Virology Lecture Notes PDF

VIROLOGY BTH-529 B.S. III YEAR (EVENING) Dr Alveena Zehra Department of Biotechnology University of Karachi  Authors Jane Flint Glenn F. Rall Vincent R. Racaniello Anna Marie Skalka Lynn W. Enquist Publisher American Society for Microbiology  VIRUSE...

VIROLOGY BTH-529 B.S. III YEAR (EVENING) Dr Alveena Zehra Department of Biotechnology University of Karachi  Authors Jane Flint Glenn F. Rall Vincent R. Racaniello Anna Marie Skalka Lynn W. Enquist Publisher American Society for Microbiology  VIRUSES ARE EVERYWHERE They are almost everywhere, and all around us We are always inhaling them with the air, we are always eating them with our food They may be entering our body with our eyes, mouths, and other points of entry when we are touching surfaces Their number is spectacular No matter what we do, we encounter billions of virus particles every day VIRUSES INFECT EVERY LIVING THING ON THE PLANET They infect plants, animals even bacteria Every species of organism has its own viruses Recently the viruses of C. elegans (nematode) were discovered, but they existed! HOW MANY VIRUSES ARE ON THE PLANET? T-even bacteriophages (bacteriophages are viruses that infect bacteria) in the World’s water supply, are 1030 and that’s a huge number! (1,000,000,000,000,000,000,000,0 00,000,000 Nonillian) Let’s see how big this number is…  WEIGHT OF A PHAGE A phage weighs around a femtogram Multiply that to 1030 and you’ll get a biomass that exceeds that of all of Earth’s elephants by more than 1,000- fold. So, that tells you how many they are! In the oceans, per teaspoon of ocean water, you got 5 million virus particles  Now if you take these 1030 phages and you line them up end to end, that line of phages would stretch 200 million light years Our nearest spiral galaxy is 2.5 million light years away  INFECTED WHALES Whales are infected with little RNA virus called the calicivirus These viruses can cause rashes and gastroenteritis in whales Sometimes this virus infect us as well The infected whales excrete 1013 particles per day. Each whale!! VIRUSES ARE THE MOST ABUNDANT ENTITIES IN THE BIOSPHERE!  VIRUSES CAN CAUSE HUMAN DISEASE Viruses are all around us all the time, but most of us are pretty healthy - thanks to our immune system It’s only when the system is down that we have problems if a person has AIDS If a person is immunosuppressed because of organ transplant If a person has undergone chemotherapy or some other kinds of virus infection like measles infection and naturally immunosuppresses  VIRUSES ARE NOT ALL BAD There are many examples of good viruses. A virus establishes in a plant and this is a certain species of grass that is often found around hot springs, grows very well at temperatures higher than 50°C The ability of this grass is to survive hot temperatures and them being colonized by a fungus and that fungus in turn have to be infected with a virus So if you take this virus out of the fungus and leave the fungus, it cannot survive at 50°C and if you take the fungus out the plant will not survive So the plant gets the little high temperature and provides home to both the fungus and the virus  WE HAVE VIRAL GENOMES IN OUR GENETIC M AT E R I A L We have viral genomes in our germline so we have inherited them from our parents and we are going to pass them on to our kids as well Different viral genetic sequences have integrated into our genetic material and these are illustrations of different such sequences that are related to retroviruses a particular class of virus that integrates its genetic material into cellular DNA and these range from nearly complete retroviral genomes if you go endogenous retroviruses to different forms 42 % of your DNA is derived from retroviral sequences  3 PA R T S T R AT E GY O F V I R U S E S All viruses have a genome that is encased in a particle and the particle is the protective device that allows the genome to be transmitted from one cell to another The genome has all the information to make new virus particles These genomes are able to establish themselves in host populations  REFERENCE Principles of Virology, 4th Edition, 2 Vol set by S. Jane Flint, Lynn W. Enquist, Vincent R. Racaniello, Glenn F. Rall, Anna Marie Skalka