriophage M13 Bacteriophage M13 model filamentous bacteriophage attaches to host pilus can be released without lysis Coat proteins cover DNA as it exits cell envelope. (Figure 10.8) no intracellular accumulation; causes chronic infection used as a cloning and DNA- sequencing vector in genetic engineering  Bacteriophage T7 dsDNA bacteriophages among best studied of all viruses Bacteriophage T7 infects E. coli and a few related enteric bacteria Virion has an icosahedral head and a very short tail. inhibits host restriction system encodes T7 RNA polymerase (widely used for biotechnology) and host RNA polymerase inhibitors The capsid is composed 60 asymmetric DNA replication employs T7 DNA units made of 7 proteins (T=7) polymerase and involves terminal repeats and the formation of concatemers.  Bacteriophage Mu temperate phage (have lytic and the lysogenic cycles) replicates by transposition _ generates mutations upon integration, so useful in bacterial genetics large virus with an icosahedral head, helical tail, and six tail fibers (Figure 10.10a) genome is linear Host range is controlled by tail fibers: One type allows infection only of E. coli; other allows infection of other enteric bacteria too. Integration requires Mu transposase Ψ θ integration into host genome required for lytic and lysogenic ^ development: _ he Imenso - – Lysogenic cycle: bacteriophage integrates itself into the host genome ^ (becoming prophage) and then replicates passively along with the host genome " θ– Lytic cycle: phage produces progenies and kills the host cell 、 pqhages Mang have this 4 Replication occurs by repeated transposition to multiple host genome sites. in lytic cycle, Mu transcription activation protein and head and tail proteins synthesized to coat the phage after self-assembly, cell lyses and mature virions released https://www.researchgate.net/figure/The-Mu-phage-life-cycle-As-a-temperate- phage-Mu-can-undergo-lysogenic-or-lytic-growth_fig7_51243350  Viruses of Archaea All characterized archaeal viruses have DNA … ' genomes. mostly double-stranded circular DNA viruses \ DNA Archaeal Viruses Hosts are Euryarchaeota and Crenarchaeota. Most Euryarchaeota viruses are “head and tail” type similar to those that infect enteric bacteria (e.g., T7). jimilar to bacterial phage One archaeal halophilic virus is enveloped and ssDNA.  DNA archaeal viruses Most distinctive archaeal viruses infect hyperthermophilic Crenarchaeota. SSV in Sulfolobus has spindle-shaped virions in rosettes. (Figure 10.11a) SIFV SSV SIFV in Sulfolobus are rigid, helical rods with linear DNA genomes. ATV in Acidianus is the first virus shown to develop without host cell contact, forming extended tails, and is lysogenic. (Figure PAV1 10.11d) PAV1 in hyperthermophile Pyrococcus ATV (Euryarchaeota) is released without lysis, likely by budding and is heat-stable.  RNA archaeal viruses - usually associcted with exotk envlronments none isolated to date, but environmental genomics suggest they exist Acidic hot springs have yielded archaeal DNA viruses (Figure 10.12) and unique viral RNA sequences originating from Baltimore class IV (ss(+)RNA). Uniquely Replicating DNA Animal Viruses Double-stranded DNA animal viruses that have unusual replication strategies Pox viruses: All replication occurs in cytoplasm. Adenoviruses: DNA replication occurs on both DNA template strands.  Pox viruses – smallpox among largest animal viruses ^ known: 240 nm by 300 nm and 130–260 kb. (Figure 10.13) Also include cowpox (historically ^ used as smallpox) and vaccinia ^ virus (used as modern smallpox ^ vaccine and lab model) Smallpox is historically and medically important: the first to be studied and have a vaccine developed. – Causing fever, vomiting, formation of sores in the mouth, skin rash, extensive skin scarring, blindness, death. – 15 million cases occurred a year in 1967. – smallpox was eradicated, and no cases of naturally occurring smallpox have happened since 1977.  Vaccinia γ model of smallpox Genome is linear dsDNA of ~ 190 kbp, encoding ~250 genes. after attachment and entry, nucleocapsids freed in cytoplasm All replication occurs in cytoplasm. Cell lyses and releases virions. has been genetically engineered to make experimental recombinant vaccines since it elicits a strong immune response without serious health effects Diagram representative of the VACV infection cycle (e.g., influenza, rabies, herpes simplex type 1, hepatitis B) Further readings on VACV engineering: The origin of vaccinia virus and https://www.ncbi.nlm.nih.gov/pmc/article s/PMC2742674/ how it came to be in the vaccine https://www.mdpi.com/1999- are not known. 4915/8/5/134/htm (https://www.statnews.com/201 7/10/11/vaccine-mystery/)  Adenoviruses major group of small, naked, icosahedral, linear, double- stranded DNA viruses (Figure 10.14a) Adenoviral terminal protein attaches to 5' end of adenoviral genomic DNA required for genome replication. DNA replicates in the nucleus. virions assembled and released after lysis a 26–45 kb size double-stranded DNA genome https://www.intechopen.com/books/adenoviruses/adenoviral-vector-based-vaccines-and-gene- therapies-current-status-and-future-prospects  Adenoviruses cause mild respiratory infections in human - common flu-like disease cmilder) s https://www.cdc.gov/adenovirus/about/symptoms.html pinkeye Viral Conjunctivitis mm https://emedicine.medscape.com/article/1191370-overview _ Clinical manifestation of child hepatitis of unknown origin Adenovirus infection as a probable cause “During April 5-July 9, 2022, the World Health Organization (WHO) recorded 1010 likely cases across 35 countries. Of these, 5% of children (n = 46) required liver transplantations and 2% (n = 22) died of hepatitis infection.” https://www.sansureglobal.com/severe-hepatitis-of-unknown-origin-in-children-adenovirus-or-covid-19-infection/