MCD – Cells 2 – Pathogenic Microbes Anil Chopra 1. Name the main types of infectious agent causing disease in humans 2. List the key differences between prokaryotes and eukaryotes 3. Give examples of each type of infectious agent and the disease it causes 4. Name the distinguishing features of the different types of infectious agent and explain how they replicate Type Example Features Bacteria Mycobacterium Prokaryotes that replicated by binary fission, they tuberculosis, E. coli, contain chromosomes, but no nucleus. Their DNA Neisseria meningitides is circular. They inhabit the gut, skin, they stimulate the immune system and aid with metabolism and provision of nutrients. Some are pathogenic and can in the immuno-compromised, cause infections (opportunistic infections). Viruses HIV, common cold, Not cells in their own right (obligate parasites), influenza inhibit host cell from replicating. Contain DNA or RNA and use reverse transcriptase to divide. Make use of a host cell nuclear synthetic machinery to replicate and divide by budding out of the host cell. Show host specificity but infect almost all other life forms including bacteria. Fungi Candida albicans Single celled eukaryotes that exist as yeasts or (thrush), aspergillus filaments. Yeasts bud or divide; filaments (hyphae) fumigatus which have cross walls or septa.Usually affect immuno-compromised people. Causes mycoses (infection). Protozoa Malaria, leishmaniasis Single celled eukaryotes, include intestinal, blood and tissue parasites. Replicate in host by binary fission or by forming trophozoites in a cell. Many have complicated life cycle involving 2 hosts. Infection acquired by ingestion or via a vector. Helminths Tapeworm, fluke, Multicellular organisms. Have life cycles outside roundworms human host, visible to the naked eye. Complex life cycle including embronation to generations in different hosts.