Microbiology

Muaaz NV2C

Lesson 1:

Goals:

• Bacteria in biology

• Understand the cell membrane of bacteria.

• Know the basic structure of prokaryotic cells.

• Read Chapter 29 pages 448-456.

• Read section 4 Prokaryotes - The First organisms

Notes:

Prokaryotic cells have no nucleus but have a nucleoid region where the DNA is floating, the DNA is naked, the organelles inside do not have a membrane, have rigid flagella and the cells are smaller than eukaryotes due to lack of organelles, can be compared to a size of mitochondria.

Agar agarose is an unbranched polysaccharide from the cell walls of some red algae or seaweed. In chemical terms, agar is a polymer made up of subunits of the sugar galactose. Agar plates are used to grow micro-organisms.

The most famous bacteria in science is E.coli. They make up 0.1% of your gut flora, and bacteria in your digestive system. E. coli is found in mammals whereas salmonella lives in the gut of birds and reptiles. Salmonella can also go through tight junctions.

Lesson 2:

Notes:

Probiotic bacteria are good and beneficial for the body. Probiotics are commonly consumed as a part of fermented foods with specially added active live cultures. Probiotic microorganisms when available in adequate amounts have a health benefit for the host.

We know that bacteria are not always pathogens but are essential for human health. The human gut contains more than 40000 different species of bacteria, 9 million bacterial genes, and 100 trillion microbial cells.

The human microbiome weighs as much as 2 kilograms. The bacteria in the microbiome help us digest food, regulate our immune system, and protect against other bacteria that cause disease. Important: The bacterial cells produce vitamins including vitamin B, B12, thiamine, riboflavin, and vitamin K, which is needed for blood coagulation.

The third domain of life is archaea. The three domains of life are bacteria, archaea, and eukarya. There is archaea in your body that creates methane gas released by humans.

Important to remember is that archaea might look like bacteria but the details are very different and they are fundamentally different.

Lesson 3:

Staph infection:

• Staphylococcus aureus which also causes staph infection, is a bacteria that can be mild or fatal depending on the type of plasmids or strains it has.

• Staphylococcus aureus is a species of bacteria. The same species has a variety of pathogens.

• There are more than 30 types of staph infections.

Shapes of a bacterial cell:

• Bacteria are classified into five groups based on their shape. Bacterial cells can be rods, spheres, comma-shaped, spirals, or corkscrew-shaped.

• The bacterial cells maintain these shapes by their rigid walls.

Terms:

• Coccus - round-shaped cell

• Bacillus - bar-shaped cell

• Spirillum - corkscrew-shaped cell

• Strepto - chained singular shapes + the name of the shape

• Diplo - pair of singular shapes + the name of the shape

Water properties: The viscosity of water at a micro level increases and it is hard for bacillus to swim through, Coccus can not swim in water on the other hand spirillum can easily corkscrew through water.

A - level: Why are there different shapes of bacteria

Ans:

• Bacteria kept these shapes through convergent evolution

• Shape has a vector through evolutionary time

Motility:

• Bacteria are so small it is very difficult for them to swim through water

Benefits of shapes:

• imporved cell division

• getting food

• escape from predators

• swimming

• attachments to surfaces

• swimming

Why they are small:

• Large surface-to-volume ratio

Lesson 4:

Notes:

Membrane proteins are the base of the flagella and the flagella moves like a rotary engine, like a boat propeller. It is fueled by the hydrogen ions.

Peptidoglycan is a layer of bacterial cell walls Bacteria need a peptidoglycan layer for cell walls, it is important for structural integrity.

Hans Joachim Gram was a Danish bacteriologist who invented the gram stain. Gram staining has not changed much over the years but a scientist called Weigert added one more step, a counter-stain.

• Gram-positive - dark purple

Gram-positive vs Gram-negative:

The stain is hydrophilic in a Gram-negative and cannot get to the cell wall. Gram-negative does not penetrate the cell membrane.

The Gram-positive, like a normal cell, has a huge cell wall on the outside. The cell stains due to the cell wall. Have a thick cell wall

A stain fixer is a mordant that makes the stain stick to gram-positive

Lysozyme is an enzyme that fights bacteria that is in the human tears and mucus. It does that by degrading the peptidoglycan, without the peptidoglycan the bacterial cells cease to exist because of the large osmotic pressure.

Fungus and mold make penicillin naturally.

Penicillin is a group of B lactam antibiotics that attack the gram-positive bacteria by disrupting peptidoglycan production which makes the cell fragile.

Lesson 5:

Notes:

Antiseptics were used as antibiotics but the disadvantage of it was that it could be used for sterilizing if used internally it would kill the white cells more effectively than the bacteria which made it lethal.

Antibiotics inhibit the growth or kill the bacteria.

• Antibiotics that hinder the cell wall synthesis of the bacterial cells (beta-lactase) are called bactericidal directly killing the bacteria.

• Bacteriostatic antibiotics interfere with bacterial protein production and DNA replication. The agents have to work with the immune system to remove the microorganisms from the body.

Many antibiotics today are based on the beta-lactam ring which stops the cell wall in the bacteria. An enzyme in the bacteria called beta-lactamase can break a bond in the beta-lactam ring making the antibiotic unfunctional against that bacteria cell.

Ampicillin is another beta-lactam antibiotic that is proven effective against gram-negative bacteria. This is because it has an amino group that helps it penetrate the outer cell membrane of bacteria.

The bacterial cells get resistant to the antibiotics in the following ways:

• The first one is when the bacteria detects an antibiotic with the beta-lactam ring and starts making beta-lactamase to break the antibiotic. Now the production of beta-lactamase has started in the bacteria which logically means that antibiotics with the beta lactam ring will be ineffective against the bacteria as it is producing its defensive mechanisms (beta lactase enzymes). The amount of beta lactase produced by the bacteria is directly proportional to the quantity of the antibiotic. In conclusion, it is crucial to start with the right antibiotic in order to prevent the excess production of beta lactase.

• Antibiotics work by binding to the penicillin-binding protein on the surface of the bacteria. B lactam is a type of antibiotic that works by fitting into this lock-like structure of the penicillin-binding protein on the surface of the cell. However some bacteria can change these locks (penicillin-binding proteins) so that the antibiotics cannot fit in them, This makes the antibiotics less effective. Some examples of bacteria that change their locks on the surface for antibiotic penicillin are MRSA and penicillin-resistant Streptococcus pneumoniae.

Lesson 6:

• How antibiotic resistance starts

• How bacteria survive antibiotic treatments

• How bacteria can sense their numbers and turn on virulent genes

• How bacteria can regulate and change gene expression using quorum sensing

• Beta-lactam antibiotics

• function of penicillin on penicillin-binding protein

• cephalosporium how it kills?

• the beta-lactam ring

• if an antibiotic becomes hydrophobic it can be semi-permeable and go through the gram-negative bacteria.

• Bacteria are resistant before the antibiotics are introduced

• why the discovery of antibiotics is getting slower

Lesson 7:

• when bacteria share their plasmids through physical contact through pili it is called conjugation. similar to gap junctions in animal cells.

• autoinducers for communications pass through the integral proteins

• quorum sensing - cross-talking between the bacterial cells using autoinducers

Lesson 8:

• Three domains of life

• Fermentation is the process of extracting energy from the oxidation of organic compounds such as sugar

• Bacteriophages are not always a positive to human health

• In lysogenic conversion, phages bring in deadly genes.