Microbes Disease

1. Microbes & Disease

2. Contents Bacteria Culturing Bacteria Commercial biotechnology Bacterial Disease Viral Disease Protection Against Disease

3. Bacteria A microbe is any organism that is not visible with the naked eye The unaided resolution of the eye is about 0.1mm Bacteria are classified according to their shape: 1) Cocci: spherical bacteria - Cocci � smallest bacteria, occur as single spheres - Diplococci � pairs of spheres, e.g. pneumonia - Staphylococci � clusters of spheres, e.g. food poisoning - Streptococci � chains of spheres, e.g. sore throat 2) Bacilli: rod-shaped bacteria: - Individual rods � e.g. typhoid fever - Chains of rods � e.g. anthrax 3) Spirilla � large, spiral-shaped bacteria - e.g. syphilis 4) Vibrio � crescent-shaped bacteria - e.g. cholera

4. Reproduction of Bacteria Cell elongation results in the synthesis of additional cytoplasm & nuclear material DNA replication takes place (there is no mitotic spindle), & the nuclear material attaches to the plasma membrane or mesosome A septum begins to develop, & the nuclear material is distributed to both sides The septum is completed, & a cell wall develops to divide the cell into two The two daughter cells grow to a critical size, & then repeat this process

5. Culturing Bacteria New genetic material can be inserted into a bacterium in three main ways: 1) Conjugation: bacteria link together by their pili. Donor passes a plasmid called the F-factor (fertility) to the recipient cell. The F-factor may be in a plasmid (replicating independently), or incorporated into the main bacterial chromosome 2) Transformation: one bacterium releases DNA which is absorbed by a second bacterium, allowing it to acquire new characteristics 3) Transduction: new genes can be inserted into the bacterial chromosome by a bacteria phage (a virus acting as a vector)

6. Culturing Bacteria The bacterial population growth curve occurs in four main phases: 1) Lag phase: cells are active, but there is little increase in number. The cells accommodate to the new conditions, take in water & synthesise ribosomes & enzymes 2) Log phase: Nutrients & space are in plentiful supply, so there is little competition, & the bacteria multiply at their maximum rate

7. Culturing Bacteria 3) Stationary phase: carrying capacity (maximum number of bacteria that the environment can support) is reached, so intraspecific competition takes place between bacteria. Hence the death rate balances the population growth rate, & the number of bacteria remains roughly constant 4) Death phase: nutrient supply is running out & waste products accumulate resulting in increased toxicity of environment. Organisms are killed & population size eventually falls to zero. Spores may be produced during stationary phase that are resistant to the adverse conditions

8. Culturing Bacteria Bacterial growth can be controlled using physical methods (gamma irradiation or in an Autoclave using high temperatures) or by chemical means: - disinfectants - antiseptics Antibiotics can be either: - narrow-spectrum (affecting a few types of bacterium) - broad-spectrum (affecting a wide range of bacteria)

9. Commercial Biotechnology Microorganisms may be cultured commercially in order to obtain a substance that they produce They must be able to: - Produce the substance in large quantities in a small amount of time - Be available in pure culture, & be genetically stable - Grow rapidly in large-scale culture - Not be harmful to humans - Be capable of easy removal from culture - Grow on readily available & cheap raw materials - Have growth conditions that do not require extremes of temperature

10. Commercial Biotechnology Yeasts are widely cultured commercially, & are used in the production of: - Food substances in their own right, & in bread production - Beers, ales, lagers & wines, & alcohol as a biofuel There are two main types of process for the production: - Batch processes: raw materials & microbes are placed together in a container vessel. The microbes are then allowed to grow to their maximum population size, then the fermenter is emptied & the products are extracted & purified - Continuous process: the nutrients are continually inputted into the fermentation vessel & the material is continually removed & processed. This may be more economical, as it doesn�t have to be shut down on a regular basis

11. Commercial Biotechnology In order to develop a large industrial fermentation process, four main stages are required: - Isolation of microorganism: organism must be able to be purified easily & give the optimum product yield - Culture preparation: master culture is stored by freeze-drying (lyophilising) in a small space. Small samples are taken from master culture in order to produce stock cultures, from which working cultures can subsequently be produced - Laboratory scale (200cm3 fermenter): optimum conditions are determined using a small-scale fermenter - Pilot plant (200 to 500 dm3 fermenter): laboratory fermenter is scaled up to make sure that it works on a larger scale. There may be problems with heating/aeration, which may require electric mixers & cooling mechanisms

12. Commercial Biotechnology Enzymes are produced using submerged culture techniques. They are produced on a commercial scale when the organism is in the post-exponential growth phase. In downstream processing: - The mixture of nutrient broth, cells and extracellular enzymes is filtered and centrifuged to remove cellular material - The liquid enzyme mixture is concentrated by evaporation, to give the bulk enzyme The bulk enzyme may be: - Concentrated by chromatography to give the pure enzyme - Added to stabilisers to give the bulk liquid enzyme - Precipitated and filtered, then sprayed and grinded to give the powdered enzyme

13. Commercial Biotechnology Immobilised enzymes are widely used commercially � they can be immobilised in three ways: - Cross linkage: the enzymes are linked together by gluteraldehyde, to form a mesh. This may damage some enzymes, but those that are not damaged remain very active - Entrapment: the enzymes are trapped in gel microcapsules or in a fibrous polymer mesh. This does not damage the enzymes, but may slow their action due to the substrate having to diffuse in - Adsorption: the enzymes are held by weak bonds on the surface of an adsorbing agent (e.g. glass bead, carbon particle, collagen). The enzymes easily come into contact with the substrate, but it is expensive, and the enzymes may become detached

14. Bacterial Disease Most bacteria are either beneficial or harmless to humans � those that cause disease are pathogens: - The symptoms of the disease are usually caused by waste products of the pathogens - An infection is when the effects are noticeable on the body - Transmission is when an infection is passed on to somebody else Diseases such as typhoid and cholera are transmitted through water, and can cause diarrhoea To avoid water contamination, water-treatment processes take place

15. Bacterial Disease Food-borne infections including Salmonella are spread in two ways: - By not cooking food thoroughly (e.g. raw eggs: newly laid eggs may be contaminated with poultry faeces) - By contaminating cooked meat from handling raw meat first e.g. chicken Air-borne infections are spread when an infected person coughs, sneezes, talks or breathes, as the pathogens are passed into the air in small droplets saliva, mucus and water Infections that can be transmitted by direct contact are said to be contagious Insect bites can transmit pathogens through the saliva of the insect

16. Bacterial Disease Pathogenicity is the ability of a bacterium to cause disease. The main factors are: - The way in which the bacterium attaches and gains entry to host cells - The types of toxin produced by the bacterium - The infectivity of the bacterium (the number needed to cause an infection) - The invasiveness of the bacterium (its ability to spread within the host) After infection, a pathogen must do three things in order to produce a disease: - Attachment - Entry (penetration) - Colonisation

17. Viral Disease Viruses cannot survive without a living host Influenza affects the upper respiratory tract Acquired immune deficiency syndrome (AIDS) is caused by the human immunodeficiency virus (HIV), and results in the immune system breaking down so that it can no longer defend the body against disease Viral diseases can be very difficult to treat because the viruses have no metabolism of their own hence antibiotics have no effect on them. There are a few antiviral drugs, however, which can work by: - Inhibiting the production of viral DNA/RNA by altering the host cell�s DNA - Preventing the enzymes essential for the production of new virus particles from working - Preventing the viral particles from entering the cells in the first place

18. Protection Against Disease The human body has a number of barriers that prevent pathogens from entering the body: - The skin - Sebum - Tears, saliva and urine - Mucus in respiratory tracts - Commensals - Stomach acid and enzymes If the body is injured, a general inflammatory response will take place: - blood clots at the site of a cut, which seals the cut, to prevent pathogens entering the blood - inflammation around the site of the injury takes place - Macrophages are attracted to the site of injury, where they destroy pathogens by phagocytosis

19. Protection Against Disease There are four main types of immunity: - Active natural immunity: memory cells develop after natural exposure to antigens - Active artificially induced immunity: memory cells develop after vaccination - Passive natural immunity: antibody transfer (e.g. through placenta or breast feeding) results in short-term immunity (a few months), as no memory cells develop - Passive artificially induced immunity: antibodies are injected (short-term immunity) It is difficult to become immune to a virus, as they undergo many mutations, resulting in many different forms producing similar symptoms, but with different antigens

20. Protection Against Disease Antibiotics are only effective against bacterial infections Antibiotics work in a number of ways: - Inhibiting cell wall synthesis - Binding to ribosomes and inhibiting protein synthesis - Interfering with prokaryotic DNA replication and transcription - Binding to the cell membrane to make it more permeable - Inhibiting cell metabolism Bacteria may become resistant to antibiotics by altering the structure of the antibiotic or by modifying the bacterial cells. Resistance develops as a spontaneous mutation, and can spread through the population asexually and sexually

21. Summary Bacteria Culturing Bacteria Commercial biotechnology Bacterial Disease Viral Disease Protection Against Disease