ALL SCIENCE CHALLENGE

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Biology: study of living things, from simple viruses and single-celled organisms to the most complex ecosystems.

Microbiology: The study of very small organisms.

Chapter 1: Biology

Single-celled organism around 3 000 nm in diameter. (human rbc ~ 10 000 nm)

The number of bacteria in your mouth is larger than the number of people who have ever lived on earth.

Earliest fossils of prokaryotes (subsection of bacteria) are over 3.5 billion years old.

Bacteria have evolved into a wide variety of different types and have adapted to variety of different environments.

Bacteria

Bacteria Structure

Classification of Bacteria Cocci: live in humans and animals

– does not commonly cause disease.

Bacilli: live in lower intestines of birds and mammals. Some strains (i.e. E. coli) can cause serious disease and even death

Spirilla: Common to poultry, lives in the digestive track of many birds. One of the most common causes of food poisoning.

Vibrios: Live in marine environments (i.e. costal reefs) and can cause infection after eating seafood (i.e. undercooked oysters)

Bad bacteria are pathogenic (cause diseases)

Examples: tetanus, typhoid fever, tuberculosis, strep throat, anthrax and food poisoning.

Some bacteria can even cause Necrotizing fasciitis (flesh eating disease)

Good vs. Bad Bacteria

Many bacteria can be helpful and promote good health

i.e. Probiotic bacteria ( live in our digestive system and prevent harmful germs from growing there)

Bacteria is also used to make certain foods like vinegar, sauerkraut and yogurt.

Good vs. Bad Bacteria

Recombinant DNA technology emerged as a response to the need for specific DNA segments in amounts sufficient for biochemical analysis. The method entails clipping the desired segment out of the surrounding DNA and copying it millions of times

Recombinant cloning

Bacteria store of their genes (pieces of DNA that code proteins) in a single molecule of DNA.

But also contain mobile segments (plasmids) used for antibiotic resistance.

Theses plasmids aren’t required for normal growing conditions, but are very helpful in aiding the bacteria fight off antibiotics such as penicillin, ampicillin, etc…which would normally kill the cell.

The plasmids (also known as vectors) are what scientists use to introduce “genes of interest” to learn more about the gene’s function, structure or sequence (the DNA coding)

The process of introducing genes into a vector to form a new DNA molecule which can be replicated in a host cell is called Recombinant Cloning

With recombinant cloning two different strands of DNA that would not normally occur together are combined and multiple copies are created.

1. Ligation Reactions: transferring the “gene of interest”. Scientist use special proteins called restriction enzymes to cut both the gene and the plasmid at specific sites that are complementary to each other.

The two loose pieces of DNA find each other with the aid of DNA ligase and are joined (ligate) to become a modified plasmid.

Four major components of bacterial recombinant cloning

The plasmid cannot clone a gene on its own. It needs a host system to make copies of the plasmid.

The most efficient host system is bacteria (specifically E. coli because they divide and grow rapidly)

To make it easier for the bacteria to take in the plasmids they are grown in a mixture of plasmids and salts.

Osmotic pressure and the presence of the plasmids will cause the plasmids to enter the E.coli cells

Transformation

Cells must be screened to determine which cells picked up the plasmids and which did not.

Plasmids carry selectable makers, usually a gene that codes antibiotic resistance.

Since the bacteria are grown in the presence of an antibiotic only the bacteria with the plasmids will be able to live

Selection and Propagation

Final step is to harvest the plasmids from the bacteria.

To do this the bacteria are lysed (cell membranes are broken open) and the plasmids are separated from the bacteria using an acidic solution which is high in salt (because plasmid DNA can withstand these conditions, but regular DNA cannot)

Finally the plasmids are separated from all other parts using centrifugation (spinning a high speed)

Isolation

Bacteria that are able to degrading xenobiotic chemicals into harmless products.

The genus Pseudomonas is capable of detoxifying more than 100 different compounds.

They are able to do this because they carry genes that code for enzymes which are able to break down toxic compounds.

This process is very slow and not always a perfect process.

Through genetic engineering scientists can combine many different plasmids (which contain the degradative enzymes) and combine them to a single strain of bacteria and create a “super-bug”

Bioremediation

Very small (17 ~ 400 nm) 100 times smaller than the average bacteria.

Made up of 3 basic parts: 1. Nucleic acid : set of genetic material (either DNA or RNA)

packaged in a protein shell

2. Capsid: a protein coat that surrounds DNA or RNA to protect it

3. Envelope: a covering for the capsid that is made up of a mix of proteins, fats and carbohydrates (complex sugars).

* Not all viruses have envelopes. The ones that don’t have are called naked or non-enveloped.

Viruses

Helical viruses: resembles long rods. Example of virus: influenza

Polyhedral viruses: many-sided. Example of virus: adenovirus which cause respiratory illnesses

Enveloped viruses: spherical in shape due to the protein,fat or carb coat. Example of virus : HIV

Complex viruses: have complicated structures attached. Example of virus: bacteriophage which infects bacteria

Classification of viruses

Viruses do not have a metabolism. Not considered alive Lack the ability to reproduce Needs a host cell to live and make more viruses.

5 Step process:

1. Attachment : the virus attaches to a host cell

2. Penetration: the nucleic acid of the virus moves through the cell membrane into the host cell.

3. Replication: virus forces host to produce the necessary components for its reproduction

4. Assembly: the newly produced virus components are assembled into new viruses.

5. Release: the complete viruses are released from the cell and infect other cells.

Viral life cycle

Our immune system is stimulated when it detects an antigen and creates antibodies.

Antigens are found on the surface of the viral envelop.

The antibodies (proteins)and specialized cells destroy the intruder.

Viruses and immune system

Vaccination is the administration of antigenic material (a vaccine) to stimulate the immune system of an individual to develop adaptive immunity to a disease. Vaccines can prevent or ameliorate the effects of infection by many pathogens.

The virus in the vaccine is either inactivated or attenuated (alive but not infectuous)

Vaccination