CHAPTER 16 The Origin and Evolution of Microbial Life: Prokaryotes and Protists

CHAPTER 16The Origin and

Evolution of Microbial Life: Prokaryotes and

Protists

• 4.8 BYA - earth

• The early atmosphere probably contained H2O, CO, CO2, N2, and possibly some CH4, but little or no O2 – reducing atmosphere

Figure 16.1A

Figure 16.1C

= 500 million years ago

Earliest animals; diverse algae

Earliest multicellular eukaryotes?

Earliest eukaryotes

Accumulation of atmosphericO2 from photosyntheticcyanobacteria

Oldest known prokaryotic fossils

Origin of life?

Formation of Earth

Bil

lio

ns

of

ye

ars

ag

o

2 Domains of prokaryotes

Domain Archaea(Kingdom Archaebacteria)

Evolved first – “extreme” bacteria– Probably gave rise to eukaryotes

based on cell structure (chart pp. 323)

Domain Bacteria

– More recent bacteria

– Most of the bacteria we are familiar with

– Contain helpful & harmful

Phyla classification

• 9 major groups or phyla (5 in book)

• P. Proteobacteria

• P. Chlamydias

• P. Spirochetes

• P. Gram +

• P. Cyanobacteria

Importance

SHAPES• Spheres• Rods• Curves & sprirals

classified by shape & clustering

Figure 16.9A-C

Clustering• Strepto

• Staphylo

Bacterial cell morphology

Bacterial Plaque

Morphology• Gram positive bacteria

• Gram negative –

Nutrition & Niche• Heterotrophs (organic C)

–

• Autotrophs (CO2 for C)• Photo- (use of sun for NRG)

or chemo- (use of inorganic compounds for NRG)

Reproduction & Growth

conjugation

How did they ever evolve??• mutations

• Conjugation

• Transduction

• Transformation

How do they cause harm?

• Exotoxins

• Endotoxins– Toxins released when bacteria die

• Enzyme destruction of tissue– Attachment of bacteria to cell, enzymes

“digest” cell

suvivorship

Common bacterial Diseases

transmission

Control of Bacteria

• Prevent entry to body

• Antibiotics– Antibiotic resistance

Viruses

… a little bit of left-over life…

What is a virus?

• Non-living

• Particle

• Obligate intra-cellular parasites–Can only “live” and make more

within a host

Effects of Viruses• Harmful

– Virulent– Temperate

• Helpful– Transduction– Breeding

• TMV and other viruses often destroy chlorophyll – unique coloration

Classified by…• Shape

– Icosahedral, spherical, rod, lunar-lander

• Genetic Material– DNA – makes mRNA & thus viral proteins OR– RNA –

• Host they infect– The living world – plants, animals, bacteria

Structure

• Protein coat surrounding a core of genetic material =

• Viroid -

• Prion -

• Bacteriophage –

How they work

• Must infect host cell - specificity

• Take over the host’s genetic machinery

• Vectored by

• Can cause immediate harm or “wait” for the right time to become “active”

Lytic Cycle • Fast cycle, immediate harm• Absorbtion

– Recognition of host

• Entry– Often only the DNA/RNA

• Replication– Many copies of viral genes made

• Assembly of new viruses• Release to reinfect other cells

– lyse

Lysogenic Cycle• Slow cycle with dormant or latent period• Absorbtion• Entry• Formation of prophage – • Replication without harm – host makes

many copies of virus as it copies its own genetic info for mitosis

• Stimulus –

HIV & the Lysogenic Cycle

• HIV + vs. AIDS

• Dormant phase of 8-10 years

• When activated, so much virus is present, symptoms appear very rapidly

• Affects T4 cells or the “white blood cell immunity army”– NO defence against other “invaders”

Control of Viruses

• NO • Prevent entry to body

– Prevent insect bites, boil water, heat food, clean, cover mouth, no unprotected sex

• Stop attachment – • Stop entry to cell• Stop replication – induced mutations• Stop lysing• White blood cells and immunity