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

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

Chapter 20Protists

20-1 The Kingdom Protista

• What is a protist?

– Anything that is not a plant, animal,

fungus or prokaryote

• First eukaryotes

• Most unicellular

• Classified by how they obtain nutrients

20-2 Animallike Protists (Protozoans)

• Heterotrophs

• Categorized by how they move:

– Flagella

– pseudopodia: temporary projection of cytoplasm

• food vacuole

– cilium: short hair-like projections

– parasitic- don’t move on own

Animallike Protists and Disease

• Malaria (mosquitoes)

– Treatments/vaccines only partially

effective

• African sleeping sickness (tsetse fly)

– Unconsciousness can be fatal

20-3 Plantlike Protists (Unicellular Algae)

• Chlorophyll and accessory pigments

• Ex: diatoms and dinoflagellates

(glowing water!)

20-4 Plantlike Protists (Red, Brown and Green Algae)

• Red algae- good at harvesting light

E- can live at great depths

• Brown algae- brown pigment

• Green algae- VERY plantlike

Human uses of algae• “grasses” of the sea- base of food chain

• O2 production

• Medicine- vitamin C and iron

• Food- sushi wraps, ice cream/pudding

thickener

• Industry- plastics, agar

20-5 Funguslike Protists

• Recycle organic matter

• Different cell walls than true fungi

• Slime molds

• Water molds- potato famine

Ecology of Protists

• Base of food chain (ex: phytoplankton)

• Symbiotic relationships (ex: termites)

• Blooms (ex: red tide)

• Recycle organic matter (ex: slime molds)

Chapter 21Fungi

21-1 What is a fungus?

• Eukaryotic heterotrophs with cell walls

(chitin)

• Digest food externally then absorb it

• Can be parasitic

Fungi Structure

• Hyphae: microfilaments that combine

to form mycelium

• Increase surface area to absorb food

• Fruiting body: reproductive structure

– “mushroom”

Fungi Reproduction

• Asexual: cells/hyphae break off

• Sexual: mating types “+” and “-”

• Spores: easily spread

21-2 Classification

• Based on structure and reproduction

• Common molds (bread mold)

• Sac fungi (yeasts)

• Club fungi

• Imperfect fungi (unknown repro.

cycle)

21-3 Fungi Ecology

• Saprobes- obtain nutrients from

decaying organisms

• Decomposers- recycle nutrients back

into earth

Ecological Relationships

• Parasites- affect crops (wheat rust) and

humans (athletes foot, ringworm)

• Symbionts (symbiosis) - work together

with other organisms

– Lichens- photosynthetic organisms + fungus

– Mycorrhizae- roots + fungus