Introduction to Microbes & Flora

Bacteria are prokaryotic organisms. Fungi & Protozoa are eukaryotic organisms. Viruses & Prions are neither.

Smallpox is caused by the Variola major or minor virus. Tuberculosis, tetanus and diptheria are all caused by bacterial infections, and malaria is caused by a protozoan infection.

Creutzfeld-Jakob disease is caused by prions. These are infectious, misfolded proteins that contain no DNA or RNA, have no independent metabolism and contain no organelles. Chickenpox is caused by Varicella-zoster virus (VZV), which has a double-stranded DNA. Japanese encephalitis is caused by the Japanese encephalitis virus (JEV), which has a single-stranded RNA genome. Rabies is caused by Lyssavirus (this includes the rabies virus), which has a single-stranded RNA genome. Tetanus is caused by toxins from the bacteria Clostridium tetani.

Leishmania donovani is an example of a protozoan infection, and causes the disease leishmaniasis.

The difference in structure between Gram negative and Gram positive cells can be demonstrated using a Gram stain technique! Gram positive bacteria have a thick outer peptidoglycan layer and no outer lipid membrane. The outer peptidoglycan layer is thick enough to retain crystal violet dye and causes them to appear purple. Gram negative bacteria have a thin peptidoglycan layer, surrounded by an outer lipid membrane. The thin layer of peptidoglycan is not able to retain the crystal violet dye, but is able to pick up the safranin counterstain, which causes them to appear pink-red.

Ribosomes are found in both bacteria and human cells - they are involved in protein synthesis. Cell capsules, cell walls and nucleoids are only found in bacteria, whereas centrioles are only found in humans cells.

The key to a commensal relationship is that only one of the organisms is receiving benefit, and the other is completely unaffected. If both organisms benefit, the relationship is mutualistic. If one organism benefits and the other is harmed, the relationship is parasitic.

The gut flora have a multitude of functions, that all aid in boosting our immunity against ingested pathogens!

An infection is not always a asymptomatic disease. It can be subclinical/asymptomatic!

This statement describes an opportunistic pathogen. An obligate pathogen is one that must cause disease in order to be transmitted from one host to another. They must infect a host in order to survive.

Koch's postulates are used to establish a causative relationship between a microbe and a given disease. A photomicrograph is not one of the requirements for this process.

The respiratory cilia are a physical barrier to infection, rather than a biochemical barrier.