pathogen.pdf

Pathogens  Learning outcome List the main characteristics of viruses, bacteria and fungi. Compare the structure of bacteria, viruses and fungi. Explain what is meant by the term lytic and latency.  What is a pathogen? Microorganisms that causes diseases. Bacteria ...

Pathogens  Learning outcome List the main characteristics of viruses, bacteria and fungi. Compare the structure of bacteria, viruses and fungi. Explain what is meant by the term lytic and latency.  What is a pathogen? Microorganisms that causes diseases. Bacteria All bacteria have: Bacterial cell wall containing peptidoglycan A cell surface membrane (phospholipid bilayer with embedded proteins) A nucleoid ( a single circular strand of DNA that is genetic material of the bacterium) 70S ribosomes which are site of protein synthesis Some bacteria have: Pili- thread like projection from the surface of the cell wall Flagella- long rapidly rotating whip-like structure which can move the bacteria about A capsule or slime layer- a thick slippery substance around the outside of the cell wall Mesosomes- internal extensions of the membrane which fold into the cytoplasm and maybe the site of cellular respiration Plasmid- small circles of additional DNA that code for specific characteristics  Virus Smallest of microorganism ( 0.02-0.3µm) Not cells ( arrangement of genetic material and protein that invade living cells) All viruses have the following characteristics A protein coat or capsid- consist of simple repeating units known as capsomeres arranged in different ways. Nucleic acid- genetic material which is either DNA or RNA Specific proteins (antigens) known as virus attachment particles (VAPs)- which target proteins in the host cell surface membrane. Some viruses have the following characteristics A lipid envelop which is produced from the host cell membrane and which covers the genetic material and protein coat.  Type of viruses DNA virus RNA virus Retrovirus  How viruses reproduce Once a virus is in the host cell, there are two different routes to infection; The lysogenic pathway The lytic pathway  Lysogenic pathway (Latency ) a viral reproductive stage where the virus's DNA is being replicated using the host cell's DNA. During lysogenic infection, the virus uses the host to help copy its DNA or genetic information, but it is not producing any proteins. virus is present in the body but exists in a resting (latent) state without producing more virus.  Lytic pathway Sometimes, the viral genetic material is replicated independently of the of the host DNA immediately after it enters the host. Mature viruses are made and eventually the host cell bursts releasing large number of new virus particles to invade other cells.  Fungi Fungi are eukaryotic organisms that include microorganisms such as yeasts, moulds and mushrooms. These organisms are classified under kingdom fungi.  Structure of fungi Almost all the fungi have a filamentous structure except the yeast cells. They can be either single-celled or multicellular organisms. Fungi consist of long thread-like structures known as hyphae. These hyphae together form a mesh-like structure called mycelium.  Fungi as a pathogen Pathogenic fungi have an enormous impact on human health. These include skin and nail infections such as athlete's foot and ringworm Difference between bacteria, fungi and virus