Microbes & DiseaseMicrobes & Disease

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BacteriaBacteria Culturing BacteriaCulturing Bacteria Commercial biotechnologyCommercial biotechnology Bacterial DiseaseBacterial Disease Viral DiseaseViral Disease Protection Against DiseaseProtection Against Disease

BacteriaBacteria A microbe is any organism that is not visible with the A microbe is any organism that is not visible with the

naked eyenaked eye The unaided resolution of the eye is about 0.1mmThe unaided resolution of the eye is about 0.1mm

Bacteria are classified according to their shape:Bacteria are classified according to their shape:1) Cocci: spherical bacteria1) Cocci: spherical bacteria- Cocci – smallest bacteria, occur as single spheres- Cocci – smallest bacteria, occur as single spheres- Diplococci – pairs of spheres, e.g. pneumonia- Diplococci – pairs of spheres, e.g. pneumonia- Staphylococci – clusters of spheres, e.g. food - Staphylococci – clusters of spheres, e.g. food poisoningpoisoning- Streptococci – chains of spheres, e.g. sore throat- Streptococci – chains of spheres, e.g. sore throat2) Bacilli: rod-shaped bacteria:2) Bacilli: rod-shaped bacteria:- Individual rods – e.g. typhoid fever- Individual rods – e.g. typhoid fever- Chains of rods – e.g. anthrax- Chains of rods – e.g. anthrax3) Spirilla – large, spiral-shaped bacteria - e.g. syphilis3) Spirilla – large, spiral-shaped bacteria - e.g. syphilis4) Vibrio – crescent-shaped bacteria - e.g. cholera4) Vibrio – crescent-shaped bacteria - e.g. cholera

Reproduction of BacteriaReproduction of Bacteria Cell elongation results in the synthesis of additional Cell elongation results in the synthesis of additional

cytoplasm & nuclear materialcytoplasm & nuclear material

DNA replication takes place (there is no mitotic DNA replication takes place (there is no mitotic spindle), & the nuclear material attaches to the plasma spindle), & the nuclear material attaches to the plasma membrane or mesosomemembrane or mesosome

A septum begins to develop, & the nuclear material is A septum begins to develop, & the nuclear material is distributed to both sidesdistributed to both sides

The septum is completed, & a cell wall develops to The septum is completed, & a cell wall develops to divide the cell into twodivide the cell into two

The two daughter cells grow to a critical size, & then The two daughter cells grow to a critical size, & then repeat this processrepeat this process

Culturing BacteriaCulturing Bacteria New genetic material can be inserted into a bacterium New genetic material can be inserted into a bacterium

in three main ways:in three main ways:

1) Conjugation: bacteria link together by their pili. 1) Conjugation: bacteria link together by their pili. Donor passes a plasmid called the F-factor (fertility) to Donor passes a plasmid called the F-factor (fertility) to the recipient cell. The F-factor may be in a plasmid the recipient cell. The F-factor may be in a plasmid (replicating independently), or incorporated into the (replicating independently), or incorporated into the main bacterial chromosomemain bacterial chromosome

2) Transformation: one bacterium releases DNA which 2) Transformation: one bacterium releases DNA which is absorbed by a second bacterium, allowing it to is absorbed by a second bacterium, allowing it to acquire new characteristicsacquire new characteristics

3) Transduction: new genes can be inserted into the 3) Transduction: new genes can be inserted into the bacterial chromosome by a bacteria phage (a virus bacterial chromosome by a bacteria phage (a virus acting as a vector)acting as a vector)

Culturing BacteriaCulturing Bacteria

The bacterial population growth curve occurs in four main The bacterial population growth curve occurs in four main phases:phases:

1) 1) Lag phaseLag phase: cells are active, but there is little increase in : cells are active, but there is little increase in number. The cells accommodate to the new conditions, number. The cells accommodate to the new conditions, take in water & synthesise ribosomes & enzymestake in water & synthesise ribosomes & enzymes

2) 2) Log phaseLog phase: Nutrients & space are in plentiful supply, so : Nutrients & space are in plentiful supply, so there is little competition, & the bacteria multiply at their there is little competition, & the bacteria multiply at their maximum ratemaximum rate

Culturing BacteriaCulturing Bacteria

3) 3) Stationary phaseStationary phase: carrying capacity (maximum number : carrying capacity (maximum number of bacteria that the environment can support) is reached, of bacteria that the environment can support) is reached, so intraspecific competition takes place between bacteria. so intraspecific competition takes place between bacteria. Hence the death rate balances the population growth Hence the death rate balances the population growth rate, & the number of bacteria remains roughly constantrate, & the number of bacteria remains roughly constant

4) 4) Death phaseDeath phase: nutrient supply is running out & waste : nutrient supply is running out & waste products accumulate resulting in increased toxicity of products accumulate resulting in increased toxicity of environment. Organisms are killed & population size environment. Organisms are killed & population size eventually falls to zero. Spores may be produced during eventually falls to zero. Spores may be produced during stationary phase that are resistant to the adverse stationary phase that are resistant to the adverse conditionsconditions

Culturing BacteriaCulturing Bacteria

Bacterial growth can be controlled using physical Bacterial growth can be controlled using physical methods (gamma irradiation or in an Autoclave using methods (gamma irradiation or in an Autoclave using high temperatures) or by chemical means:high temperatures) or by chemical means:

- disinfectants- disinfectants- antiseptics- antiseptics

Antibiotics can be either:Antibiotics can be either:- narrow-spectrum (affecting a few types of bacterium)- narrow-spectrum (affecting a few types of bacterium)- broad-spectrum (affecting a wide range of bacteria)- broad-spectrum (affecting a wide range of bacteria)

Commercial BiotechnologyCommercial Biotechnology

Microorganisms may be cultured commercially in order Microorganisms may be cultured commercially in order to obtain a substance that they produceto obtain a substance that they produce

They must be able to:They must be able to:- Produce the substance in large quantities in a small - Produce the substance in large quantities in a small amount of timeamount of time- Be available in pure culture, & be genetically stable- Be available in pure culture, & be genetically stable- Grow rapidly in large-scale culture- Grow rapidly in large-scale culture- Not be harmful to humans- Not be harmful to humans- Be capable of easy removal from culture- Be capable of easy removal from culture- Grow on readily available & cheap raw materials- Grow on readily available & cheap raw materials- Have growth conditions that do not require extremes - Have growth conditions that do not require extremes of temperatureof temperature

Commercial BiotechnologyCommercial Biotechnology

Yeasts are widely cultured commercially, & are used in the Yeasts are widely cultured commercially, & are used in the production of:production of:- Food substances in their own right, & in bread production- Food substances in their own right, & in bread production- Beers, ales, lagers & wines, & alcohol as a biofuel- Beers, ales, lagers & wines, & alcohol as a biofuel

There are two main types of process for the production:There are two main types of process for the production:- - Batch processesBatch processes: raw materials & microbes are placed : raw materials & microbes are placed together in a container vessel. The microbes are then together in a container vessel. The microbes are then allowed to grow to their maximum population size, then allowed to grow to their maximum population size, then the fermenter is emptied & the products are extracted & the fermenter is emptied & the products are extracted & purifiedpurified

- - Continuous processContinuous process: the nutrients are continually : the nutrients are continually inputted into the fermentation vessel & the material is inputted into the fermentation vessel & the material is continually removed & processed. This may be more continually removed & processed. This may be more economical, as it doesn’t have to be shut down on a economical, as it doesn’t have to be shut down on a regular basisregular basis

Commercial BiotechnologyCommercial Biotechnology In order to develop a large industrial fermentation process, In order to develop a large industrial fermentation process,

four main stages are required:four main stages are required:

- Isolation of microorganism: organism must be able to be - Isolation of microorganism: organism must be able to be purified easily & give the optimum product yieldpurified easily & give the optimum product yield

- Culture preparation: master culture is stored by freeze-- Culture preparation: master culture is stored by freeze-drying (lyophilising) in a small space. Small samples are drying (lyophilising) in a small space. Small samples are taken from master culture in order to produce stock taken from master culture in order to produce stock cultures, from which working cultures can subsequently be cultures, from which working cultures can subsequently be producedproduced

- Laboratory scale (200cm- Laboratory scale (200cm3 3 fermenter): optimum conditions fermenter): optimum conditions are determined using a small-scale fermenterare determined using a small-scale fermenter

- Pilot plant (200 to 500 dm- Pilot plant (200 to 500 dm3 3 fermenter): laboratory fermenter): laboratory fermenter is scaled up to make sure that it works on a fermenter is scaled up to make sure that it works on a larger scale. There may be problems with larger scale. There may be problems with heating/aeration, which may require electric mixers & heating/aeration, which may require electric mixers & cooling mechanismscooling mechanisms

Commercial BiotechnologyCommercial Biotechnology Enzymes are produced using submerged culture Enzymes are produced using submerged culture

techniques. They are produced on a commercial scale techniques. They are produced on a commercial scale when the organism is in the post-exponential growth when the organism is in the post-exponential growth phase. In downstream processing:phase. In downstream processing:

- The mixture of nutrient broth, cells and extracellular - The mixture of nutrient broth, cells and extracellular enzymes is filtered and centrifuged to remove cellular enzymes is filtered and centrifuged to remove cellular materialmaterial- The liquid enzyme mixture is concentrated by - The liquid enzyme mixture is concentrated by evaporation, to give the bulk enzymeevaporation, to give the bulk enzyme

The bulk enzyme may be:The bulk enzyme may be:- Concentrated by chromatography to give the pure - Concentrated by chromatography to give the pure enzymeenzyme- Added to stabilisers to give the bulk liquid enzyme- Added to stabilisers to give the bulk liquid enzyme- Precipitated and filtered, then sprayed and grinded to - Precipitated and filtered, then sprayed and grinded to give the powdered enzymegive the powdered enzyme

Commercial BiotechnologyCommercial Biotechnology Immobilised enzymes are widely used commercially – Immobilised enzymes are widely used commercially –

they can be immobilised in three ways:they can be immobilised in three ways:

- Cross linkage: the enzymes are linked together by - Cross linkage: the enzymes are linked together by gluteraldehyde, to form a mesh. This may damage gluteraldehyde, to form a mesh. This may damage some enzymes, but those that are not damaged remain some enzymes, but those that are not damaged remain very activevery active

- Entrapment: the enzymes are trapped in gel - Entrapment: the enzymes are trapped in gel microcapsules or in a fibrous polymer mesh. This does microcapsules or in a fibrous polymer mesh. This does not damage the enzymes, but may slow their action not damage the enzymes, but may slow their action due to the substrate having to diffuse indue to the substrate having to diffuse in

- Adsorption: the enzymes are held by weak bonds on - Adsorption: the enzymes are held by weak bonds on the surface of an adsorbing agent (e.g. glass bead, the surface of an adsorbing agent (e.g. glass bead, carbon particle, collagen). The enzymes easily come carbon particle, collagen). The enzymes easily come into contact with the substrate, but it is expensive, and into contact with the substrate, but it is expensive, and the enzymes may become detachedthe enzymes may become detached

Bacterial DiseaseBacterial Disease Most bacteria are either beneficial or harmless to Most bacteria are either beneficial or harmless to

humans – those that cause disease are pathogens:humans – those that cause disease are pathogens:- The symptoms of the disease are usually caused by - The symptoms of the disease are usually caused by waste products of the pathogenswaste products of the pathogens- An infection is when the effects are noticeable on the - An infection is when the effects are noticeable on the bodybody- Transmission is when an infection is passed on to - Transmission is when an infection is passed on to somebody elsesomebody else

Diseases such as typhoid and cholera are transmitted Diseases such as typhoid and cholera are transmitted through water, and can cause diarrhoeathrough water, and can cause diarrhoea

To avoid water contamination, water-treatment To avoid water contamination, water-treatment processes take placeprocesses take place

Bacterial DiseaseBacterial Disease Food-borne infections including Salmonella are spread Food-borne infections including Salmonella are spread

in two ways:in two ways:- By not cooking food thoroughly (e.g. raw eggs: newly - By not cooking food thoroughly (e.g. raw eggs: newly laid eggs may be contaminated with poultry faeces)laid eggs may be contaminated with poultry faeces)- By contaminating cooked meat from handling raw - By contaminating cooked meat from handling raw meat first e.g. chickenmeat first e.g. chicken

Air-borne infections are spread when an infected Air-borne infections are spread when an infected person coughs, sneezes, talks or breathes, as the person coughs, sneezes, talks or breathes, as the pathogens are passed into the air in small droplets pathogens are passed into the air in small droplets saliva, mucus and watersaliva, mucus and water

Infections that can be transmitted by direct contact are Infections that can be transmitted by direct contact are said to be contagioussaid to be contagious

Insect bites can transmit pathogens through the saliva Insect bites can transmit pathogens through the saliva of the insectof the insect

Bacterial DiseaseBacterial Disease Pathogenicity is the ability of a bacterium to cause Pathogenicity is the ability of a bacterium to cause

disease. The main factors are:disease. The main factors are:- The way in which the bacterium attaches and gains - The way in which the bacterium attaches and gains entry to host cellsentry to host cells- The types of toxin produced by the bacterium- The types of toxin produced by the bacterium- The infectivity of the bacterium (the number needed - The infectivity of the bacterium (the number needed to cause an infection)to cause an infection)- The invasiveness of the bacterium (its ability to - The invasiveness of the bacterium (its ability to spread within the host)spread within the host)

After infection, a pathogen must do three things in After infection, a pathogen must do three things in order to produce a disease:order to produce a disease:- Attachment- Attachment- Entry (penetration)- Entry (penetration)- Colonisation- Colonisation

Viral DiseaseViral Disease Viruses cannot survive without a living hostViruses cannot survive without a living host

Influenza affects the upper respiratory tractInfluenza affects the upper respiratory tract Acquired immune deficiency syndrome (AIDS) is Acquired immune deficiency syndrome (AIDS) is

caused by the human immunodeficiency virus (HIV), caused by the human immunodeficiency virus (HIV), and results in the immune system breaking down so and results in the immune system breaking down so that it can no longer defend the body against diseasethat it can no longer defend the body against disease

Viral diseases can be very difficult to treat because the Viral diseases can be very difficult to treat because the viruses have no metabolism of their own hence viruses have no metabolism of their own hence antibiotics have no effect on them. There are a few antibiotics have no effect on them. There are a few antiviral drugs, however, which can work by:antiviral drugs, however, which can work by:- Inhibiting the production of viral DNA/RNA by altering - Inhibiting the production of viral DNA/RNA by altering the host cell’s DNAthe host cell’s DNA- Preventing the enzymes essential for the production - Preventing the enzymes essential for the production of new virus particles from workingof new virus particles from working- Preventing the viral particles from entering the cells - Preventing the viral particles from entering the cells in the first placein the first place

Protection Against DiseaseProtection Against Disease The human body has a number of barriers that prevent The human body has a number of barriers that prevent

pathogens from entering the body:pathogens from entering the body:- The skin- The skin- Sebum- Sebum- Tears, saliva and urine- Tears, saliva and urine- Mucus in respiratory tracts- Mucus in respiratory tracts- Commensals- Commensals- Stomach acid and enzymes- Stomach acid and enzymes

If the body is injured, a general inflammatory response If the body is injured, a general inflammatory response will take place:will take place:- blood clots at the site of a cut, which seals the cut, to - blood clots at the site of a cut, which seals the cut, to prevent pathogens entering the bloodprevent pathogens entering the blood- inflammation around the site of the injury takes place- inflammation around the site of the injury takes place- Macrophages are attracted to the site of injury, where - Macrophages are attracted to the site of injury, where they destroy pathogens by phagocytosisthey destroy pathogens by phagocytosis

Protection Against DiseaseProtection Against Disease There are four main types of immunity:There are four main types of immunity:

- - Active natural immunityActive natural immunity: memory cells develop after : memory cells develop after natural exposure to antigensnatural exposure to antigens

- - Active artificially induced immunityActive artificially induced immunity: memory cells : memory cells develop after vaccinationdevelop after vaccination

- - Passive natural immunityPassive natural immunity: antibody transfer (e.g. : antibody transfer (e.g. through placenta or breast feeding) results in short-term through placenta or breast feeding) results in short-term immunity (a few months), as no memory cells developimmunity (a few months), as no memory cells develop

- - Passive artificially induced immunityPassive artificially induced immunity: antibodies are : antibodies are injected (short-term immunity)injected (short-term immunity)

It is difficult to become immune to a virus, as they It is difficult to become immune to a virus, as they undergo many mutations, resulting in many different undergo many mutations, resulting in many different forms producing similar symptoms, but with different forms producing similar symptoms, but with different antigensantigens

Protection Against DiseaseProtection Against Disease Antibiotics are only effective against bacterial infectionsAntibiotics are only effective against bacterial infections

Antibiotics work in a number of ways:Antibiotics work in a number of ways:

- Inhibiting cell wall synthesis- Inhibiting cell wall synthesis

- Binding to ribosomes and inhibiting protein synthesis- Binding to ribosomes and inhibiting protein synthesis

- Interfering with prokaryotic DNA replication and - Interfering with prokaryotic DNA replication and transcriptiontranscription

- Binding to the cell membrane to make it more permeable- Binding to the cell membrane to make it more permeable

- Inhibiting cell metabolism- Inhibiting cell metabolism

Bacteria may become resistant to antibiotics by altering Bacteria may become resistant to antibiotics by altering the structure of the antibiotic or by modifying the bacterial the structure of the antibiotic or by modifying the bacterial cells. Resistance develops as a spontaneous mutation, and cells. Resistance develops as a spontaneous mutation, and can spread through the population asexually and sexuallycan spread through the population asexually and sexually

SummarySummary

BacteriaBacteria Culturing BacteriaCulturing Bacteria Commercial biotechnologyCommercial biotechnology Bacterial DiseaseBacterial Disease Viral DiseaseViral Disease Protection Against DiseaseProtection Against Disease