Bacteria and Viruses

We mostly don't get sick. Most often, bacteria are keeping us well.- Bonnie Bassler

Prokaryote Structure

Eubacteria – cell walls contain peptidoglycan, some species have a second cell wall (gram – negative stain) that makes them resistant to damage.

The different phylums are indicated below in blue.

Kingdom Archaebacteria – Introns in DNA, lack peptidoglycan in cell walls, many live in extreme environments

Chemoheterotrophs – take in organics for energy and supply of carbonphotoheterotrophs – make food from sun, but need organics for carbon

photoautotrophs – use light to make food and get carbonchemoautrotrophs – make food and get carbon without using the sun

Escherichia coli – chemoheterotroph that lives in lower intestines of mammals. It is a facultative anaerobe which

means it can survive with or without oxygen.

Cyanobacteria – this is a phylum of bacteria that obtain their energy through photosynthesis. (photoautrophs) The slide shows Oscillatoria, a species of cyanobacteria seen in freshwater ponds.

Chemoautotrophs – use inorganic energy sources, like H2S to synthesize food.

This deep sea vent provides chemoautotrophs with food and energy.

Mycobacterium tuberculosis- the bacteria that causes tuberculosis needs oxygen in order to live. The picture below shows Mycobacterium

tuberculosis embedded in lung tissue. Note the red rods.

Tuberculosis life cycle – can be treated with antibiotics, though a resistant strain is causing problems.

Clostridium botulinum – an obligate anaerobe, exposure to oxygen kills this bacterium. It is found in soils and can contaminate

canned foods. It’s toxins cause the disease Botulism or lockjaw.

A person suffering from Botulism poisoning

Escherichia coli – is a gram negative, facultative anaerobic (do not require O2) rod-shaped bacteria that is commonly found in the lower intestines of warm-blooded animals.

Bacterial Reproduction – Binary fission – most bacteria do this

Bacterial Reproduction

• http://www.youtube.com/watch?v=7sZ5Nz8_cfc

Conjugation – a hollow bridge forms between two cells and some genetic material is exchanged. This helps to increase

genetic diversity.

Spore – In unfavorable conditions a bacterium will form a thick internal wall that encloses its DNA and a portion of its

cytoplasm. In this state the spore can survive for years until conditions improve.

Bacteria can decompose just about any type of organic matter. This process helps to recycle nutrients

Metropolitan Sewage treatment plant, Saint Paul. Treats up to 251 million gallons/day. 65 communities, 1.8 million people. Water returned to the river is cleaner than the river water.

Saint Paul plant is an advanced Secondary Treatment facility.

The dried sludge is burned in an incinerator and generates enough electricity provide 20% of the plant’s power and power

1,000 homes. The new incinerator removes over 90% of all pollutants.

Many plants have a symbiotic relationship with strains of bacteria that can remove nitrogen from the atmosphere and

make it available for the plants and then other living things. This process is called nitrogen fixing

Bacteria are genetically engineered to produce human insulin

Bacteria is used to make cheese

Streptomyces fradiae – the bacteria that produces the antibiotic neomycin.

Virus Structure of HIV virus

Lytic and Lysogenic infections with viruses.

Chicken pox and Shingles – the virus that causes chicken pox can lie dormant in nerve cells to become active, sometimes years later. Shingles, pictured below is

very painful.

Retroviruses – store their genetic information as RNA. When infecting a cell they produce a DNA copy of their RNA and

this becomes inserted into the hosts DNA.

Wendell Stanley – crystallized tobacco mosaic virus was infectious and therefore viruses were not living

things.

Bacteria cause disease by either damaging cells and/or releasing toxins that damage cells.

Meningoccoccal Disease – attack the lining (meninges) between the brain and the skull. Produce an endotoxin that cause blood vessels to rupture. Even with prompt antibiotics 10% die and

many lose one or more limbs.

Vaccine – a preparation of a killed or weakened bacteria or virus that stimulates the body’s immune system to produce

antibodies against the disease.

Antibiotics – compounds that block the growth and reproduction of bacteria. In this picture the mold penicillin notatum is producing a compound that prevents the bacteria from growing. This compound was the first antibiotic – penicillin.

Bacteriophages – ( literally bacteria eater) are viruses that attack and destroy bacteria.

Bacteriophages attack specific strains of bacteria.

Phage were used as antibacterial agents in Georgia and the US in the 1920’s and 30’s. With the discovery of antibiotics they

were abandoned in the US but continued to be used in Russia.

Bacteriophages are very specific they can attack only one specific bacterial species. So, they would not harm beneficial

bacteria (gut flora).

This picture shows a person being treated with phages for a chronic year infection at a clinic in Tbilisi, Georgia

A new company in the US, Intralytix, Inc. is marketing bacteriophage products to control bacterial pathogens in the environment, food

processing and medical settings. This may be a part of the answer in dealing with antibiotic resistant strains of bacteria. In this slide

bacteriophages help to clear this wound of multi-drug resistant S. aureus.

Viral diseases.Many Viruses infect and destroy certain cells (i.e. Polio which

destroys nerve cells). Others cause infected cells to change their pattern of growth (plantar’s warts)

Viral diseases do not respond to antibiotics. The best way to prevent viral diseases is through a vaccine. The vaccine may be the heat

killed virus, weakened virus or a part of the capsid. In the diagram below, a Viral antigen (surface protein) is put in vaccine. When

injected, the body makes antibodies against the specific viral antigen.

Dr. Jonas Salk developed the vaccine for the Polio virus in 1955. He is shown here injecting a patient with the heat killed viral protein coat.

The antibodies the girl produces will be ready in case any real viruses invade her body. In that case they will not get a chance to infect her.

Sister Kenny, a rural Australian nurse, had developed a treatment for polio. The University of Minnesota was the only institution that would allow her to present her findings (1940). The Sister Kenny institute

continues its work today in treating people with paralyzing diseases.

Viroids - are plant pathogens that consist of a short stretch (a few hundred nucleobases) of highly complementary, circular, single-stranded RNA. They are much smaller than viruses and

have no capsid

Prions are misfolded proteins. They transform correctly folded proteins in the brain to match their shape just be touch. There are no nucleic

acids involved. They cause Mad Cow disease, Creutzfeldt-Jakob Disease in humans and bovine spongiform ecephalophthy in cows.