qwasi

Hi, This is probably too late but I don't think virologists know the host range for Ebola and Marburg Viruses. I think I saw somewhere however that it may be monkeys. Hope this helps.

Bacteria of the genera Bacillus and Clostridium form endospores.

Hi, This is a very general question. There are many important bacterial genera - Neisseria; Yersinia; Escherichia; Klebsiella; Streptococcus; Staphylococcus; Salmonella; Shigella; Proteus; Chlamydia; Treponema; Leptospira; Clostridium; Bacillus; Brucella to name but a few. Bacteria are often divided into two groups: Gram-positive and Gram-negative. These are 2 major groups. Also, bacteria can also be named according to their shape: - Streptococci are cocci arranged into chains - Staphylococci are cocci arranged into grape-like clusters Bacteria can also be subdivided as follows: - obligate aerobes = if they use oxygen - obligate anaerobes = if oxygen is toxic - facultative anaerobes = if they use oxygen but can also survive without it Hope this helps

Hi, NK cells form part of the innate immune system which means that they are always "switched on" if you like. NK cells form an early line of defence against viruses and they do this by killing virally-infected cells. This is achieved by the release of two agents contained within granules in the NK cell. The first agent is called Perforin which forms pores in the virally-infected host cell. The second agent are called Granzymes which cause the apoptosis (programmed cell death) of the virally-infected host cell. NK cells recognise the virally-infected cells due to the lack of MHC Class I on the surface of the cells. Viruses are capable of redirecting MHC Class I away from the surface of host cells so that it is not expressed. When MHC Class I is present on the surface of host cells it interacts with an inhibitory receptor on the NK cell to prevent the NK cell from releasing Perforin and Granzymes. When the MHC Class I is absent it cannot interact with the NK cells inhibitory receptor and so the NK cell is stimulated to release the Perforin and Granzymes. Cytotoxic T-cells form part of the adaptive immune response and this means that they are only "switched on" to deal with persistent viruses e.g. HIV, Hepatitis. Similarly to NK cells, cytotoxic T-cells kill virally-infected host cells using perforin and granzymes. Therefore, the killing mechanism used by NK cells and cytotoxic T-cells is the same. Cytotoxic T-cells recognise virally-infected cells due to the presence of MHC Class I on the surface of that cell. This MHC Class I presents peptide fragments of the virus infecting the cell to the Cytotoxic T-cell. The Cytotoxic T-cell recognises the MHC Class I and viral peptide fragment and then releases the Perforin and Granzymes to kill the virally-infected host cell. Hope this helps.

Hi, HIV mutations occur a lot and are completely random. HIV has a RNA genome which, during replication, it must convert to a DNA genome. The enzyme involved is called reverse transcriptase and, unlike other enzymes involved in DNA replication, it has no proof-reading activity. This means that when copying the RNA to DNA it makes a lot of mistakes that go uncorrected. Therefore, when the DNA copy of the HIV genome is made it is different to the original RNA copy. Many different HIV genomes can be generated. The mutations are completely random and so any region of the virus' structure can be changed. However, only those mutations that benefit the virus will be retained. This means if a mutation occurs in a region the virus uses to adhere to cells, the virus will be unable to adhere efficiently and will be unable to enter cells and replicate. These viruses will be selected against. A mutation in a region that is not involved in essential stages like adherence etc. may be useful to the virus and enable it to evade the host's immune system. Viruses with these mutations will therefore survive so this mutation will be retained. Hope this helps.

Microbiology encompasses the following - bacteria - viruses - parasites e.g. protozoa - fungi - prions You will study the lives of all of the above in detail e.g. their structure; their replication/reproduction; how they obtain nutrition etc. You will no doubt cover the immune system in some detail and probably do some biochemistry as well for grounding. You will study things like: - how viruses and bacteria infect humans and how they cause disease - how viruses and bacteria evade the host's immune system - how these diseases can be treated e.g. antibiotics and their mechanisms of action - epidemiology You will look at specific viruses and bacteria, and the diseases they cause, in detail - usually ones like HIV, Hepatitis, Smallpox, Influenza, Meningitis, Tuberculosis to name a few. You will also obtain practical skills e.g. how to culture bacteria; microscopy etc and probably study DNA technology to some degree. Hope this helps.