Chapter 19 Bacteria and Viruses

Remember homeostasis? Maintaining proper internal conditions pH, temp., water/salt balance, O2, CO2, etc.

Factors for Disease 1. genetics- inheritance 2. microorganisms – pathogen: disease-causing agent 3. pollutants/poisons (ex: asbestos, lead) 4. organ malfunction 5. harmful lifestyles (tobacco, alcohol, lack of nutrition or exercise)

19-1 Bacteria Prokaryotes Monera Can be beneficial or disease-causing – Good: intestinal bacteria – Bad: strep throat, pneumonia Everywhere!

Identified by: Shape- bacilli (rod), cocci (round), spirilla (spiral) Cell walls- Gram +/- (peptidoglycan) Movement- flagella, slime Metabolic diversity- heterotrophs and autotrophs (chemo- or photo-)

Bacteria Energy Production Respiration or fermentation (with or without O2) Obligate aerobes: needs O2 to live Obligate anaerobes: cannot live with O2 Facultative anaerobes: can live with or without O2

Bacteria Reproduction Binary fission: (asexual) DNA is replicated and the organism splits in half Conjugation: (sexual) genetic info is exchanged across a “bridge” Spore formation: haploid cell that can withstand hard conditions and form a new organisms when the time is right

Importance of Bacteria Decomposers- break things down Nitrogen fixation- cycles N thru atmosphere Human uses: food, oil spills, medicine, intestines

Treating Bacteria Bacteria have homeostasis too! Change the conditions to stop growth – Temp, salt, pH, etc. Sterilization (heat), disinfection (chemicals) Antibiotics- kill bacteria or stop reproduction

19-2 Viruses Categorized by what they infect: – Plant, animal, bacteriophage Capsid- protein coat- signifies which host to infect (host must have a receptor) NOT alive- has genetic material but can’t repro on own Ex: flu virus, HIV

Virus Replication Lytic: enters host cell, copies itself continuously and bursts (lyses) Lysogenic: combines/replicates viral DNA with host DNA – Prophage: viral DNA embedded within host DNA

Treating Viruses Antibiotics WILL NOT work! Prevention is key! Vaccination: inject a weak form of a virus in order to get the antibodies (immunity)

The Body’s Defense System homeostasis= includes regulating microbes Lines of defense: 1. physical barriers- block entry (skin) 2. inflammation- increased blood flow 3. immune system

Immune System Recognizes the “bad guys” Every bacteria/virus has antigens (proteins) Immune system makes antibodies Antibodies fight the antigens Vaccines- shows antigens ahead of time- allows body to create antibodies (immunity)

White Blood Cells (WBCs) Immune system MVP 2 types: 1. B cells: make antibodies – Memory B cells 2. T cells: – Killer T cells: kill infected cells – Helper T cells*: help all other WBCs

When the immune system goes wrong … Allergic reactions- increase in system- produces histamines Autoimmune diseases- system attacks self Immunodeficiency- decrease in system- helper T cells destroyed (ex: AIDS) inflammation- older people

Other Pathogens Protozoa- unicellular parasites Algae/Dinoflagellates- produce toxins – ex: red tide Fungi- athletes foot, ringworm Parasitic Worms- tapeworm

Viroids and Prions Viroids: single stranded RNA molecules enter infected cells Prions: tiny protein particles enter the brain and affect the nervous system- no DNA/RNA – Ex: mad cow disease