Microbiology Bacteria and Viruses Chapter 19 I Classification

Microbiology: Bacteria and Viruses Chapter 19

I. Classification of Bacteria A. All bacteria are prokaryotic cells 1. Prokaryotes are the smallest living organisms and they lack a nucleus and organelles

B. Bacteria are separated into 2 kingdoms: Eubacteria and Archeabacteria 1. Eubacteria are the largest group of bacteria and live almost everywhere a. Generally surrounded by a cell wall made of peptidoglycan, and have a cell membrane

2. Archeabacteria are structurally different from eubacteria because they lack peptidoglycan in their cell walls and their DNA is more closely related to eukaryotes a. Live in extremely harsh environments such as: hot springs, salty environments, digestive tracts of animals

C. Bacteria are identified 4 ways: By their shape, Cell walls, Movement, and ways they obtain energy 1. Shape: There are 3 different shapes bacilli (rod), cocci (sphere), and spirilla (spiral) a. These bacteria can then arrange themselves in different ways: long chains or clusters

2. Cell Walls- Eubacteria have 2 different types of cell wall and these can be distinguished by a test called Gram Staining 1. Gram-positive bacteria turn violet due to their cell wall containing mainly peptidoglycan 2. Gram-negative bacteria have an extra outer layer that absorbs red stain, so they appear pink

Gram Staining – Gram Staining is the process used to differentiate between types of cell walls There are 2 dyes used in Gram Staining: l Crystal Violet (dye)- all cells turn violet. This is absorbed by peptidoglycan in the cell wall l Methyl Red (dye)- dyes cells red. This is absorbed by the outer cell wall that is rich in carbohydrates and lipids

S. aureus: Gram + or -?

3. Movement: Bacteria move in different ways or they may not move at all a. Flagella are whip-like structures that propel a bacteria forward b. Cilia are small hair-like structures that create a current c. Bacteria can also lash, snake, or spiral forward

4. Obtaining Energy: Prokaryotes can be classified as either autotrophs or heterotrophs a. Autotrophs make their own food using either the energy from light (photoautotrophs) or the energy from chemicals (chemoautotrophs) b. Heterotrophs obtain energy from absorbing food c. Photoheterotrophs are unique organisms that make their own food by photosynthesis, but also need to take in organic compounds for nutrition

D. Bacteria also release energy by either cellular respiration or fermentation 1. Aerobes require oxygen to live and anaerobes do not require oxygen a. Obligate anaerobes cannot live in the presence of oxygen. Botulism is produced by this type of organism b. Facultative anaerobes can switch between cellular respiration and fermentation

E. Prokaryotes can multiply in as quickly as 20 minutesin 48 hours they would be 4000 x the mass of the Earth! 1. They reproduce by binary fission- does not exchange DNA with other bacteria so this is asexual reproduction 2. Conjugation is how bacteria genetically recombine their DNA and increase diversity a. a hollow bridge connects 2 bacteria 3. Bacteria can produce spores when conditions are not favorable. It is a thick internal wall that encloses DNA and cytoplasm and allows the cell to remain dormant

II. Bacteria in Nature A. Bacteria are decomposers and are responsible for recycling essential nutrients through the ecosystem 1. Bacteria break down and digest dead tissues into simpler substances, which are then released into soil 2. Decomposition is essential for breaking down human sewage

B. Nitrogen is essential to making amino acids and proteins, but cannot be directly taken from the atmospheric form 1. Bacteria are responsible for nitrogen fixation- they convert atmospheric nitrogen into ammonia and other forms that plants can absorb through their roots 2. In some cases bacteria live in the roots of plants and do nitrogen fixation and the plant absorbs the ammonia

C. Some bacteria are pathogens, meaning they cause disease 1. Disease is caused by 2 means: damaging the tissue they are eating or releasing toxins

a. Tetanus is a bacterial disease that causes muscles to tighten and severe muscle spasms. This can lead to breathing problems and be lifethreatening and occurs when bacteria enters an open wound

b. Necrotizing fasciitis is also known as the flesh eating disease. Cause by a bacteria that infects the tissue around muscles and destroys the tissues. This can be fatal

c. Tooth decay: Bacteria can make acid in the presence of sugars and carbohydrates and the acid will eat through the enamel of a tooth

d. Chlamydia is a sexually transmitted bacterial infection that can cause damage to the reproductive organs, sterilization, discharge, and a burning sensation

e. Gonorrhea is a sexually transmitted disease cause by bacteria. Symptoms include discharge, burning sensations, and swelling

2. Antibiotics prevent the growth and reproduction of bacteria and can cure many bacterial diseases a. Bacteria can be resistant to antibiotics

b. Methacillin Resistant Staphylococcus Aureus MRSA is a staph infection that occurs in healthy people and appears as a skin infection. S. aureus is resistant to many common antibiotics

D. Humans are now able to use bacteria to their advantage 1. Bacteria are used in the production of many foods: sourdough, cheese, yogurt, pickles

2. Bacteria can be used in industry to remove waste, break down toxins, cleaning up oil spills, and synthesizing drugs

E. Sterilization kills bacteria with heat or chemical products 1. Most cannot withstand high temperatures 2. Refrigeration slows the growth of bacteria

Controlling Bacteria l l Most bacteria are harmless, and many are beneficial. However, the risks of bacterial infections are great enough to warrant efforts to control bacterial growth. SO WHAT IS THE BEST WAY TO PREVENT A BACTERAL INFECTION IN YOU

WASH YOUR HANDS WELL FOR AT LEAST 20 SECONDS WITH SOAP

III. Viruses A. Viruses are not living things, but are defined as a piece of nucleic acid encased in protein 1. Viruses must infect a cell to reproduce 2. Viruses can be many different shapes and sizes l They are particles of nucleic acid, proteins, and lipids that reproduces only by infecting other organisms

B. The structure of a viruses is either DNA or RNA, which contain between 1 and 100+ genes, and a protein coat called a capsid that surrounds the DNA center 1. The capsid allows viruses to attach to other cells and inject them with the DNA or RNA

C. Viruses are very specific to the type of cell they infect 1. Viruses bind to specific proteins in cells 2. Plant viruses usually cannot infect animal cells 3. Viruses that infect bacteria are call bacteriophages

D. Viral Infections occur when a virus breaks into a cell and takes over the cell, which destroys the cell in the process 1. In the lytic cycle a virus enters a cell, makes copies of itself, and causes the cell to burst a. At the end of the lytic cycle the infected cell is destroyed immediately

2. In the lysogenic cycle, the viral DNA is inserted into the cell’s DNA and when the cell’s DNA is copied, so is the viral DNA a. Lysogenic cycle does not destroy the cell immediately

3. How are the Lytic and Lysogenic Cycles similar and different? Lytic Cycle Similarities Lysogenic Cycles

E. Viral Diseases- When viruses attack cells, the cells are destroyed, which causes symptoms 1. Polio is a viral infection that can cause flulike symptoms or can cause muscle paralysis and death. It was eradicated in the western hemisphere

2. Influenza Virus causes fever, headache, muscle and body aches, sore throat, dry cough, stuffy nose, and extreme tiredness a. This is contagious and can lead to death

3. Herpes Simplex 1 is a virus that causes cold sores, painful blisters found on or around the mouth

4. Herpes Simplex 2 is a sexually transmitted disease and is expressed as blisters around the genitals that can rupture and lead to painful sores- there is NO cure

5. Human Immunodeficiency Virus (HIV) kills and damages cell’s of the body’s immune system and leaves people unable to fight off illness and cancers a. HIV/AIDS is a retrovirus- a retrovirus contains RNA as the genetic information and inserts a copy of itself into the DNA of a host cell b. Retroviruses are incurable

HIV

Why are some flu strains just a nuisance, while others are dangerous? Because of the way our immune system identifies and attacks pathogens.

6. Oncogenic viruses carry genes that interrupt the cell growth and division, which can lead to cancer and HPV in eukaryotes. F. The best way to treat viral infections is prevention! 1. Vaccines are weakened or killed viral proteins that stimulate an immune response and produce protection against the disease